Physiology

1. PHYSIOLOGY
Written by Michael Mutisya Msc, Public Health Bsc Public Health (JKUAT),
clinical,medicine and surgery (Kmtc ) Nrb

3.  Defination of anatomy, physiology and pathophysiology
 Cells types
 Cell organelles
 Functions of cells
 Transport across cell
 Cell metabolism

4.  The human body is a precisely structured container of chemical reactions. Have
you ever thought of yourself in this way?
 Probably not, and yet, in the strictly physical sense, that is what each one of us
is.
 The body has got trillions of atoms in a specific arrangements and thousands of
chemical reactions proceeding in a very orderly manner.
 This is what indeed laterally describes us and it's not the whole story.
 The keys to understanding human consciousness and self awareness are still
beyond our grasp.
 We do not yet know what enables to us to study ourselves- no other animals do,
as far as we know but we have accumulated a great deal of knowledge about
what we are mad of and how it works
 That is basic what we will be studying in this unit.

5.  Anatomy: is the studying body structure which included size, shape, composition
and perhaps even coloration
 Physiology: is the study of how the body functions
 Pathophysiology: is the study of disorders of fuctioning and so the knowledge of
normal physiology makes such disorders easier to understand.

6.  The human body is organized in to structural and functional levels of increasing
complexity
 Each higher level incorporates the structures and functions of the previous level
as you will see.
 The body is organized into the following:

7.  The chemicals that make up the body may be divided into two categories:
i. Inorganic chemicals : are usually simple molecules made of one or two elements
other than carbon. Examples are water, oxygen. Exceptions include : carbon
dioxide, minerals such as iron, calcium and sodium
ii. Organic chemicals: They a very complex and and always contain elements of
carbon and hydrogen. In this category we have, carbohydrates, fats, proteins
and nuclei can acid

8.  The smallest living units,of a structure and function is a cell. There are many
different types of human cells of which we shall study them in due course.
 Though they have a similar characteristics, each type is made up of chemicals and
carries out specific functions.

10.  A tissue is a group of cells with similar structure and function. There are four
types of tissues:
i. Epithelial tissues: cover or line the body surface; some are capable of producing
secretions with specific functions. E.g. Outer layer of the skin and seat glands .
The internal epithelial include wall of capillaries (squamous epithelial ) and the
kidney tubules
ii. Connective tissues: connect and support parts of the body and some store and
transport materials . Blood, and adipose tissues, bone and cartilages
iii. Muscle tissues: specialized for contractions which bring about skeletal and
heart muscle are examples
iv. Nerve tissues: are specialized to generate and transmit electrochemical
impulses that regulate body functions.

11.  An organ is a group of tissues precisely arranged so as to accomplish specificity
functions.
 Examples are :
i. Kidneys
ii. Individual bones
iii. Liver
iv. Lungs
v. Stomach

12. ORGANIC SYSTEMS
 The organic system is a group of organs that all contribute to a particular
function.
 Example: urinary system, digestive system, respiratory system

13. SYSTEM FUNCTIONS ORGANS
INTEGUMENTARY Barriers to pathogen's entry Skin, sub cutaneous
Skeletal Supports the body
Provides body frame works
Bones , ligaments
Muscular Moves the skeleton muscles and
tendons
Muscles and tendons
Nervous Interpreted sensory information Brains, eyes, nerves, ears
Endocrine Metabolism regulations Thyroid, pancreas
Circulatory Transports oxygen and nutrients Heart, blood , arteries
Lymphatic Returns tissue fluid to the blood Spleen, lymph nodes
Respiratory Exchange oxygen and carbon
dioxide
Lungs, trachea, larynx
Digestive Changes food to chemicals Stomach
Urinary Removes waste products Kidneys be

14. CELLS

15.  All living thing are made up,of cells and cell products. Hence, the cell the
structural and functional units of all the organisms.
 Some organisms such as bacteria,are unicellular, consisting of a single cell. Other
organisms such as human beings are multicellular, indicating that humans are
made up of many cells
 Thus, cells are the smallest independent units of life with different parts that
perform their own functions
 Some of this activities include: cellular growth, metabolism and reproduction.
Each cell is an amazing unit of life; it can take in nutrients, convert this nutrients
into energy, carry out specialized functions and reproduce as necessary
 Most importantly,each cell stores its own set of instructions so as to carry out this
activities.

17.  Called plasma membrane.
 Has phospholipids , cholesterol and proteins
 The phospholipids form a bilayer or a double layer why make most of the
membrane
 The phospholipids allow lipid- soluble material to easily enter or leave the cell by
diffusion through the the cell membrane. The presence of cholesterol decrease the
fluidity of the cell making it more stable.
 The functions of the protein are: forms pores or channels to permit the passage of
materials such as water or ions, others are transporters, act as antigens mans also
play the role of receptors.
 The cell membrane is selectively permeable that is some substances are allowed to
go through but others are resisted

18. i. Are selective semi- permeable membranes, which means that some molecules
can diffuse across the lipid bilayer but others can not. Small hydrophobic
molecules and gases like O2 and CO2 cross the membrane rapidly. Small polar
molecules , such as water and ethanol cannot not pass through membranes, but
they do more so slowly.
ii. Membranes antigen (e.g blood group antigens, transplantation antigen)
iii. Cell receptors for cell recognitions and communications

19.  Made up,of DNA, RNA and proteins.
 The nucleoli form a type of RNA called ribosomal RNA, which become part of
ribosomes and is involved in protein synthesis
 The nucleus is the control center of the cell because it contains the chromosomes
who I are made up of DNA and proteins
 Some chromosomal proteins provide the structural frame work for the coiling of
the chromatin into chromosomes so that cell division can occur.
 Other chromosomal proteins help to regulate the activity of the DNA

20.  Cytoplasm is a watery solution of minerals, gases, organic molecules and cell
organelles that is between the cell membrane and the nucleus.
 Cytosol is the water portion of cytoplasm, and many chemical reactions take place
within it.
 Cell organelles are intracellular structures, often bounded by their own fluid.
 The major organelles are the cytoskeleton, mitochondria, ribosomes, endoplastic
reticulum, Golgi apparatus or complex lysosomes

21.  Is an extensive network of membranous tubules that extend fro the nuclear meme
range to the cell membrane.
 Rough ER has numerous ribosomes on it whereas the smooth ER has no
ribosomes.
 As a net work of interconnected tunnels, the ER Is a passage way for transport of
materials necessary for cell functions
 This includes: protein synthesized by the ribosomes on the rough ER and lipids
synthesized by try smooth ER

22.  Tiny structures made of ribosomal RNA and proteins
 Some are found to surround the rough ER while other are freely floating within
the cytoplasm
 Are the the site for proteins synthesis. This includes hormones, collagen in
thespian and enzyme
 This proteins may function within the cell or elsewhere.
 Some proteins are needed for a very short time and so they get destroyed

23.  Play a role of secretions and also synthesizing carbohydrates and are packaged
with other materials for sections from the cells

24.  Are oval organelles with double me membrane
 The inner membrane of the mitochondria has foods which are regarded as cristae.
 Within the mitochondria, the aerobic (oxygen requiring) reactions of cell
respiration occur.
 Therefore, mitochondria are the site for ATP (and hence energy) production.
 Some cells sneed large a,outs of ATP like the muscles cells so as to ,wet the need
for energy

26.  Have digestive enzymes
 When certain white cells engulf bacteria, the Bactria are destroyed and disgusted
by lysosomes
 Worn out cell parts are also disgusted by these enzymes

27.  Many of our cells are capable of dividing, or reproducing themselves hence
centrioles help in cell division

28.  Are mobile threads –like projections through the cell membrane,
 Cilia are shorter than flagella
 They are used for movement and motion

29.  Are foods of the cell membrane on the free surface of an cell
 These folds greatly increase the surface area of the membrane, and are part of the
cells lining organs that absorb materials. Eg. Cells of the small intestines

30. Organelle Function
Endoplasmic reticulum Passage for transport of materials within the cell
Ribosomes Synthesis for lipids
Proteas omens Site for protein synthesis
Golgi apparatus Synthesis of carbohydrates the and packaging of
materials for secretions
Mitochondria Site aerobic cell respiration
Lysosomes Has enzymes to digest ingested materials
Centrioles Organize spindle fibers in cell division
Cilia For sweeping materials across th cell service
Flagellum Enables cell to move
Micro villi Increase cell surface area for absorption

31.  Cell division is the process by which a cell reproduces itself.
 There are two types of cell division:
i. Mitosis
ii. Meiosis
The period between the mitosis is called interphase the time between mitotic
divisions.
The cell cycle is the phase between two consecutive divisions

32.  Each of us began life as one cell, a fertilized egg. Each us consists of billionaires of
cells produced by the process of mitosis
 In mitosis, one cell with the diploid number of chromosomes ( the usual number is
46) devices into two identical cells, each with diploid number of chromosomes.
 This production of identical cells is necessary for the growth of the organism and
for repair of tissues
 Before mitosis can take place, a cell must have two complete sets of chromosomes,
because each new cell must have the diploid number.
 The process of DNA replication enables each chromosome ( inform of chromatin)
to make a copy of itself

33.  Although interphase is sometimes referred to as the resting stage, resting means,
not dividing rather than inactive. The cell is quite actively producing a second set
of chromosomes and storing energy in ATP.
 The log thin and invisible chromatin molecules start to coil very precisely and
extensively and they appear like letter X in the microscope because of original
DNA and its copy

34.  The skin repair in mitosis of epidermal cell
 Stomach lining replacement
 Production of red blood cells in the bone marrow
AREAS OF THE BODY WHERE MITOSIS DOES NOT TAKE PLACE
MUSCLES
SPINAL CORD INJURY
SKELETAL MUSCLES
MUSCLES OF THE HEART

35. There are over 200 different types of cancer .of which all of them are characterized by
abnormal cellular functions
Normally, our body cells undergo mitosis only when necessary and stop when appropriate.
A cut on the skin for example heal by mitosis Usually without forming extra tissues.
The new cells fill in the da,aged area, and mitosis slows when the CEOs make contact with
the surrounding cells. This is called contact inhibition which limits the new tissue to just
what is needed.
Malignant (cancer) cells however are characterized by uncontrolled cell division. Our cells
are genetically programmed to have particular life spans and to device of die.
One gene can act as a break on cell division and another one enables cels to live longer

36.  The stages of mitosis are:
i. Prophase: chromosome divide into two chromatids
ii. Metaphase: the micro tubules become arranged between two centrioles
forming spindle
iii. Anaphase: the centromere divide and each set is separated by chromosomes
iv. Telophase: Formation of nuclear membrane around each set of chromosomes

37.  Is more complex process of cell division that results in formation of gametes which
are good and sperms cells.
 In meiosis, one cell with diploid number of chromosomes decides twice to form four
cells, each with the haploid number ( half of the usual number) of chromosomes
 In women, meiosis takes place in the ovaries and is called oogenesis. In men
meiosis takes place in the tastes and is called spermategenesis

38.  Multicellular organisms, including people, age and eventually die, our cells do not
have infinite life spans.

39. TRANSPORT ACROSS THE
CELL

40.  Living cells constantly interact with the blood or tissue fluid around them, taking
in some substances and secreting or excreting others.
 There are several mechanism of transport that enable cells to move materials
into and out cell. This are:
i. Diffusion
ii. Osmosis
iii. Facilitated diffusion
iv. Active transport
v. Filtration
vi. Phagocytosis
vii. Pinocytosis
Some need energy and others don't

41.  Is the movement of molecules from an area of greater concentration to an area of
lesser concentration ( that is, with or along a concentration gradient).
 Diffusion occurs because molecules have free energy, that is they are always in
motion .
 The molecules in a solid move very slowly, those in a liquid move faster, and those
in gas move faster still such as when ice absorbs heat energy , melts and then
evaporate
 If you put green sugar cube at the bottom of a glass, it starts to dissolve for the
sugar molecules collide with each other and the green color rises up to the top of
the glass.
 This collision spreads out the green sugar molecules until they are evenly
dispersed and the water becomes green eventually

42.  The molecules are still moving which may take long but at the end, equilibrium is
reached or a steady state.
 Diffusion is a very slow process, but may be an effective transport mechanism
across microscopic distances.
 Within the body, the gases O2 and CO2 move by diffusion. In the lungs, there is
high concentration of oxygen in the lung sacs than in the blood. There is also low
concentration of carbon dioxide in the alveoli and high concentration in the
pulmonary capillaries

43. i. Gases diffuse rapidly and liquids diffuse more slowly
ii. At high temperatures, the rate of diffusion is much faster
iii. Smaller particles such as glycerol will diffuse faster than larger molecules
iv. Surface area of the cell membrane
v. Solubility of the molecules
vi. Concentration gradient

44.  When water diffuses through a selectively permeable membrane.
 That is, water will move from an area with water present to an area with less water.
 Another way to say this is that water will naturally tend to move to an area where there is
more dissolved materials,such as salt or sugar.
 If a 2% salt solution and a 6% salt,solution are separated by a membrane allowing water but
not salt to pass through it, water will,diffuse from 2% salt solution to the 6% salt solution.
 The result is that the solution 2% solution will become more concentrated, and the 6%
solution will become more dilute.
 In the body, the cells lining the small intestines absorb water from digested food by osmosis.
This cells have first absorbed salts, have become more "salty" and water follows salt into cell.
 The process of osmosis also takes place in the kidneys which absorb large amounts of water
to prevent its loss through urine.

45.  Human cells or other body fluids contain many dissolved substances ( called
solutes) such as salts, sugars, acids and bases
 The concentration of solutes in a fluid creates the osmotic pressure of
solutions,which in turn determines the movement of water through membranes
 Isotonic – a solution with as,e salt concentration as in the cells :- if RBCs are
placed in plasma,,water moves into and out of them at equal rates and the cells
remain Norma
 Hypotonic – a solution with a lower salt concentration than in cells: if RBCs are
placed in distilled water, more water will enter the cells than leave and the cells
will swell and eventually burst
 Hypertonic :- a solution with higher concentration than the cells :- if RBCs are
placed in sea water, more water will leave the cells than enter and they shrink
and die

46.  The word facilitate means to help or assist .
 In facilitated diffusion, molecules move through a membrane from an area of greater
concentration to area of lesser concentration, but they need some help to do this.
 In the body, our cells must take in glucose to use for ATP production. Glucose, however,
will not diffuse through most cell membranes by itself, even if there is more outside the
cells requires a glucose transporter, which may be called a carrier enzyme.
 These transporters are proteins that are part of the cell membrane. Glucose bonds to
the transporter and by doing so changes the shape of the protein.
 This physical change propels the glucose into the interior bog the cell. Other
transporters are specific for other organic molecules such as amino acids

47.  Active transport requires the energy of ATP to move molecules from an area of lesser
concentration to an area of greater concentration.
 Notice that this is the opposite of diffusion, in which the free energy of molecules causes
them to move to where there are fewer of them.
 Hence active transport is therefore said to be movement against a concentration
gradient.
 In the body, nerve cells and muscles cells have "sodium pumps" to move sodium ions
(Na+) out of ten cells.
 Sodium ions are more abundant outside the cells, and they constantly diffuse into the
cell (through specific diffusion channels), their area of lesser concentration.
 Thus without sodium pumps to return them outside, the incoming sodium ions would
bring about unwanted nerve impulses or muscle contraction.
 Nerve and muscle cells constantly produce ATP to keep their sodium pumps working
and prevent spontaneous impulses

48.  The process of filtration also requires energy, but the energy needed does not come directly
from ATP.
 It is the energy of mechanical pressure.
 Filtration means that water and dissolved materials are forced through a membrane from an
area of higher pressure to an area of lower pressure.
 In the body, blood pressure is created by the pumping of the heart.
 Filtration occurs when blood flows through capillaries, whose walls are only one cell thick and
very permeable.
 The blood pressure in capillaries is higher than the pressure of the surrounding tissue fluid.
 In capillaries throughout the body, blood pressure forces plasma (water) and dissolved
materials through the capillary membranes into the surrounding tissue spaces.
 This creates more tissue fluid and is how cells receive glucose, amino acids, and other
nutrients.
 Blood pressure in the capillaries of the kidneys also brings about filtration hence formation of
urine.

49.  Endocytosis (means to take into ) is the process by which cells take in molecules
such as proteins from outside the cell by engulfing them with their cell
membranes.
 It is used by all cells of the body because most substances important to them are
big and thus cannot pass through the cell membrane.
 There are three types of endocytosis:
i. Pinocytosis : cell drinking ( cells of the kidney tubules reabsorb small proteins
ii. Phagocytosis: cell eating e.g white blood cells engulf bacteria

50. Mechanism Defination Example in the body
Diffusion Movement of molecules from an
area of greater concentration to an
area of lesser concentration
Exchange of gases in the lungs or
body tissue
Osmosis The diffusion of water Absorption of water by the small
intestines
Facilitated diffusion Carrier and transporter enzymes
molecules across cell membrane
Intake of glucose by most cells
Active transport Movement of molecules from an
area of lesser concentration than
area of higher concentration
Absorption of amino acids and
glucose from food by the cells of
small intestine. Sodium and
potassium pumps in muscles
Filtration Movement of water and dissolved
substances from an area of higher
pressure to an area of lower
pressure
Formation of tissues fluid the first
step in the formation of urine
Phagocytosis A moving cells engulfs something White blood cells engulf bacteria
Pinocytosis A stationary cell engulfs
something
Cells,of the kid yet tubules
reabsorbed proteins

51. HOMEOSTASIS
 Is the body's attempt to maintain a stable internal environment by achieving
some sort of balance.
 The body is normally able to achieve a relatively stable internal environment even
though the external environment is constantly changing-from cold to hot, or from
dry to wet and so on.
 The body uses various homeostatic mechanisms to monitor and maintain dynamic
state of equilibrium within the body – that is, balance in which the internal
environment conditions can react to external environmental conditions by
changing within quite narrow limits

52. i. Receptors: the body has receptors that sense external and internal environment
changes and provide information on the changes to the control center
ii. Control center: the control center determines what a particular value (e.g. pH
value or blood pressure ) and sends out a message to the receptors.
iii. Effectors: once they have received the information from the control center, the
effectors cause the receptors to take place within the body's internal
environment that hopefully will,produce the changes that will enable the
internal environment to return to normal values.