Chapter 4: The Action Potential

Question 1

the info that the brain deals with

Answer 1

neural code

Question 2

the neural code can be obtained from the () of the action potentials fired in the nervous system

Answer 2

frequency and pattern

Question 3

other names for the action potential (3)

Answer 3

1. spike
2. nerve impulse
3. discharge

Question 4

used to study APs

Answer 4

oscilloscope

Question 5

properties of the action potential

Answer 5

1. rising phase
2. overshoot
3. falling phase
4. undershoot

Question 6

2 ways to measure membrane potential

Answer 6

1. intracellular recording (more sensitive)
2. extracellular recording (collective action of 100s of neurons together)

Question 7

the generation of an AP is caused by (1) of the membrane beyond (2)

Answer 7

1. depolarization
2. threshold

Question 8

AP is generated if and only if membrane potential goes beyond threshold = () response

Answer 8

all-or-none

Question 9

when generating multiple action potentials, the firing frequency reflects the () of the depolarizing current

Answer 9

magnitude

Question 10

max AP firing frequency

Answer 10

1000 Hz (1000 impulses per second)

Question 11

() delas the next firing of AP

Answer 11

absolute and relative refractory periods

Question 12

in theory, depolarization of membrane potential is due to ()

Answer 12

influx of Na+

Question 13

in theory, repolarization of membrane potential is due to ()

Answer 13

efflux of K+

Question 14

current across membrane is largely due to movement of (1) across membrane (aka 2)

Answer 14

1. K+ ions
2. Ik

Question 15

the K+ channel number is proportional to ()

Answer 15

electrical conductance

Question 16

ideally, resting membrane potential is due to ()

Answer 16

equilibrium of K+

Question 17

Hodgkin and Huxley’s experiment found that there was a transient increase in () during the rising phase

Answer 17

Na+ conductance -> influx of Na+

Question 18

similarly, Hodgkin and Huxley’s experiment found that there was a transient increase in () during the falling phase

Answer 18

K+ conductance -> efflux of K+ ions

Question 19

Na+ gates in the axonal membrane are activated by (1) and deactivated when the membrane acquires a (2)

Answer 19

1. depolarization beyond threshold
2. positive membrane potential

Question 20

structure of the voltage-gated Na+ channel

Answer 20

transmembrane domains and an ion-selective (to Na+) pore

Question 21

the voltage-gated Na+ channel has (1) distinct domains, each consisting of () transmembrane alpha helices

Answer 21

1. 4
2. 6

Question 22

voltage sensor in voltage-gated Na+ channels

Answer 22

S4

Question 23

how does depolarization affect the S4 domain of voltage-gated Na+ channels

Answer 23

depolarization causes S4 to twist and results in S4 moving upwards and outwards to open the channel

Question 24

() method allows one to record ionic currents through single channels

Answer 24

patch-clamp

Question 25

the absolute refractory period is due to the () of the channel

Answer 25

inactivation

Question 26

genetic diseases that cause mutations in the voltage-gated Na+ channels

Answer 26

channelopathies

Question 27

toxin that clogs Na+ permeable pore and blocks all Na+ dependent APs

Answer 27

tetrodotoxin (TTX)

Question 28

Na+ channel-blocking toxin

Answer 28

(red tide) saxitoxin

Question 29

toxin that blocks inactivation so channels remain open

Answer 29

batrachotoxin (frog)

Question 30

toxins with similar effects as batrachotoxin

Answer 30

veratridine (lilies), and aconitine (buttercups)

Question 31

because (some) K+ channels open later than Na+ channels, the K+ channels serve as ()

Answer 31

delayed rectifiers -> rectify or reset membrane potential

Question 32

the threshold of the membrane is mainly determined by open ()

Answer 32

Na+ channels

Question 33

undershoot is described as (1) due to (2)

Answer 33

1. hyperpolarization
2. high K+ conductance

Question 34

greater stimuli (depolarization) is required to initiate another AP during the relative refractory period due to ()

Answer 34

open K+ channels (rectifiers) -> K+ efflux

Question 35

spike initiation zones in neurons

Answer 35

1. sensory nerve endings
2. axon hillock

Question 36

what characterizes spike initiation zones

Answer 36

higher expression (number) of voltage-gated Na+ channels

Question 37

2 types of AP propagation

Answer 37

1. orthodromic
2. antidromic

Question 38

action potential travels in one direction (towards axon terminal) due to inactivation of sodium channels

Answer 38

orthodromic

Question 39

experimental AP propagation wherein AP propagates backwards

Answer 39

antidromic

Question 40

factors influencing conduction velocity

Answer 40

1. axon structure
2. path of positive charge
3. axonal excitability

Question 41

synthetic anesthetic that prevents APs by binding to voltage-gated Na+ channels; affect smaller axons before larger axons

Answer 41

lidocaine

Question 42

lidocaine binds to the () alpha helix to inhibit APs

Answer 42

S6

Question 43

insulate axons to facilitate current flow

Answer 43

myelin

Question 44

keep axons myelinated in peripheral NS

Answer 44

Schwann cells

Question 45

keep axons myelinated in central NS

Answer 45

oligodendroglia

Question 46

propagation of APs along myelinated axons

Answer 46

saltatory conduction

Question 47

like spike initiation zones, nodes of Ranvier have () to facilitate AP generation

Answer 47

increased number of ion channels

Question 48

types of AP firing patterns

Answer 48

1. fast spiking
2. burst spiking
3. regular spiking