Chapter 7 Study Questions (Part 2)

Question 1

what occurs to move the membrane potential from -70mV to -55mv?

Answer 1

postsynaptic membrane gets stimulated, by NT being released, which is determined by presynaptic neuron stimulation

Question 2

what occurs to move the membrane potential from -55mV to +30mv?

Answer 2

@ -55mV, voltage-gated Na+ channels open at the axon hillock, and sodium ions rush in

Question 3

what occurs to move the membrane potential from +30mV to a negative -Vm ?

Answer 3

• AP moves down the axon to the axon terminal
• @ +30, sodium channels close
• K+ channels are open when AP= +30mV, and closed when AP is below -70mV

Question 4

what occurs to move the membrane potential from a more negative Vm to close to -94mv, and back to -70mV?

Answer 4

• K+ is closed
• ions being moved through leak channels and ATPase pumps

Question 5

what is the name of the condition of being below -70mV, and how would you describe it?

Answer 5

hyperpolarized

bigger difference between (+) and (-)

Question 6

how is depolarization of the postsynaptic neuron initiated?

Answer 6

NTs released into the synaptic cleft by the presynaptic neuron

Question 7

what is threshold for an AP?

Answer 7

-55mV

Question 8

name the players involved in stimulating a neuron (4)

Answer 8

1. ligand-gated ion channel
2. voltage-gated Na+ channel (activation gate, voltage sensors, inactivation gate)
3. voltage-gated K+
4. voltage-gated Ca+2

Question 9

where is a ligand-gated ion channel located?

Answer 9

soma and dendrites

Question 10

the AP always travels in one direction. how would you describe that direction?

Answer 10

starts at the axon hillock and ends at the axon terminal

Question 11

what is a “graded potential” ?

Answer 11

membrane potential varies on how many ion channels are open

Question 12

what determines how many ion channels are open in a graded potential?

Answer 12

how many NTs have been released

Question 13

what determines how many NTs have been released in a graded potential?

Answer 13

presynaptic neuron stimulation

Question 14

why is the effect of a graded potential variable, while an action potential is all or none and always flips the membrane potential from -70mV to +30 mV?

Answer 14

GP: depends on the strength of stimulus

strength of stimulus depends on amount of NT released

amount of NT released depends on the presynaptic AP frequency

depends on the amount of Na+, which depends on different things, but once you get an action potential going it is all or nothing

Question 15

for a voltage-gated Na+ channel, what is the status of the VOLTAGE SENSORS as the neuron cycles through an AP and back to resting state?

Answer 15

resting state: down
threshold/phase 1: up
phase 2: up
phase 2/3: down
phase 3: down

Question 16

for a voltage-gated Na+ channel, what is the status of the ACTIVATION GATE as the neuron cycles through an AP and back to resting state?

Answer 16

resting state: closed
threshold/phase 1: open (membrane gets depolarized)
phase 2: open
phase 2/3: closed
phase 3: closed

Question 17

for a voltage-gated Na+ channel, what is the status of the INACTIVATION GATE as the neuron cycles through an AP and back to resting state?

Answer 17

resting state: open
threshold/phase 1: open
phase 2: closed
phase 2/3: open
phase 3: open