graded potentials and action potentials

Question 1

what are graded potentials

Answer 1

transient electric signals that travel short distances

Question 2

what are action potentials

Answer 2

self-replicating transient electrical signals that travel long distances

Question 3

are graded potentials depolarizing or hyperpolarizing?

Answer 3

can be either

Question 4

characteristics of graded potentials

Answer 4

• vary in amplitude and duration - produced by chemical, physical, or electrical stimuli - exhibit decremental conduction

Question 5

what is decremental conduction

Answer 5

the more frequently the nerve is stimulated, the slower it conducts

Question 6

how do graded potentials propagate

Answer 6

local current flow

Question 7

how does the excitatory post-synaptic potential work?

Answer 7

• neurotransmitter binds to receptor
• activates ion channel permeable to sodium
• results in depolarization of the post-synaptic membrane

Question 8

give two neurotransmitter examples that are used to initiate a excitatory post-synaptic potential

Answer 8

• glutamate
• acetylcholine

Question 9

explain how a inhibitory post-synaptic potential works

Answer 9

1. neurotransmitter binds to receptor
2. opens potassium or chloride channels
3. hyperpolarizes the cell

Question 10

give 2 examples of neurotransmitters that initiate a inhibitory post-synaptic potential

Answer 10

• GABA
• Glycine

Question 11

how long do chemically gated ion channels generally stay open

Answer 11

stay open as long as the neurotransmitter is bound to the receptor

Question 12

is there a change in intracellular concentrations of ions during graded potentials

Answer 12

no significant change

Question 13

what effects the amplitude of the graded potential

Answer 13

amplitude varies with magnitude or strength of specific stimulus

Question 14

what happens to the magnitude of the graded potential as it leaves the site of origin

Answer 14

maginitude decreases

Question 15

where does integration of graded potentials occur

Answer 15

cell body

Question 16

where is the site of axon potential generation

Answer 16

axon hillock

Question 17

what is temporal summation

Answer 17

synaptic potentials produced by the SAME pre-synaptic neuron on the same post-synaptic cell overlap in time

• postsynaptic potentials overlap and add to one another
• thus, if the first potential hasn’t completely decayed before the second one arrives, it will add on to the first one

Question 18

what is spatial summation

Answer 18

synaptic potentials produced by DIFFERENT pre-synaptic neurons on the same post-synaptic cell

• individual postsynaptic potentials add together in space
• effect of multiple inputs in additive

Question 19

what is the purpose of dendrites

Answer 19

conduct graded potentials to the cell body

Question 20

What is the potential that is a self-replicating transient electrical signal that travels long distances

Answer 20

action potential

Question 21

what is the potential that is a transient electric signal that travels short distances

Answer 21

graded potential

Question 22

give some characteristics of action potentials

Answer 22

• stereotypical size and shape
• all-or-none phenomenon
• non-decremental propagation

Question 23

what is the all-or-none property of action potentials?

Answer 23

• once action potential is fired, the amplitude remains constant and independent of stimulus above this threshold
• an action potential occurs in total or it does not occur at all

Question 24

an action potential results from transient changes in the what to certain ions

Answer 24

permeability of membrane (concentrations do not change)

Question 25

what controls depolarization

Answer 25

voltage-gated “fast” sodium channels

• Na+ channels are closed at rest
• channel opens very rapidly when Vm depolarizes by a certain amount (threshold)
• channels quickly inactivate - NOT involved in resting Vm

Question 26

Describe what is going on in repolarization

Answer 26

• voltage-gated Na+ channels inactivate
• voltage-gated K+ channels open

Question 27

What is the absolute refractory period

Answer 27

interval during which NO stimulus can elicit an action potential

• inactivation gates, once closed, remain closed until membrane is repolarized

Question 28

what is the relative refractory period

Answer 28

interval when a supernormal stimulus is required to elicit an action potential

• due to elevated gk coupled with the residual inactivation of sodium channels

Question 29

what is the relationship between conduction velocity and fiber diameter

Answer 29

conductional velocity is proportional to fiber diameter

Question 30

myelinated axons prevent current flow where

Answer 30

across the surface of the membrane

Question 31

where do action potentials occur on the axon

Answer 31

occur at the nodes of ranvier

Question 32

segments of axons covered by myelin have many or few voltage gated Na+ channels

Answer 32

few

Question 33

nodes contain high or low concentrations of voltage gated Na+ channels

Answer 33

high! action potentials occur at the nodes

Question 34

saltatory conduction

Answer 34

leaping of action potential from node to node

Question 35

how can you distinguish the level of stimuli

Answer 35

via the frequency of action potentials

• a single action potential cannot convey information about the magnitude of the stimulus that initiated it

Question 36

stimulus strength affects amplitude in graded or action potentials

Answer 36

graded response: amplitude varies with stimulus intensity

Question 37

which, graded or action potentials, have decremental conduction

Answer 37

graded potential

Question 38

which, graded or action potential, has a refractory period

Answer 38

action potential