Neuro 4 PG

Question 1

how are action potentials produced and how are they conducted along the axon?

Answer 1

through the action of voltage-activated ion channels

Question 2

what are voltage-activated ion channels

Answer 2

ion channels that open or close in response to changes in the level of the membrane potential

Question 3

why is membrane potential of of a neuron at rest is relatively constant despite the high pressure acting to drive Na+ ions into the cell?

Answer 3

This is because the resting membrane is relatively impermeable to Na+ ions and because those few that do pass in are pumped out

Question 4

what marks the end of the rising phase in action potential?

Answer 4

the sodium channel closing

Question 5

what is the beginning of depolarization in action potential?

Answer 5

the continued leaving of K+ ions.

Question 6

what ions does action potential involve?

Answer 6

only those right next to the membrane

Question 7

what is the absolute refectory period?

Answer 7

a brief period of about 1 to 2 milliseconds after the initiation of an action potential during which it is ­impossible to elicit a second one.

Question 8

what is the relative refractory period?

Answer 8

the period during which it is possible to fire the neuron again but only by applying higher-than-­normal levels of stimulation. The end of the relative refractory period is the point at which the amount of stimulation ­necessary to fire a neuron returns to baseline.

Question 9

what are the two important ways that axons differ from conduction of EPSPs and IPSPs

Answer 9

-conduction of action potentials along an axon is nondecremental (action potentials do not grow weaker as they travel through axonal membranes)
-action potentials are conducted more slowly than postsynaptic potentials

Question 10

the conduction os EPSPs and IPSPs is

Answer 10

passive

Question 11

axonal conduction of action potential is

Answer 11

largely active

Question 12

antidromic conductions

Answer 12

if electrical stimulation of sufficient intensity is applied to the terminal end of an axon, an action potential will be generated and will travel along the axon back to the cell body

Question 13

orthodromic conduction

Answer 13

axonal conduction in the natural direction

Question 14

where can myelinated axons pass through the axonal membrane

Answer 14

at the nodes of Ranvier

Question 15

what is saltatory conduction

Answer 15

the transmission of action potentials in myelinated axons

Question 16

where do axodendritic synapses terminate

Answer 16

dendritic spines

Question 17

what are axiomatic synapses

Answer 17

synapses of axon terminal buttons on somas

Question 18

what can axoaxonic synapses do

Answer 18

mediate presynaptic facilitation and inhibition

Question 19

directed synapses

Answer 19

synapse at which the site of a neurotransmitter release and the sire of neurotransmitter reception are in close proximity

Question 20

non directed synapse

Answer 20

synapse at which the site of release is at some distance from the site of reception
-also referred to as string-of-bead synapses

Question 21

what are large neurotransmitters

Answer 21

neuropeptides

Question 22

neuropeptides

Answer 22

short amino acid chains composed of between 3 and 36 amino acids; short proteins

Question 23

coexistence

Answer 23

many neurons contain two neurotransmitters

Question 24

exocytosis

Answer 24

process of neurotransmitter release

Question 25

reuptake

Answer 25

The drawing back into the terminal button of neurotransmitter molecules after their release into the synapse; the most common mechanism for deactivating a released neurotransmitter.