General Physiology BY MASS (4) - rmp.ppt

Resting membrane potential

1.  Introduction to Physiology
 Structure and Function of Cell

2. What is PHYSIOLOGYPHYSIOLOGY ………?

3. Physiology.....
Study of processes that depend
on interplay of many widely
separated organs in the body.

4. In simple words……
“Physiology is the study of
physical and chemical processes that takes
Place in living organisms
during performance of life functions”

5. Physiology is the study of
“HOW LIVING ORGANISMS WORK ”
in little more simple words……

6. 19
th
Century Physiologist… “CLAUDE BERNARD”
“After carrying out an analysis of phenomena,
we must… always reconstruct our physiological synthesis,
so as to see the joint action of all the parts
we have isolated…….”

7. Physiology Medicine

8. How Is The Body Organised .. ?

9. How various organs
developed/organized ?

10. The simplest structural units into which
a complex multicellular organism
can be divided and still retain
the functions characteristic of life
are called ‘CELLS’

11.  Circulatory system
 Respiratory system
 Digestive system
 Urinary system
 Musculo-Skeletal
 Immune system
 Nervous system
 Endocrine system
 Reproductive system

12. THE CELL
STRUCTURE AND FUNCTION

13. The fundamental unit of life is
CELL

14. A. Cell Membrane
B. Nucleus and its chromosomes
C. Cytoplasm and its organelles

15. PROTOPLASMPROTOPLASM

The different substances that make up the cellThe different substances that make up the cell

Composed of 5 basic substancesComposed of 5 basic substances
Water (70 – 85%)Water (70 – 85%)
ElectrolytesElectrolytes
Proteins (10 – 20%)Proteins (10 – 20%)
Lipids, andLipids, and
Carbohydrates.Carbohydrates.

16. CELL MEMBRANECELL MEMBRANE

Also called the Plasma membraneAlso called the Plasma membrane

7.5 to 10nm thick7.5 to 10nm thick

Composed almost entirely of Proteins and LipidsComposed almost entirely of Proteins and Lipids
Proteins – 55%Proteins – 55%
Phospholipids – 25%Phospholipids – 25%
Cholesterol – 13%Cholesterol – 13%
Other Lipids – 4%Other Lipids – 4%
Carbohydrates – 3%Carbohydrates – 3%

17. MEMBRANE STRUCTUREMEMBRANE STRUCTURE

Danielli – Davson ModelDanielli – Davson Model

Fluid – Mosaic ModelFluid – Mosaic Model
Widely accepted oneWidely accepted one
Proposed by Singer & Nicholson in Proposed by Singer & Nicholson in
19721972
Dynamic in natureDynamic in nature
Presence of Transmembrane proteinsPresence of Transmembrane proteins

19. MEMBRANE LIPIDSMEMBRANE LIPIDS

Amphipathic in natureAmphipathic in nature

Are having Hydrophobic fatty acid tails and Are having Hydrophobic fatty acid tails and
Hydrophilic polar headsHydrophilic polar heads

They show different types of movements They show different types of movements
(Asymmetry) within the membrane(Asymmetry) within the membrane
Lateral diffusion Lateral diffusion
Rotational motionRotational motion
Flip – flop motionFlip – flop motion

20. Membrane LipidsMembrane Lipids

Asymmetric distribution is maintained by Asymmetric distribution is maintained by
Lipid TransportersLipid Transporters
FlippaseFlippase
FloppaseFloppase
Scramblase.Scramblase.

21. MEMBRANE CARBOHYDRATES MEMBRANE CARBOHYDRATES
(Glycocalyx)(Glycocalyx)

Occur in the form of Glycoproteins or Occur in the form of Glycoproteins or
GlycolipidsGlycolipids

Gives most cells an overall negative surface Gives most cells an overall negative surface
chargecharge

Helps in cell adhesion (Glycocalyx – Helps in cell adhesion (Glycocalyx –
Glycocalyx)Glycocalyx)

Some of them enter into immune reactionsSome of them enter into immune reactions

22. Carbohydrates
Carbohydrates
A. Cell Membrane

23. Membrane Proteins

24. - Intrinsic proteins serves mainly as ‘enzymes’
- Extrinsic proteins contribute to the frame
work of cell
- Integral Proteins can serve as
.. Channels
.. Carriers
.. Pumps
.. Receptors

25. Functions :
• Protective
• Digestive
• Selective Permeability
• Frame Work
• Cell Adhesion
A. Cell Membrane

26. B. Nucleus and its Chromosomes
• Structure
Nuclear Membrane
Perinuclear Cistern
Chromosomes
Nucleolus

27. B. Nucleus and its Chromosomes
• Functions
Synthesis of RNA
Hereditary Characteristics
Cellular Reproduction
Cellular Multiplication

28. C. Cytoplasm and its Organelles
1. Endoplasmic Reticulum (ER)
- Agranular (or) Smooth
- Granular (or) Rough

29. C. Cytoplasm and its Organelles
2. Golgi Complex (or Golgi Bodies)
-Packaging Department
-Secretion Granules
-Lysosomes
-Glycoproteins

30. C. Cytoplasm and its Organelles
3. Mitochondrion
-Outer
Membrane
-Inner
Membrane

31. C. Cytoplasm and its Organelles
4. Lysosomes
-Digestive (lytic) System of cell
-Engulf exogenous substances
-Autolysis

32. C. Cytoplasm and its Organelles
5. Centrioles (or) Centrosomes
-Movement of the chromosomes
during cell division

33. C. Cytoplasm and its Organelles
6. Microtubules and Microfilaments
-Movement of the chromosomes
-Cell Movement
-Movement of Proteins

34. C. Cytoplasm and its Organelles
7. Secretion Granules

35. CELLULAR RECEPTORSCELLULAR RECEPTORS

Proteins (Glycoproteins), located either in the Proteins (Glycoproteins), located either in the
cell’s plasma membrane or inside the cell, cell’s plasma membrane or inside the cell,
mainly in the nucleusmainly in the nucleus

Intracellular receptorsIntracellular receptors

Plasma membrane receptorsPlasma membrane receptors

36. Plasma Membrane ReceptorsPlasma Membrane Receptors

Are Transmembrane Proteins. Are Transmembrane Proteins.

They have segments within the membrane, one They have segments within the membrane, one
or more segments extending out from the or more segments extending out from the
membrane in to the extra cellular fluid and membrane in to the extra cellular fluid and
other segments extending in to the cytosolother segments extending in to the cytosol

May be distributed over the entire surface of May be distributed over the entire surface of
the cell or confined to a particular regionthe cell or confined to a particular region

37. ClassificationClassification

Receptors that themselves function as ion channelsReceptors that themselves function as ion channels

Receptors that function as enzymes or are closely Receptors that function as enzymes or are closely
associated with cytoplasmic enzymesassociated with cytoplasmic enzymes

Receptors that activate G proteins, which inturn act Receptors that activate G proteins, which inturn act
upon effector proteins – either ion channels or upon effector proteins – either ion channels or
enzymes – in the plasma membraneenzymes – in the plasma membrane

38. Receptors – Function as ion channels

42. INTRACELLULAR RECEPTORSINTRACELLULAR RECEPTORS

Function in the nucleus as transcription factors Function in the nucleus as transcription factors
to alter the rate of transcription of particular to alter the rate of transcription of particular
genes.genes.

44. Messenger – Receptor InteractionsMessenger – Receptor Interactions

SpecificitySpecificity

SaturationSaturation

CompetitionCompetition
a) antagonisma) antagonism
b) agonismb) agonism

45. Regulation of ReceptorsRegulation of Receptors

Up – regulationUp – regulation

Down – regulationDown – regulation

RECEPTOR ACTIVATIONRECEPTOR ACTIVATION
The event of combination of messenger The event of combination of messenger
with receptor that causes a change in the with receptor that causes a change in the
conformation of the receptor conformation of the receptor

46. Cell to Cell Signaling
AUTOCRINE
PARACRINE
ENDOCRINE

47. Signal Transduction PathwaysSignal Transduction Pathways

The sequence of events between receptor The sequence of events between receptor
activation and the responsesactivation and the responses

Signal - - - Receptor activationSignal - - - Receptor activation

Transduction - - - The process by which a Transduction - - - The process by which a
stimulus is transformed in to a response stimulus is transformed in to a response

48. Transport across the
Cell Membrane

49. Chemical Compositions
of Extracellular &
Intracellular Fluids

50. Passive Transport Active Transport
• Diffusion
Simple
Facilitated
• Osmosis
Osmotic Pressure
Tonicity
• Primary
• Secondary
• Vesicular

51. Passive Transport

52.  Diffusion
The movement of molecules from one location
to another solely as a result of their random thermal
motion is known as ‘diffusion’.

53.  Simple Diffusion
The kinetic movement of molecules or ions occurs
through a membrane opening or through intermolecular
spaces without necessity of binding with carrier proteins
in the membrane is called as ‘Simple Diffusion’

54.  Simple Diffusion
• Factors affecting diffusion
- Thickness (or) Distance (T)
- Gradient (C
in
– C
out
)
- Surface Area (A)
- Temperature
- Molecular Size
- Lipid Solubility

55.  Simple Diffusion
Fick’s Law of Diffusion :
Net rate diffusion
(net flux)
=
Diffusion Coefficient (D) x Surface Area (A)
Thickness of membrane (T)
(or diffusion distance)
(C
in
– C
out
)x

56.  Simple Diffusion
Gated Channels :
- Voltage gated
- Ligand gated
- Mechano Sensitive

57.  Facilitated Diffusion
• Difusion of substance through the membrane with the help
of specific carrier protein without any energy expenditure
is called ‘Facilitated Diffusion’.
• It is also called ‘Carrier mediated diffusion’

59.  Facilitated Diffusion
Eg.. Glucose transport by the glucose transporter (GLUT)

60.  Facilitated Diffusion

61.  Facilitated Diffusion
• Factors determining
- Transporter binding sites
- No. of transporters
- Confirmational changes

63. Osmosis

64.  Osmosis
The diffusion of solvent molecules into a
region in which there is a higher concentration
of a solute to which the membrane is imperme
-able is called ‘Osmosis’.

65.  Osmosis

66.  Osmotic Pressure
The pressure necessary to prevent solvent
migration/movement is called ‘osmotic pressure’
of the solution.
Osmotic Pressure of solution depends upon
- No. of particles
- Temperature
- Pressure

67.  Osmolal Concentration of Plasma:
Tonicity
What is concentration ?
Concentration of osmotically active particles is expressed
in ‘osmoles(osm)’ or ‘milliosmoles’(1/1000 of 1 osm).
Osmolarity – The number of osmoles per liter of solution.
Osmolality – The number of osmoles per kilogram of the
solvent.

68. The osmolality of normal human plasma is 290 mosm/L.
 Tonicity
The osmolality of a solution relative to plasma is called
‘tonicity’.
Isotonic  same osmolality as plasma
(eg. 0.9% Sodium Chloride or 5% glucose)
Hypertonic  grater osmolality than plasma
Hypotonic  lesser osmolality than plasma

69. Clinical Significance :
 Tonicity
Assessment of dehydration, overhydration
and other fluid and electrolyte abnormalities

70.  Tonicity

72. Active Transport

73. Active Transport
When a substance moves through cell
Membrane against chemical (or) electrical
(or) pressure gradient by utilizing the energy
is called ‘active transport.’
Energy is provided by ATP (or) other
high energy phosphate compounds

74.  Primary Active Transport
Active transport is of two types according
to the source of energy used
 Secondary Active Transport

75.  Primary Active Transport
Substances utilizes the energy
directly from the breakdown of ATP (or)
other high energy phosphate compounds
to cross the cell membrane.
It is also called as direct energy utilizing
process.

76.  Primary Active Transport

77. 1. Na
+
- K
+
ATPase Pump in most of the cell membranes
2. Calcium(Ca
2+
) Pump sarcoplasmic reticulum
3. H
+
pump by distal tubular cells of nephron
 Primary Active Transport

78.  Secondary Active Transport
When the transport of a substance across
the membrane is coupled to the active trans-
port of other substance is called ‘secondary
active transport’.

79.  Secondary Active Transport

80.  Secondary Active Transport
It is of two types
- Symport (co-transport)
- Antiport (counter transport)

81. Examples :
1. Na+ and Glucose transport in the intestine and
renal tubules
2. Cl ¯ – HCO
3
¯
in Red Blood Cells
3. H
+
- K
+
pump in gastric parietal cells
 Secondary Active Transport

82. Active transport Through
Cellular Sheets

83.  Vesicular Transport
• This is also called as Transcytosis.
• It is the process by which extracellular substances
(macro molecules such as proteins, lipids, dead
cells, foreign particles, bacteria and small amount
of fluids) are moves into the cells.

84.  Vesicular Transport
It is of two types :
1.Endocytosis
2.Exocytosis

85.  Endocytosis

86.  Endocytosis

87. What is pinocytosis .. ?

88.  Exocytosis
I
n
s
i
d
e

o
f

t
h
e

c
e
l
l
O
u
t
s
i
d
e

o
f

t
h
e

c
e
l
l

89. Example : Secretion of hormones, digestive enzymes
and synaptic transmitter etc…
 Exocytosis

90. MOVEMENT THROUGH
LIPID
BILAYER
PROTEIN
CHANNEL
FACILI-
TATED
PRIMARY
ACTIVE
SECONDARY
ACTIVE
Non-polar,
O2, CO2,
fatty acids
Ions :
Sodium,
Potassium,
Calcium
Polar :
Glucose
Ions :
Sodium,
Potassium
Calcium
Hydrogen
Polar :
Amino acids
Glucose
Some ions

91. Diffusion Mediated Transport
Through
lipid
bilayer
Through
Protein
channel
Facilitated
diffusion
Primary
active
transport
Secondary
active
transport
Direction of net
flux High to lowHigh to lowHigh to lowLow to highLow to high
Equilibrium or
steady state
can be
achieved
Yes Yes Yes No No
Use of integral
membrane
protein
No Yes Yes Yes Yes
Maximal flux at
high
concentration
No No Yes Yes Yes
Use of energy and
source No No No Yes Yes

92. • Structure and Functions of
DNA & RNA
• Body Water & Body Fluids

93. Structure and Functions of
DNA & RNA

94. Nucleic acids are responsible for the storage, expression,
and transmission of genetic information.
There are two classes of nucleic acids –
1. Deoxyribonucleic Acid (DNA)
2. Ribonucleic Acid (RNA)
Both types nucleic acids are polymers and are therefore
composed of linear sequences of repeating subunits – known as
‘nucleotide’

95. Each nucleotide has three components –
… a phosphate group
… a sugar
… a ring of carbon & nitrogen atoms (base)

96. • DNA is made up of two extremely
long nucleotide chains containing the
bases adenine(A), guanine(G), thymine(T)
and cytosine(C).
• The chains are bound together by
hydrogen bonding between the bases,
with adenine bonding to thymine and
guanine to cytosine.
DOUBLE HELICAL STRUCTURE
DNA double helical structure was proposed
by Watson & Crick
Deoxyribo Nucleic Acid

97. • DNA is component of chromosomes
that carry the “genetic message”.
• Major Groove – 34 A
o
• Minor Groove – 3.4 A
o
• DNA is made up of 3 x 10
9
base pairs
• Genes are the functional units DNA
• DNA acts as template for the synthesis
of RNA.
• DNA molecules store genetic informa-
tion in the sequence of purine and
pyramidine bases.
• Mutations occur when the base seque-
nce in the DNA is altered by X-rays,
Cosmic rays, or mutagenic agents.

98. • RNA consists of a single chain of nucleotides
• Sugar in the each nucleotide is ribose
• Pyramidine base thymine is replaced by
Uracil which can pair with the purine
Adenine
• RNA molecules are involved in the
decoding of information in DNA into
instructions for linking together a
specific sequence of amino acids
to form a specific polypetide chain.
Ribonucleic Acid (RNA)

99. • 3 types RNA are present
- mRNA
- tRNA
- rRNA
• tRNA transfers the amino acids for
protein synthesis
• mRNA acts as messenger

100. RNA DNA
Single-StrandedDouble-Stranded
Has Uracil as a
base
Has Thymine as a
base
Ribose as the
sugar
Deoxyribose as
the sugar
Uses protein-
encoding
information
Maintains protein-
encoding
information
Differences between

101. BODY WATER
and
BODY FLUIDS

102. The body water is distributed in two compartments :
1. Intracellular space
2. Extracellular space

103. Extracellular Fluid : The fluid which is present in extracellular space
is called ‘extracellular fluid’.
Extracellular fluid includes :
A. Extravascular –
1. Interstitial
fluid
2. Transcellular
fluid
3. Lymph
B. Intravascular –
1. Plasma
CSFCSF
Ocular FluidsOcular Fluids
Peritoneal fluidPeritoneal fluid
Pleural fluidPleural fluid
Synovial fluidSynovial fluid
GIT secretionsGIT secretions
Intracellular Fluid : The fluid which is present in intracellular space
is called ‘intracellular fluid’.

104. Intracellular fluid
Volume = 28 L, 2/3 TBW
Interstitial fluid
Volume = 10.5 L
75% of ECF
Plasma
Volume=3.5 L
25% of ECF
Total Body Water (TBW)
Volume = 42 L, 60% of body weight
Extracellular
fluid
Volume = 14 L, 1/3 TBW
DISTRIBUTION OF TOTAL BODY WATER (TBW)

105. MEASUREMENT OF BODY FLUID VOLUMES :
The volume of fluid in each compartment can be measured
by the ‘indicator dilution principle’.
Volume of distribution =
Amount of substance injected (A)
Concentration of substance (C)
If indicator leaves compartment by excretion (or) metabolism
during the mixing period. Then
Volume of distribution =
Amount of substance injected (A) - Removed
Concentration of substance (C)

106. Indicator – dilution method for Indicator – dilution method for
measuring fluid volumesmeasuring fluid volumes

107. Characteristics of the indicator :
- Nontoxic
- Uniform distribution
- Should not alter water distribution
- No changes during mixing period or amount
changed must be known
- Easy to measure

108. Total Body Water :
It can be determined by using Deuterium (or) Tritium (or)
Antipyrin.
Total Body Water in ml =
Total radioactivity injected
Average radioactivity/ml

109. Extracellular Fluid :
It can be measured by using Inulin.
It can also be measured by radioactive isotopes of Cl¯ ,
82
Br, Sulphate, thiosulphate, thiocyanate and ferrocyanide.
Mannitol and sucrose can also be used to measure ECF.

110. It can be measured by using Evans Blue Dye (T-1824), Radio-
iodinated human serum albumin (RISA) and Radio-iodinated gamma
globulin & fibrinogen.
Plasma Volume
Total Blood Volume
Total Blood Volume =Plasma Volume X
100
100
¯ Hematocrit
Interstitial Fluid Volume = ECF Volume
¯
Plasma Volume
Interstitial Fluid Volume

111. Intracellular Fluid :
It cannot be measured.
It can be measured by indirect method by measuring
the total body water and extracellular fluid.
Intracellular Fluid = Total Body Water - Extracellular Fluid

112. Clinical Significance :
When the water intake is more than output then a positive water
balance develops.
Physiological Positive Physiological Positive
Water BalanceWater Balance
Pathological Positive Pathological Positive
Water BalanceWater Balance
1. During growth1. During growth
2. Convalescence2. Convalescence
3. Pregnancy3. Pregnancy
1. Heart failure1. Heart failure
2. Renal failure2. Renal failure
3. Malnutrition3. Malnutrition
4. Inflammation of tissue (local)4. Inflammation of tissue (local)
When the water intake is less than output then a negative water
balance develops.
Physiological Negative Physiological Negative
Water BalanceWater Balance
Pathological Negative Pathological Negative
Water BalanceWater Balance
1. Exercise1. Exercise 1. Dehydration1. Dehydration
2. Burns2. Burns
3. Haemorrhage3. Haemorrhage
4. Vomitting4. Vomitting
5. Diarhoea5. Diarhoea

113. IONIC DISTRIBUTION IN THE VARIOUS BODY FLUIDS
(Concentration in mEq/L of water)
Ion Plasma Interstitial FluidIntracellular Fluid
Cations   
Sodium 153 145 12
Potassium 5.4 5 155
Magnesium 1.9 5 15
Others 2.7 5 2
Total Cations 163 154 184
    
Anions   
Chloride 111 110 8
Bicarbonate 26 27 8
Phosphate 1 2 90
Proteins 17.2 15 60
Others 7.6 - 18
Total Anions 163 154 184
Total Ions326 308 368

114. Ion
Concentration
( mmol/L of water )
Inside of cellOutside of cell
Sodium 15 150
Potassium 150 5.5
Chloride 9 125

115. Ion
Concentration
( mmol/L of water )
Inside of cellOutside of cell
Sodium 15 150
Potassium 150 5.5
Chloride 9 125
What is the barrier between ECF and ICF ?
What causes differences in ionic composition ?
Why are there differences in the permeability of cell membrane
to various small ions ?

116. Increased Water Intake
Decreased
Plasma Osmolality
Decreased ADH secretion
Decreased water reabsorption
by collective ducts
Increased water excretion
Increased thirst
Increased Water Intake
Normal Osmolality
Water loss
Increased
plasma osmolality
Increased ADH secretion
Increased Water
reabsorption
by coll.ducts
Decreased urine output
Maintenance of the Osmolality of the Body Fluids
After a Water load or Pure Water loss

117. Clinical Abnormalities of Fluid Clinical Abnormalities of Fluid
Volume RegulationVolume Regulation
Hyponatremia:- Plasma sodium Hyponatremia:- Plasma sodium
concentration is reduced below concentration is reduced below
normalnormal
Hypernatremia:- Plasma sodium Hypernatremia:- Plasma sodium
concentration is elevated above concentration is elevated above
normalnormal

118. Hyponatremia: causesHyponatremia: causes
Hypo - osmotic dehydrationHypo - osmotic dehydration
diarrhea and vomitingdiarrhea and vomiting
Hypo – osmotic overhydrationHypo – osmotic overhydration

119. Hypernatremia: causesHypernatremia: causes
Hyperosmotic dehydrationHyperosmotic dehydration
Hyperosmotic overhydrationHyperosmotic overhydration

120. EDEMAEDEMA
Presence of excess fluid in the body Presence of excess fluid in the body
tissuestissues
Intracellular edemaIntracellular edema
Extracellular edemaExtracellular edema

121. EdemaEdema
Intracellular edemaIntracellular edema
1) depression of the metabolic 1) depression of the metabolic
systems of the tissuessystems of the tissues
2) lack of adequate nutrition to the 2) lack of adequate nutrition to the
tissuestissues

122. EdemaEdema
Extracellular edemaExtracellular edema
1) abnormal leakage of fluid from the 1) abnormal leakage of fluid from the
plasma to the interstitial spaces plasma to the interstitial spaces
across the capillariesacross the capillaries
2) failure of the lymphatics to return 2) failure of the lymphatics to return
fluid from the interstitium back into fluid from the interstitium back into
the blood the blood

123. Edema and HypoproteinaemiaEdema and Hypoproteinaemia
Hypoproteinaemia because of either Hypoproteinaemia because of either
failure to produce normal amounts of failure to produce normal amounts of
proteins or leakage of proteins from proteins or leakage of proteins from
the plasmathe plasma
Plasma colloid osmotic pressure fallsPlasma colloid osmotic pressure falls
Increased capillary filtration Increased capillary filtration
throughout the body as well as throughout the body as well as
Extracellular edemaExtracellular edema

124. Conditions that lead to Conditions that lead to
hypoproteinaemiahypoproteinaemia
Nephrotic syndromeNephrotic syndrome
Cirrhosis of liver:- development of Cirrhosis of liver:- development of
large amounts of fibrous tissue large amounts of fibrous tissue
among the liver parenchyma cells among the liver parenchyma cells

125. Resting Membrane Potential
( RMP )

126. Resting Membrane Potential :
The potential difference that exists between the
extracellular fluid and intracellular fluid when the cell
is at rest. This potential is the ‘resting membrane
potential (RMP)’.
All cells under resting conditions have a potential
difference across their plasma membranes with the inside
of the cell negatively charged with respect to the outside.

127. Resting Membrane Potential :

128. Resting Membrane Potential :
It is also termed as ‘steady potential’ (or) ‘trans-
membrane potential’.
The polarity of the membrane potential is stated in
terms of the sign of the excess charge on the inside of
the cell.
The magnitude of RMP varies from about -5 mV to
-100 mV.
Eg.. Nerve Cells – 40 to – 70 mV

129. Genesis of RMP : The distribution of ions across
the membrane and nature of the membrane explains
reason for resting membrane potential.
• The concentration gradient and electrical gradient for K
+
•

Na
+
influx can’t compensate for K
+
influx
• The concentration gradient and electrical gradient for Cl¯
•

Na
+
- K
+
ATPase pump maintains the RMP
No. of ions responsible for RMP…. ?
Administration of metabolic inhibitors…. ?

130. Variations in RMP :
The magnitude of membrane potential at any
given time depends upon the distribution of Na
+
, K
+
and Cl¯
and the permeability of the membrane to each of the ions.
The relationship can be described by Goldman-
Hodgkin-Katz equation.

131. Goldman-Hodgkin-Katz (GHK) equation :-
P
K
[K
+
]
in
+ P
Na
[Na
+
]
in
+ P
Cl
[Cl¯]
out
P
K
[K
+
]
out
+ P
Na
[Na
+
]
out
+ P
Cl
[Cl¯]
in
RT
N
lnV =
where,
V = membrane potential
R = the natural gas constant
T = absolute temparature
F = the Faraday constant
ln= symbol for natural logarithm
P
Cl
, P
K
and P
Na
= permeability of membrane
[ ]
in
and [ ]
out
= concentration of ions inside
and outside the cell

132. Factors that determine the RMP :
• The concentration gradient for each ion to which the
membrane is permeable
• The relative permeability (or) conductance of the
membrane for each ion

133. Action Potential ( AP )
• Definition
• Origin
• Phases
• Ionic basis
• Properties
• Electrotonic Potentials

134. Definition :
The brief sequence of changes that takes
place in the membrane potential in response to
threshold stimulus following its restoration to
the resting level is called ‘action potential’.

135. Origin :
Electrically excitable cells
eg.. nerve cells
muscle cells

136. Phases :
-70
-55
0
+35
m
e
m
b
r
a
n
e

p
o
t
e
n
t
i
a
l

(

m
V

)
Time ( msec )
1
2
3
4
5
6
7
8
Overshoot
Spike

137. Ionic Basis :
-70
-55
0
+35
m
e
m
b
r
a
n
e

p
o
t
e
n
t
i
a
l

(

m
V

)
Time ( msec )
1
2
3
4
5
6
7
8
Overshoot
Spike

138. Properties :
1. Threshold Stimulus
2. All or none response
3. Refractory Period
4. Conductivity
5. Accommodation

139. -70
-55
0
+35
m
e
m
b
r
a
n
e

p
o
t
e
n
t
i
a
l

(

m
V

)
Time ( msec )
1
2
3
4
5
6
7
8
Overshoot
Spike

140. Electrotonic Potentials – Graded Potential
Graded potentials are changes in the
Membrane potential which fail to elicit action
Potential and that are confined to a relatively
Small region of the membrane and their
Magnitude is variable.
eg. End-plate potential
Pacemaker potential
Post-synaptic potential
Receptor potential

141. Properties :
Graded Potential Action Potential
Amplitude varies with conditions of the
initiating event All-or-none
Can be summed Cannot be summed
No threshold Elicited to threshold stimulus
No refractory period Refractory period is present
Conducted decrementally
Conduction is without
decrement
Duration varies with initiating conditions
Duration is constant for a
given cell type
Can be depolarisation (or) hyperpolarisationIs only a depolarisation
Initiated by environmental
stimulus(receptor), by neurotransmitter
(synapse), or spontaneously Initiated by graded potential

143. a.Desmosomes

145. c.Gap junctions :

146. CELLULAR RECEPTORSCELLULAR RECEPTORS

Proteins (Glycoproteins), located either in the Proteins (Glycoproteins), located either in the
cell’s plasma membrane or inside the cell, cell’s plasma membrane or inside the cell,
mainly in the nucleusmainly in the nucleus

Intracellular receptorsIntracellular receptors

Plasma membrane receptorsPlasma membrane receptors

147. Plasma Membrane ReceptorsPlasma Membrane Receptors

Are Transmembrane Proteins. Are Transmembrane Proteins.

They have segments within the membrane, one They have segments within the membrane, one
or more segments extending out from the or more segments extending out from the
membrane in to the extra cellular fluid and membrane in to the extra cellular fluid and
other segments extending in to the cytosolother segments extending in to the cytosol

May be distributed over the entire surface of May be distributed over the entire surface of
the cell or confined to a particular regionthe cell or confined to a particular region

148. Messenger – Receptor InteractionsMessenger – Receptor Interactions

SpecificitySpecificity

SaturationSaturation

CompetitionCompetition
a) antagonisma) antagonism
b) agonismb) agonism

149. Regulation of ReceptorsRegulation of Receptors

Up – regulationUp – regulation

Down – regulationDown – regulation

RECEPTOR ACTIVATIONRECEPTOR ACTIVATION
The event of combination of messenger The event of combination of messenger
with receptor that causes a change in the with receptor that causes a change in the
conformation of the receptor conformation of the receptor

150. Cell to Cell Signaling
AUTOCRINE
PARACRINE
ENDOCRINE

151. Signal Transduction PathwaysSignal Transduction Pathways

The sequence of events between receptor The sequence of events between receptor
activation and the responsesactivation and the responses

Signal - - - Receptor activationSignal - - - Receptor activation

Transduction - - - The process by which a Transduction - - - The process by which a
stimulus is transformed in to a response stimulus is transformed in to a response

152. ClassificationClassification

Receptors that themselves function as ion channelsReceptors that themselves function as ion channels

Receptors that function as enzymes or are closely Receptors that function as enzymes or are closely
associated with cytoplasmic enzymesassociated with cytoplasmic enzymes

Receptors that activate G proteins, which inturn act Receptors that activate G proteins, which inturn act
upon effector proteins – either ion channels or upon effector proteins – either ion channels or
enzymes – in the plasma membraneenzymes – in the plasma membrane

153. Receptors – Function as ion channels

156. INTRACELLULAR RECEPTORSINTRACELLULAR RECEPTORS

Function in the nucleus as transcription factors Function in the nucleus as transcription factors
to alter the rate of transcription of particular to alter the rate of transcription of particular
genes.genes.

158. HOMEOSTASIS
Maintenance of internal environment of the cell
i.e. millieu interior in terms of volume, composition, con-
centration, p
H
and temperature with in the physiological
limits with respect to minor changes in the body. The
mechanisms which act to stabilize the internal environment,
are called ‘Homeostasis’. This concept is put forward by
Walter B. Cannon(1871- 1945) an American Physiologist

159. Homeostatic Regulation : The mechanisms in
physiological systems that are responsible for
the preservation of homeostasis are referred to
as Homeostatic Regulation.
It is brought about by two mechanisms
1. Negative Feedback Mechanisms
2. Positive Feedback Mechanisms

160. Feed Back System – Components.Feed Back System – Components.

Control Centre – receives informationControl Centre – receives information

Receptor – monitors changes in the Receptor – monitors changes in the
controlled condition, send inputs to the controlled condition, send inputs to the
control centrecontrol centre

Effector – receives output form the Effector – receives output form the
control centre and produces a responsecontrol centre and produces a response

161. Stimulus
Controlled condition
Receptors
Control centre
Effectors
Response
Components of Feed Back System

162. Feed Back SystemFeed Back System

Homeostasis of BP - -ve feed backHomeostasis of BP - -ve feed back

Homeostasis of Labor Contractions - +ve feed Homeostasis of Labor Contractions - +ve feed
backback

163. Stimulus (stress)
Controlled condition (BP)
Receptors
Control centre (brain)
Effectors
*heart rate decrease
*arterioles dilate
Response (decrease in BP)
NEGATIVE FEED BACK SYSTEM

164. Stimulus (stretching of the uterus)
Receptors (pressure – sensitive nerve cells in uterine wall)
Control centre
Controlled condition
(muscular contraction of the uterus increases)
input
output Release of oxytocin
Positive Feed Back Mechanism

165. Disease – Homeostatic ImbalanceDisease – Homeostatic Imbalance

A Disease is a pathological process, with a A Disease is a pathological process, with a
definite set of characteristics in which a part or definite set of characteristics in which a part or
all of the body is not carrying on its normal all of the body is not carrying on its normal
functions.functions.

Local disease and Systemic disease.Local disease and Systemic disease.

May experience certain symptoms for a May experience certain symptoms for a
disease.disease.

Symptoms – either Subjective or Objective Symptoms – either Subjective or Objective
changes. changes.