Chapter 8 Study Questions (Part 2)

Question 1

what is a graded potential?

Answer 1

a change or variation in the membrane potential

Question 2

how can you increase the strength of a graded potential?

Answer 2

a few ways.

strength of input –> presynaptic –> NT –> how many receptors are bound

Question 3

NT diffuses rapidly across, but… (Ca2+)

Answer 3

there is a small time elay moving Ca2+ in and out

Question 4

what are three ways that NTs are removed from the synaptic cleft?

Answer 4

1. enzyme degradation (postsynaptic neuron)
2. reuptake by proteins (presynaptic)
3. diffuses out of the cell, taken up by an astrocyte

Question 5

how does an excitatory synapse affect the postsynaptic membrane potential?

Answer 5

depolarizes, aka membrane potential goes back towards the positive

Question 6

how does an inhibitory synapse affect the postsynaptic membrane potential?

Answer 6

hyperpolarizes, aka inside of the cell gets more negative

Question 7

at rest, is Vm positive or negative?

Answer 7

negative

Question 8

how might you make it harder to depolarize the membrane?

aka what ions would you use and would you bring them in or let them out? (Na+, Ca+2, K+, Cl-)

Answer 8

harder to depolarize = hyperpolarize

Na+: block, keep out
Ca+2: block, keep out
K+: out
Cl-: in

Question 9

what is the function of an inhibitory synapse? (2)

Answer 9

• counteract a stimulus
• prevent action potential from getting there/delivering message

Question 10

what happens when a ligand-gated Na+ channel on the postsynaptic membrane opens?

Answer 10

depolarizes

Question 11

what happens when a ligand-gated K+ channel on the postsynaptic membrane opens?

Answer 11

hyperpolarized

Question 12

what happens when a ligand-gated K+ channel on the postsynaptic membrane closes?

Answer 12

depolarizes

Question 13

what happens when a ligand-gated Cl- channel on the postsynaptic membrane opens?

Answer 13

hyperpolarizes

Question 14

what happens when a voltage-gated Na+ channel on the axon hillock opens?

Answer 14

initiate action potential

Question 15

what happens when a voltage-gated Na+ channel on the axon opens?

Answer 15

propagate action potential

Question 16

what happens when a voltage-gated K+ channel on the axon opens?

Answer 16

repolarizes

Question 17

what happens when a voltage-gated Ca2+ channel at the axon terminal opens?

Answer 17

calmodulin –> exocytosis

Question 18

what is one relevant consequence of a membrane potential being hyperpolarized?

Answer 18

no action potential can be fired

Question 19

what determines if a excitatory or inhibitory response wins?

Answer 19

number of NTs

Question 20

what’s the difference between an impulse not reaching threshold, vs. an impulse being inhibited by inhibitory impulse

Answer 20

signal not sent because the stimulus isn’t strong enough to get to threshold vs. strong enough to get stimulate but gets inhibited cause it’s a numbers game