2. Introduction
• Human physiology explain the specific characteristics
and mechanisms of the human body that make it a
living being (functions) .
• Types: viral physiology, bacterial physiology, cellular
physiology, plant physiology, human physiology, and
many more subdivisions.
• Goal of physiology is to explain the physical and
chemical factors that are responsible for the origin,
development, and progression of life.
29/7/2021
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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3. Introduction
• Father of modern human physiology
– Claude Bernard was born on 12 July 1813 in the village of
Saint-Julien, in France’s Beaujolais region.
• Basic living unit of the body is the cell.
• Each organ is an aggregate of many different cells held together
by intercellular supporting structures.
• Body as an organized “solution”
– About 1/3rd of total body water (TBW) is extracellular
(interstitial fluid & circulating blood plasma)
– remaining 2/3rd is intracellular (intracellular fluid)
29/7/2021
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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5. Illustrate the structure and basic parts of a cell. Organization of Cell
• Membranous Structures of the Cell
• Cytoplasm and Its Organelles
• Nucleus, Nuclear Membrane, Nucleoli, Formation of Ribosomes
Illustrate the structure and function of cell membrane.
• Functional Systems of the Cell
o Ingestion by the Cell-Endocytosis : Pinocytosis and
Phagocytosis of Foreign Substances Inside the Cell-Function
of Lysosomes
o Synthesis and Formation of Cellular Structures by
Endoplasmic Reticulum and Golgi Apparatus
o Extraction of Energy from Nutrients-Function of Mitochondria
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Prof Dr K M Padmavathy MD Physiology,
Wollega University
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Contents
6. Functional organization
• Cell
– Structure of the cell membrane
– Cytoplasm and its organelles
– Nucleus and its membrane
– Nucleoli and formation of ribosomes
• Functional systems of cells
– Endocytosis : Pinocytosis, Phagocytosis
– Extraction of energy from nutrients (from mitochondria)
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Prof Dr K M Padmavathy MD Physiology,
Wollega University
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7. Structure of cell membrane
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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Arrangement of integral and peripheral membrane proteins
in association with a bimolecular layer of phospholipids
Hydrophilic
Hydrophobic
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8. Prof Dr K M Padmavathy MD Physiology,
Wollega University
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Cell Membrane
• Lipid bilayer made up of phospholipid, cholesterol and
triglyceride molecules
• Phospholipid molecules contains
• phosphate head - hydrophilic
• two fatty acid chains attached to phosphate head -
hydrophobic
• Membrane proteins are Globular masses floating in the
lipid bilayer – glycoproteins
• Types of proteins:
1. Integral proteins -protrude all the way through the
membrane
2. Peripheral proteins - attached only to one surface of
membrane and do not penetrate all the way through.
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9. Prof Dr K M Padmavathy MD Physiology,
Wollega University
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Cell membrane proteins and their functions
1. Integral proteins
Function as :
a. Channels/Pores: water
molecules, water-soluble
substances (ions) diffuse
between ECF and ICF
b. Pumps: actively transporting
ions across the membrane
c. Carrier proteins
d. Enzymes
e. Receptors
2.Peripheral proteins
attached to integral proteins
Function as:
a. Enzymes
b. Controllers of transport of
substances through the
“pores” of cell membrane.
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10. Prof Dr K M Padmavathy MD Physiology,
Wollega University
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Functions of Carbohydrate moieties “Glycocalyx” attached to the
outer surface of the cell (glycoproteins or glycolipids)
Functions of “Glycocalyx”:
(1) They have a negative electrical charge, which repels other
negative objects.
(2) The glycocalyx of some cells attaches to glycocalyx of other cells
(3) Act as receptor substances for binding hormones, (e.g. insulin)
activates internal proteins activate a cascade of intracellular
enzymes.
(4) Some carbohydrate moieties enter into immune reactions
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11. Functions of cell membrane:
1. Regulate the passage of substances into and out of
cells; and between cell organelles and cytosol
2. Detect chemical messengers arriving at the cell
surface
3. Link adjacent cells together by membrane junctions
4. Anchor cells to the extracellular matrix
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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29/7/2021
12. Prof Dr K M Padmavathy MD Physiology,
Wollega University
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Ion channel (integral)
• Allows specific ion to move through
water-filled pore.
• Most plasma membranes include
specific channels for several common
ions.
Carrier proteins/ transporters (integral)
• Transports specific substances across
membrane by changing shape.
• For example, amino acids, glucose
enter body cells via carriers.
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13. Prof Dr K M Padmavathy MD Physiology,
Wollega University
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Receptor (integral)
• Recognizes specific ligand and alters
cell's function in some way.
• For e.g: antidiuretic hormone binds to
receptors in kidneys and changes
water permeability of plasma
membranes.
Enzyme (integral and peripheral)
• Catalyzes reaction inside or outside
cell (depending on which direction
the active site faces).
• For eg: lactase protruding from
epithelial cells lining small intestine
splits disaccharide lactose in milk
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14. Prof Dr K M Padmavathy MD Physiology,
Wollega University
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Linker (integral and peripheral)
• Anchors filaments inside and
outside the plasma membrane,
providing structural stability and
shape for the cell.
• May also participate in movement
of the cell or link two cells together.
Cell identity marker (glycoprotein)
• Distinguishes self cells from
anyone else's
• An important class of such markers
are the major histocompatibility
(MHC) proteins
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15. Prof Dr K M Padmavathy MD Physiology,
Wollega University
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Structure of the eukaryotic cell
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16. • Membranous organelles: covered with membrane
• Cell membrane
• Nucleus with nuclear membrane
• Cytoplasmic organelles
• Golgi apparatus
• Rough (Granular) and smooth endoplasmic reticulum
• Lysosomes
• Mitochondria
• Other cytoplasmic organelles
• Peroxisomes
• Secretory vesicles
• Filament and tubular structures of cell
• e.g.,Cillium, flagellum, centrioles, mitotic spindles of mitosing
cell
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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29/7/2021
17. Nucleus and its functions :
1. Nucleus contains chromosomes in
the form of chromatin
- Contains genetic information
- Composed of DNA
- Thicken for cellular division
- Set number per species
(i.e. 23 pairs for human)
2. Nuclear membrane
- Surrounds nucleus : Composed of two layers
- Numerous openings for nuclear traffic
3. Nucleolus
- Spherical in shape
- Visible when cell is not dividing
- Contains RNA for protein manufacture
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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29/7/2021
18. Nucleoli and formation of ribosomes
• Nucleoli is simply an accumulation of large amounts of RNA
and proteins of the types found in ribosomes.
• Nucleolus becomes considerably enlarged when the cell is
actively synthesizing proteins.
• Formation of the nucleoli (and ribosomes in the cytoplasm)
begins in the nucleus.
• First, specific DNA genes in the chromosomes cause RNA to be
synthesized.
• Some of RNA is stored in the nucleoli, but most of it is
transported outward through nuclear pores into cytoplasm.
• “Mature” ribosomes that play an essential role in forming
cytoplasmic proteins
29/7/2021
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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19. Plasma membrane
- Outer membrane of cell that controls cellular traffic.
- Contains proteins that span through the membrane and
allow passage of materials.
- Proteins are surrounded by a phospholipid bilayer.
Protoplasm is composed mainly of five basic substances:
- water, electrolytes, proteins, lipids, and carbohydrates
Peroxisome
- membrane bounded organelle that contain oxidative
enzyme and catalases.
- formed by self-replication by budding off from the smooth
endoplasmic reticulum rather than from the Golgi apparatus.
- they contain oxidases rather than hydrolases.
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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29/7/2021
20. Centrioles
- Paired cylindrical organelles near nucleus.
- Composed of nine tubes, each with three tubules.
- Involved in cellular division.
- Lie at right angles to each other.
Lysosome
• Membrane bounded sac that contain hydrolytic enzyme.
• It provide an intracellular digestive system that allows the
cell to digest :
o damaged cellular structures
o food particles that have been ingested by cell
o unwanted matter such as bacteria
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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29/7/2021
21. Endocytosis
• Include Pinocytosis & Phagocytosis mainly
• Other types are:
– Clathrin mediated endocytosis,
– Caveolae-dependent uptake,
– nonclathrin/noncaveolae endocytosis.
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Prof Dr K M Padmavathy MD Physiology,
Wollega University
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22. Phagocytosis (cell eating)
• Process by which bacteria,
dead tissue, or other
microscopic materials are
engulfed by
polymorphonuclear
leukocytes of blood
• These material makes
contact with cell membrane,
then invaginates.
• Invagination is pinched off,
leaving the engulfed material
in the membrane-enclosed
vacuole and the cell
membrane intact.
Pinocytosis (cell drinking)
• Similar process with the
vesicles much smaller in
size and the substances
ingested are in solution.
• The small size membrane is
ingested that should not
affect cell as it undergo
active pinocytosis
• (eg, macrophages) can
ingest the equivalent of
their entire cell membrane
in just 1 hour.
29/7/2021
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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23. Prof Dr K M Padmavathy MD Physiology,
Wollega University
Rough endoplasmic reticulum (RER):
- Synthesis protein molecules as cell’s exterior
products or products within the cells.
Smooth endoplasmic reticulum (SER):
- Buds off the raw materials from RER to GA.
- Focus more on lipid synthesis.
Golgi Apparatus (GA):
-It process newly synthesized molecules from
SER into final product.
- Sorts and directs the final products according
to its functions and destinations.
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24. Endoplasmic reticulum
• Network of tubular and flat vesicular structures in the cytoplasm
• Walls are constructed of lipid bilayer membranes that contain
large amounts of proteins
• Space inside the tubules and vesicles is filled with endoplasmic
matrix, which is connected with the space between two layers of
nuclear membrane
• Vast surface area and multiple enzyme systems attached to its
membranes provide machinery for a major share of the
metabolic functions of the cell.
29/7/2021
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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25. 29/7/2021
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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https://www.youtube.com/watch?v=fKEaTt9heNM
26. Rough (granular) endoplasmic reticulum.
• Attached to the outer surfaces of endoplasmic reticulum are
large numbers of minute granular particles called ribosomes.
• Ribosomes are composed of a mixture of RNA and proteins,
and they function to synthesize new protein molecules in the
cell.
Agranular, or smooth, endoplasmic reticulum
• Endoplasmic reticulum has no attached ribosomes.
• Functions for synthesis of lipid substances and other
processes of the cells promoted by intra-reticular enzymes
29/7/2021
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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27. Golgi apparatus
• Closely related to the endoplasmic reticulum.
• It has membranes similar to those of agranular endoplasmic
reticulum.
• It usually is composed of four or more stacked layers of thin,
flat, enclosed vesicles lying near one side of the nucleus.
• This apparatus is prominent in secretory cells, located on side
of the cell from which the secretory substances are extruded.
• Substances entrapped in ER vesicles are transported from ER
to Golgi apparatus and processed to form lysosomes,
secretory vesicles, and other cytoplasmic components
29/7/2021
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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29. 29/7/2021
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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Mitochondria
- Rod-shaped double membrane organelle.
- Has its own DNA distinct from DNA found in nucleus
- Outer membrane surrounds the organelle
- Inner membrane forms folds or shelves called cristae.
- Cristae is filled with gel-like solution known as matrix.
- Cristae contain crucial protein which convert energy in
food into useable form.
-Its function as power house of the cell.
32. Prof Dr K M Padmavathy MD Physiology,
Wollega University
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Cytoskeleton of cell:
- A system of fibers made up primarily of microtubules,
intermediate filaments, and microfilaments, along with proteins
that anchor them and tie them together.
Functions of cytoskeleton of cells:
a. Maintains the structure of the cell
b. Permits it to change shape and move.
c. Retain asymmetrical shape of cell.
d. Transport secretory vesicle and other materials from one
part to another part of cell - microtubules
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33. Intercellular junctions in the mucosa of the small
intestine. The various types of desmosomes
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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Linkage between cells – tight junctions,
desmosomes and gap junctions
Occurs in
Choroid [plexus
Kidney tubules
Wall of intestines
Electrical synapses
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34. Prof Dr K M Padmavathy MD Physiology,
Wollega University
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Two main types of junctions form between the cells
1a. Tight junctions/ zonula occludens/desmosomes:
- fasten the cells to one another and to surrounding tissues.
- Provides strength and stability.
1b. Desmosomes and zonula adherens:
- Hold cells together.
- Hemidesmosomes and focal adhesion attach cell to their
basal laminas
2. Gap junctions:
- Permit transfer of ions and other molecules from one cell to
another.
- These junctions tie cells together.
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35. e.g., for Gap junction
Visceral type of smooth muscle fibers are electrically
connected with one another through large numbers of gap
junctions that allow low-resistance movement of ions from
one muscle cell to the next.
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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29/7/2021
36. Modifications of cell membrane: Cilia and flagella
1. Cilia - motile projections of the cell surface
- microtubules are present
- causes steady movement along the cell surface
e.g.,
a. Respiratory tract: cilia help sweep foreign particles
trapped in mucus away from the lungs
b. In cystic fibrosis, thick mucous secretions interfere with
ciliary action ; Movement of cilia is paralysed by nicotine in
cigarette smoker.
c. Uterine tubes also have cilia that sweep oocytes toward
uterus
2. Flagellum
e.g., Sperm cells tail, propels sperm toward the oocyte in uterine tube.
Prof Dr K M Padmavathy MD Physiology,
Wollega University
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37. Prof Dr K M Padmavathy MD Physiology,
Wollega University
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Receptor modification:
Receptor numbers are not static, but increase or decrease in
response to various stimuli, and their properties change with
changes in physiological conditions.
• Down regulation: when a hormone or neurotransmitter is
present in excess, the number of receptors generally decreases
• Up-regulation: In deficiency of the chemical messenger, there is
an increase in the number of active receptors.
• Diseases caused by receptor modification e.g.,
• Nephrogenic diabetes insipidus
• NIDDM
• Myasthenia gravis
• Graves disease
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