Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

AP II Exam 1 > Chapter 12 Part 4 > Flashcards

Chapter 12 Part 4 Flashcards

1
Q

what are action potentials?

A

propagated changes in the transmembrane potential that affect an entire excitable membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

voltage gated sodium channels are most abundant where?

A

on the axon, its branches, and synaptic terminals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the FIRST STEP in generating an action potential

A

the opening of voltage-gated sodium channels at one site (usually the initial segment of the axon)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

the action potential is propagated (spread) along the length of the axon, eventually reaching….

A

the synaptic terminals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what does threshold mean? what is the typical threshold for an axon?

A

threshold is the transmembrane potential at which an action potential begins

average threshold for an axon is typically -60mV to -55mV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

is the threshold for an axon is -60mV, what would be the depolarization?

A

10mV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

will a stimulus that shifts the resting membrane potential from -70mV to -62mV produce an action potential?

A

no – only a graded depolarization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what causes the depolarization of the initial segment of the axon?

A

local currents resulting from the graded potential of the axon hillock

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

explain the “all or nothing” principle

A

as long as the depolarizing stimulus exceeds threshold, the properties of the action potential remain the same.
the force of depolarization doesnt matter. action potential remains the same regardless as long as threshold is reached

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

list the 4 steps of the generation of an action potential

A
  1. depolarization to threshold – this opens voltage-gated sodium channels
  2. activation of sodium channels and rapid depolarization – sodium ions rush into the cell and the transmembrane potential is now positive
  3. inactivation of sodium channels and activation of potassium channels – as the transmembrane potential approaches +30mV, sodium channels are inactivated and voltage gated potassium channels open, causing potassium ions to leave the cell. repolarization now begins
  4. closing of potassium channels – they begin closing as the membrane reaches the normal resting potential of about -70mV. Until ALL of these potassium channels have closed, potassium continues to leave the cell, producing a brief HYPERPOLARIZATION (-90mV)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

as the voltage gated potassium channels close, what is happening to the transmembrane potential?

A

the transmembrane potential is returning back to normal resting levels. the action potential is now over

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

the resting potential depends on ___ channels
the graded potential depends on ___ channels
the action potential depends on ____ channels

A

resting – leak channels
graded – chemically gated
action – voltage gated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

WHAT brings an area of excitable membrane to threshold?

A

graded depolarization of axon hillock that is large enough to open voltage-gated sodium channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the refractory period

A

the time in which the membrane cannot respond to further stimulation from the moment the voltage-gated sodium channels open at threshold until sodium channel inactivation ends, because all the voltage gated sodium channels are either already open or inactivated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are the 2 parts of the refractory period and how long do they last

A

part 1 = absolute refractory period. last 0.1msec-1msec (the smaller the axon diameter, the longer the duration)

part 2 = relative refractory period. begins when sodium channels regain their normal resting conditions and continues until the transmembrane potential stabilizes at resting levels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

can another action potential occur during the relative refractory period? explain

A

yes
the depolarization, however, requires a larger than normal stimulus because…

-the local current must deliver enough Na+ to counteract the exit of K+ ions (through the voltage gated potassium channels)

-the membrane is hyperpolarized to some degree through most of the relative refractory period (due to the exit of K+ ions until every channel is closed)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

in an action potential, depolarization results from the influx of Na+ ions and repolarization involves the loss of K+.
What returns these ion concentrations to prestimulation levels? Is it essential? explain

A

the sodium potassium exchange pump

it is NOT essential. The number of ions involved in a single action potential is insignificant compared to the total number of ions inside and outside of the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

explain when the sodium-potassium exchange pump is ESSENTIAL

A

a maximally stimulated neuron can generate action potentials 1000/second

this is when the exchange pump is needed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

explain how the sodium-potassium exchange pump works

A

each time the pump brings 2 potassium ions in and 3 sodium ions out, one molecule of ATP is broken down into ADP.

the transmembrane protein of the pump is sodium-potassium ATPase which gets the energy to pump ions by splitting a phosphate group from a molecule of ATP, forming ADP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

action potentials may travel along an axon by ____ or ____

A

continuous propagation or saltatory propagatio

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

explain what continuous propagation is

A

continuous propagation occurs in UNMYELINATED axons.

an action potential moves across the membrane in a series of tiny steps.
the local current depolarizes adjacent portions of the membrane and continues in a chain reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

explain how continuous propagation does not move backwards

A

because the previous segment of the axon is still in the absolute refractory period and cannot respond again to a stimulus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

continuous propagation along an unmyelinated axon occurs at a speed of….

A

1 meter/second (2 miles an hour)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

explain saltatory propagation

A

occurs in myelinated axons of the PNS and CNS. much faster than continuous propagation

when an action potential appears at the initial segment of a myelinated axon, the local current SKIPS the myelinated internodes and depolarizes the closest node.
“jumps” from one node to another instead of moving in a series of tiny steps (continuous)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

which uses less energy — continuous or saltatory propagation?

A

saltatory. because less surface area is involved and fewer sodium ions must be pumped out of the cytoplasm (and into the cell)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

the larger the diameter, the ___ the speed of the action potential

A

greater (faster)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

classify axons into 3 groups according to the relationships between diameter, myelination, and propagation speed

A

Type A fibers = largest myelinated axons. (4-20micro meters) carry action potentials 120m/sec or 268mph

Type B fibers = smaller myelinated axons. diameter (2-4 micrometers) 18m/sec or 40mph

Type C fibers UNMYELINATED less than 2 micrometers in diameter. 1m/sec or 2mph

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what is the FUNCTION of type A fibers

A

type A fibers carry sensory information about position, balance, and delicate touch and pressure senses FROM THE SKIN SURFACE TO THE CNS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what is the FUNCTION of types B and C fibers

A

carry information to the CNS and carry instructions to smooth muscle, cardiac muscle, glands, and other peripheral effectors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

why isnt every axon in the nervous system large and myelinated?

A

physically impossible – too large

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

action potentials can also be called

A

nerve impulses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

to be effective, an action potential must not only be propagated along an axon, but also…..

A

be transferred in some way to another cell (transfer takes place at synapses)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

a synapse may be _____, involving DIRECT PHYSICAL CONTACT between the cells, or it may be ______, involving a neurotransmitter

A

electrical synapse – direct physical contact
chemical —- involving a neurotransmitter

34
Q

at electrical synapses, the presynaptic and postsynaptic membranes are locked together at…..

A

gap junction

35
Q

the lipid portions of opposing membranes at a synapse are held in position by binding between….

A

integral membrane proteins called CONNEXONS

36
Q

What do connexons do?

A

form pores that permit ions to pass between cells

37
Q

explain the advantage of the 2 cells being linked in this way (gap junctions, binding between connexons)

A

changes in the transmembrane potential of one cell produce local currents that affect the other cell as if the 2 shared a common membrane.

therefore, an electrical synapse propagates action potentials quickly and efficiently from 1 cell to the next

38
Q

are electrical synapses common?

A

NO – they are extremely rare in both the PNS and CNS.
they occur in some areas of the brain, the eye, and in at least 1 pair of PNS ganglia

39
Q

what is the most abundant type of synapse

A

a chemical synapse

40
Q

neurotransmitters are either classified as ___ neurotransmitters or ____ neurotransmitters

A

excitatory or inhibitory

41
Q

explain the difference between excitatory and inhibitory neurotransmitters

A

excitatory neurotransmitters – cause depolarization and promote the generation of action potentials

inhibitory neurotransmitters – cause hyperpolarization and suppress the generation of action potentials

42
Q

in which synapse is an action potential ALWAYS propagated to the next cell — chemical or electrical?

A

electrical

43
Q

explain how an action potential MAY OR MAY NOT be propagated to the next cell at a chemical synapse

A

-an action potential may or may not release enough neurotransmitter to bring the postsynaptic neuron to threshold

-other factors may intervene and make the postsynaptic cell more or less sensitive to arriving stimuli

44
Q

the effect of a neurotransmitter on the postsynaptic membrane depends on ____ NOT ____

give a specific example

A

effect of a neurotransmitter on a postsynaptic membrane depends on THE PROPERTIES OF THE RECEPTOR, NOT the neurotransmitter itself

ACh typically causes depolarization in the postsynaptic membrane, but ACh released at neuromuscular junctions in the heart has an inhibitory effect

45
Q

Synapses that release ACh (acetylcholine) are known as……

A

cholinergic synapses

46
Q

the ___ junction is an example of a cholinergic synapse

A

neuromuscular

47
Q

name 4 areas in which ACh is released

A
  1. ALL neuromuscular junctions involved with skeletal muscle fibers
  2. at many synapses in the CNS
  3. at ALL neuron-neuron synapses in the PNS
  4. ALL neuromuscular and neuroglandular junctions in parasympathetic divisions of the ANS
48
Q

describe the events in the functioning of a cholinergic synapse

A
  1. action potential arrives and depolarizes the synaptic terminal
  2. extracellular calcium enters the synaptic terminal. this triggers the exocytosis of ACh
  3. ACh binds to receptors and depolarizes the postsynaptic membrane
  4. ACh is removed by acetylcholinesterase (AChE)
49
Q

what exactly is ACh binding to on the postsynaptic membrane?

A

CHEMICALLY GATED SODIUM ION CHANNELS.
This will initiate an action potential if threshold is reached at the initial segment

50
Q

the depolarization of the synaptic terminal causes calcium (Ca2+) ions to rush in. What do they rush in through?

A

voltage gated calcium channels

51
Q

the depolarization of the postsynaptic membrane due to the influx of sodium ions through chemical-gated channels is a ___ potential.
explain

A

a GRADED potential
the greater the amount of ACh released at the presynaptic membrane, the greater the number of open channels in the postynaptic membrane, THUS, THE LARGER DEPOLARIZATION

52
Q

Where does AChE reside?

A

in the synaptic cleft and in the postsynaptic membrane

53
Q

around what percent of acetylcholine released at the presynaptic membrane is broken down before it reaches receptors at the postsynaptic membrane?

A

around half is broken down

54
Q

AChE breaks down molecules of ACh by ____ into ___ and ____

A

by hydrolysis into acetate and choline

55
Q

how is more ACh synthesized?

A

the choline resulting from the breakdown of ACh by AChE is actively absorbed by the synaptic terminal and used to synthesize more ACh

also acetate is used too and is provided by CoA (coenzyme A)

56
Q

the acetate that results from the hydrolysis reaction by AChE goes where?

A

it can be absorbed and metabolized by the postsynaptic cell or by other cells and tissues

57
Q

what is synaptic delay and how long is it

A

0.2-0.5msec

occurs between the arrival of an action potential (depolarization) at the synaptic terminal and the effect on the postsynaptic membrane

58
Q

most of the synaptic delay is contributed by…

A

calcium influx and the RELEASE of neurotransmitter (not its diffusion across the cleft)

59
Q

the fastest reflexes have how many synapses?

A

ONE
the more synapses, the more synaptic delay

60
Q

when does ACh release from the presynaptic cell cease?

A

when active transport mechanisms quickly remove calcium from the synaptic terminal

61
Q

is the synaptic terminal totally dependent on the ACh synthesized in the cell body of the neuron?

A

NO
ACh is made from recycled choline and acetate

62
Q

when under intensive stimulation, resynthesis and transport mechanisms may not be able to keep up with the demand for neurotransmitter.

What is the term for this?

A

synaptic fatigue

63
Q

during synaptic fatigue, the synapse weakens until….

A

Acetylcholine has been replenished

64
Q

name some important neurotransmitters

A

norepinephrine
dopamine
serotonin
GABA (gamma-aminobutyric)

65
Q

if the neurons that produce ______ are damaged or destroyed, the result can be the characteristic stiffness or rigidity that is Parkinson’s disease
(this is a _____ effect)

A

DOPAMINE
inhibitory

66
Q

Explain the excitatory effect of dopamine

A

cocaine inhibits the removal of dopamine from synapses in specific areas of the brain. This rise in dopamine concentration creates a “high”

67
Q

inadequate ____ production causes severe chronic depression

A

serotonin

68
Q

GABA has an ___ effect

A

inhibitory

69
Q

what do SSRI’s do? (selective serotonin reuptake inhibitors)

A

inhibit the reabsorption of serotonin by synaptic terminals, increasing the concentration of serotonin

70
Q

what are 4 major CATEGORIES of neurotransmitters

A

-biogenic amines
-amino acids
-neuropeptides
-dissolved gasses

71
Q

what are adrenergic synapses?

A

synapses that release norepinephrine

72
Q

norepinephrine has a __ effect

A

excitatory, depolarizing effect

73
Q

norepinephrine (NE) is widely distributed where>?

A

in the brain and portions of the ANS

74
Q

Name 2 “dissolved gases” neurotransmitters

A

nitric oxide (NO)
carbon monoxide (CO)

75
Q

Nitric oxide is generated by synaptic terminals that innervate ________

A

smooth muscle in the walls of blood vessels of the PNS, and at synapses in several regions of the brain

76
Q

where is CO generated

A

similar to NO, at specialized synaptic terminals in the brain

77
Q

what are neuromodulators?

A

active compounds that are released from synaptic terminals along with neurotransmitters.

they alter the rate of neurotransmitter release by the presynaptic cell OR change the post synaptic cell’s response to neurotransmitters

78
Q

neuromodulators are typically _____

A

neuropeptides (small peptide chains synthesized and released by the synaptic terminal)

79
Q

explain how neuromodulators act

A

they bind to receptors in the pre or post synaptic membranes and activate cytoplasmic enzymes

80
Q
A

AP II Exam 1 (17 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions