Chapter 7 Study Questions (Part 3)

Question 1

the inactivation gate ensures that the AP only goes _____, and ______ the maximum AP firing rate. in other words, it prevents _____

Answer 1

downstream/one direction

sets the maximum AP frequency

prevents a sustained AP

Question 2

what is the reason for the refractory period during an AP, and what structure is responsible for the refractory period?

Answer 2

• allows for unidirectional propagation of AP
• sets the maximum AP frequency
• inactivation gate

Question 3

what are the two components of a refractory period?

Answer 3

absolute and relative refractory period

Question 4

what is responsible for the absolute refractory period? what’s one reason why it may be called the “absolute” refractory period?

Answer 4

inactivation gate.

will always occur and can’t be overridden

Question 5

what’s one difference between a relative and absolute refractory period?

Answer 5

relative: can be overridden

absolute: can’t be overridden

Question 6

how can you override the relative refractory period?

Answer 6

strong graded potential, increase Na+

Question 7

what is the advantage of overriding the relative refractory period?

Answer 7

differentiate between weak and strong stimulus, and not respond to same way to each

Question 8

how can the relative refractory period be overridden in order to fire the next AP sooner?

Answer 8

strong graded potential, increase sodium

Question 9

how is repolarization affected by voltage-gated K+ channels closing slowly?

Answer 9

keeping K inside by closing the channel would allow the Ap to increase faster during repolarization

Question 10

what effect does voltage-gated K+ channels closing slowly have on when the next AP can be fired?

Answer 10

can’t fire until the last one is done

Question 11

what is the effect of a very large graded potential Na+ influx?

Answer 11

• counters the loss of K+
• lots of Na+ influx can depolarize enough to reach threshold and trigger an action potential

Question 12

what parts of the membrane potential graph are affected by a very large graded potential Na+ influx?

Answer 12

phase 1

Question 13

what ion gates are closed and opened during repolarization of an AP?

Answer 13

ligand-gated ion channels

voltage-gated Na+ channel

voltage-gated K+

voltage-gated Ca+2

Question 14

how does neuron diameter affect AP transmission rate?

Answer 14

laminar:
larger diameter, easier to move

turbulent:
smaller diameter, too crowded, harder to move

Question 15

how does myelination affect AP transmission rate? why?

Answer 15

mylenation provides a barrier between + and - charges.

(-) charges repel against each other.

lower ion density requires less Na+ influe to fil the Vm, and AP travels faster along the internode

less Na+ exits in myelinated area and therefore more Na+ diffuses to the next node of Ranvier

myelination increases the distance between the outside and inside and lowers ion density along the internode in between the nodes of Ranvier.

Question 16

grey matter =

Answer 16

unmylenated axon

Question 17

white matter =

Answer 17

mylenated axon