1. 14 exam questions (8 on Lectures 1-3 6 on lecture 4)
Logothetis Review
14 exam questions
(8 on Lectures 1-3
6 on lecture 4)

2. Lecture 1
Membrane Potentials:
Ion Movement - Forces

3. The distribution of unbalanced charges at the membrane boundary accounts for the membrane potential
V = Q / C
C =  A / 4  d

4. Distribution of Ions and the Resting Potential
Na+ = 145 mM
Na+ = 15 mM
K+ = 5 mM
K+ = 145 mM
Depolarization
Plateau
Repolarization
Cl- = 125 mM
Cl- = 10 mM
In the normal myocyte, depolarization results from inward sodium current.
The plateau phase results from a balance of inward calcium current and outward potassium current,
and finally, repolarization results from unopposed outward potassium current.
Ca++ = 2 mM
Ca++ = mM

5. Equlibrium potentials for major permeable ionic species
In myocytes:
ENa = 61 log (145/15) = + 60 mV
ECa = 30.5 log (2/.0001) = mV
ECl = -61 log (125/ 10) = - 67 mV
EK = 61 log (5/ 145) = mV

6. V = I R => I = V/R or I = g V (where g = 1/R)
Ohm’s Law
V = I R => I = V/R or I = g V (where g = 1/R)

7. The direction of ion movement
An example:
Chemical vs electrical force and Net force
Ohms law
Rule of thumb: Whenever Vm is more negative than Ex, the current is inward. Whenever Vm is more positive than Ex, the current is outward. At Ex the current is zero (i.e. equilibrium)
Whenever an ion channel opens and ions move down the electrochemical gradient, the membrane potential will move towards the equilibrium potential for that ion

8. Ion channel nomenclature (by gating stimulus)

9. Resting potential, Measurement of Ion Movement
Lecture 2
Resting potential, Measurement of Ion Movement
Voltage-gated channels

10. gK (VR – EK) = -gNa (VR – ENa)
At the resting membrane potential the individual ionic currents sum up to zero
I = g V
IK = gK (Vm – EK)
INa = gNa (Vm – ENa)
At rest IK = -INa
gK (VR – EK) = -gNa (VR – ENa)
If gK:gNa = 5, solve for VR
VR = -64 mV
VR = (ENagNa/gK+gNa) +
(EKgK/gK+gNa)

11. Voltage Clamp

12. The Patch-clamp technique

13. Driving Force: Vm - Ex I = g Vm IK = gK (Vm – EK)
EK = 61 log (150/ 150) = 0 mV
EK = 61 log (150/ 45) = + 32 mV
EK = 61 log (30/ 150) = mV

14. The depolarization-induced biphasic current of squid giant axons

15. Sodium and Potassium whole-cell currents

16. The ionic basis of the Action Potential
Lecture 3
The ionic basis of the Action Potential

17. Effect of K+ or Na+ channel activation on membrane potential

18. Mechanism of fast inactivation of voltage-gated channels

19. The Action Potential (AP) of a Squid Giant Axon

20. Absolute Refractory Period – This is the time interval after the peak of an action potential during which a second depolarizing stimulus will fail to produce a second action potential, irrespective of the stimulus intensity. The reason such a period exists is that for a period of msec following the peak of an action potential a large proportion of the Na+ channels are in the nonconducting inactivation state.  
Relative Refractory Period – This is the time interval after the peak of an action potential during which a second depolarizing stimulus will produce a second action potential, but only if the stimulus intensity is increased. The relative refractory period arises because toward the end of an action potential the K+ permeability remains higher than the resting K+ permeability for a brief period. The membrane potential is, therefore, more hyperpolarized than the normal resting potential (the hyperpolarizing afterpotential or undershoot). It, therefore, requires a stronger depolarizing stimulus to take the potential to threshold. Also a small proportion of the Na+ channels remaining in the inactive state may also contribute to the relative refractory period.  
Accommodation – Whether or not a depolarizing stimulus will produce an action potential depends on the rate of depolarization as well as the magnitude. If the rate of depolarization is too slow the threshold for firing will be raised or firing will not occur at all. The reason is that a slow rate of depolarization allows a large proportion of the Na+ channel inactivation gates to close before a large proportion of the activation gates have opened.

21. Threshold potential for AP generation

22. Action Potential Propagation Neuromuscular Transmission
Lecture 4
Action Potential Propagation
Neuromuscular Transmission

23. The propagation of an AP along an axon

24. Passive spread of depolarization
 = distance over which Vm falls to 1/e of initial depolarized value
From Lodish et al., Molecular Cell Biology, 4th edition – Fig

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© 2005 Elsevier

27. The conduction velocity of action potentials
 = time it takes for Vm to reach 63% of steady state

28. Action Potential Propagation: Saltatory Conduction
Myelin: a fatty sheath made by wrapping membranes around axons
Myelination carried out by Schwann cells (PNS) or oligodendrocytes
(CNS)
Node of Ranvier
Internode regions

29. Nodes of Ranvier

30. AP propagation: the circuit and the effect of myelin

31. Extracellular Recordings

32. Signaling in the neuromuscular junction

33. End Plate Potential (EPP)

34. Effect of AChE on EPP

35. Ionic basis of the EPP

36. ACh release from the presynaptic nerve terminal

37. The Ca2+ influx hypothesis for transmitter release

38. Miniature EPPs (or MEPPs)

39. Relation of MEPPs and EPPs