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Introduction to Human Physiology
For Pharmacy students
By Yibeltal Y (MSc in Medical Physiology)
Email: yibeltalyismaw7@gmail.com
Department of Human Physiology
4/9/2024
1
Brain storming
2
 What does mean physiology ?
 What does it deal about?
4/9/2024
Presentation Outline
 Introduction
 Homeostasis
 Control systems
 Control mechanisms
 Negative feedback control systems
 Positive feedback mechanisms
 Communications between cells (types of
junctions)
 Cell structure and function
3 4/9/2024
Objectives
At the end of this chapter the students will be able to:
1. Explain homeostasis.
2. Discuss negative & positive feed back mechanism.
3. Define physiology
4. Discuss cell physiology.
5. Enumerate the cell organelles with their function.
6. List the types of cellular transport
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General Introduction
What is Physiology? Two Greek words: Physis: nature, origin, Logia:
study of
 Physiology is the science that seeks to explain the physical and
chemical mechanisms that are responsible for the Origin,
Development, and Progression of life
 Each type of life, from the simplest virus to the largest complicated
human being, has its own functional characteristics.
 Therefore, the vast field of physiology can be divided into
 Viral physiology, bacterial physiology, cellular physiology, plant
physiology, invertebrate physiology, vertebrate physiology,
mammalian physiology, Human Physiology, & many more
subdivisions.
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General introduction cont’d…
 Physiology is the study of functionality of living organisms at the
cellular, organ and systemic levels.
Historical background
Aristotle (384 - 322 B.C.) was
 The father of natural history &
 The 1st person to coin the term physiology.
According to Aristotle, Physiology meant the study of nature-
“Physio - nature, logus - study.
This means studying practically everything in the Universe and
in the human body.
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General introduction
William Harvey in 1628,
Correctly described the direction of circulation of blood
 Described that the heart pumps blood, arteries transport oxygenated
blood, exchange of substances occur at the systemic capillaries and
veins return deoxygenated blood.
For this reason he is known to be
 the father of physiology.
Claud Bernard,
a French physiologist in the 19th C. described that every cell
in body is bathed with the fluid environment called ECF.
ECF contains all the needed substances for cells.
He called ECF is the internal environment of the body.
Walter cannon,
another great physiologist of the 1st half of 19th century, termed the
maintenance of nearly constant conditions in the ECF as
homeostasis
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Relation of physiology with other sciences
o Physiology is closely related to several other branches of
science such as anatomy, pharmacology, biochemistry,
pathology etc.
o Therefore, Physiology is not an isolated science, but highly
associated with other sciences.
o Physiology as a quantitative science
-All physiological parameters are expressed in numbers
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Fluid Compartments
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9
Fluid Compartments
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10
Extracellular Fluid
 Cell is the basic structural & functional unit of life.
 The human organism consists of 100 trillions of cells.
 for the maintenance of the entire organism
 These cells are bathed with the fluid that is called ECF
(fluid that fills the space between cells).
 About 60% of the adult human body is fluid, mainly the
water solution of ions and other substances.
 Although most of this fluid is inside the cells(2/3th) & is
called intracellular fluid-ICF, about one third is in the
spaces outside the cells and is called extracellular fluid.
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Internal environment cont’d…”
 This extracellular fluid is in constant motion throughout the
body.
 It is transported rapidly in the circulating blood and then mixed
between the blood and the tissue fluids by diffusion through the
capillary walls.
 In the extracellular fluid are the ions and nutrients needed by the
cells to maintain life.
 While cells may perform very different functions, all the cells are
quite similar in their metabolic requirements:
 Oxygen , Glucose, Mineral ions, Waste removal …
 Thus, all cells live in essentially the same environment the
extracellular fluid.
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internal environment cont’d…
 For this reason, the extracellular fluid is also called the internal
environment of the body, or the milieu intérieur, a term
introduced by the great 19th-century French physiologist Claude
Bernard (1813–1878).
 Cells are capable of living and performing their special functions
as long as
 The proper concentrations of gases ,oxygen, glucose, different ions,
amino acids, fatty substances, hormones, enzymes, water & electrolytes
and other constituents are available in this internal environment.
 Therefore, Maintaining a nearly constant internal environment is
necessary for the well-being of individual cells & the well-being
of the entire body
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Extracellular VS Intracellular Fluids
 The extracellular fluid contains large amounts of
 Sodium, chloride, and Bicarbonate ions plus
 Nutrients for the cells, such as oxygen, glucose, fatty acids, and amino
acids.
 It also contains
 Carbon Dioxide that is being transported from the cells to the lungs to be
excreted, plus
 Other cellular waste products that are being transported to the kidneys
for excretion.
 The intracellular fluid differs significantly from the extracellular fluid; for
example, it contains
 Large amounts of potassium, magnesium, and phosphate ions instead
of the sodium and chloride ions found in the extracellular fluid.
 Special mechanisms for transporting ions through the cell membranes
 maintain the ion concentration differences between the extracellular
and intracellular fluids.
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Homeostasis
 Gk homoios (same) & stasis (standing still)
 It is maintenance of nearly static or constant conditions in
the internal environment (ECF).
 Essentially all organs of the body perform their functions to
maintain constant conditions in the ECF.
For example
 Lungs maintain the normal concentration of respiratory
gases in blood.
 The CVS transports required substances and removes waste
produces,
 The kidneys maintain constant ionic concentration and
 The GIT provides nutrients.
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Homeostasis cont’d…
 Homeostasis in a general sense refers to:
 Stability, balance or equilibrium.
 Maintaining a stable internal environment requires constant
monitoring & adjustments as conditions change.
 Adjustment of physiological systems within the body is called
homeostatic regulation; which involves 3 parts or mechanisms:
 Receptor, Control Centre & Effector
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Homeostasis…cont’d
1. Receptor
 Receives information that something in the environment
is changing.
2. Control center or integration center
 Receives & processes information from the receptor.
3. Effector
 Responds to the commands of the control center by
either opposing or enhancing the stimulus.
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Homeostasis…cont’d
Homeostatic regulation is an ongoing process that
continually works to restore & maintain homeostasis.
For example
 In regulating body temperature there are
temperature receptors in the skin,
 Which communicate information to the brain,
which is the control center, &
 The effector is our blood vessels and sweat glands.
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Homeostasis…cont’d
Homeostatically regulated variables
 Body Temperature
 Blood Composition
 Ions, sugars, proteins, water,
 O2 and CO2 , PH & Osmolality
 Blood Pressure,
 Cardiac Output, Cardiac Rate
 Respiratory Rate and depth
 Secretions of Endocrine Glands
 Rate of intracellular chemical reactions
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Homeostasis…cont’d
Factors Disrupting Homeostasis:
 External stimuli
 Heat, cold,
 Lack of O2,
 Pathogens & Toxins
 Internal stimuli
 Abnormalities in visceral organs
Function of homeostasis
 It allows an organism to function effectively in a broad
range of environmental conditions
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Stimulus:
Produces
change
in variable
1
2
3
Change
detected
by receptor
Input:
Information sent
along afferent
pathway to
5
Response of effector feeds
back to influence
magnitude of stimulus &
returns variable to
homeostasis
Variable (In homeostasis)
Control
center
4
Output:
Information sent along
efferent pathway to
Homeostatic Control Mechanisms
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Regulatory Systems of Homeostasis
 The nervous system and the endocrine
system are the two controlling bodies of
homeostasis
1. The Nervous Regulatory Mechanism
 The nerves system is composed of three
major components the sensory portion, the
integrative portion and the motor portion.
 The sensory receptor detects any change in
the body (BGC, BT, ABP, pain etc.) and
send impulse to the brain, spinal cord
(CNS).
 The CNS associate the information store
some, generate thought and send
appropriate response to the effecter organs
(muscle + glands) through the motor
system.
Effector cell
NTs
R
Nerve Impulse
Hormone
Receptor
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Regulatory Systems of Homeostasis cont’d….
2. The Hormonal Regulatory Mechanism
 Hormones are chemical messengers secreted by endocrine
glands, and transported in blood to the target gland (Organs).
Examples:
 PTH act on the kidney, bone, and intestine = [Ca2+]
 Aldosterone  to the kidney   [Na+]
 ADH controls water electrolyte balance
 An organism is said to be in homeostasis when its internal
environment contains an optimum amount of nutrients, gases,
electrolytes, water, hormones, enzymes and temperature.
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Blood Glucose Homeostasis
Normal BGC
70-110 mg/dl
4. Brain
All neurons
Feeding center
5. Hormones
Hyperglycemic hormones
Hypoglycemic hormones
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Homeostatic values
25
1. Body fluid volume = 40 L
ECF = 15L
ICF = 25L
2. Osmolality = 300 mosm/L,
(285 – 300 mosm/L)
3. Body T. = 36.3 – 37.1OC
4. pH = 7.35 – 7.45
5. Blood Gases
PCO2 = 35 – 45
mm Hg
PO2 = 40 – 104
mm Hg
6. Electrolytes (ECF)
Ca2+ = 10 mg/dl
or 5 meq/L
K+ = 4 meq/L
Na+ = 142 meq/L
Cl- = 103 meq/L
HCO3
- = 27 meq/L
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Homeostatic values
7. Waste Products
Bilirubin = 0.5 mg/dl
Creatinine = 0.6 – 1.5 mg/dL
Blood urea nitrogen (BUN) = 8 – 25 mg/dL
Uric acid (s): Women = 2.3 – 6.6 mg/dL
Men = 3.6 – 8.5 mg/dL
8. Blood Glucose level (fasting): 70 – 110 mg/dL
9. Arterial Blood pressure (systemic circulation).
Systolic pressure = 120 mm Hg (90 – 140 mm Hg)
Diastolic pressure = 80 mm Hg (60 – 90 mm Hg)
Pulse pressure = 40 mm Hg
Mean BP = 96 mm Hg
Pulmonary AP = 25/10 mm Hg
Cardiac output = 5 L/min
Blood Flow = 5 L /min
10. RBC count = 4-6 millions/mm3
11. WBC count = 4000-11,000/mm3
12. Hgb = 12-18 g/dl in F, 14-20 g/dl in M
 Differences in normal ranges = pathology
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Normal values of ECF & ICF
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Disturbances of homeostasis
Disturbances of homeostasis
 Deviations from normal ranges = PATHOLOGY
 Hypo/ Hyperthermia ….. ↓or↑ Temperature
 Hypo/ Hypercapnea ….. ↓or↑ PCO2
 Acidosis/Alkalosis ….. ↓or↑ PH
 Hypoxia/ Hyperoxia …. ↓or↑ PO2
 Hypo/ Hypercalcemia …. ↓or↑ Ca 2+
 Hypo/ Hyperglycemia … ↓or↑ Glucose
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Homeostatic control systems…
Depending on the site of regulation process
homeostatic controls may be classified in to;
1. Intrinsic controls
•Inherent in an organ
•The changes are automatically regulated by the
organ
Examples
• Reduction of 02 makes tissue release dilators
• Vascular auto regulation in exercising skeletal
muscle
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2. Extrinsic controls
 External stimuli initiate the regulation process
 The most common type of controls
 Nervous or endocrine system
 The control mechanism initiated outside the organ & alter
the organ activities via coordinators
 Maintain most of the factors in the internal environment.
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Homeostatic control systems…
 Depending on the type/characteristics of
response homeostatic control may be;
I. Feedback control
 Change in the controlled variable brings a corrective
response.
 The regulatory processes established after the change
is developed
II. Feed-forward control
 Anticipation of a change in the controlled variable
brings an anticipatory response.
 The regulatory processes established before the
change is developed
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Feedback control mechanisms
There are two types of feed back mechanisms:
 The Negative Feedback Mechanism (NFM)
 The Positive Feedback Mechanism (PFM)
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Negative Feedback Mechanism (NFM)
 It works by producing an effect which opposes the
previous condition
 The NFM is a mechanism that opposes or counter acts the
deviation of a controlled variable from its normal value
(range/average).
 Nature of Most Control Systems
 For example: If the PCO2 is increased in the blood,
 the negative feedback mechanism stimulates pulmonary ventilation
rate, which has an effect on decreasing PCO2 in blood to normal.
 Most homeostatic values of the body are controlled by
NFM.
 Control of ABP
 Control of BGL
 Control of BT
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Blood glucose regulation (NFM)
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The Positive Feedback Mechanism (PFM)
 It works by producing an effect which enhances or repeats
the same action like that of the starting stimulus.
 The PFM also called Viscous Circle.
 Most of the action of this mechanism disturbs the internal
environment and cause disease & death.
 Fore example, if a person suffers from a heart attack that
damages the heart function, then the heart pumps less
amount of blood to the tissues including the heart muscle
and brain.
 If the heart muscle does not get sufficient nutrients and
O2, the activity of the heart becomes weaker and weaker
and the weaker the heart the lesser blood is pumped and
then death may occur.
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The Positive Feedback Mechanism cont’d…
Examples of the PFM
 Blood clotting is an example of a very valuable use of
PFM.
 Generation and propagation of the action potential.
 Stimulated nerve fiber  opening of Na+ channels 
entry of few Na+ stimulates the opening of more and
more Na+ channels.
 Labor during child birth, uterine contraction is enhanced as
the head of the baby stretches the cervix.
 LH-surge
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Uterine contractions during parturition (PFM)
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LH surge: the positive feedback mechanism
HT
Pituitary
Ovary
GnRH
LH
Estrogen
>200 µg/ml
activates
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Feed-forward
 In physiology, feed-forward control is exemplified by the
normal anticipatory regulation of heartbeat in advance
of actual physical exertion.
 Feed-forward control can be likened to learned
anticipatory responses to known stimulus.
 Feedback regulation of the heartbeat provides further
adaptiveness to the running eventualities of physical
exertion.
 Some activities needed be rapid that no enough time for
the brain to bring change after actual change occurred.
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Feed-forward…
The brain anticipates the change that will be developed.
 Help for adaptation of the organ where correction will
be occurred
 Correction is by anticipation
Example
-  HR and RR before actual exercise
-  Digestive juice before food inter into GIT
 Used to adapt and rapid rate of response to the
change
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Levels of organization in the body
1. Chemical level
2. Organelle level
3. Cellular level
4. Tissue level
5. Organ level
6. System level
7. Organism level
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Organization of the human body
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Cellular characteristics and structure
44
 The different substances that make up the cell are
collectively called protoplasm
 Protoplasm is composed mainly of five basic substances:
 Water ,
 Electrolytes
 Proteins
 Lipids &
 Carbohydrates
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1.Chemical
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45
 Includes all chemical substances necessary for life.
a. Atoms:
* Smallest chemicals such as; H, O, C, N
* Minerals- Ca, P, K, S, Na, Cl
* Trace element - Fe, I, Cu, Zn
b. Molecules:
* Collection of atoms or small molecules
E.g. H2O, CO2 , PO4 , NaCl & HCl
Biomolecules = carbohydrates, lipids, proteins, &
nucleic acids.
1. Carbohydrates
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46
 Carbohydrates- have little structural function in the cell except as
parts of glycoprotein molecules, but they play a major role in
nutrition of the cell
 Composed of C, H2, & O2 atoms.
E.g. Glucose (C6H12O6 )
 Combined with other biomolecules. Used for:
 Structure & source of Energy for cells.
 Amount usually averages about 1% their total mass, but increases to
as much as 3% in muscle cells &,
 Occasionally, 6% in liver cells
 Includes:
 - Monosaccharide, Disaccharide, Polysaccharide
2. Lipids
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47
 Lipids- several types that are grouped together because of
their common property of being soluble in fat solvents.
 Important lipids are phospholipids & cholesterol, which
together constitute about 2 % of the total cell mass.
 Significance of phospholipids & cholesterol is that they
are mainly insoluble in water
 Used to form the cell membrane & intracellular membrane
barriers that separate the different cell compartments
2. Lipids…
48
‣ In addition to phospholipids & cholesterol, some
cells contain large quantities of triglycerides, also called
neutral fat.
‣ In the fat cells, triglycerides often account for
as much as 95% of the cell mass.
‣ The fat stored in these cells represents the body’s main
storehouse of energy-giving nutrients that can later be used to
provide energy wherever in the body it is needed
‣ About 40% of the dry mass of a typical cell.
‣ Composed largely of C & H2.
‣ Used for:
Energy storage, structural components & chemical messengers
Includes:
- Triglyceride, Fatty acids, Steroids
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3. Proteins
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49
 About 50 - 60% of the dry mass of a typical cell
 Subunit is the amino acids
 Two functional categories :
 Structural &
 Functional
4. Nucleic Acids
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50
 Biological molecules essential for life, and include:
 DNA (deoxyribonucleic acid) and
 RNA (ribonucleic acid)
 Function in encoding, transmitting and expressing
genetic information.
Electrolytes
51
 Ions-Important ions in the cell include potassium,
magnesium, phosphate, sulfate, bicarbonate, and smaller
quantities of sodium, chloride, and calcium.
 The ions provide inorganic chemicals for cellular reactions
and also are necessary for operation of some of the
cellular control mechanisms.
 For instance, ions acting at the cell membrane are required
for transmission of electrochemical impulses in nerve &
muscle fibers
4/9/2024
Water
52
 Water. The principal fluid medium of the cell
which is present in most cells, except for fat cells, in a
conc. of 70 to 85 %.
 Many cellular chemicals are dissolved in water.
 Others are suspended in water as solid particulates.
 Chemical reactions take place among the dissolved
chemicals or at the surfaces of the suspended particles or
membranes
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 Embedded within the cytoplasm
 Highly organized structures that perform specialized
functions within the cell
 On average, nearly half of the total cell volume is occupied
by two categories of organelles—membranous organelles &
nonmembranous organelles
 Machineries of the given cell
 Combination of biological macromolecules.
 Nearly all human cells contain five main types of
membranous organelle
These include
 the endoplasmic reticulum,
 Golgi complex,
 lysosomes, peroxisomes, and mitochondria.
53
II. Organelle
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Cellular organelles
54
 Membranous organelles are like intracellular “specialty
shops.”
 Each is a separate internal compartment that contains a
specific set of chemicals for carrying out a particular cellular
function.
 This compartmentalization permits chemical activities that
would not be compatible with one another to occur
simultaneously within the cell
 For example, enzymes that destroy unwanted proteins operate
within the protective confines of the lysosomes without the risk
of destroying essential cell proteins.
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The nucleus
 The nucleus is the control center for the cells.
 It contains the genes, which are units of heredity.
 Chemically each gene consists of highly compressed DNA,
the double strand genetic code that stores and transmits
genetic material, & also coordinates protein synthesis in
ribosomes- organelles of protein synthesis in the form of
chromosomes
 Genes Control Cellular activity by determining the type
of proteins, enzymes, and other substances that are made by
the cell.
 The nucleus is also the site of RNA Synthesis.
 There are three kinds of RNA
 Messenger RNA (mRNA), which carries the instruction from
DNA for protein synthesis to the cytoplasm
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The Nucleus
 Ribosomal RNA (rRNA), which moves to the cytoplasm where it
becomes the site of protein synthesis
 Transfer RNA (tRNA), serves as an amino acid transporter system
within the cell for protein synthesis.
 Transcription phase of protein synthesis undertake in the
nucleus.
 Following transcription, the mRNA ( single strand
template of protein synthesis) leaves the nucleus and
travels to the cell's ribosomes, where translation occurs.
In summary, the flow of genetic information in the cell
is: DNA → RNA induces to facilitate protein
transcription in nucleus →complex moves out of
nucleus → protein translation in ribosomes
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Are the sites of protein synthesis in the cell
Small particles composed of Ribosomal RNA &
proteins
Found in two forms:
Attached to the wall of ER or
As free ribosomes.
 Free Ribosomes are found in two forms
-Scattered in the cytoplasm &
-Clustered (aggregated) to form functional
units called polyribosomes
Ribosomes
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Endoplasmic Reticulum (ER)
 It is an extensive membranous structure that connects
various parts of the inner cell.
 ER is also connected with the Nuclear Membrane.
 There are two types of ER:
 Rough ER &
 Smooth ER.
 The function of rER is to Segregate/isolate proteins
that are being exported from the cell.
 rER is the site of protein synthesis
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Smooth Endoplasmic Reticulum (sER)
 The sER is free of ribosome.
 Function of sER varies in different cells.
 The Sarcoplasmic Reticulum of skeletal & cardiac muscle cells are
forms of sER.
 Calcium ions needed for muscle contraction are stored & released
from the sarcoplasmic reticulum of muscle cells.
 In the Liver, the sER is involved in glycogen storage & drug
metabolism.
 ER can synthesize a group of drugs metabolizing enzymes called
Microsomal System.
Function of sER:-
1. Glycogen storage
2. Calcium storage
3. Lipid biosynthesis
4. Drug metabolism (Detoxification) Endoplasmic reticulum (rER and sER)
59
Golgi Complex
 The Golgi complex consists of
flattened membranous saccules &
cisterns that communicate with the
ER & acts as a receptacle/container
for hormones and others substances
that the ER produces.
 It then modifies and packages these
substances into secretary granules.
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Rough ER and Golgi complex
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Mitochondria-power house
 It is called “power house of the
cell” or “power plants-factory”
because many of the reactions that
produce energy (energy rich
compound ATP which is required for
various cellular activities.) take place
in mitochondria.
 The mitochondria require O2 to
produce energy (ATP) from food stuffs.
Lysosomes
• Membraneous structures in the cytoplasm that contains aggregates
of enzymes. Well developed in macrophages.
Function:
• Degrade old dead cells and phagocytosis of microorganisms
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Peroxisomes፡-
63
 Produce & decompose hydrogen peroxide (H2O2) in
the process of degrading potentially toxic molecules
(peroxi refers to “hydrogen peroxide”).
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Cellular organelles
64
 Nonmembranous Organelles- not surrounded by
membrane & thus are in direct contact with the cytosol
 They include
Chromosomes,
Nucleoli,
Ribosomes,
Microtubules,
Microfilaments and centrioles.
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III. The Cell theory
 Is the idea that all organisms are composed of cells.
 In its modern form, the cell theory includes the ff
principles:
1. All organisms are composed of one or more cells
2. Cells are the smallest living things
3. Evolution of life:
. Prokaryotes (single-celled animals with no nucleus,
e.g. bacteria) evolved 3.5 billion years ago.
. Eukaryotes (nucleated single-celled animals),
evolved 1.5 billion years ago
4. Cells arise only by division of a previously existing cell
5. Cells are constructed of the same basic elements and share the
same basic materials and biosynthetic machinery, but differ by
shapes and molecular structures
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Cell…
 The smallest, structural & functional unit of life.
 It is the smallest living unit of the human body.
 Contain basic characteristics of a given organism.
 Numerous in number & estimates being 75 - 100 trillion cells
in the average adult human.
 The red blood cells, numbering 25 trillion in each human
being, transport oxygen from the lungs to the tissues.
 There are many different types of cells in the body including:
1. Epithelial cell
2. Connective tissue cell
3. Muscle cell
4. Nervous tissue cell
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Generalized cell
Components of cells
Trillions of cells in a human body are classified into about 200
types based on specific variations in structure & function.
Despite their diverse structural & functional specializations,
however, different cells share many features in common.
 Most cells have three major subdivisions:
 The plasma membrane, which encloses the cells
 The nucleus, which contains the cell’s genetic material &
 The cytoplasm, the portion of the cell’s interior not occupied
by the nucleus
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Generalized cell
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The Cytoskeletal System
 Microfilament &
microtubules
 They are long, rigid thread like
structures dispersed through
out the cytoplasm.
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Functions of Cytoskeletal System
1) Maintain shape of the cells.
E.g. Axon
2) Serve as a transport system for the movement of
compounds and organelles within the cell.
3) Construct the mitotic spindle. E.g. Centriols
4) Provide for the support & movement of cilia & flagella
5) Cell to cell contact: to fasten cell membranes together
6) Essential for appropriate leukocyte migration.
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Communication Function of the Cell
 How do cells get information?
A very few specialized cells have “ears” or “eyes” sensitive to
pressure or light.
 Almost all cells, sense their environment primarily by detecting
chemical or electrical signals probably by employing surface
proteins (receptors)
 Mechanisms of signaling are: autocrine, paracrine, endocrine
and synaptic. The major mechanisms are neural & endocrine.
 Embedded within the plasma membrane, i.e. all cells can receive
& process information.
72 4/9/2024
Intercellular signaling cont’d…
 Intercellular Communication Classifications
 Endocrine signals
 Produced by endocrine cells
 Travel through the blood to reach all parts of the body.
 Paracrine signals
 Target only cells in the surrounding area of the releasing cell.
E.g. Neurotransmitters
 Autocrine signals
 Affect only cells that are of the same cell type as the emitting
cell.
 An example for autocrine signals is found in immune cells
73 4/9/2024
Intercellular signaling
74 4/9/2024
Intracellular Connections and Communications
 Most cells (epithelial, muscle, some nerve) cells are
tightly joined to form a close functional unit.
 Points of contact between two adjacent plasma
membranes are called cell junctions. There are 3- types of
cell junction:
1. Tight (occluding) junctions
 form fluid-tight seals between cells
2. Desmosomes (anchoring junctions)
 fasten cells together
3. Gap (communicating) junctions permit electrical
signals to pass.
75 4/9/2024
Intracellular Connections…
76 4/9/2024
Tight Junctions (Occludens)
 Are tightly stitched seams between cells.
 Prevent movement of material between the cell
 Are common among epithelial cells that line the stomach, intestine, and
urinary bladder.
 where materials are required to pass through cells (rather than intercellular
spaces) to penetrate the bloodstream.
 Provide the interface between masses of cells and a cavity or space (a lumen)
apical structures (Fig. below) that tie cells together and endow them with
strength and stability.
77 4/9/2024
Adherens Junctions
 Provide strong mechanical attachments between adjacent
cells
 They hold cardiac muscle cells tightly together as the
heart expands and contracts
 They hold epithelial cells together
 Some adherens junctions are present in narrow bands
connecting adjacent cells
78 4/9/2024
Gap Junctions
 Gap junctions are intercellular channels
some 1.5–2 nm in diameter
 Formed by two connecting trans-
membrane protein rings (connexins), They
are cylinders constructed from 6 copies of
Transmembrane proteins called connexins
facilitate;
 free passage of ions and small molecules
including water and small solutes(up to a
molecular weight of about 1000 Daltons)
between the cells
 Permit electrical or chemical signals to pass
from cell to cell
 It allows the rapid spread of AP from one cell
to the next in the nervous system & muscle.
 Each connection in membrane of one cell
lines up with a connection in the
membrane of neighboring cell
79 4/9/2024
Gap Junctions
80 4/9/2024
Desmosomes
 Intercellular rivets creating tight bonds b/n cells, but allow fluids to
pass through intercellular spaces
 Inside the plasma membrane, a desmosome bears a disk-shaped
structure from which protein fibers extend into the cytoplasm.
 Act like spot welds to hold together tissues that undergo considerable
stress (such as skin or heart muscle).
 They are common in epithelia (e.g., the skin).
 Desmosomes are attached to intermediate filaments of keratin in the
cytoplasm
81 4/9/2024
FIGURE Desmosome. Desmosomes are adhering junctions
that spot-rivet cells, anchoring them together in tissues subject to
considerable stretching.
82 4/9/2024
IV The Tissue
 Tissues are groups of cells, and the
surrounding environment, which
work together to produce a specific
function.
 There are only four types of tissues
in the body:
1. Epithelial tissue
2. Connective tissue
3. Muscle tissue
4. Nervous tissue
This is an illustration of muscle
tissue. The muscle cells and
surrounding matrix make up the
structure that works in concert
with the brain to produce
movement in the body.
83 4/9/2024
VI. The Organ
 Organs are structures that are made of two or
more different types of tissues.
 They have specific functions and a defined shape.
 Head, Heart , Stomach, Spinal cord…
The heart is an example of an organ.
It is made of muscle, as well as
connective and nervous tissue.
The tissues work in concert to move
blood through the body.
84 4/9/2024
VI. System
 Consists of Related organs that have common function.
 Lung, trachea, chest wall, bronchioles, alveoli, diaphragm form
respiratory system.
 Brian, spinal cord, special senses, nerve form nervous system.
 Mouth, esophagus, stomach, small intestine etc. form digestive
system etc.
 There are Eleven Organ systems in the body:
1. The Integumentary System
2. The Skeletal System
3. Muscular System
4. Nervous System
5. Endocrine System
6. Cardiovascular System
7. Lymphatic & Immune System
8. Respiratory System
9. Digestive System
10. Urinary System
11. Reproductive System
85 4/9/2024
Body systems
86 4/9/2024
Body systems…
87 4/9/2024
Organ systems interrelations
88 4/9/2024
VII. Organism
 The highest level of organization
 Coordinated interaction activities in each of the levels
that enable us to exist
 We are more than sum of parts
89 4/9/2024
Structural levels of organization of human body summary
Muscle cells
Nerve cells
Cells: 4 types Epithelial cells
Cells in the connective tissues
Muscle tissue
Tissues 4 types Nerve tissue
Epithelial tissue
connective tissues
Organs: Example: Heart, lungs
Organ system: Example: Respiratory system, CVS
Organism: Human organism
90 4/9/2024
Level of organization: summary
91 4/9/2024
THANK YOU
92 4/9/2024

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1.Introduction to human physiology-1 (1).pptx

  • 1. Introduction to Human Physiology For Pharmacy students By Yibeltal Y (MSc in Medical Physiology) Email: yibeltalyismaw7@gmail.com Department of Human Physiology 4/9/2024 1
  • 2. Brain storming 2  What does mean physiology ?  What does it deal about? 4/9/2024
  • 3. Presentation Outline  Introduction  Homeostasis  Control systems  Control mechanisms  Negative feedback control systems  Positive feedback mechanisms  Communications between cells (types of junctions)  Cell structure and function 3 4/9/2024
  • 4. Objectives At the end of this chapter the students will be able to: 1. Explain homeostasis. 2. Discuss negative & positive feed back mechanism. 3. Define physiology 4. Discuss cell physiology. 5. Enumerate the cell organelles with their function. 6. List the types of cellular transport 4 4/9/2024
  • 5. General Introduction What is Physiology? Two Greek words: Physis: nature, origin, Logia: study of  Physiology is the science that seeks to explain the physical and chemical mechanisms that are responsible for the Origin, Development, and Progression of life  Each type of life, from the simplest virus to the largest complicated human being, has its own functional characteristics.  Therefore, the vast field of physiology can be divided into  Viral physiology, bacterial physiology, cellular physiology, plant physiology, invertebrate physiology, vertebrate physiology, mammalian physiology, Human Physiology, & many more subdivisions. 5 4/9/2024
  • 6. General introduction cont’d…  Physiology is the study of functionality of living organisms at the cellular, organ and systemic levels. Historical background Aristotle (384 - 322 B.C.) was  The father of natural history &  The 1st person to coin the term physiology. According to Aristotle, Physiology meant the study of nature- “Physio - nature, logus - study. This means studying practically everything in the Universe and in the human body. 6 4/9/2024
  • 7. General introduction William Harvey in 1628, Correctly described the direction of circulation of blood  Described that the heart pumps blood, arteries transport oxygenated blood, exchange of substances occur at the systemic capillaries and veins return deoxygenated blood. For this reason he is known to be  the father of physiology. Claud Bernard, a French physiologist in the 19th C. described that every cell in body is bathed with the fluid environment called ECF. ECF contains all the needed substances for cells. He called ECF is the internal environment of the body. Walter cannon, another great physiologist of the 1st half of 19th century, termed the maintenance of nearly constant conditions in the ECF as homeostasis 7 4/9/2024
  • 8. Relation of physiology with other sciences o Physiology is closely related to several other branches of science such as anatomy, pharmacology, biochemistry, pathology etc. o Therefore, Physiology is not an isolated science, but highly associated with other sciences. o Physiology as a quantitative science -All physiological parameters are expressed in numbers 8 4/9/2024
  • 11. Extracellular Fluid  Cell is the basic structural & functional unit of life.  The human organism consists of 100 trillions of cells.  for the maintenance of the entire organism  These cells are bathed with the fluid that is called ECF (fluid that fills the space between cells).  About 60% of the adult human body is fluid, mainly the water solution of ions and other substances.  Although most of this fluid is inside the cells(2/3th) & is called intracellular fluid-ICF, about one third is in the spaces outside the cells and is called extracellular fluid. 11 4/9/2024
  • 12. Internal environment cont’d…”  This extracellular fluid is in constant motion throughout the body.  It is transported rapidly in the circulating blood and then mixed between the blood and the tissue fluids by diffusion through the capillary walls.  In the extracellular fluid are the ions and nutrients needed by the cells to maintain life.  While cells may perform very different functions, all the cells are quite similar in their metabolic requirements:  Oxygen , Glucose, Mineral ions, Waste removal …  Thus, all cells live in essentially the same environment the extracellular fluid. 12 4/9/2024
  • 13. internal environment cont’d…  For this reason, the extracellular fluid is also called the internal environment of the body, or the milieu intérieur, a term introduced by the great 19th-century French physiologist Claude Bernard (1813–1878).  Cells are capable of living and performing their special functions as long as  The proper concentrations of gases ,oxygen, glucose, different ions, amino acids, fatty substances, hormones, enzymes, water & electrolytes and other constituents are available in this internal environment.  Therefore, Maintaining a nearly constant internal environment is necessary for the well-being of individual cells & the well-being of the entire body 13 4/9/2024
  • 14. Extracellular VS Intracellular Fluids  The extracellular fluid contains large amounts of  Sodium, chloride, and Bicarbonate ions plus  Nutrients for the cells, such as oxygen, glucose, fatty acids, and amino acids.  It also contains  Carbon Dioxide that is being transported from the cells to the lungs to be excreted, plus  Other cellular waste products that are being transported to the kidneys for excretion.  The intracellular fluid differs significantly from the extracellular fluid; for example, it contains  Large amounts of potassium, magnesium, and phosphate ions instead of the sodium and chloride ions found in the extracellular fluid.  Special mechanisms for transporting ions through the cell membranes  maintain the ion concentration differences between the extracellular and intracellular fluids. 14 4/9/2024
  • 15. Homeostasis  Gk homoios (same) & stasis (standing still)  It is maintenance of nearly static or constant conditions in the internal environment (ECF).  Essentially all organs of the body perform their functions to maintain constant conditions in the ECF. For example  Lungs maintain the normal concentration of respiratory gases in blood.  The CVS transports required substances and removes waste produces,  The kidneys maintain constant ionic concentration and  The GIT provides nutrients. 15 4/9/2024
  • 16. Homeostasis cont’d…  Homeostasis in a general sense refers to:  Stability, balance or equilibrium.  Maintaining a stable internal environment requires constant monitoring & adjustments as conditions change.  Adjustment of physiological systems within the body is called homeostatic regulation; which involves 3 parts or mechanisms:  Receptor, Control Centre & Effector 16 4/9/2024
  • 17. Homeostasis…cont’d 1. Receptor  Receives information that something in the environment is changing. 2. Control center or integration center  Receives & processes information from the receptor. 3. Effector  Responds to the commands of the control center by either opposing or enhancing the stimulus. 17 4/9/2024
  • 18. Homeostasis…cont’d Homeostatic regulation is an ongoing process that continually works to restore & maintain homeostasis. For example  In regulating body temperature there are temperature receptors in the skin,  Which communicate information to the brain, which is the control center, &  The effector is our blood vessels and sweat glands. 18 4/9/2024
  • 19. Homeostasis…cont’d Homeostatically regulated variables  Body Temperature  Blood Composition  Ions, sugars, proteins, water,  O2 and CO2 , PH & Osmolality  Blood Pressure,  Cardiac Output, Cardiac Rate  Respiratory Rate and depth  Secretions of Endocrine Glands  Rate of intracellular chemical reactions 19 4/9/2024
  • 20. Homeostasis…cont’d Factors Disrupting Homeostasis:  External stimuli  Heat, cold,  Lack of O2,  Pathogens & Toxins  Internal stimuli  Abnormalities in visceral organs Function of homeostasis  It allows an organism to function effectively in a broad range of environmental conditions 20 4/9/2024
  • 21. Stimulus: Produces change in variable 1 2 3 Change detected by receptor Input: Information sent along afferent pathway to 5 Response of effector feeds back to influence magnitude of stimulus & returns variable to homeostasis Variable (In homeostasis) Control center 4 Output: Information sent along efferent pathway to Homeostatic Control Mechanisms 21 4/9/2024
  • 22. Regulatory Systems of Homeostasis  The nervous system and the endocrine system are the two controlling bodies of homeostasis 1. The Nervous Regulatory Mechanism  The nerves system is composed of three major components the sensory portion, the integrative portion and the motor portion.  The sensory receptor detects any change in the body (BGC, BT, ABP, pain etc.) and send impulse to the brain, spinal cord (CNS).  The CNS associate the information store some, generate thought and send appropriate response to the effecter organs (muscle + glands) through the motor system. Effector cell NTs R Nerve Impulse Hormone Receptor 22 4/9/2024
  • 23. Regulatory Systems of Homeostasis cont’d…. 2. The Hormonal Regulatory Mechanism  Hormones are chemical messengers secreted by endocrine glands, and transported in blood to the target gland (Organs). Examples:  PTH act on the kidney, bone, and intestine = [Ca2+]  Aldosterone  to the kidney   [Na+]  ADH controls water electrolyte balance  An organism is said to be in homeostasis when its internal environment contains an optimum amount of nutrients, gases, electrolytes, water, hormones, enzymes and temperature. 23 4/9/2024
  • 24. Blood Glucose Homeostasis Normal BGC 70-110 mg/dl 4. Brain All neurons Feeding center 5. Hormones Hyperglycemic hormones Hypoglycemic hormones 24 4/9/2024
  • 25. Homeostatic values 25 1. Body fluid volume = 40 L ECF = 15L ICF = 25L 2. Osmolality = 300 mosm/L, (285 – 300 mosm/L) 3. Body T. = 36.3 – 37.1OC 4. pH = 7.35 – 7.45 5. Blood Gases PCO2 = 35 – 45 mm Hg PO2 = 40 – 104 mm Hg 6. Electrolytes (ECF) Ca2+ = 10 mg/dl or 5 meq/L K+ = 4 meq/L Na+ = 142 meq/L Cl- = 103 meq/L HCO3 - = 27 meq/L 4/9/2024
  • 26. Homeostatic values 7. Waste Products Bilirubin = 0.5 mg/dl Creatinine = 0.6 – 1.5 mg/dL Blood urea nitrogen (BUN) = 8 – 25 mg/dL Uric acid (s): Women = 2.3 – 6.6 mg/dL Men = 3.6 – 8.5 mg/dL 8. Blood Glucose level (fasting): 70 – 110 mg/dL 9. Arterial Blood pressure (systemic circulation). Systolic pressure = 120 mm Hg (90 – 140 mm Hg) Diastolic pressure = 80 mm Hg (60 – 90 mm Hg) Pulse pressure = 40 mm Hg Mean BP = 96 mm Hg Pulmonary AP = 25/10 mm Hg Cardiac output = 5 L/min Blood Flow = 5 L /min 10. RBC count = 4-6 millions/mm3 11. WBC count = 4000-11,000/mm3 12. Hgb = 12-18 g/dl in F, 14-20 g/dl in M  Differences in normal ranges = pathology 26 4/9/2024
  • 27. Normal values of ECF & ICF 27 4/9/2024
  • 29. Disturbances of homeostasis  Deviations from normal ranges = PATHOLOGY  Hypo/ Hyperthermia ….. ↓or↑ Temperature  Hypo/ Hypercapnea ….. ↓or↑ PCO2  Acidosis/Alkalosis ….. ↓or↑ PH  Hypoxia/ Hyperoxia …. ↓or↑ PO2  Hypo/ Hypercalcemia …. ↓or↑ Ca 2+  Hypo/ Hyperglycemia … ↓or↑ Glucose 29 4/9/2024
  • 30. Homeostatic control systems… Depending on the site of regulation process homeostatic controls may be classified in to; 1. Intrinsic controls •Inherent in an organ •The changes are automatically regulated by the organ Examples • Reduction of 02 makes tissue release dilators • Vascular auto regulation in exercising skeletal muscle 30 4/9/2024
  • 31. 2. Extrinsic controls  External stimuli initiate the regulation process  The most common type of controls  Nervous or endocrine system  The control mechanism initiated outside the organ & alter the organ activities via coordinators  Maintain most of the factors in the internal environment. 31 4/9/2024
  • 32. Homeostatic control systems…  Depending on the type/characteristics of response homeostatic control may be; I. Feedback control  Change in the controlled variable brings a corrective response.  The regulatory processes established after the change is developed II. Feed-forward control  Anticipation of a change in the controlled variable brings an anticipatory response.  The regulatory processes established before the change is developed 32 4/9/2024
  • 33. Feedback control mechanisms There are two types of feed back mechanisms:  The Negative Feedback Mechanism (NFM)  The Positive Feedback Mechanism (PFM) 33 4/9/2024
  • 34. Negative Feedback Mechanism (NFM)  It works by producing an effect which opposes the previous condition  The NFM is a mechanism that opposes or counter acts the deviation of a controlled variable from its normal value (range/average).  Nature of Most Control Systems  For example: If the PCO2 is increased in the blood,  the negative feedback mechanism stimulates pulmonary ventilation rate, which has an effect on decreasing PCO2 in blood to normal.  Most homeostatic values of the body are controlled by NFM.  Control of ABP  Control of BGL  Control of BT 34 4/9/2024
  • 35. Blood glucose regulation (NFM) 35 4/9/2024
  • 36. The Positive Feedback Mechanism (PFM)  It works by producing an effect which enhances or repeats the same action like that of the starting stimulus.  The PFM also called Viscous Circle.  Most of the action of this mechanism disturbs the internal environment and cause disease & death.  Fore example, if a person suffers from a heart attack that damages the heart function, then the heart pumps less amount of blood to the tissues including the heart muscle and brain.  If the heart muscle does not get sufficient nutrients and O2, the activity of the heart becomes weaker and weaker and the weaker the heart the lesser blood is pumped and then death may occur. 36 4/9/2024
  • 37. The Positive Feedback Mechanism cont’d… Examples of the PFM  Blood clotting is an example of a very valuable use of PFM.  Generation and propagation of the action potential.  Stimulated nerve fiber  opening of Na+ channels  entry of few Na+ stimulates the opening of more and more Na+ channels.  Labor during child birth, uterine contraction is enhanced as the head of the baby stretches the cervix.  LH-surge 37 4/9/2024
  • 38. Uterine contractions during parturition (PFM) 38 4/9/2024
  • 39. LH surge: the positive feedback mechanism HT Pituitary Ovary GnRH LH Estrogen >200 µg/ml activates 39 4/9/2024
  • 40. Feed-forward  In physiology, feed-forward control is exemplified by the normal anticipatory regulation of heartbeat in advance of actual physical exertion.  Feed-forward control can be likened to learned anticipatory responses to known stimulus.  Feedback regulation of the heartbeat provides further adaptiveness to the running eventualities of physical exertion.  Some activities needed be rapid that no enough time for the brain to bring change after actual change occurred. 40 4/9/2024
  • 41. Feed-forward… The brain anticipates the change that will be developed.  Help for adaptation of the organ where correction will be occurred  Correction is by anticipation Example -  HR and RR before actual exercise -  Digestive juice before food inter into GIT  Used to adapt and rapid rate of response to the change 41 4/9/2024
  • 42. Levels of organization in the body 1. Chemical level 2. Organelle level 3. Cellular level 4. Tissue level 5. Organ level 6. System level 7. Organism level 42 4/9/2024
  • 43. Organization of the human body 43 4/9/2024
  • 44. Cellular characteristics and structure 44  The different substances that make up the cell are collectively called protoplasm  Protoplasm is composed mainly of five basic substances:  Water ,  Electrolytes  Proteins  Lipids &  Carbohydrates 4/9/2024
  • 45. 1.Chemical 4/9/2024 45  Includes all chemical substances necessary for life. a. Atoms: * Smallest chemicals such as; H, O, C, N * Minerals- Ca, P, K, S, Na, Cl * Trace element - Fe, I, Cu, Zn b. Molecules: * Collection of atoms or small molecules E.g. H2O, CO2 , PO4 , NaCl & HCl Biomolecules = carbohydrates, lipids, proteins, & nucleic acids.
  • 46. 1. Carbohydrates 4/9/2024 46  Carbohydrates- have little structural function in the cell except as parts of glycoprotein molecules, but they play a major role in nutrition of the cell  Composed of C, H2, & O2 atoms. E.g. Glucose (C6H12O6 )  Combined with other biomolecules. Used for:  Structure & source of Energy for cells.  Amount usually averages about 1% their total mass, but increases to as much as 3% in muscle cells &,  Occasionally, 6% in liver cells  Includes:  - Monosaccharide, Disaccharide, Polysaccharide
  • 47. 2. Lipids 4/9/2024 47  Lipids- several types that are grouped together because of their common property of being soluble in fat solvents.  Important lipids are phospholipids & cholesterol, which together constitute about 2 % of the total cell mass.  Significance of phospholipids & cholesterol is that they are mainly insoluble in water  Used to form the cell membrane & intracellular membrane barriers that separate the different cell compartments
  • 48. 2. Lipids… 48 ‣ In addition to phospholipids & cholesterol, some cells contain large quantities of triglycerides, also called neutral fat. ‣ In the fat cells, triglycerides often account for as much as 95% of the cell mass. ‣ The fat stored in these cells represents the body’s main storehouse of energy-giving nutrients that can later be used to provide energy wherever in the body it is needed ‣ About 40% of the dry mass of a typical cell. ‣ Composed largely of C & H2. ‣ Used for: Energy storage, structural components & chemical messengers Includes: - Triglyceride, Fatty acids, Steroids 4/9/2024
  • 49. 3. Proteins 4/9/2024 49  About 50 - 60% of the dry mass of a typical cell  Subunit is the amino acids  Two functional categories :  Structural &  Functional
  • 50. 4. Nucleic Acids 4/9/2024 50  Biological molecules essential for life, and include:  DNA (deoxyribonucleic acid) and  RNA (ribonucleic acid)  Function in encoding, transmitting and expressing genetic information.
  • 51. Electrolytes 51  Ions-Important ions in the cell include potassium, magnesium, phosphate, sulfate, bicarbonate, and smaller quantities of sodium, chloride, and calcium.  The ions provide inorganic chemicals for cellular reactions and also are necessary for operation of some of the cellular control mechanisms.  For instance, ions acting at the cell membrane are required for transmission of electrochemical impulses in nerve & muscle fibers 4/9/2024
  • 52. Water 52  Water. The principal fluid medium of the cell which is present in most cells, except for fat cells, in a conc. of 70 to 85 %.  Many cellular chemicals are dissolved in water.  Others are suspended in water as solid particulates.  Chemical reactions take place among the dissolved chemicals or at the surfaces of the suspended particles or membranes 4/9/2024
  • 53.  Embedded within the cytoplasm  Highly organized structures that perform specialized functions within the cell  On average, nearly half of the total cell volume is occupied by two categories of organelles—membranous organelles & nonmembranous organelles  Machineries of the given cell  Combination of biological macromolecules.  Nearly all human cells contain five main types of membranous organelle These include  the endoplasmic reticulum,  Golgi complex,  lysosomes, peroxisomes, and mitochondria. 53 II. Organelle 4/9/2024
  • 54. Cellular organelles 54  Membranous organelles are like intracellular “specialty shops.”  Each is a separate internal compartment that contains a specific set of chemicals for carrying out a particular cellular function.  This compartmentalization permits chemical activities that would not be compatible with one another to occur simultaneously within the cell  For example, enzymes that destroy unwanted proteins operate within the protective confines of the lysosomes without the risk of destroying essential cell proteins. 4/9/2024
  • 55. The nucleus  The nucleus is the control center for the cells.  It contains the genes, which are units of heredity.  Chemically each gene consists of highly compressed DNA, the double strand genetic code that stores and transmits genetic material, & also coordinates protein synthesis in ribosomes- organelles of protein synthesis in the form of chromosomes  Genes Control Cellular activity by determining the type of proteins, enzymes, and other substances that are made by the cell.  The nucleus is also the site of RNA Synthesis.  There are three kinds of RNA  Messenger RNA (mRNA), which carries the instruction from DNA for protein synthesis to the cytoplasm 55 4/9/2024
  • 56. The Nucleus  Ribosomal RNA (rRNA), which moves to the cytoplasm where it becomes the site of protein synthesis  Transfer RNA (tRNA), serves as an amino acid transporter system within the cell for protein synthesis.  Transcription phase of protein synthesis undertake in the nucleus.  Following transcription, the mRNA ( single strand template of protein synthesis) leaves the nucleus and travels to the cell's ribosomes, where translation occurs. In summary, the flow of genetic information in the cell is: DNA → RNA induces to facilitate protein transcription in nucleus →complex moves out of nucleus → protein translation in ribosomes 56 4/9/2024
  • 57. Are the sites of protein synthesis in the cell Small particles composed of Ribosomal RNA & proteins Found in two forms: Attached to the wall of ER or As free ribosomes.  Free Ribosomes are found in two forms -Scattered in the cytoplasm & -Clustered (aggregated) to form functional units called polyribosomes Ribosomes 57 4/9/2024
  • 58. Endoplasmic Reticulum (ER)  It is an extensive membranous structure that connects various parts of the inner cell.  ER is also connected with the Nuclear Membrane.  There are two types of ER:  Rough ER &  Smooth ER.  The function of rER is to Segregate/isolate proteins that are being exported from the cell.  rER is the site of protein synthesis 58 4/9/2024
  • 59. Smooth Endoplasmic Reticulum (sER)  The sER is free of ribosome.  Function of sER varies in different cells.  The Sarcoplasmic Reticulum of skeletal & cardiac muscle cells are forms of sER.  Calcium ions needed for muscle contraction are stored & released from the sarcoplasmic reticulum of muscle cells.  In the Liver, the sER is involved in glycogen storage & drug metabolism.  ER can synthesize a group of drugs metabolizing enzymes called Microsomal System. Function of sER:- 1. Glycogen storage 2. Calcium storage 3. Lipid biosynthesis 4. Drug metabolism (Detoxification) Endoplasmic reticulum (rER and sER) 59
  • 60. Golgi Complex  The Golgi complex consists of flattened membranous saccules & cisterns that communicate with the ER & acts as a receptacle/container for hormones and others substances that the ER produces.  It then modifies and packages these substances into secretary granules. 60 4/9/2024
  • 61. Rough ER and Golgi complex 61 4/9/2024
  • 62. Mitochondria-power house  It is called “power house of the cell” or “power plants-factory” because many of the reactions that produce energy (energy rich compound ATP which is required for various cellular activities.) take place in mitochondria.  The mitochondria require O2 to produce energy (ATP) from food stuffs. Lysosomes • Membraneous structures in the cytoplasm that contains aggregates of enzymes. Well developed in macrophages. Function: • Degrade old dead cells and phagocytosis of microorganisms 62 4/9/2024
  • 63. Peroxisomes፡- 63  Produce & decompose hydrogen peroxide (H2O2) in the process of degrading potentially toxic molecules (peroxi refers to “hydrogen peroxide”). 4/9/2024
  • 64. Cellular organelles 64  Nonmembranous Organelles- not surrounded by membrane & thus are in direct contact with the cytosol  They include Chromosomes, Nucleoli, Ribosomes, Microtubules, Microfilaments and centrioles. 4/9/2024
  • 65. III. The Cell theory  Is the idea that all organisms are composed of cells.  In its modern form, the cell theory includes the ff principles: 1. All organisms are composed of one or more cells 2. Cells are the smallest living things 3. Evolution of life: . Prokaryotes (single-celled animals with no nucleus, e.g. bacteria) evolved 3.5 billion years ago. . Eukaryotes (nucleated single-celled animals), evolved 1.5 billion years ago 4. Cells arise only by division of a previously existing cell 5. Cells are constructed of the same basic elements and share the same basic materials and biosynthetic machinery, but differ by shapes and molecular structures 65 4/9/2024
  • 66. Cell…  The smallest, structural & functional unit of life.  It is the smallest living unit of the human body.  Contain basic characteristics of a given organism.  Numerous in number & estimates being 75 - 100 trillion cells in the average adult human.  The red blood cells, numbering 25 trillion in each human being, transport oxygen from the lungs to the tissues.  There are many different types of cells in the body including: 1. Epithelial cell 2. Connective tissue cell 3. Muscle cell 4. Nervous tissue cell 66 4/9/2024
  • 67. Generalized cell Components of cells Trillions of cells in a human body are classified into about 200 types based on specific variations in structure & function. Despite their diverse structural & functional specializations, however, different cells share many features in common.  Most cells have three major subdivisions:  The plasma membrane, which encloses the cells  The nucleus, which contains the cell’s genetic material &  The cytoplasm, the portion of the cell’s interior not occupied by the nucleus 67 4/9/2024
  • 70. The Cytoskeletal System  Microfilament & microtubules  They are long, rigid thread like structures dispersed through out the cytoplasm. 70 4/9/2024
  • 71. Functions of Cytoskeletal System 1) Maintain shape of the cells. E.g. Axon 2) Serve as a transport system for the movement of compounds and organelles within the cell. 3) Construct the mitotic spindle. E.g. Centriols 4) Provide for the support & movement of cilia & flagella 5) Cell to cell contact: to fasten cell membranes together 6) Essential for appropriate leukocyte migration. 71 4/9/2024
  • 72. Communication Function of the Cell  How do cells get information? A very few specialized cells have “ears” or “eyes” sensitive to pressure or light.  Almost all cells, sense their environment primarily by detecting chemical or electrical signals probably by employing surface proteins (receptors)  Mechanisms of signaling are: autocrine, paracrine, endocrine and synaptic. The major mechanisms are neural & endocrine.  Embedded within the plasma membrane, i.e. all cells can receive & process information. 72 4/9/2024
  • 73. Intercellular signaling cont’d…  Intercellular Communication Classifications  Endocrine signals  Produced by endocrine cells  Travel through the blood to reach all parts of the body.  Paracrine signals  Target only cells in the surrounding area of the releasing cell. E.g. Neurotransmitters  Autocrine signals  Affect only cells that are of the same cell type as the emitting cell.  An example for autocrine signals is found in immune cells 73 4/9/2024
  • 75. Intracellular Connections and Communications  Most cells (epithelial, muscle, some nerve) cells are tightly joined to form a close functional unit.  Points of contact between two adjacent plasma membranes are called cell junctions. There are 3- types of cell junction: 1. Tight (occluding) junctions  form fluid-tight seals between cells 2. Desmosomes (anchoring junctions)  fasten cells together 3. Gap (communicating) junctions permit electrical signals to pass. 75 4/9/2024
  • 77. Tight Junctions (Occludens)  Are tightly stitched seams between cells.  Prevent movement of material between the cell  Are common among epithelial cells that line the stomach, intestine, and urinary bladder.  where materials are required to pass through cells (rather than intercellular spaces) to penetrate the bloodstream.  Provide the interface between masses of cells and a cavity or space (a lumen) apical structures (Fig. below) that tie cells together and endow them with strength and stability. 77 4/9/2024
  • 78. Adherens Junctions  Provide strong mechanical attachments between adjacent cells  They hold cardiac muscle cells tightly together as the heart expands and contracts  They hold epithelial cells together  Some adherens junctions are present in narrow bands connecting adjacent cells 78 4/9/2024
  • 79. Gap Junctions  Gap junctions are intercellular channels some 1.5–2 nm in diameter  Formed by two connecting trans- membrane protein rings (connexins), They are cylinders constructed from 6 copies of Transmembrane proteins called connexins facilitate;  free passage of ions and small molecules including water and small solutes(up to a molecular weight of about 1000 Daltons) between the cells  Permit electrical or chemical signals to pass from cell to cell  It allows the rapid spread of AP from one cell to the next in the nervous system & muscle.  Each connection in membrane of one cell lines up with a connection in the membrane of neighboring cell 79 4/9/2024
  • 81. Desmosomes  Intercellular rivets creating tight bonds b/n cells, but allow fluids to pass through intercellular spaces  Inside the plasma membrane, a desmosome bears a disk-shaped structure from which protein fibers extend into the cytoplasm.  Act like spot welds to hold together tissues that undergo considerable stress (such as skin or heart muscle).  They are common in epithelia (e.g., the skin).  Desmosomes are attached to intermediate filaments of keratin in the cytoplasm 81 4/9/2024
  • 82. FIGURE Desmosome. Desmosomes are adhering junctions that spot-rivet cells, anchoring them together in tissues subject to considerable stretching. 82 4/9/2024
  • 83. IV The Tissue  Tissues are groups of cells, and the surrounding environment, which work together to produce a specific function.  There are only four types of tissues in the body: 1. Epithelial tissue 2. Connective tissue 3. Muscle tissue 4. Nervous tissue This is an illustration of muscle tissue. The muscle cells and surrounding matrix make up the structure that works in concert with the brain to produce movement in the body. 83 4/9/2024
  • 84. VI. The Organ  Organs are structures that are made of two or more different types of tissues.  They have specific functions and a defined shape.  Head, Heart , Stomach, Spinal cord… The heart is an example of an organ. It is made of muscle, as well as connective and nervous tissue. The tissues work in concert to move blood through the body. 84 4/9/2024
  • 85. VI. System  Consists of Related organs that have common function.  Lung, trachea, chest wall, bronchioles, alveoli, diaphragm form respiratory system.  Brian, spinal cord, special senses, nerve form nervous system.  Mouth, esophagus, stomach, small intestine etc. form digestive system etc.  There are Eleven Organ systems in the body: 1. The Integumentary System 2. The Skeletal System 3. Muscular System 4. Nervous System 5. Endocrine System 6. Cardiovascular System 7. Lymphatic & Immune System 8. Respiratory System 9. Digestive System 10. Urinary System 11. Reproductive System 85 4/9/2024
  • 89. VII. Organism  The highest level of organization  Coordinated interaction activities in each of the levels that enable us to exist  We are more than sum of parts 89 4/9/2024
  • 90. Structural levels of organization of human body summary Muscle cells Nerve cells Cells: 4 types Epithelial cells Cells in the connective tissues Muscle tissue Tissues 4 types Nerve tissue Epithelial tissue connective tissues Organs: Example: Heart, lungs Organ system: Example: Respiratory system, CVS Organism: Human organism 90 4/9/2024
  • 91. Level of organization: summary 91 4/9/2024

Editor's Notes

  1. Physiology is the study of study of the mechanisms and functions within living systems from the ionic level up to the whole animal. To maintain healthy function, all of these aspects must operate optimally, including adapting to changes in the internal or external environment. This course will develop your understanding from the ionic level through to the integration of whole systems that are required to sustain life. This will provide a foundation for understanding how often subtle changes can underlie disease, how we are able to treat disease and how future generations of scientists may develop improved and new treatments
  2. Osmolality:- (OZ-mo-LAL-ih-tee) The molar concentration of dissolved particles in 1 kg of water
  3. Frank-Starling mechanism in the heart
  4. Organelles are distinct, highly organized structures that perform specialized functions within the cell. On average, nearly half of the total cell volume is occupied by two categories of organelles—membranous organelles and nonmembranous organelles. Each membranous organelle is a separate compartment within the cell that is enclosed by a membrane similar to the plasma membrane. Thus, the contents of a membranous Nearly all human cells contain five main types of membranous organelle. Membranous organelles are like intracellular “specialty shops.” Each is a separate internal compartment that contains a specific set of chemicals for carrying out a particular cellular function. This compartmentalization permits chemical activities that would not be compatible with one another to occur simultaneously within the cell. For example, enzymes that destroy unwanted proteins operate within the protective confines of the lysosomes without the risk of destroying essential cell proteins. .
  5. The nucleus houses the cell’s genetic material, deoxyribonucleic acid (DNA), which, along with associated nuclear proteins, is organized into chromosomes. Each chromosome consists of a different DNA molecule that contains a unique set of genes. Body cells contain 46 chromosomes that can be sorted into 23 pairs on the basis of their distinguishing features. DNA has two important functions: 1. Serving as a genetic blueprint during cell replication. Through this role, DNA ensures that the cell produces additional cells just like itself, thus continuing the identical type of cell line within the body. Furthermore, in the reproductive cells (eggs and sperm), the DNA blueprint passes on genetic characteristics to future generations. 2. Directing protein synthesis. DNA provides codes, or “instructions,” for directing synthesis of specific structural and enzymatic proteins within the cell. Proteins are the main structural component of cells, and enzymes govern the rate of all chemical reactions in the body. By specifying the kinds and amounts of proteins that are produced, the nucleus indirectly governs most cell activities and serves as the cell’s control centere
  6. Like lysosomes, Peroxisomes are membrane-enclosed sacs containing enzymes, but unlike lysosomes, which contain hydrolytic enzymes, peroxisomes house several powerful oxidative enzymes and contain most of the cell’s catalase. Oxidative enzymes, as the name implies, use oxygen (O2), in this case to strip hydrogen from certain organic molecules. This reaction helps detoxify various wastes produced within the cell or foreign toxic compounds that have entered the cell, such as alcohol consumed in beverages. The major product generated in the peroxisome, H2O2, is formed by molecular oxygen and the hydrogen atoms stripped from the toxic molecule. H2O2 is potentially destructive if allowed to accumulate or escape from the confines of the peroxisome. However, peroxisomes also contain an abundance of catalase, an enzyme that decomposes potent H2O2 into harmless H2O and O2. This latter reaction is an important safety mechanism that destroys the potentially deadly H2O2 at its site of production, thereby preventing its possible devastating escape into the cytosol.
  7. The nonmembranous organelles are not surrounded by membrane and thus are in direct contact with the cytosol. They include ribosomes, proteasomes, vaults, and centrioles. Like membranous organelles, nonmembranous organelles are organized structures that carry out specific functions within the cell. Organelles are similar in all cells, although some variations occur depending on the specialized capabilities of each cell type. Just as each organ plays a role essential for survival of the whole body, each organelle performs a specialized activity necessary for survival of the whole cell A proteasome, a nonmembranous organelle, is a protein degradation machine: It is a cylinder shaped complex about the size of a ribosomal subunit that contains multiple protein-digesting enzymes that break down ubiquinated proteins into recyclable building blocks
  8. The trillions of cells in a human body are classified into about 200 types based on specific variations in structure and function. Despite their diverse structural and functional specializations, however, different cells share many features. Most cells have three major subdivisions: the plasma membrane, which encloses the cells; the nucleus, which contains the cell’s genetic material; and the cytoplasm, the portion of the cell’s interior not occupied by the nucleus