Lecture 3

Question 1

an _____ _______ is generated by the glow of ions through voltae gated channels

Answer 1

action potential

Question 2

t/f the nervous sustem expresses a rich variety of voltage gaed ion channels

Answer 2

true

Question 3

t/f the opening of voltage gated ion channels is all or none

Answer 3

true

Question 4

list the 4 phases of an action potential

Answer 4

rising phase, overshoot, falling phase, undershoot phase

Question 5

t/f the rising and overshoot phase is potassium dependent

Answer 5

false , it is sodium dependent

Question 6

t/f the rising and overshoot phase is sodium dependent

Answer 6

true

Question 7

are sodium channels voltage gated

Answer 7

yes

Question 8

define threshold potential

Answer 8

voltage at which many of the sodium channels start to open

Question 9

does sodium move into or out of a cell during the rising and overshoot phase

Answer 9

it goes into the cell

Question 10

during the rising and overshoot phase does hyperpolarization or depolarization occur

Answer 10

depolarization

Question 11

is the falling and undershoot phase sodium or potassium dependent

Answer 11

potassium

Question 12

a potassium channels voltage gated

Answer 12

yes

Question 13

which opens and closes faster a sodium or potassium channel

Answer 13

sodium

Question 14

during the falling phase is hyperpolarization or depolarization occuring

Answer 14

hyperpolarization

Question 15

during which phases are sodium channels inactivated

Answer 15

falling and undershoot phase

Question 16

can sodium channels pass current if they are inactivated

Answer 16

no

Question 17

during the falling and undershoot phase if hyperpolarization or depolarization occuring

Answer 17

hyperpolarization

Question 18

when a cell is returning to resting membrane potential what channels are closing

Answer 18

the potassium channels close

Question 19

when na channels open and na rushes in this is an example of ______

Answer 19

depolarization

Question 20

when k channels open , k rushes out this is an example of ______

Answer 20

hyperpolarization

Question 21

when k channels close it shuts off the hyperpolarizing or depolarizing current?

Answer 21

hyperpolarizing

Question 22

what did hodkin and huxley want to know

Answer 22

which ions gave rise to an action potential

Question 23

what is the main point of a voltage current

Answer 23

it measures current at specific voltages

Question 24

if you hold an axon at 0mv what 3 currents will you see

Answer 24

1. very transient capacitative current
2. fast transient current inward , rising phase
3. delayed sustained current, outward part of the falling phase

Question 25

what ion is responsible for the transient current

Answer 25

sodium

Question 26

at the reversal potential is there any net movement of ions

Answer 26

no

Question 27

what does the reversal potential equal

Answer 27

the diffusional force

Question 28

what is the name of the chemical that is responsible for blocking sodium

Answer 28

tetrodotoxin (ttx)

Question 29

t/f ttx block the ouward current

Answer 29

false, ttx only blocks the early inward current

Question 30

the inward current is dependent on which ion

Answer 30

sodium

Question 31

is the sustained current sodium dependent

Answer 31

no

Question 32

the sustained current is dependent on which ion

Answer 32

potassium

Question 33

what is the name of the potassium channel blocker

Answer 33

tetraethylammonium (tea)

Question 34

does TEA block early inward currents

Answer 34

no , it only blocks late outward current

Question 35

if you want to have no action potential which 2 chemicals would you use

Answer 35

tea and ttx

Question 36

changing the resting potential to a value above threshold produces what 2 effects

Answer 36

1. an early influz of sodium into the axon , followed by sodium rapidly coming into the cell. 2. a delayed efflus of the potassium slowly leaving the cell

Question 37

what cause a transient current

Answer 37

an early influz of sodium

Question 38

what causes a sustained current

Answer 38

delayed efflux of potassium

Question 39

ion membrane permiability changes with what

Answer 39

voltage

Question 40

t/f as you hyperpolarize you get more conductance

Answer 40

false, as you depolarize you get more conductance

Question 41

t/f an increase in sodium permiability inactivates after awhile

Answer 41

true

Question 42

t/f t/f an increase in potassium permeability inactivates after awhile

Answer 42

false

Question 43

t/f it is possible to get an action potential during an absoulte refractory period

Answer 43

false

Question 44

is it possible to get an action potential during the relative refractory period

Answer 44

yes, but unlikely

Question 45

why isnt it possible to have an action potential during the absolute refractory period

Answer 45

because sodium channels are inactive

Question 46

during the closed state of a sodium channel is the core open or closed

Answer 46

closed

Question 47

during the closed state of a sodium channel is the gate open or closed

Answer 47

open

Question 48

during the inactivated state of a sodium channel is the core open or closed

Answer 48

open

Question 49

during the inactivated state of a sodium channel is the gate open or closed

Answer 49

open

Question 50

can current flow in the inactivated state

Answer 50

no

Question 51

can current flow in the closed state

Answer 51

no

Question 52

can the closed state of a sodium channel occur when the membrane potential is low

Answer 52

no

Question 53

can the closed state of a sodium channel occur when the membrane potential is high

Answer 53

yes

Question 54

when the membrane potential is high and the channel is still shut off what do we call this state

Answer 54

inactive state

Question 55

t/f the sodium channel only lets in negative ions

Answer 55

false, the sodium channel only lets in postive ions

Question 56

voltage sensors are composed of lots of positively charged ______ _______

Answer 56

amino acids

Question 57

if a sodium channel goes from the pore being closed to open , is depolarization or hyperpolarization occuring

Answer 57

depolarization

Question 58

if a sodium channel goes from the pore being open to closed , is depolarization or hyperpolarization occuring

Answer 58

hyperpolarization

Question 59

where are action potentials generated

Answer 59

in the axon hillock

Question 60

the highes expression of sodium channels is in the

Answer 60

axon hillock

Question 61

what is the cable theory

Answer 61

if you simply inject current into a cable , the voltage will change locally, then die out as ions leak

Question 62

do action potentials decay

Answer 62

no , they are actively regenerated

Question 63

how are action potentials propegated

Answer 63

the action potential moves a short distance and triggers the opening of more sodium channels

Question 64

are action potentials able to go backwards

Answer 64

no

Question 65

why arent action potentials able to go backwards

Answer 65

because the sodium channels are inactivated

Question 66

t/f action potentials are bi directional

Answer 66

false , they are unidirectional

Question 67

what is myelin

Answer 67

an insulative material that prevents current (ions) from leaking out

Question 68

where are sodium channels located

Answer 68

at the nodes of ranviwe

Question 69

what does saltatory conduction enable

Answer 69

faster transmission of signals

Question 70

what is saltatory conduction

Answer 70

action potentials jumping from one node to the next

Question 71

does continuous conduction invovle an unmylenated axon

Answer 71

yes

Question 72

t/f myelin is only found in vertebrates

Answer 72

true

Question 73

name 2 places where mylenated axons are found

Answer 73

optic nerve and motor nerves

Question 74

name a place where unmylenated axons are found

Answer 74

olfactory nerves