2.6 Lundy Ch. 2 (3)

Question 1

How is the meaning of an action potential determined?

Answer 1

by the neural pathway in which it is conducted, not the signal itself

Question 2

all-or-none

Answer 2

• minimally sufficient stimuli trigger

- stronger stimuli don’t change signal

Question 3

trigger zone/axon hillock

Answer 3

region in neurons with a high concentration of Na+ channels

Question 4

AP generation involves a sudden influx of this into the cell

Answer 4

Na+

through Na+ channels in axon hillock

Question 5

How do local potentials produce an action potential?

Answer 5

• summated membrane depolarization beyond threshold

- causes Na+ channels to open

Question 6

What is the threshold membrane potential to develop an AP?

Answer 6

-55 mV

Question 7

depolarization and repolarization in action potential

Answer 7

1: -55 mV » Na+ channels open
2: Na+ flows in and depolarizes
3: K+ channels open and get rapid repolarization

Question 8

Why is there hyperpolarization?

Answer 8

K+ flowing out

Question 9

refractory period

Answer 9

• membrane is hyperpolarized

- difficult to regenerate action potential

Question 10

absolute refractory period

Answer 10

membrane unresponsive to stimuli

Question 11

relative refractory period

Answer 11

• stimulus may activate

- must be stronger than normal to activate an AP

Question 12

purpose of refractory period

Answer 12

• promotes forward propagation

- prevents backflow

Question 13

What restores the membrane to normal RMP from hyperpolarization?

Answer 13

Na/K pump

Question 14

contributing factors to faster AP propagation

Answer 14

• increased diameter of axon

- myelination

Question 15

benefit of insulation through myelination

Answer 15

prevents current flow across axonal membrane

Question 16

Without insulation, the amplitude of the potential would

Answer 16

dissipate down the axon

Question 17

nodes of Ranvier allow

Answer 17

ion flow across the membrane

Question 18

nodes have high densities of

Answer 18

Na+ and K+ channels

Question 19

What causes regeneration of the AP?

Answer 19

depolarization at the nodes of Ranvier

Question 20

saltatory conduction

Answer 20

AP seems to jump from node to node

Question 21

AP maintains this due to saltatory conduction

Answer 21

• size

- shape