3. Secondary Active Transport
In secondary active transport the energy is derived secondarily from energy that has been stored in the form of ionic concentration differences of secondary molecular or ionic substances between the two sides of a cell membrane created originally by primary active transport.

4. Co Transport Sodium Glucose Co transport
Sodium Amino acid Co transport

5. Sodium Glucose Co - transport

6. Counter Transport Sodium calcium counter transport
Sodium Hydrogen counter transport

9. MEMBRANE POTENTIALS

10. OBJECTIVES At the end of this lecture you should know:
1. Ionic distribution across the cell membrane
2. Different types of channels present in the cell membrane.
3. Role of different ions in the development of Resting Membrane Potential

11. Excitable Tissues -Muscle Definition: Imp.
Tissues which are capable of responding to stimuli to highest degree than other tissues of the body in the form of electrical signals.
Imp.
Excitable tissues have LOW Threshold of Stimulation
-Nerve
-Muscle

12. Resting Membrane Potential
Definition
Potential difference existing across the
cell membrane under resting condition .

13. Distribution of Ions across the membrane
Na+ mainly extracellular---
142 mEq/L
K+ mainly intracellular-----
140 mEq/L
Cl- mainly extra cellular–
108 mEq/L
Non-diffusible intracellular anions.
-- HPO4 –
-- SO4--
---Intracellular proteins
(4 times as in the plasma)
Proteins x 10 times
HPO4--

14. Types of Channels in the cell Membrane
Na+
* Leak Channels (Slow) K+
-Voltage gated channels ( Fast ) — For Na+ & K+
Slow Ca++ - Na+ Channels
-Ligand Gated Channels --- Neurotransmitters, Hormones
Na+, K+ & Cl- channels
-Na+ - K+ Pump ( ATP ase )
-Mechanical Gated Channels – Hair Cells ( inner Ear)

15. Leak Channels
Why K+ Leak Channels are More Permeable than Na+ Leak Channels
0.5 x 0.3 nm
0.3 x 0.3 nm
Na+ K+

17. Nernst Potential EMF = ± 61 x log (Cin / Cout)
The potential across the cell membrane at which the net diffusion of ions across the cell membrane due to concentration gradient stops.
Nernst Equation:
EMF = ± 61 x log (Cin / Cout)
Where 61 is constant & is = RT / z F
Where R= Universal Gas constt
T = Absolute Temp, z = ion Valence
F = Faraday, an electrical Constt

18. Equilibrium (Nernst) Potential for Na+
Na+ outside = 142 m Eq/L
} 61x log 0.1 = +61mv
Na+ inside = 14 m Eq/L

19. Equilibrium(Nernst) Potential for K+
K+ outside = 4.0 m Eq/L
}61x log 35= –94mv
K+ inside = 140 m Eq/L

20. Na+ - K+ PUMP (ATPase) Intracellular portion of alpha subunit has:
Na+ binding site (1),
Phosphorylation site (4)
an ATP binding site (5).
Extracellular portion has :
K+ binding site (2) &
Ouabain site (3)

21. Contribution of Na+-K+ Pump (ATPase)
-4mv

22. Functions of Na+ - K+ Pump (ATPase)
1. As an Enzyme (Cleaves ATP to ADP)
2. Electrogenic. (Contributes -4mv in RMP)
3. Homeostasis of Main Electrolytes and Water & hence volume of the cell.
Hormones Increasing functions of ATPase
-Thyroxin, Aldosterone & Insulin.
- Dopamin decreases its function

23. Goldman Hodgkin-Katz- Equation
EMF(mv)=
CNa+ in PNa+ + CK+ in PK+ + CCl-out PCl-
-61. Log
CNa+ out PNa+ + CK+out PK+ + CCl- inPCl-
Where ‘C’=Concentration
P= Permeability

24. Goldman Hodgkin-Katz- Equation
Is used to calculate the Diffusion potential when the membrane is permeable to different ions .
1.Polarity of electrical charge.
2.Permeability of the membrane to ions.
3.Concentration of the respective ion on inside or outside

25. Resting Membrane Potential in Various Excitable Tissues
Large Mylinated Nerve fibers
Skeletal Muscle Fibers = -90mv
Ventricular Muscle fibers
Smooth Muscle fiber & } = -55 o -60 mv
Self Excitatory Tissues

26. Measurement of RMP

27. Types of Disturbances across the Cell Membrane
TWO Types:
Non-Propagated Potentials.
- Synaptic
- Generator Catelectrotonic
- Electrotonic {
Anelctrotonic
Propagated – Action Potential

28. ACTION POTENTIAL Definition: c. Chemical
Abrupt / sudden Change (reversal) in resting membrane potential in response to a threshold stimulus.
Stimulus:
Defn: “Any Change in the environment”
TYPES: a. Electrical
b. Mechanical
c. Chemical

29. Phases of Action Potential
-Polarized state
(Resting membrane Potential)
-Depolarization
- Repolarization
-Positive After Potential
(After-Hyper polarization)

30. Types of Channels involved in Various Excitable Tissues
Voltage gated channels (fast) Na / K
Slow Ca++- Na+ Channels
Ligand Gated Channels
Na+ - K+ Pump
Mechanical Gated Channels (Hair Cells )

31. Voltage Gated Na+ Channels

32. Voltage Gated Na+ Channels

33. Voltage Gated K+ Channels

34. Action Potential in Large Myelinated Nerve fiber

35. Action Potential with Plateau (Cardiac Muscle)
Red curve shows rise and fall in tension of ventricular myocyte

36. Action Potential in Self Excitatory Tissues(S-A Node)
-55-
-55
Diastolic DepolarizationDepolarization)

37. Action Potential in Smooth Muscle

38. Compound Action Potential

39. Biphasic Action Potential (Both electrodes are outside the membrane)

40. Recording of Membrane and Action Potential

41. Propagation (Transmission) of Action Potential
Electrotonic Conduction.

42. Propagation of Action Potential-II (Saltatory Conduction)
channels/ Sq Micro Meter

43. (Saltatory Conduction)
channel/
Sq Micro Meter