PHYSIOLOGY FOR C.S.S, P.C.S, M.SC,B.SC,LECTURER POST

TAHIR HABIB
Physiology for C.S.S, P.C.S, M.Sc,B.Sc,Lecturer post

TAHIR HABIB [PHYSIOLOGY FOR C.S.S, P.C.S, M.SC,B.SC,LECTURER POST]
What is Physiology?
Physiology is the science of life. It is a broad science which aims to understand the mechanisms
of living, from the molecular basis of cell function to the integrated behaviour of the whole body.
Research in physiology helps us to understand how the body works; it also helps us to realise
what goes wrong in disease and to identify new treatments for disease.
Physiology forms an integral part of pre- and post-16 biology education, and can also be studied
at university – either as a stand-alone discipline or as part of an integrated degree, such as
biomedical sciences. For more information about career paths in physiology, please visit the
careers section of this website.
Pre-16, the study of physiology focuses primarily on how the body moves, and the structure and
function of some of the major organ systems (including the cardiovascular and respiratory
systems). Post-16, the study of physiology leans more towards the understanding of
physiological processes such as homeostasis and excretion.
THE ENDOCRINE SYSTEM
The endocrine system is a set of hormone secreting glands within the body of an animal. The
function of the endocrine system is homeostasis, communication and response to stimuli. The
endocrine system regulates the internal environment of the animal for growth, survival and
reproduction as well as allowing it to respond to changes in its external environment.
The endocrine system‘s glands secrete chemical messages we call hormones. These signals are
passed through the blood to arrive at a target organ, which has cells possessing the
appropriate receptor. Exocrine glands (not part of the endocrine system) secrete products that
are passed outside the body. Sweat glands, salivary glands, and digestive glands are examples of
exocrine glands.

The other communication method in the body is the nervous system. Although there are
differences between them, they complement each other in many responses, e.g., response to
danger.
The difference between nervous and endocrine control are as follows:
1. Nervous response is faster.
2. Nervous response is shorter in duration.
3. Nervous response stops quicker.
4. Nervous response is much more local.
5. Nerve ‗messages‘ are conducted electrically; endocrine ‗messages‘ are carried
chemically.
Hormones:
Most hormones are made of protein. They are called peptides. Peptides are short chains of amino
acids; most hormones are peptides. They are secreted by the pituitary,
parathyroid, heart, stomach, liver, and kidneys.
Some hormones are steroid based. Steroids are lipids derived from
cholesterol. Testosterone is the male sex hormone. Estradiol, similar in structure to testosterone,
is responsible for many female sex characteristics. Steroid hormones are secreted by the gonads,
adrenal cortex, and placenta.
Hormones are usually slow to act but, once they act, they remain active for long periods of
time and, also, their effects remain for a long time.

Endocrine Glands
There are 10 endocrine glands. As stated previously, other organs such as the stomach, intestines,
kidneys, heart, brain, and placenta also make hormones.
THE PITUITARY GLAND
The pituitary gland is often called the master gland. That is because the pituitary gland
produces hormones that regulate other endocrine glands. Some hormones produced by the
pituitary gland are:
1. Follicle Stimulating Hormone (FSH): Will be discussed in a later Chapter of the
syllabus.
2. Luteinising Hormone (LH): Will be discussed in a later Chapter of the syllabus.
3. Growth Hormone (GH): Causes body cells to absorb amino acids and form protein
for growth. The main function is to cause the elongation of bones.
4. Prolactin: stimulates milk formation by the breast after the birth of the baby.

5. Oxytocin: stimulates muscle contraction of uterus during birth, stimulates muscle
contraction in the milk ducts during breast-feeding.
6. Antidiuretic Hormone (ADH): causes increased water reabsorption by kidneys.
7. Thyroid Stimulating Hormone (TSH): Combines with iodine at the thyroid gland
to produce thyroxine.
Overproduction of GH causes gigantism and underproduction causes dwarfism.
THE HYPOTHALAMUS
The hypothalamus links the nervous system with the endocrine system. It produces
hormones that control the pituitary gland‘s responses to messages from the brain and other
hormones. Some these hormones, called releasing hormones, stimulate the pituitary gland to
make other hormones. Others, called release inhibiting hormones, prevent the production of
pituitary hormones.
An example is growth hormone releasing factor. This causes the production of growth
hormone (GH) by the pituitary gland.

THE THYROID GLAND
The thyroid gland produces the hormone called thyroxin. Thyroxin controls the rate of all
the body‘s internal reactions. In other words, thyroxin controls the rate of the
body‘s metabolism.
Physical conditions related to abnormal thyroid function are:
Hypothyroidism- Under Production of Thyroxine
1. Cretinism- Under production of thyroxin in young children. This results in low
metabolic rates and results in retarded physical and mental development.
2. Myxoedema- Under production of thyroxin in adults. Characteristics are tiredness,
lack of energy, slow mental and physical activity, and weight gain.
3. Goitre- Swelling of the thyroid caused by myxoedema.
Thyroxine Excess (Hyperthyroidism)

Thyroxine secretion is above normal. This causes a raised level of metabolism. Symptoms of
over production of thyroxin are bulging eyes, weight loss heat production, nervousness,
irritability, and anxiety. This condition is called Grave’s Disease. Corrective measures for
Grave‘s Disease are:
1. Drugs to suppress thyroid activity
2. Surgically remove part of the gland
3. Use radioactive iodine to destroy some of the gland.
THE PARATHYROIDS
There are 4 parathyroid glands. They are located within the
thyroid gland. The hormone they produce is
called parathormone. This hormone stimulates the release of
calcium from the bones. That is why we must continue to
include calcium in our diet even when our bones are fully
grown.
ADRENAL GLAND ESSENTIALS
The adrenal glands are two glands that sit on top of your kidneys that are made up of two distinct
parts.
 The adrenal cortex—the outer part of the gland—produces hormones that are vital to life,
such as cortisol (which helps regulate metabolism and helps your body respond to stress)
and aldosterone (which helps control blood pressure).
 The adrenal medulla—the inner part of the gland—produces nonessential (that is, you
don‘t need them to live) hormones, such as adrenaline (which helps your body react to
stress).
HORMONES OF THE ADRENAL GLANDS

The adrenal cortex and the adrenal medulla have very different functions. One of the main
distinctions between them is that the hormones released by the adrenal cortex are necessary for
life; those secreted by the adrenal medulla are not.
ADRENAL CORTEX HORMONES
The adrenal cortex produces two main groups of corticosteroid hormones—glucocorticoids and
mineralcorticoids. The release of glucocorticoids is triggered by the hypothalamus and pituitary
gland. Mineralcorticoids are mediated by signals triggered by the kidney.
When the hypothalamus produces corticotrophin-releasing hormone (CRH), it stimulates the
pituitary gland to release adrenal corticotrophic hormone (ACTH). These hormones, in turn, alert
the adrenal glands to produce corticosteroid hormones.
Glucocorticoids released by the adrenal cortex include:
 Hydrocortisone: Commonly known as cortisol, it regulates how the body converts fats,
proteins, and carbohydrates to energy. It also helps regulate blood pressure and
cardiovascular function.
 Corticosterone: This hormone works with hydrocortisone to regulate immune response
and suppress inflammatory reactions.
The principle mineralcorticoid is aldosterone, which maintains the right balance of salt and
water while helping control blood pressure.
There is a third class of hormone released by the adrenal cortex, known as sex steroids or sex
hormones. The adrenal cortex releases small amounts of male and female sex hormones.
However, their impact is usually overshadowed by the greater amounts of hormones (such as
estrogen and testosterone) released by the ovaries or testes.
ADRENAL MEDULLA HORMONES
Unlike the adrenal cortex, the adrenal medulla does not perform any vital functions. That is, you
don‘t need it to live. But that hardly means the adrenal medulla is useless. The hormones of the
adrenal medulla are released after the sympathetic nervous system is stimulated, which occurs
when you‘re stressed. As such, the adrenal medulla helps you deal with physical and emotional
stress. You can learn more by reading a SpineUniverse article about the sympathetic nervous
system.
You may be familiar with the fight-or-flight response—a process initiated by the sympathetic
nervous system when your body encounters a threatening (stressful) situation. The hormones of
the adrenal medulla contribute to this response.

Hormones secreted by the adrenal medulla are:
 Epinephrine: Most people know epinephrine by its other name—adrenaline. This
hormone rapidly responds to stress by increasing your heart rate and rushing blood to the
muscles and brain. It also spikes your blood sugar level by helping convert glycogen to
glucose in the liver. (Glycogen is the liver‘s storage form of glucose.)
 Norepinephrine: Also known as noradrenaline, this hormone works with epinephrine in
responding to stress. However, it can cause vasoconstriction (the narrowing of blood
vessels). This results in high blood pressure.
PANCREAS:
In addition, the pancreas produces the hormone called insulin. This hormone is produced in
groups of cells called Islets of Langerhans Insulin is needed because it reduces blood glucose
levels in the blood. It causes cells, especially fat and muscle cells, to absorb glucose from the
blood. The glucose is needed for cellular respiration or converted into glycogen. The glycogen is
stored in the liver or the muscles for future use in cellular respiration.
Pancreas
• A triangular gland, which has both exocrine and endocrine cells, located behind the stomach
• Acinar cells produce an enzyme-rich juice used for digestion (exocrine product)
• Pancreatic islets (islets of Langerhans) produce hormones (endocrine products)
• The islets contain two major cell types:
•
•
Glucagon
• A 29-amino-acid polypeptide hormone that is a potent hyperglycemic agent
• Its major target is the liver, where it promotes:
• Glycogenolysis – the breakdown of glycogen to glucose
• Gluconeogenesis – synthesis of glucose from lactic acid and noncarbohydrates
• Releases glucose to the blood from liver cells
Insulin
• A 51-amino-acid protein consisting of two amino acid chains linked by disulfide bonds
• Synthesized as part of proinsulin and then excised by enzymes, releasing functional insulin
• Insulin:
• Lowers blood glucose levels
• Enhances transport of glucose into body cells
• Counters metabolic activity that would enhance blood glucose levels

Diabetes is a serious condition that results from 1 of 2 causes. In type 1 diabetes,
the pancreas no longer makes insulin and therefore blood glucose cannot enter the cells to be
used for energy. In type 2 diabetes, either the pancreas does not make enough insulin or the
body is unable to use insulin correctly. Symptoms of diabetes are high glucose levels in the
blood and urine, the production of large amounts of urine, severe thirst, loss of weight, and
tiredness.
Injections of insulin, which are taken daily, the control of carbohydrate intake, exercise, and
weight control treat diabetes.
Review Chart of Major Hormonal Glands
Where the Hormone
is Produced
Hormone(s) Secreted Hormone Function
Adrenal Glands Adrenalin Causes Emergency Responses
(fight/flight)
Pituitary Gland Growth hormone Affects growth and development;
stimulates protein production
Pancreas Insulin Lowers blood sugar levels;
stimulates metabolism of glucose,
protein, and fat
Hypothalamus Growth Hormone
Releasing Factor
Causes growth hormone to be
made
Pineal Gland Melatonin Controls body rhythms
Parathyroid Glands Parathyroid hormone
(Parathormone)
Affects bone formation and
excretion of calcium and
phosphorus

Thyroid Thyroxine Controls Metabolism
Thymus Thymosin Matures white blood cells
CIRCULATION OF BLOOD
CARDIAC CYCLE
Sequence of events which take pace during completion of one heart beat is called ―Cardiac
Cycle‖
PHASES
(I) DIASTOLE
It is resting period of heart chambers.
II) SYSTOLE
During which heart‘s chambers contract. In cardiac cycle, blood is circulated in whole body.
TYPES OF CIRCULATION
PULMONARY CIRCULATION
In pulmonary circulation following events take place.
RT. ATRIAL SYSTOL
First the blood from whole systems of body, except lungs enter in right Atrium through superior
and Inferior vena cavae into the right atrium by atiral systole, blood comes into right ventricle
from right atrium via Tricuspid valve.
RT. VENTRICLE SYSTOLE
After coming of blood into the Rt. Ventricle, it goes to the lungs via pulmonary trunk by
ventricular systole, for oxygenation of blood by passing through pulmonary valve.
SYSTEMIC CIRCULATION
In systemic circulation, following events take place.
LEFT ATRIAL SYSTOLE
When oxygenated blood comes into left atrium, then left atrial sytole causes blood to enter left
ventricle through bicuspid valve
LEFT VENTRICULAR SYSTOLE

When blood reaches here it sends into aorta through aortic valve to provide blood to body
systems.
CARDIAC OUTPUT
The blood volume pump per minute by left ventricle into the systemic circulation
HEART BEAT
The contraction of heart chambers are known heart beat which are regular, rhythmic.
Ventricular systole is LUB
Ventricular diastole is DUB
TIME FOR HEART BEAT
0.8 sec is time for one heart beat.
CONDUCTING SYSTEM OF HEART
It consists of
1.AV-NODE
2.SA-NODE
3)AV-BUNDLE
4) PURKINJI FIBERS.
1. SA-NODE
SA NODE found near upper end of superior vena cava in RT. atrium
PARTS
1. Specialized cardiac Muscles.
2. Autonomic Nerve endings.
FUNCTIONS
It Initiates the contraction of heart chambers through impulses & also transmit to AV node.
2. AV- NODE
It is found in lower end of RT. Atrium. Structurally it is smilar to SA-NODE
FUNCTION
It transmit nerve impulses to ventricles for contraction rhythmically.
3. AV-BUNDLE
AV BUNDLE are the fibers originate from AV node. The bundle divided into Right AV bundle,
Left AV bundle
FUNCTION
It transmit nerve impulses to ventricles.
4. PURKINJI FIBERS
AV bundles red divided into small fibres which penetrate the ventricle wall also known as
purkinji fibers / Bundle of His small thin fibers.
LEUKEMIA
DEFINATION
“The malignant disorder of increase number of abnormal leucocytes in blood.”
CAUSE

The cause of leukemia is unknown.
FACTORS
Factors associated with leukemia are
 Ionizing Radiation
 Cytotoxic drugs.
 Retroviruses.
 Genetic
EFFECTS OF DISEASE
 In result of leukemia, normal leucocytes counts become less.
 This is progressive, and fatal condition which leads to heamorrhage or infection
THALASSEMIA
DEFINITION
“Genetically impaired globin chains formation leads to impaired or defected formation of
hemoglobin.”
GENETIC DISEASE
Thalassemia is a genetic disorder, it may be
1. Hetrozygous /Mild thalassemia:
2. Homozygous.
TYPE
BETA – Thalassemia
α – Thalassemia
BETA-THALASSEMIA
When globin chain is impaired or defected. It is most common one.
ALPHA-THALASSEMIA
when α-thalassemia globin chain of (HB) hemoglobin is defected.
KINDS OF THALASSEMIA
THALASSEMIA MINOR
When thalassemia is of heterozygous type with mild anemia.
THALASSEMIA MAJOR
When thalassemia is of homozygous type with profound hypochromic anemia. It is more
common in children & results with enlargement of kidney.
REMEDY
The only remedy is transfusion of blood at regular intervals.
CVD CARDIOVASCULAR DISEASE

Diseases of heart, blood vessels and blood circulation are generally term as CVD.
ATHEROSCLEROSIS
The disease of arterial wall with lose of elasticity, thickness of inner wall causing narrowing of
lumen, results in impairing of blood flow.
ATHEROMATOUS PLAQUES
The narrowing is due to formation of fatty lesions called atheromatous plaque in inner lining of
arteries.
COMPONENTS OF PLAQUE
These plaques consist of
 LDL-LOW DENSITY LIPO PROTEINS
 DECAYING MUSCLES CELLS
 FIBROUS TISSUE
 PLATELETES
 CLUMP OF BLOOD
CAUSES
Smoking, Hypertension, Obesity, Diabetes (Severe), family history of arterial disease
EFFECTS
Atherosclerosis produces no symptoms until the damage to artery is so severe that it restricts
blood flow.
ANGINA PECTORIS
If blood flow to heart muscles is restricted causes (cell damage) necrosis called angina pectoris.
Pain in chest, arm, or jaws usually during exercise.
THROMBUS FORMATION
The formation of blood clot with in the intact blood vessel initiated by atheromatous plaque.
REASON FOR THROMBUS FORMATION
Due to formation athromatous plaque loss of elasticity, intact blood vessel get destroyed, blood
from vessel wall comes out & later change to blood clot and blocks the lumen of small arteries.
RESULT OF THROMBUS FORMATION
Initially thrombus block the lumen partially result in decrease blood flow to organs & leading to
impairment of physiology of organs. Later on, thrombus blocks the lumen completely so due to
complete loss of blood supply, cells damage occur.
CORONARY THROMBOSIS
Type of thrombosis when narrowing of lumen occurs in coronary blood vessels due to formation
of clot.
EFFECT

Occulsion of coronary atery causes myocardial infarction and heart attack.
HEAMORRHAGE
The escaping of blood from intact blood vessels.
STROKE
Most dangerous type of heamorrhage is that of brain which results in paralysis or strokes.
HAEMATOMA
The accumalation of blood in interstitial spaces known as haematoma.
This will lead to edema.
STROKE
DEFINITION
The damage to the part of brain caused by, restriction in blood supply or leakage of blood outside
the vessels.
CHARACTERISTICS
Impairment of sensation, movement & function controlled by damage part of brain.
CAUSES
 Hypertension
 Atherosclerosis
HEMIPLEGIA
Damage to any, one cerebral hemisphere can cause weakness or paralyses of one side of body
called hemiplegia
PRECAUTIONARY MEASURES
Blood pressure should be with in normal range through proper diet. Salt should be used in less
quantities exercise should be the regular habit. Smoking must be avoided. Person life should be
free of worries.
BLOOD VESSELS
DEFINITION
―The closed vessels or tubes through which transporting medium or blood circulate with in body
called ―blood vessels‖.
TYPES OF BLOOD VESSELS
1. Arteries.
2. Capillaries.
3. Veins.
ARTERIES
DEFINITION
Thick walled blood vessels which carry blood from heart to the organs of body.
LAYERS

It consists of three layers.
1. Tunica Externa/ Adventitia
2. Tunica Media
3. Tunica Intima
1-TUNICA EXTERNA
It is thin but tough layer, having abundant amount of collagen fibers. It is outer most layer.
2-TUNICA MEDIA
The middle layer has smooth muscle fibers & elastin fibers. It is the thickest layer.
3-TUNICA INTIMA
It consists of squamous endothelium.
LUMEN
Thick walled vessels & having smaller lumen than that of veins except arteries of brain & related
to cranium having large lumen.
SEMILUNAR VALVES
They are not present in arteries.
BRANCHES – DIVISIONS
Aorta divides into large arteries, large arteries into smaller arteries, smaller arteries into
arterioles, then they give rise to capillary.
At arteriole level, small sphincters are present which are known as PRE-CAPILLARY
SPHINCTER.
SPHINCTER
FUNCTION
They are for regulating the diastolic pressure.
CHARACTERSTICS
 Arteries are elastic so during systolic pressure, they do not rupture and dilate.
 During ceasement/ stopage of systolic pressure of heart, arteries contract & supply even
flow of blood.
 The arteries carry oxygenated blood except pulmonary arteries.
VEINS
DEFINITION
The thin walled blood vessels that drian blood from body parts/organs into heart called veins.
LAYERS
Tunica Externa
Tunica Media
Tunica Intima
1. TUNICA EXTERNA

Thickest layer in veins. It contains collagen, elastin and smooth muscles cells.
2. TUNICA MEDIA
Not thicker as that of arteries. Elastic tissues and small smooth muscle.
3. TUNICA INTIMA
Contains endothelial cells layer.
LUMEN
It has large lumen and thin wall.
SEMILUNAR VALVES
They are present in veins to prevent back flow of blood in the influence of gravity.
TRIBUTARIES
Veninules -> small veins -> large veins -> vena cava.
BLOOD PRESSURE
In veins blood pressure is low and are non pulsatile.
CHARACTERISTICS
The blood flows slowly and smoothly in veins. Veins are superficial and collapse when empty.
CAPILARIES
The intimate microscopic closed channels of both arterial & veinous interconnected network is
called capillaries.
DIAMETER
Capillaries are extremely narrow in diameter of about 7-10 μ.
LAYERS
Capillaries are thin walled vessels & contains single layer of endothelium which offers small
resistance in transport of material across the capillary wall.
FUNCTION
Through diffusion and active transport of oxygen is transported to tissues & CO2 to capillaries.
Nitrogenous waste is filtered through the capillaries into excretory tubules.
BLUE BABIES (CYANOSIS)
Blue baby is a layman terminology. In medical science it is known as cyanosis.
DEFINITION
The term cyanosis‖ means the blueish discolouration of the skin & mucous membrane due to
excessive cone of reduced (deoxygenated haemoglobin) in the blood & it appears when reduced
Hb conc in capillaries is more than 5 gm/dl of blood. The reduced Hb has an intense dark blue
purple colour that is transmitted through the skin.
MOST COMMON CAUSE OF CYANOSIS
Although there are various other causes of cyanosis but the most common cause is
CONGENITAL CYANOTIC HEART DISEASE.
BASIC CAUSE OF CYANOSIS
In congenital heart diseases, there is an abnormal connection b/w right and left side of heart,
which permits the large amount of unoxygenated venous blood to bypass the pulmonary

capillaries & dilute the oxygenated blood in systemic arteries i.e RIGHT TO LEFT SHUNT,
which results in cyanosis.
SOME EXAMPLES OF CONGENITAL HEART DISEASES
 Some congenital heart diseases which are responsible for the abnormal connection
between right and left sides of heart are as follows.
 ATRIAL SEPTUM DEFECT (ASD)
 VENTRICULAR SETPUM DEFECT (VSD)
 PERSISTANT DUCTUS ARTEROSUS
 In all these conditions, blood begins to flow from the aorta (left side) into pulmonary
arteries (right side) & the people donot show cyanosis until late in life when heart fails or
lungs become congested.
TETRALOGY OF FALLOT (RIGHT –TO-LEFT SHUNT)
It is the most common cause of cyanosis or blue baby in which aorta originates from right
ventricles rather than left & receives deoxygenated blood.
Circulatory System
HUMAN HEART
INTRODUCTION
Heart, the most powerful organ in the circulatory system is conical, hollow & muscular organ,
situated in middle mediastinum.
POSITION OF HEART
Heart lies in the thoracic cavity between the lungs slightly towards left, enclosed with in ribcage
with the sternum in front & vertebral column behind.
SIZE & WEIGHT
The heart measures about 3 ½ Inches & weighs about 300 gm in males & 250 gm in females.
MAIN FUNCTION OF HEART
Heart works continuously like a muscular pump & pumps the blood to various parts of the body
to meet their nutritive requirements.
COVERING OF HEART PERICARDIUM
Heart is surrounded by a double layered pericarcdium. The outer layer is called Fibrous

pericardium & inner layer is called as serous pericardium.
PERICARDIAL FLUID
Fluid is secreted in b/w the two layers of pericardium which is known as pericardial fluid.
FUNCTION
Pericardial fluid acts as LUBRICANT & reduces friction b/w heart walls & surrounding tissues
during beating of heart.
STRUCTURE OF HEART
Human heart consists of four chambers.
CHAMBERS OF HEART
1. RIGHT ATRIUM
Right Atrium is the right upper chamber of heart & acts as thin walled low pressure pump.
OPENINGS (INLETS) OF RIGHT ATRIUM
1. Superior Vena Cava
2. Anfenior Vena Cava
3. Coronary Sinus
FUNCTION
It receives venous blood from the whole body & pump it to the right ventricle through the right
atrioventricular (tricuspid opening) valve.
2. LEFT ATRIUM
Left atrium is upper triangular chamber which is present posteriorly. It also acts as low pressure
pump.
OPENINGS (INLETS) OF LEFT ATRIUM
Two pairs of pulmonary veins.
FUNCTION
It receives oxygenated blood from the lungs through 4 pulmonary veins and pumps it to the left
ventricle through the left atrioventricular orifice (mitral or bicuspid).
3. RIGHT VENTRICLE
Right ventricle is the right lower chamber of heart, which is triangular in shape.
OPENINGS OF RIGHT VENTRICLE
 Tricuspids valve
 Pulmonary Aorta through pulmonary valve.
THICKNESS OF WALL
 The wall of right ventricle is thinner than that of left ventricle in a ratio of 1:3

SIZE OF CAVITY
Cavity of right ventricle is broader than left because of thin muscular walls, and both of these
features are due to the fact that right ventricle has to pump the blood into lungs only against low
pressure system (i.e. pulmonary circulation).
FUNCTION
Right ventricle receives deoxygenated blood from right Atrium and pumps it to the lungs through
pulmonary aorta for oxygenation.
4. LEFT VENTRICLE
Left ventricle is the most thick walled chamber and forms the apex of heart.
OPENING OF LEFT VENTRICLE
 Bicuspid or Mitral valve
 Systemic Aorta through aortic valve.
THICKNESS OF WALL
The walls of left ventricle are 3 times thicker than those of right ventricle. Blood pressure is 6
times high.
SIZE OF CAVITY
The cavity of left ventricle is narrower than the right ventricle because of more muscular walls. It
is due to the fact that left ventricle has to pump the blood to the entire body against high pressure
system (Systemic Circulation).
FUNCTION
It receives oxygenated blood from left atrium & pumps it into the aorta.
INTERNAL STRUCTURE OF VENTRLES
Interior of ventricles show two parts
1. Rough in flowing part
2. Smooth out flowing part
1. ROUGH PART
TRABECULAE CARNEAE
Inflowing part of each ventricle is rough due to presence of muscular ridges called as Trabeculae
carneae.
2. SMOOTH PART
Out flowing part of each ventricle is smooth which gives origin to pulmonary trunk in right
ventricle & Ascending Aorta in left ventricle.
PAPILLARY MUSCLES
Papillary muscles are the type of Trabeculae carneae being attached by their bases to ventricular
walls, & their apices are connected to, the cusps of valves through chorda tendinae.
CHORDA TENDINAE:

These are delicate fibrous chords, which connect the papillary muscles to the cusps of
Atriovertritcular valves.
FUNCTION
Chorda Tendinae don‘t left the valves open back into the atria when the ventricles contract.
SEPTUM OF HEART
1. INTERATRIAL SEPTUM
Internally, the right & left atria are separated by a vertical membranous septum called as
Interatrial septum.
2. INTERVENTRICULAR SEPTUM:
The right & left verticals are also separated by a thick muscular septum called as Interventricular
septum.
3. ATRIOVENTRICULAR SEPTUM
Atria lie above & behind the ventricles & are separated from ventricles by Atrioven-tricular
septum.
HEART VALVES
Heart possesses two types of valves, which regulate the flow of blood with in the heart.
TYPES OF HEART VALVES
1. Atrioventricular valves -> Bicuspid, Tricuspid
2. Semilunar vlaves -> Aortic valve, Pulmonary valve
1. ATRIOVENTRICULAR VALVES
INTRODUCTION
Valves, which are present in b/w the Atria & ventricles are called Atrioventricular valves.
TYPES OF ATRIOVENTRICULAR VALVES
They are of two types.
1. Bicuspid or Mitral
2. Tricuspid.
1. BICUSPID OR MITRAL VALVE
Blood flows from left Atrium to the left ventricle through left atrioventricular on orifice, which is
guarded by bicuspid or Mitral valves.
CUSPS
It has tow (2) cusps so it is called as bicuspid.
2.TRICUSPID VALVE
Blood flows from right Atrium to the Right ventricle through right Atrioventricular orifice,
which is guarded by Tricuspid.
CUSPS
It has 3 cusps so it is called as TRICUSPID.
2. SEMILUNAR VALVES
This is the second category of heart valves, which guard the emergence of pulmonary & systemic
Aorta.

TYPES OF SEMILUNAR VALVES
It has Two Types:
1. Aortic Valve
2. Pulmonary Valve
1. AORTIC VALVE
This valve guards the Aortic orifice in left ventricle
CUSPS
It consists of 3 Semilunar cusps.
2. PULMONARY VALVE
This valve guards the pulmonary orifice in right ventricle.
CUSPS
It also consists of 3 semi lunar cusps.
FUNCTIONS OF VALVES
Heart valves maintain unidirectional flow of the blood & prevents its regurgitation in the
opposite direction.

A myogenic heart contracts by itself without any external stimulus, while a neurogenic heart
contracts after receiving an external stimulus in the form of a nerve impulse

Explanation:
MYOGENIC
Myogenic is the term used for muscles or tissues that can contract on their own, without any
external electrical stimulus, from the brain or spinal cord for example.
An example of this phenomena is actually present in our kidneys to regulate the flow of blood in
vessels.
Another example is the human heart.
The muscles of the human heart are stimulated to contract by nerve impulses generated by
the Sino Atrial(SA) node. It is a cluster of cells which are part of the heart muscle.
Hence the human heart is myogenic. It does not require nerves to start contracting, it can contract
on its own . There are nerves supplied to the heart but they only change the rate of heartbeat and
cannot initiate muscle contraction.
The impulse from the SA Node, which is just an electric current, then goes down a path through
the heart, stimulating the contraction of each muscle in turn as shown here in dark red lin
NEUROGENIC
Neurogenic is the term used to describe a muscle or tissue that requires an external electrical
stimulus to start contracting.
As an interesting side point: Crustaceans have neurogenic hearts.

Lecture: Physiology of Blood
I. Components, Characteristics, Functions of Blood
A. Major Components of Blood
1. formed elements - the actual cellular components of blood (special connective tissue)
a. erythrocytes - red blood cells
b. leukocytes - white blood cells
c. platelets - cell fragments for clotting
2. blood plasma - complex non-cellular fluid surrounding formed elements; protein &
electrolytes
B. Separation of Components in a Centrifuge
VOLUME LAYER
1. clear/yellowish PLASMA 55% top
2. thin/whitish buffy coat <1% middle
with LEUKOCYTES & PLATELETS
3. Reddish mass – ERYTHROCYTES(RBCs) 45% bottom
Hematocrit - percentage by VOLUME of erythrocytes when blood is centrifuged (normal =
45%)
C. Characteristics of Blood
1. bright red (oxygenated)
2. dark red/purplish (unoxygenated)
3. much more dense than pure water
4. pH range from 7.35 to 7.45 (slightly alkaline)
5. slightly warmer than body temperature 100.4 F
6. typical volume in adult male 5-6 liters

7. typical volume in adult female 4-5 liters
8. typically 8% of body weight
D. Major Functions of Blood
1. Distribution & Transport
a. oxygen from lungs to body cells
b. carbon dioxide from body cells to lungs
c. nutrients from GI tract to body cells
d. nitrogenous wastes from body cells to kidneys
e. hormones from glands to body cells
2. Regulation (maintenance of homeostasis)
a. maintenance of normal body pH
i. blood proteins (albumin) & bicarbonate
b. maintenance of circulatory/interstitial fluid
i. electrolytes aid blood proteins (albumin)
c. maintenance of temperature (blushed skin)
3. Protection
a. platelets and proteins "seal" vessel damage
b. protection from foreign material & infections
i. leukocytes, antibodies, complement proteins
II. Erythrocytes (red blood ells; RBCs)
A. Structure
1. 7.5 micron diameter; 2.0 micron thick
2. biconcave disk shape; ideal for gas exchange
i. spectrin - elastic protein; allows shape change
3. mature cells are anucleate (no nucleus)
3. very few organelles; mainly a hemoglobin carrier

i. hemoglobin – 33% of cell mass; carries oxygen
5. no mitochondria; only anaerobic respiration
6. ratio erythrocytes:leukocytes = 800:1
7. red blood cell count: # cells per cubic millimeter
i. normal male count - 5.1 to 5.8 million
ii. normal female count - 4.3 to 5.2 million
B. Functions (oxygen & carbon dioxide transport)
1. hemoglobin - large molecules with globin and hemes
a. globin - complex protein with 4 polypeptides (2 alpha and 2 beta polypeptides)
b. heme group - IRON containing pigment part of hemoglobin to
which oxygen binds
i. each polypeptide has one heme group;each heme carries one
O2
c. normal hemoglobin levels (grams/l00 ml blood)
i. infants 14-20 grams/l00 ml
ii adult female 12-16 grams/100 ml
iii adult male 13-18 grams/l00 ml
2. states of hemoglobin
a. oxyhemoglobin - when oxygen is bound to IRON
b. deoxyhemoglobin - no oxygen bound to IRON
c. carbaminohemoglobin - when carbon dioxide bound (to polypeptide chain)
C. Hematopoiesis and Erythropoiesis
1. hematopoiesis (hemopoiesis) - the maturation, development and formation of blood cells

a. red bone marrow (myeloid tissue) - location of hematopoiesis; in blood sinusoids which
connect with capillaries; mainly in axial skeleton and heads of femur & humerus
b. hemocytoblast (stem cell) - the mitotic precursor to blood cells
before differentiation
i. differentiation - maturing cell becomes "committed" to being certain type blood cell
2. erythropoiesis - the maturation, development, and formation of Red Blood Cells
(erythrocytes)
hemocytoblast ->
proerythroblast ->
early (basophilic) erythroblast ->
late (polychromatophilic) erythroblast ->
(hemoglobin) normoblast -> (nucleus ejected when enough hemoglobin)
reticulocyte -> (retaining some endoplasmic reticulum)
ERYTHROCYTE
hemocytoblast -> reticulocyte 3-5 DAYS
reticulocyte -> ERYTHROCYTE 2 DAYS (in blood)
ERYTHROCYTE lifespan 100-120 DAYS
(primarily destroyed by macrophages in the spleen)
3. Regulation of Erythropoiesis
a. hormonal controls - erythropoietin is the hormone that stimulates
RBC production
DECREASED oxygen level in blood causes KIDNEYS to increase release of erythropoietin
1. Less RBCs from bleeding

2. Less RBCs from excess RBC destruction
3. Low oxygen levels (high altitude, illness)
4. Increased oxygen demand (exercise)
Eythropoietin now genetically engineered and synthesized by AMGEN of Thousand Oaks.
Testosterone can also mildly stimulate production of RBCs in humans
b. Iron - essential for hemoglobin to carry oxygen
i. 65% of Fe in body is in hemoglobin
ii. liver and spleen store most excess Fe bound to ferritin and hemosiderin
iii. Fe in blood bound to transferrin
iv. daily Fe loss: 0.9 mg men/l.7 mg women
v. women also lose Fe during menstrual flow
c. B-complex Vitamins - Vitamin B12 and Folic Acid essential for DNA synthesis in early
mitotic divisions leading to erythrocytes
D. Erythrocyte Disorders (Anemias & Polycythemias)
1. Anemias - a symptom that results when blood has lower than normal ability to carry
oxygen
a. Insufficient erythrocyte count
i. hemorrhagic anemia - loss of blood from bleeding (wound, ulcer, etc.)
ii. hemolytic anemia - erythrocytes rupture (hemoglobin/transfusion problems, infection)
iii. aplastic anemia - red marrow problems (cancer treatment, marrow disease, etc.)
b. Decrease in Hemoglobin
i. iron-deficiency anemia - low Iron levels (diet; absorption, bleeding, etc.)
ii. pernicious anemia - low Vitamin B12 (diet, intrinsic factor for Vit B absorption)
c. Abnormal Hemoglobin (usually genetic)

i. thalassemia - easily ruptured RBCs (Greek & Italian genetic link)
ii. sickle-cell anemia - sickle-shaped RBCs (genetic Africa, Asia, southern Europe link)
2. Polycythemia - excess RBC count, causes thick blood
a. polycythemia vera - bone marrow problem; hematocrit may jump to 80%
b. secondary polycythemia - high altitude (normal); or too much erythropoietin release
c. blood doping in athletes - RBCs previously withdrawn are transfused before an event;
more RBCs, more oxygen delivery to the body
III. Leukocytes (white blood cells; WBCs)
A. General Structure and Function
1. protection from microbes, parasites, toxins, cancer
2. 1% of blood volume; 4-11,000 per cubic mm blood
3. diapedesis - can "slip between" capillary wall
4. amoeboid motion - movement through the body
5. chemotaxis - moving in direction of a chemical
6. leukocytosis - increased "white blood cell count" in response to bacterial/viral infection
7. granulocytes - contain membrane-bound granules (neutrophils, eosinophils, basophils)
8. agranulocytes - NO membrane-bound granules (lymphocytes, monocytes)
B. Granulocytes - granules in cytoplasm can be stained with Wright's Stain; bilobar nuclei;
10-14
micron diameter; all are phagocytic cells (engulf material)
1. neutrophils - destroy and ingest bacteria & fungi (polymorphonuclear leuks.; "polys")
a. most numerous WBC
b. basophilic (blue) & acidophilic (red)
c. defensins - antibiotic-like proteins (granules)
d. polymorphonuclear - many-lobed nuclei
e. causes lysis of infecting bacteria/fungi
f. HIGH poly count --> likely infection

2. eosinophils - lead attack against parasitic worms
a. only 1-4% of all leukocytes
b. two-lobed, purplish nucleus
c. acidophilic (red) granules with digest enzymes
d. phagocytose antigens & antigen/antibody complex
e. inactivate chemicals released during allergies
3. basophils - releases Histamine which causes inflammation, vasodilation, attraction of
WBCs
a. RAREST of all leukocytes (0.5%)
b. deep purple U or S shaped nucleus
c. basophilic (blue) granules with HISTAMINE
d. related to "mast cells" of connective tissue
e. BOTH release Histamine with "IgE" signal
f. antihistamine - blocks the action of Histamine in response to
infection or allergic antigen
C. Agranulocytes - WBCs without granules in cytoplasm
1. lymphocytes - two types of lymphocytes
a. T lymphocytes - (thymus) respond against virus infected cells and tumor cells
b. B lymphocytes - (bone) differentiate into different "plasma cells" which each produce
antibodies against different antigens
c. lymphocytes primarily in lymphoid tissues
d. very large basophilic (purple) nucleus
e. small lymphocytes in blood (5-8 microns)
f. larger lymphocytes in lymph organs (10-17 mic)
2. monocytes - differentiate to become macrophages; serious appetites for infectious
microbes
a. largest of all leukocytes (18 microns)
b. dark purple, kidney shaped nucleus
4. Hemostasis (stoppage of blood flow after damage)

A. General Characteristics
1. vascular spasms (vasoconstriction at injured site)
2. platelet plug formation (plugging the hole)
3. coagulation (blood clotting - complex mechanism)
B. Vascular Spasms
1. first response to vascular injury - VASOCONSTRICTION is stimulated by:
a. compression of vessel by escaping blood
b. injury "chemicals" released by injured cells
c. reflexes from adjacent pain receptors
C. Formation of a Platelet Plug
1. damage to endothelium of vessel
2. platelets become spiky and sticky in response
3. platelets attach to damaged vessel wall to plug it
4. platelets produce thromboxane A2 - granule release
5. serotonin release enhances vascular spasm
6. ADP - attracts and stimulates platelets at site
7. prostacylin - inhibits aggregation at other sites
5. Coagulation (blood clotting)
A. General Events in Clotting
platelet cells activated by damage->
PF3 and/or Tissue Factor produced by platelet cells->
Factor X activated->
prothrombin activator (enzyme) produced->
prothrombin conversion -> thrombin (another enzyme)
thrombin stimulates: fibrinogen----> fibrin mesh
1. anticoagulant - chemical that inhibits clotting
2. procoagulant - chemical that promotes clotting
3. intrinsic pathway - within the damaged vessel

a. more procoagulants needed (I-XIII) toward PF3 and Factor X
b. allows more "scrutiny" before clotting occurs
4. extrinsic pathway - in outer tissues around vessel
a. tissue thromboplastin (Tissue Factor) - skips intrinsic steps straight to PF3 and Fac X
b. allows rapid response to bleeding out of vessel (clot can form in 10 to 15 seconds)
5. After activation of Factor X, common pathway:
Factor X, PF3 (thromboplastin), Factor V, Ca++
-->
prothrombin activator ->
prothrombin converted -> thrombin (active enzyme)
thrombin stimulates: fibrinogen -> fibrin (meshwork)
Ca++
& thrombin -> Factor XIII (fibrin stabilizer)
B. Clot Retraction (shrinking of clot)
1. actomyosin - causes contraction of platelets
2. blood serum - plasma WITHOUT clotting Factors
3. platelet-derived growth factor (PDGF) - stimulates fibroblast migration and endothelial
growth
C. Clot Eradication (Fibrinolysis)
1. healing occurs over 2 - 10 days
2. tissue plasminogen activator (TPA) - causes the activation of plasminogen
3. plasminogen--> plasmin
4. plasmin degrades proteins within the clot
D. Factors Limiting Growth and Formation of Clots
1. Limiting Normal Clot Growth
a. blood moves too fast to allow procoagulants
b. factors interfere with normal clotting
i. prothrombin III - deactivates thrombin
ii. protein C - inhibits clotting Factors

iii. heparin - inhibits thrombin; prevents adherence of platelets to injured site
VII. Disorders of Hemostasis
A. Thromboembolytic Disorders (undesirable clotting)
1. thrombus - blood clot in normal blood vessel
2. embolus -blood clot/gas bubble floating in blood
a. TPA, streptokinase - can dissolve a clot
b. aspirin - inhibits Thromboxane formation
c. heparin - inhibits thrombin & platelet deposit
d. dicumarol - anticoagulant, blocks Vitamin K
B. Bleeding Disorders
1. thrombocytopenia - reduced platelet count; generally below 50,000 per cubic millimeter;
can cause excessive bleeding from vascular injury
2. impaired liver function - lack of procoagulants (Clotting Factors) that are made in liver a.
vitamin K - essential for liver to make Clotting Factors for coagulation
3. hemophilias - hereditary bleeding disorders that occur almost exclusively in males
a. hemophilia A - defective Factor VIII (83%)
b. hemophilia B - defective Factor IX (10%)
c. Genentech. Inc. - now produces genetically engineered TPA and Factor VIII; patients do
not need transfusions as often
Blood Transfusions and Blood Typing
A. Transfusion of Blood
1. whole blood transfusion - all cells and plasma; anticoagulants (citrate and oxalate salts)
used
2. packed red blood cells - most of the plasma has been removed prior to transfusion
B. Human Blood Groups

1. agglutinogens - glycoproteins on the surface of blood cells; causes "agglutination"
(clumping)
1. ABO Blood Groups - determined by presence or absence of Type A and
Type B agglutinogen proteins on cell membrane
TYPE GENES PEOPLE Antibodies Receive Blood from:
type A A/A, A/O, O/A (30-40%) Anti-B A, O
type B B/B, B/O, O/B (l0-30%) Anti-A B,O
type AB A/B or B/A (3-5%) none A, B, AB, O
type O no A or B (40-50%) Anti-A, Anti-B O only
3. agglutinins - antibodies against either A or B agglutinogen (whichever is not present) a.
transfusion reaction - patient's antibodies attack the donor blood
i. A (anti-B) receives A,O (not B)
ii. B (anti-A) receives B,O (not A)
iii. AB (none) receives A, B, AB, O universal recipient
iv. O (anti-A,anti-B) receives O universal donor
b. agglutination - when incorrect blood transfused, antibodies will "clump" new blood
c. hemolysis - after clumping, RBCs may rupture, releasing
hemoglobin, harming kidney
i. dilute hemoglobin, administer diuretics
4. Rh factor - a different group of agglutinogens
a. Rh positive (Rh+) - an Rh factor is present
b. Rh negative (Rh-) - NO Rh factor
c. transfusion reaction - delayed and less severe than in ABO confrontation
d. erythroblastosis fetalis - Rh- mother antibodies attack Rh+ of older newborn; results in
anemia and low oxygen levels (hypoxia)
i. RhoGAM - serum with anti-Rh agglutinins which will clump the Rh factor, blocking the
reaction of mothers antibodies
ii. exchange transfusion - directly from the mother (Rh-) to the newborn (Rh+)
5. Blood Typing - mixing Donors Blood with Recipient Antibodies (Anti-A, Anti-B,
anti-Rh) in order to identify agglutination

6. Expanding Blood Volume to Avoid Shock
a. pure plasma without antibodies
b. plasma expanders - purified human serum albumin, plasminate, dextran
c. isotonic saline - normal electrolyte solution isotonic to blood plasma (Ringer's Solution)
7. Diagnostic Blood Tests
a. anemia - low hematocrit (below 35%)
b lipidemia - high in fat; yellowish plasma
c. diabetes - blood glucose level
d. infection - generally higher WBC count
e. leukemia - significantly higher WBC count
f. differential WBC count - counts % of each of the different leukocytes (helps diagnose)
g. prothrombin time - time for clotting to occur
h. platelet count - diagnose thrombocytopenia
i. complete blood count - overall

LYMPHATIC SYSTEM
MAIN FUNCTION OF LYMPHATIC SYSTEM
All body tissues are bathed in a watery fluid derived from the blood stream. This intercellular or
tissue fluid is formed when blood passes trough the capillaries. The capillary walls are permeable
to all components of blood except the R.B.C‘s & blood proteins. The fluid passes from the
capillary into the intercellular spaces as the inter-cellular or tissue fluid. About 85% of the tissue
fluid returns into the blood at the venous end of capillary. The rest 15 % of tissue fluid drains
into lymphatic capillaries as lymph along with W.B.C‘s, cell debris & micro organism like
Bacteria , are transported back to the heart through lymphatic system.
COMPONENTS OF LYMPHATIC SYSTEM
Lymphatic System Consists of
1. Lymph
2. Lymphatic tissues
3. Lymphatic vessels or Lymphatics
4. Lymph nodes (type of lymphatic tissue)
DETAILS OF COMPONENTS
1. LYMPH
DEFINITION
“Lymph is the name given to the tissue fluid once it has entered a lymphatic vessel. OR It can be
defined as “Colour less body fluid that contains lymphocytes (agranular WBC‟S), small proteins
& fats”.
EXPLANATION
Lymph is a medium of exchange between blood & body cells. It takes the fluid substances from
cell of tissues & intercellular spaces, which cannot penetrate the blood capillaries.
2.LYMPHATIC TISSUES
DEFINITION
“Lymphatic tissues are a type of connective tissues that contain large no. of lymphocytes”
ORGANS THAT CONTAIN LYMPHATIC TISSUES
Lymphatic tissue is organized into following structures (organs).
 Lymph nodes
 Thymus
 Spleen
 Tonsils
 Some of the patches of tissues in vermiform appendix & in small intestine.

FUNCTION
Lymphatic tissue is essential for immunologic defenses of the body against viruses & bacteria.
3. LYMPHATICS
DEFINITION
Lymphatic vessels or lymphatics are blind tubes that assist the cardiovascular system in removal
of tissue fluid from tissues spaces of the body, the vessels then return the fluid to the blood.
AREAS WHERE LYMPHATIC ARE NOT PRESENT
Lymphatics are present in all tissues & organs of the body except.
 Central Nervous System
 The eye ball
 Internal Ear
 Epidermis of Skin
 Cartilage & bone
TYPES
Two Types of Lymphatics are there:-
SMALL - LYMPH CAPILLARIES
LARGE - LYMPH VESSELS.
1. LYMPH CAPILLARIES
DEFINITION
―Lymph capillaries are a network of thin walled, anastomosing, microscopic vessels which are
closed towards the tissue sinuses & drain the Lymph from tissues.‖
2. LYMPH VESSELS
DEFINATION
The capillaries are in turn drained by lymph tubes having larger diameters & beaded appearance,
called the Lymph vessels.
These vessels contain smooth muscles in them as well as Internal valves to prevent the back flow
of Lymph. The Lymph circulates through the Lymph vessels by the contraction of surrounding
skeletal muscles in one direction (towards the heart). These vessels converge into collecting
ducts i.e right
Lymphatic duct & thoracic duct that drain into large veins at the root of neck.
4. LYMPH NODES
DEFINITION
“Lymph nodes are lymphoid tissue which are present through out the course of Lymphatics,
through which the lymph must passes”
INTERNAL STRUCTURE

Each node consists of a thin, fibrous, outer capsule & an inner mass of lymphoid tissue.
AFFERENT VESSELS
Several small Lymphatics which carry the lymph into the lymph node are referred to as
―Afferent vessels.‖
EFFERENT VESSEL
A single large vessel which carry the lymph away from the node is called ―Efferent vessel‖
FUNCTION
Lymph nodes act as filters that trap the microorganisms & other foreign bodies in the lymph. The
Lymphocytes & macro-phages present here, neutralize & engulf the microorganisms,
respectively.
MAJOR FUNCTIONS OF LYMPHATIC SYSTEM.
From Text Book Pg. 379.
EDEMA
DEFINITION
“Whenever the tissue fluid accumulates rather than being drained into the blood by the
lymphatic system, tissue & body cavities become swollen. This condition is known as “Edema”.
TYPES OF EDEMA
There are two types of Edema.
1. INTRACELLULAR
2. EXTRACELLULAR
1. INTRACELLULAR EDEMA
―Accumulation of excess of fluid within the cells causing cellular swelling is called ―Intra
cellular Edema. It usually occurs after severe extracellular Edema.
2. EXTRACELLULAR EDEMA
―Excess fluid accumulation in extra cellular spaces is called Extracellular Edema. ‖
It is the most commonly occurring form of Edema.
FACTORS CAUSING EDEMA
Any factor that increases the tissue fluid high enough than normal value can cause excess tissue
fluid volume causing edema. Some of these factor are as follows.
 High blood pressure
 Kidney failure
 Hart failure & etc.
CAUSES OF EDEMA
Following are three main causes of Edema.
1. HYPOPROTEINEMIA (SEVERE DIETARY PROTEIN DEFICIENCY)

When body is starving for Amino acids, it consumes its own blood proteins. This reduces the
osmotic potential of the blood causing tissue fluid to accumulate in body tissues rather than
being drawn back into capillaries, resulting in Edema.
2. LYMPHATIC OBSTRUCITON (COMMONEST CAUSE –FILARIASIS )
Another cause of edema is lymphatic obstruction, which results in more & more protein
collection in the local tissue fluid hence, the increased volume. Commonest cause of lymphatic
obstruction is FILARIASIS (infection by NEMOTODES) such condition is also called as
―Elephantiasis‖ (because of swollen legs).
3. INCREASED PERMEABILITY OF CAPILLARIES (CAUSES-BURNS & ALLERGIC
REACTIONS)
Sometimes the permeability of capillaries increase due to burns or allergic reactions, so blood
proteins & plasma come out of capillaries & enter the tissue fluid.

DIGESTIVE SYSTEM:
The digestive system is a group of organs working together to convert food into energy and basic
nutrients to feed the entire body. Food passes through a long tube inside the body known as the
alimentary canal or the gastrointestinal tract (GI tract). The alimentary canal is made up of the
oral cavity, pharynx, esophagus, stomach, small intestines, and large intestines. In addition to the
alimentary canal, there are several important accessory organs that help your body to digest
food...
but do not have food pass through them. Accessory organs of the digestive system include the
teeth, tongue, salivary glands, liver, gallbladder, and pancreas. To achieve the goal of providing
energy and nutrients to the body, six major functions take place in the digestive system:
 Ingestion
 Secretion
 Mixing and movement
 Digestion
 Absorption
 Excretion
Mouth
Food begins its journey through the digestive system in the mouth, also known as the oral cavity.
Inside the mouth are many accessory organs that aid in the digestion of food—the tongue, teeth,
and salivary glands. Teeth chop food into small pieces, which are moistened by saliva before the
tongue and other muscles push the food into the pharynx.
 Teeth. The teeth are 32 small, hard organs found along the anterior and lateral edges of
the mouth. Each tooth is made of a bone-like substance called dentin and covered in a
layer of enamel—the hardest substance in the body. Teeth are living organs and contain
blood vessels and nerves under the dentin in a soft region known as the pulp. The teeth
are designed for cutting and grinding food into smaller pieces.
 Tongue. The tongue is located on the inferior portion of the mouth just posterior and
medial to the teeth. It is a small organ made up of several pairs of muscles covered in a
thin, bumpy, skin-like layer. The outside of the tongue contains many rough papillae for
gripping food as it is moved by the tongue‘s muscles. The taste buds on the surface of the
tongue detect taste molecules in food and connect to nerves in the tongue to send taste

information to the brain. The tongue also helps to push food toward the posterior part of
the mouth for swallowing.
 Salivary Glands. Surrounding the mouth are 3 sets of salivary glands. The salivary glands
are accessory organs that produce a watery secretion known as saliva. Saliva helps to
moisten food and begins the digestion of carbohydrates. The body also uses saliva to
lubricate food as it passes through the mouth, pharynx, and esophagus.
Pharynx
The pharynx, or throat, is a funnel-shaped tube connected to the posterior end of the mouth. The
pharynx is responsible for the passing of masses of chewed food from the mouth to the
esophagus. The pharynx also plays an important role in the respiratory system, as air from the
nasal cavity passes through the pharynx on its way to the larynx and eventually the lungs.
Because the pharynx serves two different functions, it contains a flap of tissue known as the
epiglottis that acts as a switch to route food to the esophagus and air to the larynx
Esophagus
The esophagus is a muscular tube connecting the pharynx to the stomach that is part of the upper
gastrointestinal tract. It carries swallowed masses of chewed food along its length. At the inferior
end of the esophagus is a muscular ring called the lower
Stomach
The stomach is a muscular sac that is located on the left side of the abdominal cavity, just
inferior to the diaphragm. In an average person, the stomach is about the size of their two fists
placed next to each other. This major organ acts as a storage tank for food so that the body has
time to digest large meals properly. The stomach also contains hydrochloric acid and digestive
enzymes that continue the digestion of food that began in the mouth.
Small Intestine
The small intestine is a long, thin tube about 1 inch in diameter and about 10 feet long that is part
of the lower gastrointestinal tract. It is located just inferior to the stomach and takes up most of
the space in the abdominal cavity. The entire small intestine is coiled like a hose and the inside
surface is full of many ridges and folds. These folds are used to maximize the digestion of food
and absorption of nutrients. By the time food leaves the small intestine, around 90% of all
nutrients have been extracted from the food that entered it.
Liver and Gallbladder
The liver is a roughly triangular accessory organ of the digestive system located to the right of
the stomach, just inferior to the diaphragm and superior to the small intestine. The liver weighs
about 3 pounds and is the second largest organ in the body. The liver has many different

functions in the body, but the main function of the liver in digestion is the production of bile and
its secretion into the small intestine. The gallbladder is a small, pear-shaped organ located just
posterior to the liver. The gallbladder is used to store and recycle excess bile from the small
intestine so that it can be reused for the digestion of subsequent meals.
Pancreas
The pancreas is a large gland located just inferior and posterior to the stomach. It is about 6
inches long and shaped like short, lumpy snake with its ―head‖ connected to the duodenum and
its ―tail‖ pointing to the left wall of the abdominal cavity. The pancreas secretes digestive
enzymes into the small intestine to complete the chemical digestion of foods.
Large Intestine
The large intestine is a long, thick tube about 2 ½ inches in diameter and about 5 feet long. It is
located just inferior to the stomach and wraps around the superior and lateral border of the small
intestine. The large intestine absorbs water and contains many symbiotic bacteria that aid in the
breaking down of wastes to extract some small amounts of nutrients. Feces in the large intestine
exit the body through the anal canal.
PHYSIOLOGY OF DIGESTION:
The digestive system is responsible for taking whole foods and turning them into energy and
nutrients to allow the body to function, grow, and repair itself. The six primary processes of the
digestive system include:
1. Ingestion of food
2. Secretion of fluids and digestive enzymes
3. Mixing and movement of food and wastes through the body
4. Digestion of food into smaller pieces
5. Absorption of nutrients
6. Excretion of wastes
Ingestion
The first function of the digestive system is ingestion, or the intake of food. The mouth is
responsible for this function, as it is the orifice through which all food enters the body. The
mouth and stomach are also responsible for the storage of food as it is waiting to be digested.
This storage capacity allows the body to eat only a few times each day and to ingest more food
than it can process at one time.
Secretion
In the course of a day, the digestive system secretes around 7 liters of fluids. These fluids include
saliva, mucus, hydrochloric acid, enzymes, and bile. Saliva moistens dry food and contains
salivary amylase, a digestive enzyme that begins the digestion of carbohydrates. Mucus serves as

a protective barrier and lubricant inside of the GI tract. Hydrochloric acid helps to digest food
chemically and protects the body by killing bacteria present in our food. Enzymes are like tiny
biochemical machines that disassemble large macromolecules like proteins, carbohydrates, and
lipids into their smaller components. Finally, bile is used to emulsify large masses of lipids into
tiny globules for easy digestion.
Mixing and Movement
The digestive system uses 3 main processes to move and mix food:
 Swallowing. Swallowing is the process of using smooth and skeletal muscles in the
mouth, tongue, and pharynx to push food out of the mouth, through the pharynx, and into
the esophagus.
 Peristalsis. Peristalsis is a muscular wave that travels the length of the GI tract, moving
partially digested food a short distance down the tract. It takes many waves of peristalsis
for food to travel from the esophagus, through the stomach and intestines, and reach the
end of the GI tract.
 Segmentation. Segmentation occurs only in the small intestine as short segments of
intestine contract like hands squeezing a toothpaste tube. Segmentation helps to increase
the absorption of nutrients by mixing food and increasing its contact with the walls of the
intestine.
Digestion
Digestion is the process of turning large pieces of food into its component chemicals.
Mechanical digestion is the physical breakdown of large pieces of food into smaller pieces. This
mode of digestion begins with the chewing of food by the teeth and is continued through the
muscular mixing of food by the stomach and intestines. Bile produced by the liver is also used to
mechanically break fats into smaller globules. While food is being mechanically digested it is
also being chemically digested as larger and more complex molecules are being broken down
into smaller molecules that are easier to absorb. Chemical digestion begins in the mouth with
salivary amylase in saliva splitting complex carbohydrates into simple carbohydrates. The
enzymes and acid in the stomach continue chemical digestion, but the bulk of chemical digestion
takes place in the small intestine thanks to the action of the pancreas. The pancreas secretes an
incredibly strong digestive cocktail known as pancreatic juice, which is capable of digesting
lipids, carbohydrates, proteins and nucleic acids. By the time food has left the duodenum, it has
been reduced to its chemical building blocks—fatty acids, amino acids, monosaccharides, and
nucleotides.
Absorption
Once food has been reduced to its building blocks, it is ready for the body to absorb. Absorption

begins in the stomach with simple molecules like water and alcohol being absorbed directly into
the bloodstream. Most absorption takes place in the walls of the small intestine, which are
densely folded to maximize the surface area in contact with digested food. Small blood and
lymphatic vessels in the intestinal wall pick up the molecules and carry them to the rest of the
body. The large intestine is also involved in the absorption of water and vitamins B and K before
feces leave the body.
Excretion
The final function of the digestive system is the excretion of waste in a process known as
defecation. Defecation removes indigestible substances from the body so that they do not
accumulate inside the gut. The timing of defecation is controlled voluntarily by the conscious
part of the brain, but must be accomplished on a regular basis to prevent a backup of indigestible
materials.
Function of the Small Intestine (Digestive System)
Here is a brief description of what happens in the human small intestine.
The small intestine is the part of the gastrointestinal tract (also called the 'digestive tract' and
the alimentary canal) located after the stomach and before the large intestine. It is the part of the
digestive tract where approx 90% of the digestion and absorption of food occurs, the other 10%
taking place in the stomach and large intestine.
The main function of the small intestine is absorption of nutrients and minerals.
That is, absorption of the nutrients and minerals in the food ingested, usually via the mouth,
at an earlier stage in the digestive process.
Digestion is the process by which ingested (food) material is
broken down into a form that can then be absorbed, then
assimilated into the tissues of the body.
It is one of the main stages in the digestive process and takes two
forms:
 Mechanical digestion (e.g. chewing, grinding, churning,
mixing), and
 Chemical digestion (e.g. action of
digestive enzymes, bile, acids, etc.).
Chemical digestion occurs in the small intestine (and, to a lesser

extent, also in some other part of the gastrointestinal tract - incl.
the action of saliva on food in the mouth and the actions of some
chemicals secreted by cells located in the lining of the stomach).
The three main categories of nutrients that undergo digestion within the small
intestine are proteins, lipids (fats) and carbohydrates.
 Proteins
Proteins and peptides amino acids.
Proteolytic enzymes e.g. including trypsin and chymotrypsin, secreted by the
pancreas, break proteins into smaller peptides. (Chemical breakdown begins in the
stomach and continues in the large intestine.)
 Lipids (Fats)
Lipids (fats) fatty acids and glycerol.
Pancreatic lipase breaks triglycerides into free fatty acids and monoglycerides.
It is helped by bile salts secreted by the liver and the gall bladder. They attach to
triglycerides, which aids access to the triglycerides by the pancreatic lipase. This is
because lipase is water-soluble but the fatty triglycerides are hydrophobic so position
themselves towards each other and away from the watery intestinal surroundings. The
bile salts hold the triglycerides in the watery environment until the lipase can break
them into the smaller parts that can enter the villi for absorption - see below.
 Carbohydrates
Some carbohydrates simple sugars, or monosaccharides (e.g., glucose).
Pancreatic amylase breaks down some carbohydrates, e.g. starch into
oligosaccharides.
Other carbohydrates pass undigested into the large intestine where they may,
depending on their type, be broken-down by intestinal bacteria.
Absorption in the small intestine of specific
nutrients
Nutrients / Molecules Absorption from the Small Intestine, then into the Blood:
Monosaccharides Transport into the epithelial cells (of the villi): Glucose and

galactose are transported by active transport. Fructose is
transported by facilitated diffusion.
Transport from epithelial cells into the bloodstream is by
facilitated diffusion.
Amino Acids, Dipeptides,
Tripeptides
Transport into the epithelial cells (of the villi) is generally by
active transport processes - mainly in
the duodenum and jejunum.
Transport from epithelial cells into the bloodstream is by
passive diffusion.
Lipids (Fats) Dietary lipids are absorbed by diffusion.
Water Most of the water in ingested food and beverages is absorbed
by osmosis.
Approx 80% is absorbed by the small intestine, 10% by
the large intestine and the remaining 10% excreted in the
faeces.
Electrolytes Some electrolytes are from gastrointestinal secretions and
others from ingested foodstuffs.
 Sodium ions (Na+
) move from the lumen of the small
intestine into epithelial cells by diffusion and active
transport. They are then actively transported into blood
capillaries on the other side of the epithelial cells.
 Chloride (Cl-
) can passively follow Na+
ions into
epithelial cells, or be actively transported.
 Iodine (I-
ions into epithelial
cells, or be actively transported.
 Nitrate (NO3
-
ions into
epithelial cells, or be actively transported.
 Calcium ions (Ca2+
) are absorbed actively in a process
stimulated by calcitriol (active form of Vitamin D).

 Iron ions (Fe2+
and Fe3+
) are absorbed by active
transport mechanisms.
 Potassium ions (K+
) are absorbed by active transport
mechanisms.
 Magnesium ions (Mg2+
) are absorbed by active
transport mechanisms.
 Phospate ions (PO4
3-
) are absorbed by active transport
mechanisms.
Vitamins Fat soluble vitamins (A, D, E and K) are absorbed together
with dietary triglycerides.
Most water-soluble vitamins (C and the B vitamins) are
absorbed by diffusion.
Vitamin B12 combined with intrinsic factor (from the stomach)
is absorbed by active transport.

The Human Urinary System
The human urinary system is an excretory system. It helps to miantain homeostasis in the body.
 Excretion: the getting rid of the waste products of metabolism.
 Homeostasis: the maintenance of a constant internal environment.
Structure of the urinary system

 Kidneys: filter the blood taking out the waste products of metabolism such as urea.
 Ureters: carry urine from the kidney to the urinary bladder.
 Urinary bladder: stores urine.
 Urethra: carries urine outside of the body.
Functions of the kidney:
 Excretion: the main function of the kidney is to filter the blood taking out waste products
producing urine.
 Osmoregulation: the kidneys control the amount of water in the body. If there is too
much water in the body, the kidneys will excrete the excess water and if there is not
enough water in the body, the kidneys will excrete much less water in an effort to
conserve the remaining water in the body.
 pH control: the kidneys can control the acidity and alkalinity of the blood by excreting
hydrogen ions or conserving hydrogen ions.
 Hormone production: the kidneys produce the hormone erythropoietin (EPO). EPO
stimulates the bone marrow to produce red blood cells (erythrocytes).

Urine production
1. Filtration:
 Filtration occurs in the cortex of the kidney.
 Blood flows through capillaries of the kidneys and water, salts, urea, glucose and amino
acids are filtered out of the blood.
 Red blood cells, white blood cells, platelets and large plasma proteins (such as
antibodies) are not filtered through as they are too big.
 The liquid that results after filtration is called the filtrate - it contains wastes as well as
useful substances that need to be reabsorbed.
2. Reabsorption:
 Reabsorption occurs in both the cortex and medulla.
 Substances in the filtrate that are useful to the body (such as glucose and amino acids) are
taken out of the filtrate back into the bloodstream.
3. Secretion:
 The kidney also transports substances such as drugs and hydrogen ions out of the
bloodstream into the tubules of the kidney to contribute to the urine produced by the
kidneys.
Urination (Micturition): the passing of urine from the body.
The nephron - the functional unit of the kidney

There are approximately 1 million nephrons in each kidney.
They are composed of four main parts:
1. Bowman's capsule - where filtration occurs.
2. Proximal convoluted tubule - where most reabsorption occurs.
3. Loop of Henle - where more reabsorption occurs.
4. Distal convoluted tubule - where reabsorption of water and secretion of drugs and
hydrogen ions occurs.
Blood supply
 The nephron receives blood from the renal arterioles.
 The renal arterioles carry blood to afferent arterioles.
 Each afferent arteriole enter the Bowman's capsule.
 The 'ball' of blood vessels within in the Bowman's capsule is called the glomerulus.
 The blood is then carried away from the Bowman's capsule via the efferent arteriole.
 This blood is then circulated around the nephron for reabsorption of useful substances.

 The afferent arteriole is slightly wider than the efferent arteriole - which causes an
increased blood pressure within the glomerulus. This increased blood pressure helps with
the process of filtration in the Bowman's capsule.
Urine production - detailed process
1. Filtration:
 Filtration occurs from the glomerulus into Bowman's capsule.
 Blood enters the glomerulus from the afferent arteriole.
 Blood is under high pressure in the glomerulus and substances such as water, salts, urea,
glucose and amino acids pass through.
 The liquid that passes through is called the glomerular filtrate.
The glomerulus and the Bowman's capsule are adapted to carry out their functions by having the
following characteristics:
 The Bowman's capsule is cup-shaped to provide maximum surface area for filtration.
 The endothelium of the Bowman's capsule is only one cell thick.
 The capillary walls of the glomerulus are one cell thick and more leaky than normal
capillaries.
2. Reabsorption:
 Useful substances (such as glucose and amino acids) in the glomerular filtrate pass back
into the bloodstream.
 Water is reabsorbed in the proximal convoluted tubule, descending loop of Henle, the
dital convoluted tubule and the collecting duct.
 All the glucose and amino acids are reabsorbed in the proximal convoluted tubule.

 Salts are reabsorbed in the proximal convoluted tubule, the ascending loop of Henle and
the distal convoluted tubule.
3. Secretion:
 Certain substances pass into the tubules of the nephron from the bloodstream by active
transport.
 Drugs and poisons are actively transported out of the bloodstream into the proximal and
distal convoluted tubules.
Kidney failure
 Occasionally the nephrons of the kidney might not work properly and kidney failure may
result.
 Patients with total kidney failure have to undergo dialysis.
 Dialysis is where a machine takes blood from the body and removes wastes and excess
water from the blood before returning it to the body.
 In the long term, kidney failure patients usually receive a kidney transplant.
Osmoregulation - detailed process
The kidneys control the amount of water that is excreted.
Too much water in the body:

The brain detects the amount of water in the body. If it is too high, the pituitary stops secreting a
hormone called anti-diuretic hormone (ADH). This travels in the bloodstream to the distal
convoluted tubules and collecting ducts of the kidney and causes them to become less permeable
and therefore, more water is excreted.
Too little water in the body:
The brain detects a reduced amount of water in the body and causes the pituitary to release ADH
that travels in the bloodstream to the distal convoluted tubules and collecting ducts and causes
them to become more permeable. Water is then reabsorbed into the blood and less is excreted in
the urine.
THE CONCENTRATION AND DILUTION OF URINE
LEARNING OBJECTIVE.
At the end of lecture students should be able to know,
•Dilute urine,
•Mechanism,
•Formation of concentration urine,
•Factors that built high solute concentration in medulla,
•Countercurrent mechanism.
DILUTE URINE
•When there is excess water in the body, the body osmolarity is decreased, the kidney excrete
urine with osmolarity as low as 50 mosm/l (normal osmolarity of body fluids is 300 mosm/l)
•When there is deficit of water of water, fluid osmolarity is high, the kidney can excrete urine
with concentration of 1200 mosm/l
•So kidney can excrete large volume of dilute urine or small amount of concentrated urine,
without major changes in the excretion of solutes
MECHANISM OF DILUTE URINE
•After glomerular filtration fluid flows through pct, and remain isosmotic with plasma(300
mosm/l)
•In descending loop of henle water reabsorb by osmosis because high osmolarity in med
inerstitium(1200 mosm/l)
•In ascend thick L H active reabsorption of Na, k, and Cl, tubular fluid becomes more
diluted(100 mosm/l) because this segment is impermeable for water
•In the absence of ADH the DCT, CCT are impermeable for water
•Large volume of diluted urine is excreted(50 mosm/l)
FORMATION OF CONCENTRATED URINE
•Depend upon two factors
•High levels of ADH

•-increases the permeability of dct and cct for water
•Hyper osmotic renal medulla
•-provide osmotic gradient for water
•-this involve the countercurrent mechanism
COUNTERCURRENT MECHANISM
•This mechanism depend upon the special anatomy of loop of henle and vasa recta
•25% nephrons are juxta medulary, their loops are very long and dip into the deep of medulla, so
as the vasa recta
•This produces hyper osmotic medulla upto 1200 mosm/l
•It means that med interest accumulates more solutes than water
•When high solute conc is achieved , it is maintained by balanced inflow and out flow of solutes
and water in medulla
•FACTORS THAT BUILD HIGH SOLUTE CONC IN MEDULLA
•Active transport of Na, co transport of K, Cl, other ions out of thick ascend loop
•Active transport of ions from medullary ducts
•Passive diffusion of urea from medullay ducts
•Diffusion of small volume of water from M duct as compare to high solute reabsorb
•COUNTER-CURRENT MECHANISMS
•The first takes place in the region of the nephron called Henle's loop.
•The second occurs in a region of the peritubular capillary bed called the 'vasa recta'.
•Both are involved in establishing an osmotic gradient throughout this region.
•HENLE'S LOOP
•The portion of the nephron called the 'Henle's loop' is consists of a descending limb and
an ascending limb
•The ascending limb has a thick and a thin segment.
The thick walls of the ascending limb indicates that this region is impermeable to water.
•VASA RECTA
•This capillary bed is also also consists of a descending limb and an ascending limb.
•COUNTER-CURRENTS
•Counter-currents exist when fluids flow in opposite directions in parallel and adjacent tubes.
•The two limbs of Henle's loop are a counter-current.
•The two limbs of the vasa recta are also a counter-current.
•It is apparent that these two sets of tubes are parallel and adjacent.
•Not apprent in the mind map is the fact that the descending limb of Henle is also counter-
current with the ascending limb of the vasa recta; the same is true of the ascending limb of Henle
and the descending vasa recta.
•COUNTER-CURRENT EXCHANGER
•Examination of both limbs of the vasa recta shows theconcentration of solutes is the same at
any horizontal level.

•However, imagine the fluid flowing through the vasa recta for a short distance then stopping.
•Now compare the concentration of solutes at any level and they will not be the same.
•At any level the solute concentration in the descending limb will be less than in the ascending
limb! But, because both limbs are freely permeable, sodium chloride will diffuse from the
ascending into the descending while water will diffuse from the descending to the ascending
•When equilibrium is reached both limbs will, once again, have the same concentration of water
and solutes.
•Water is exchanged for sodium chloride thecounter-current exchange mechanism.
•COUNTER-CURRENT MULTIPLIER
•The above described counter-current exchanger would not exist if there were not some
mechanism to initially make the vasa recta more concentrated at the bottom of the loop. This is
accomplished by the loop of Henle.
•The ascending limb of Henle and the early distal tubule are impermeable to water as indicated
by their thick wall. These regions actively transports sodium chloride (NaCl) out of the filtrate
and into the surroundings. (The asterisk
(*)in the block arrow indicates that a more complex mechanism is involved but the net effect is
that only NaCl is moved out of the filtrate.)
•The NaCl diffuses into the descending limb of the vasa recta...block arrow. Any that might
diffuse into the descending limb of Henle will only get pumped back out when it enters the
ascending limb so this is not shown in the mind map. It will not diffuse into the ascending vasa
recta because that fluid is already highly concentrated. This is the mechanism that 'multiplies' the
concentration of NaCl in the descending vasa recta making the countercurrent exchanger
possible!
•OSMOSIS
•Both blood and filtrate descending into their respective loops have low solute concentrations.
•Both flow beside upcoming columns having higher solute concentrations. As they move past
one another, water from the down-flowing fluid columns will diffuse into the more
concentrated up-flowing columns.
•However, only the up-flowing vasa recta is permeable to water meaning all is returned to the
blood and none to the filtrate.
•This also insures that a high solute concentration will be maintained at the bottom of both loops.

Nerve Cell Structure and Function
Introduction to nerve cell structure and function :
A Nerve cell with all its processes is called a neurone.It is the structural and functional unit of
the nervous system.A neurone has cell body called soma and two types of processes called axons
and dendrites.
A nerve or neuron is a specialized cell in the body for transmitting nerve impulses. The
peripheral nervous system consists of over 100 billion nerve cells. These nerve cells run
throughout the body to connect the brain and spinal cord to all other parts of the body. Nerve
cells impulses or signals are used to control body muscles and organ, or to sense information
from the body. Read on to learn more about nerves, and what they do in your body.
Nerve Cell Structure and Function : the Cell Body
The nucleated cytoplasmic portion of a neurone is termed cell body or soma.Typically each cell
body which may be 4 to 100µm in diameter may be fusiform,pyramidal, pyriform or irregular
stellate in shape.Cell body contains a large spherical central nucleus along with large number
of Nissl's granules within the cytoplasmic matrix called neuroplasm.The Nissl's granules
contain ribonucleoprotein and are involved in protein synthesis.The neuroplasm also contains
mitochondria,golgi bodies , melanin , lipochrome pigment granules.The amount of these cell
organelles varies with the functional activity of the cell. The cell body is with non functional
centrosome because of which neurones cannot divide.Therefore number of neurones present in
an adult is same as that present at birth.Delicate cytoplasmic threads called neurofibrils are
present throughout the entire length of axon and dendrites arising from cell body.The cell body
and its processes are surrounded externally by a thin membrane ,the neurone membrane.The cell
body is present in grey matter of the central nervous system-brain and spinal cord.
Nerve Cell Structure and Function : Dendrites
The short cytoplasmic processes of cell body which receives stimulus from other neurone are
called dendrites.The dendrites conduct nerve impulses induced by stimuli towards the cell
body.The dendrites at their origin from cell body are 5-10 µm in thickness but gradually their
thickness decreases by profuse branching.
Function: Dendrites receives impulses from axon of another neurone through synapse and
conducts the impulse towards the cell body ,therefore it is called the receptive organ.
Nerve Cell Structure and Function : Axon
The long cytoplasmic process of cell body which transmits impulse from cell body to other
neurone is termed axon.Axon is considerably longer than dendrites.The axon arises from the cell

body in a conical elevation called axon hillock ,which is devoid of nissl's granules.The length of
axon is variable and depends on the functional relationship of the neurone.The cytoplasm of
axon known as axoplasm contains mitochondria ,neurofibrils but no nissl's granules.The
membrane covering axon is called axolemma.Axon can give of branches, called collaters along
its course and near the end it undergoes considerable branching into axon terminals or end brush
,the last part of which is enlarged to form end bulb.Axon is present in white matter of central
nervous system and peripheral nervous system.The nerve fibres or axon are covered by a lipid
rich membrane called myelin sheath.The myelin sheath is formed by schwann cells and each
schwann cell covers a part of the nerve fibre.The region where axon is not covered by myelin
sheath is the junction of adjacent myelinated segments called node of ranvier.
Function : Axon transmits impulse from cell body of one neurone to dendron of another neurone
through synapse.
Nerves and Nerve Types
There three types of nerves in the central nervous system: motor neurons, sensory neurons and
autonomic neurons.
Motor nerves send impulses or signals from the brain and spinal cord to all of the muscles in the
body. These nerves control muscle contraction allowing movements and activities such as
wiggling your fingers, walking, catching a baseball, or kicking a soccer ball.

Sensory nerves send messages from parts of the body, such as skin and muscles, back to the
spinal cord and the brain. The information is then processed to let you feel pain and other
sensations. Sensory nerves in the skin help you identify if an object is sharp, rough or smooth,
hot or cold, or if a body part is still or in motion.
Autonomic nerves control involuntary or semi-voluntary functions, such as heart rate, blood
pressure, digestion, temperature regulation, and sweating.
Some people also refer to another nerve type, called interneurons. Interneurons are located
entirely within the central nervous system and interconnect other nerve cells. They act as a link
between sensory neurons and motor neurons. An interneuron may receive information from
sensory neurons and pass it along to the brain for processing, or it may process the information
itself and send a signal to a motor neuron to act. For example, touching a hot stove generates
sensory nerve signals to the interneuron. The interneuron processes the information from the
sensory neuron itself and sends a signal to a motor neuron to take action. This quick reaction is
called a reflex action.
Signals are transmitted from neuron to neuron via an action potential, when the axon membrane
rapidly depolarizes and repolarizes.
 Explain the formation of the action potential in neurons
KEY POINTS
 Action potentials are formed when a stimulus causes the cell membrane to
depolarize past the threshold of excitation, causing all sodium ion channels to
open.
 When the potassium ion channels are opened and sodium ion channels are closed,
the cell membrane becomes hyperpolarized as potassium ions leave the cell; the
cell cannot fire during this refractory period.
 The action potential travels down the axon as the membrane of the axon
depolarizes and repolarizes.
 Myelin insulates the axon to prevent leakage of the current as it travels down the
axon.
 Nodes of Ranvier are gaps in the myelin along the axons; they contain sodium and
potassium ion channels, allowing the action potential to travel quickly down the
axon by jumping from one node to the next.
TERMS
 saltatory conduction
the process of regenerating the action potential at each node of Ranvier
 node of Ranvier
a small constriction in the myelin sheath of axons
 hyperpolarize
to increase the polarity of something, especially the polarity across a biological membrane

 depolarization
a decrease in the difference in voltage between the inside and outside of the neuron
 action potential
a short term change in the electrical potential that travels along a cell
Action Potential
A neuron can receive input from other neurons via a chemical called a neurotransmitter. If this
input is strong enough, the neuron will pass the signal to downstream neurons. Transmission of a
signal within a neuron (in one direction only, from dendrite to axon terminal) is carried out by
the opening and closing of voltage-gated ion channels, which cause a brief reversal of the
resting membrane potential to create an action potential . As an action potential travels down the
axon, the polarity changes across the membrane. Once the signal reaches the axon terminal, it
stimulates other neurons.
Formation of an action potential
The formation of an action potential can be divided into five steps. (1) A stimulus from a sensory
cell or another neuron causes the target cell to depolarize toward the threshold potential. (2) If
the threshold of excitation is reached, all Na+ channels open and the membrane depolarizes. (3)
At the peak action potential, K+ channels open and K+ begins to leave the cell. At the same
time, Na+ channels close. (4) The membrane becomes hyperpolarized as K+ ions continue to

leave the cell. The hyperpolarized membrane is in a refractory period and cannot fire. (5) The
K+ channels close and the Na+/K+ transporter restores the resting potential.
Depolarization and the Action Potential
When neurotransmitter molecules bind to receptors located on a neuron's dendrites, voltage-
gated ion channels open. At excitatory synapses, positive ions flood the interior of the neuron
and depolarize the membrane, decreasing the difference in voltage between the inside and
outside of the neuron. A stimulus from a sensory cell or another neuron depolarizes the target
neuron to its threshold potential (-55 mV), and Na+
channels in the axon hillock open, starting an
action potential. Once the sodium channels open, the neuron completely depolarizes to a
membrane potential of about +40 mV. The action potential travels down the neuron as Na+
channels open.
Hyperpolarization and Return to Resting Potential
Action potentials are considered an "all-or nothing" event. Once the threshold potential is
reached, the neuron completely depolarizes. As soon as depolarization is complete, the cell
"resets" its membrane voltage back to the resting potential. The Na+
channels close, beginning the
neuron's refractory period. At the same time, voltage-gated K+
channels open, allowing K+
to
leave the cell. As K+
ions leave the cell, the membrane potential once again becomes negative.
The diffusion of K+
out of the cell hyperpolarizes the cell, making the membrane potential more
negative than the cell's normal resting potential. At this point, the sodium channels return to their
resting state, ready to open again if the membrane potential again exceeds the threshold potential.
Eventually, the extra K+
ions diffuse out of the cell through the potassium leakage channels,
bringing the cell from its hyperpolarized state back to its resting membrane potential.
Myelin and Propagation of the Action Potential
For an action potential to communicate information to another neuron, it must travel along the
axon and reach the axon terminals where it can initiate neurotransmitter release . The speed of
conduction of an action potential along an axon is influenced by both the diameter of the axon
and the axon's resistance to current leak. Myelin acts as an insulator that prevents current from
leaving the axon, increasing the speed of action potential conduction. Diseases like multiple
sclerosis cause degeneration of the myelin, which slows action potential conduction because
axon areas are no longer insulated so the current leaks.

Cranial nerves:

PARTS OF THE BRAIN AND THEIR FUNCTIONS
The human brain is a specialized organ that is ultimately responsible for all thought and
movement that the body produces. Many different parts of the brain and their functions are
shown in the article. Each part has a unique function that allows humans observe and interact
with their environment effectively.
The human brain is ultimately responsible for all thought and movement that the body produces.
This allows humans to successfully interact with their environment, by communicating with
others and interacting with inanimate objects near their position. If the brain is not functioning
properly, the ability to move, generate accurate sensory information or speak and understand
language can be damaged as well.
The brain is made up of nerve cells which interact with the rest of the body through the spinal
cord and nervous system. These cells relate information back to specific centers of the brain
where it can be processed and an appropriate reaction can be generated. Several chemicals are
also located in the brain, which help the body maintain homeostasis, or a sense of overall
comfort and calm as its basic needs are met. Keeping these chemicals balanced and the nerve
cells firing properly are essential to healthy brain function.
Parts of the Brain and Their Functions
Cerebrum
The cerebrum is the largest portion of the brain, and contains tools which are responsible for
most of the brain's function. It is divided into four sections: the temporal lobe, the occipital lobe,
parietal lobe and frontal lobe. The cerebrum is divided into a right and left hemisphere which are
connected by axons that relay messages from one to the other. This matter is made of nerve cells
which carry signals between the organ and the nerve cells which run through the body.
Frontal Lobe: The frontal lobe is one of four lobes in the cerebral hemisphere. This lobe
controls a several elements including creative thought, problem solving, intellect, judgment,
behavior, attention, abstract thinking, physical reactions, muscle movements, coordinated
movements, smell and personality.
Parietal Lobe:Located in the cerebral hemisphere, this lobe focuses on comprehension. Visual
functions, language, reading, internal stimuli, tactile sensation and sensory comprehension will
be monitored here.
 Sensory Cortex- The sensory cortex, located in the front portion of the parietal lobe,
receives information relayed from the spinal cord regarding the position of various body
parts and how they are moving. This middle area of the brain can also be used to relay

information from the sense of touch, including pain or pressure which is affecting
different portions of the body.
 Motor Cortex- This helps the brain monitor and control movement throughout the body.
It is located in the top, middle portion of the brain.
Temporal Lobe: The temporal lobe controls visual and auditory memories. It includes areas that
help manage some speech and hearing capabilities, behavioral elements, and language. It is
located in the cerebral hemisphere.
 Wernicke's Area- This portion of the temporal lobe is formed around the auditory cortex.
While scientists have a limited understanding of the function of this area, it is known that
it helps the body formulate or understand speech.
Occipital Lobe: The optical lobe is located in the cerebral hemisphere in the back of the head. It
helps to control vision.
 Broca's Area- This area of the brain controls the facial neurons as well as the
understanding of speech and language. It is located in the triangular and opercular section
of the inferior frontal gyrus.
Cerebellum
This is commonly referred to as "the little brain," and is considered to be older than the cerebrum
on the evolutionary scale. The cerebellum controls essential body functions such as balance,
posture and coordination, allowing humans to move properly and maintain their structure.
Limbic System
The limbic system contains glands which help relay emotions. Many hormonal responses that the
body generates are initiated in this area. The limbic system includes the amygdala, hippocampus,
hypothalamus and thalamus.
Amygdala:The amygdala helps the body responds to emotions, memories and fear. It is a large
portion of the telencephalon, located within the temporal lobe which can be seen from the
surface of the brain. This visible bulge is known as the uncus.
Hippocampus: This portion of the brain is used for learning memory, specifically converting
temporary memories into permanent memories which can be stored within the brain. The
hippocampus also helps people analyze and remember spatial relationships, allowing for accurate
movements. This portion of the brain is located in the cerebral hemisphere.
Hypothalamus:The hypothalamus region of the brain controls mood, thirst, hunger and
temperature. It also contains glands which control the hormonal processes throughout the body.
Thalamus:The Thalamus is located in the center of the brain. It helps to control the attention
span, sensing pain and monitors input that moves in and out of the brain to keep track of the
sensations the body is feeling.
Brain Stem

All basic life functions originate in the brain stem, including heartbeat, blood pressure and
breathing. In humans, this area contains the medulla, midbrain and pons. This is commonly
referred to as the simplest part of the brain, as most creatures on the evolutionary scale have
some form of brain creation that resembles the brain stem. The brain stem consists of midbrain,
pons and medulla.
Midbrain:The midbrain, also known as the mesencephalon is made up of the tegmentum and
tectum. These parts of the brain help regulate body movement, vision and hearing. The anterior
portion of the midbrain contains the cerebral peduncle which contains the axons that transfer
messages from the cerebral cortex down the brain stem, which allows voluntary motor function
to take place.
Pons: This portion of the metencephalon is located in the hindbrain, and links to the cerebellum
to help with posture and movement. It interprets information that is used in sensory analysis or
motor control. The pons also creates the level of consciousness necessary for sleep.
Medulla: The medulla or medulla oblongata is an essential portion of the brain stem which
maintains vital body functions such as the heart rate and breathing.

PHYSIOLOGY FOR C.S.S, P.C.S, M.SC,B.SC,LECTURER POST

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