Action Potentials

Question 1

action potential threshold

Answer 1

voltage point that once exceeded initiates the all or nothing response of neurons firing. Inward flow of Na, outward flow of K+

Question 2

Na_v gates

Answer 2

at resting inactivation gate is open and activation is closed. Depolarization both are open. Repolarization activation gate is open, inactivation is closed

Question 3

positive-feedback of rising phase

Answer 3

rising voltage due to Na channels causes the opening of adjacent Na channels, which further increases Vm

Question 4

Na/K pump during AP

Answer 4

Na/K pump is responsible is called upon to restore proper ion balance. If poisoned axon will fill with Na and lose K. pump is always on, doesn’t go into mega mode or anything

Question 5

Refactory period

Answer 5

after AP, axon cannot produce another one for a few milliseconds. Divided into absolute refractory and relative refractory. Results from inactivation gate closer of Na channel requiring time to reopen after repolarization. Even with a stimulus, Na activation gate may open, but inactivation stays closed. thus no AP

Question 6

internal resistance

Answer 6

high Ri => smaller spread of current

Question 7

membrane resistance

Answer 7

higher Rm => larger spread of current

Question 8

membrane capacitance

Answer 8

higher Cm => smaller spread of current

Question 9

Axons are poor cables

Answer 9

Rm is low, Ri is high, Cm is high, lambda is 1mm

Question 10

diameter and conduction velocity

Answer 10

larger diameter, slower conductance (temp and pain receptors smaller than skin mechanoreception)

Question 11

Myelination and conduction

Answer 11

increase conduction speed by requiring less Na channels to fire