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Introduction and
Cell Physiology

2. Introduction
What is Physiology?
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3. What is Physiology
The term physiology literally means study of nature
/knowledge of nature (Greek: physis = nature; logia =
study of)
Physiology is the study of the normal functioning of a
living organism and its component parts, including all
its chemical and physical processes
It is the study of mechanical, physical and biochemical
properties of living organisms
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4. Fields of Physiology
• Physiology has many subfields:
 Viral physiology
 Bacterial physiology
 Cellular physiology
 Plant physiology
 Mammalian physiology
 Human physiology
 Others
Human physiology is the study of function of human
body parts (cells, tissues, organs & organ systems)
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5. Historical background…
• Physiology is the most fascinating and ancient branch of
science.
• It is an experimental science to which a number of
scientists contributed a lot.
• Most of our present knowledge of human physiology
has been gained in the twentieth century. Further, new
knowledge in the twenty-first century is being added at
an ever more rapid pace.
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6. Significance of studying physiology
 Diseases states are physiology “gone wrong”
which makes an understanding of physiology
essential for the study and practice of medicine
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7. Relationship of Physiology with other sciences
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Physio
logy
Anato
my
Pharm
acolog
y
Pathol
ogy
Bioche
mistry
Other
scienc
es

8. Levels of organization of human body
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10. Components of Body System
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11. Composition of Human Body
The approximate composition of an average
adult human per body weight is that
• Water = 60%
• Proteins = 17%
• Fats = 15%
• Carbohydrates = 1%
• Nucleic acids = 2%
• Minerals = 7%
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12. Components of cells
• A typical cell has two parts: nucleus and
cytoplasm.
• The nucleus is separated from the cytoplasm
by a nuclear membrane and
• The cytoplasm is separated from the
surrounding fluid (ECF) by the plasma
membrane
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13. Cell Physiology
Components of
Eukaryotic Cell
1. Cell membrane
2. Karyoplasm (Nucleus)
3. Protoplasm

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15. Plasma membrane
• It is a sheet-like structure that surround (enclose) the
cell, separating the cellular contents from the ECF
• It is entirely composed of proteins, lipids and
carbohydrates
Percent proportion:
1. Proteins: 55 %
Phospholipids 25 %
2. Lipids: 42 % Cholesterol 13 %
Neutral tats 4 %
3. Carbohydrate: 3 %
 The level of cholesterol determines rigidity of the
membrane
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17. Lipid component of the cell membrane
• Lipids form the basic
structure of the
membrane.
• The lipid molecules are
arranged in two parallel
rows, forming a lipid
bilayer.
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18. Cont’d
• The lipid bilayer portion of the cell membrane is
impermeable to water and water soluble substances such as
– ions
– glucose
– urea and others
• On the other hand, fat soluble substances such as
– O2
– CO2
– Alcohol and
– drugs can penetrate this portion of the membrane
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19. Cont’d
• The lipid molecules
(primarily phospholipids)
contain a
– polar phosphate heads,
soluble in water
(hydrophilic) and
– a non-polar tails that does
not mix with water
(hydrophobic)
• The hydrophilic ends face
the ICF and ECF
• The hydrophobic face each
other in the interior of the
bilayer
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20. Membrane proteins
Two types
A. Integral or intrinsic
proteins:
• Interdingitated in the
hydrophobic center of
the lipid bilayer
• Transmembrane proteins
are integral proteins that
span the entire bilayer.
B. Peripheral or extrinsic
proteins:
• Bind to the hydrophilic
polar heads of the lipid
or on integral proteins 20

21. Cont’d
Transmembrane proteins serve as:
– Channels through which ions pass
– Carriers which transports materials across the bilayer
e.g. glucose
– Pumps which actively transport ions
– Receptors for neurotransmitters and hormones
Peripheral proteins serve as:
– Enzymes
– Contribute to the cytoskeleton on the intracellular
surface
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22. Membrane carbohydrates
 Attached on the outside surface of the membrane, binding
with protruded integral proteins and lipid →form
glycoproteins and glycolipids
 Function
– It is the site of hormonal receptors (act as receptors for
NTs, hormones and drugs) and
– Antigenic activity in ABO blood groups (immune
reaction , antigenical importance),
– Cell to cell attachment
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23. Functions of cell membrane
1. Separates cellular contents from the ECF
2. Regulates the passage of substances in and out
3. It provides receptors for NTs, hormones and drugs
4. It is a means of cell to cell contact
5. Plays an important role in the generation and transmission
of electrical impulse in nerves & muscle
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24. Nucleus
• Is the control center for
the cells and it sends
messages to the cell to
grow, mature, replicate
or die
• Contains large
quantities of DNA,
which comprise the
genes (units of
heredity)
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25. Cont’d
• The nuclear contents are surrounded by a double walled
nuclear membrane
• The pores present in this membrane allow fluids,
electrolytes, RNA, and other materials to move between
the nuclear and cytoplasmic compartments
• The nucleus is also the site of RNA synthesis
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26. Nucleolus
• An accumulation of large amounts of RNA and
proteins
• Does not have a limiting membrane
• One or more per cell
• Most prominent and numerous in growing cells
• The site of synthesis of ribosomes, the structures
in the cytoplasm in which proteins are
synthesized
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27. Protoplasm
1. Cytoplasm
(cytosol)
2. Organelles
3. Inclusions

28. Protoplasm
• Cytoplasm (cytosol) containing:
– Water making 75-90% and containing
• Proteins
• Carbohydrates
• Lipids
• Inorganic substances

29. Protoplasm
• Organelles.
– Metabolically active structures
performing distinct functions.
– Divided into:
1. Membrane bound organelles.
2. Non-membrane bound
organelles.

30. Membranous organelles
1. Endoplasmic reticulum
2. Golgi complex (bodies or apparatus)
3. Lysosomes
4. Peroxisomes (microbodies)
5. Mitochondria

31. Non membranous organelles
1. Ribosomes
2. Cytoskeleton
- Microtubule
- Microfilaments
- Intermediate filaments
- Centrioles

32. Ribosomes
• The sites of protein synthesis in the cell
• 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 and
 clustered (aggregated) to form
functional units called polyribosomes
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33. Endoplasmic reticulum (ER)
• It is an extensive
membranous
structure connected
with the nuclear
membrane
• Two types
Rough ER- contains
ribosome
Smooth ER- no
ribosome
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34. Functions of ER
• Helps to process molecules made by the cell and transports
them to their specific destinations inside or outside the cell
• Rough ER is involved in protein synthesis
• Smooth ER Functions for:
1. Glycogen storage- in liver cells
2. Calcium storage – in muscle cells
3. Lipid biosynthesis
4. Drug metabolism (detoxify)
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35. Golgi Complex
• A collection of membrane-enclosed sacs (cisternae)
that are stacked like dinner plates
• One or more Golgi apparatus are present in all
eukaryotic cells, usually near the nucleus
• There are more than 200 enzymes that function to add,
remove, or modify sugars from proteins and lipids in
the Golgi apparatus
• It then modifies and packages these substances into
secretary granules
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36. Cont’d
• Vesicles containing newly
synthesized proteins bud
off from the rER and fuse
with the cistern on the cis
side of GA
• The proteins are then
passed via other vesicles
to the cistern on the trans
side
• From the trans Golgi,
vesicles shuttle to the
lysosomes and to the cell
exterior
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37. • Functions in:
a. Synthesis of polysaccharides
b. Modifications of secretory
products
c. Packaging of secretory products
received from the RER for
exocytosis.
Ex:- Lysosomes are also
packaged here.
d. Concentration and storage of
secretory products prior to
secretion
Golgi complex (bodies or apparatus)

38. Lysosomes
• Vesicular organelles that are formed by breaking off
from the Golgi apparatus
• Contains over 40 hydrolase enzymes
• Provide an intracellular digestive system that allows the
cell to digest:
 Damaged cellular structures
 Food particles that have been ingested by the cell
 Unwanted matter such as bacteria.
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39. Peroxisomes
• Similar physically to lysosomes, but different in two
important ways:
1. They are believed to be formed by self-replication or
by budding off from sER rather than from the Golgi
apparatus
2. Contain oxidases rather than hydrolases
• Contains more than 40 enzymes, which catalyze a variety
of reactions (eg, breakdown of lipids)
• Oxidases form H2O2 which oxidize many substances that
might otherwise be poisonous to the cell
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40. Mitochondria
• The “powerhouses” of the
cell, capable of producing the
energy rich compound ATP,
which is required for various
cellular activities.
• Total number per cell varies
from less than a hundred up
to several thousand
• Have their own genome
(DNA) which is responsible
for certain key components of
the pathway for oxidative
phosphorylation
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41. Cytoskeletal system of the cell
• They are
microfilament,
intermediate
filaments and
microtubules, rigid
threadlike structures
dispersed through
out the cytoplasm
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42. Function of cytoskeletal system:
1. Maintain shape of the cells. eg. Neurofibrils in axon
2. Serve as a transport system for the movement of
compounds and organelles within the cell. E.g.
axoplasmic transport
3. Construct the mitotic spindle
4. Provide for the support and movement of cilia and
flagella
5. Cell to cell contact: to fasten cell membranes together42

43. Junctions between Cells
• Is the connection between the neighboring
cells or the contact between the cell and
extracellular matrix.
• Cell-cell or cell-matrix adhesions are essential
for normal growth and development and also
for holding the cells together.
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46. 1. Tight junctions
• Are occluding junctions that restrict the
movement of material between the cells they link
• The cell membranes of adjacent cells partly fuse
together with the help of proteins called claudins
and occludins, thereby making a barrier.
• Are commonly found in epithelial tissue lining
hollow structures (intestinal mucosa, renal
tubules)
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48. 2. Gap Junctions
• Two adjacent cells are
connected by membrane
proteins called connexons
• Gap junctions are
intercellular channels some
1.5–2 nm in diameter
• It allows both chemical and
electrical signals to pass
rapidly from one cell to the
next.
• Found in smooth muscle and
in the heart muscle

49. 3. Anchoring junctions
• Attach cells to each other (cell-cell anchoring
junctions) or to the extracellular matrix (cell-
matrix anchoring junctions).
• Cell-cell anchoring junctions are created by
cadherins and Cell-matrix junctions use
integrins.
• Provides strength to the cells by acting like
mechanical attachments
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50. Cont’d
• Present in the tissues like heart muscle and
epidermis of skin, which are subjected to severe
mechanical stress.
• Tissues held together with anchoring junctions
allow materials to pass through paracellular
pathway.
• It has different subtypes:
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51. 3.1 Adherens junction
• link actin fibers in
adjacent cells together
3.2 Focal adhesion
• Tie intracellular actin
fibers to different matrix
proteins, such as
fibronectin
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52. Cont’d
3.3 Desmosomes
• Attach to intermediate
filaments of the
cytoskeleton
• Strongest cell-cell
junctions in tissues
subjected to stress.
3.4 Hemidesmosomes
• Similar to desmosomes
but anchor intermediate
fibers of the cytoskeleton
to fibrous matrix proteins
such as laminin.
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53. Cell to cell communication
• Cell to cell communication refers to the transfer of
information from one cell to another cell through
chemical messengers.
• Classification of Chemical messengers
 Endocrine
 Neuroendocrine
 Neurocrine
 Paracrine or
 Autocrine
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54. Cont’d
Type of
Chemical
messengers
Description Examples
Endocrine
messengers
a chemical messenger, synthesized
by endocrine glands and transported by blood to
the target organs
growth
hormone and
insulin
Paracrine
messengers
chemical messengers, diffuse from the control cells to
the target cells through the interstitial fluid
prostaglandins
and histamine
Autocrine
messengers
chemical messengers
control the source cells which secrete them
leukotrienes
Neurocrine Neurotransmitters are secreted from neurons at
synapses and act on postsynaptic cell
acetylcholine
Neuroendocrine a chemical is released
by neurons directly into the blood and transported
to the target cells
oxytocin, ADH
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56. THANK YOU!!!
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