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Biology II > ch. 48 part 2 > Flashcards

ch. 48 part 2 Flashcards

1
Q

action potentials

A
  • carry electrical signals along an axon
  • all-or-none - not graded
  • actively propagated
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2
Q

actively propagated

A

regenerates itself as it travels

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3
Q

action potential sequences

A
  1. graded potential depolarizes to threshold potential (-50mV)
  2. voltage-gated Na+ channels open and trigger action potential
  3. Na+ rapidly diffuses into cell causing spike
  4. inactivation when gate in Na+ channel swings shut when membrane positively polarized
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4
Q

threshold potential

A

-50 mV

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5
Q

resting potential

A

-70 mV

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6
Q

when do voltage-gated K+ channels open

A

1 sec later than Na+ channels

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7
Q

opening of K+ channels for hyperpolarization

A
  • voltage-gated K+ channels open by threshold potential
  • K+ leaves cell and membrane becomes negative again
  • membrane hyperpolarizes
  • voltage-gated K+ channels close and resting potential restored
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8
Q

where do graded potentials reach threshold potential

A

axon hillock

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9
Q

what do graded potentials trigger just beyond the hillock region

A

opening of voltage-gated Na+ channels

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10
Q

what does the sequential opening of Na+ channels do?

A

conduct a wave of depolarization from axon hillock to axon terminal

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11
Q

what does the inactivation gate of Na+ channels do?

A

prevent backward movement toward cell body

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12
Q

absolute refractory period

A
  • while Na+ gate is closed, cell is unresponsive to another stimulus
  • limit on frequency of action potentials
  • ensures action potential does not move backward toward cell body
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13
Q

relative refractory period

A
  • K+ channels still open
  • membrane hyperpolarizes
  • graded potential would have to be huge to reach the threshold
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14
Q

what does speed of conduction depend on

A
  1. axon diameter
  2. myelination
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15
Q

axon diameter and speed

A

broad axons provide less resistance and action potential moves faster

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16
Q

myelination and speed

A
  • myelination faster than unmyelinated
  • oligodendrocytes and Schwann cells
  • gaps at nodes of Ranvier
  • saltatory conduction
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17
Q

saltatory conduction

A

action potential seems to “jump” from node to node

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18
Q

synapses

A

junction where nerve terminal meets a neuron, muscle cell, or gland

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19
Q

order at junction

A
  • presynaptic cell sends signal
  • synaptic cleft
  • postsynaptic cell receives signal
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20
Q

2 types of synapses

A
  1. electrical
  2. chemical
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21
Q

electrical synapse

A

electric charge freely flows through gap junctions from cell to cell

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22
Q

chemical synapse

A

neurotransmitter acts as signal from presynaptic to postsynaptic cell

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23
Q

details of chemical synapse

A
  • presynaptic cell contains vesicles of neurotransmitter
  • exocytosis releases neurotransmitter into synaptic cleft
  • diffuses across cleft
  • binds to channels/receptors in postsynaptic cell membrane
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24
Q

what does binding of a neurotransmitter at a chemical synapse do

A

change membrane potential of postsynaptic cell

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25
Q

excitatory postsynaptic potential (EPSP)

A
  • brings membrane closer to threshold potential
  • less negative
  • sodium channels opening
26
Q

inhibitory postsynaptic potential (IPSP)

A
  • takes membrane farther from threshold (hyperpolarization)
  • more negative
  • opening of chlorine channels (Cl- enters cells)
27
Q

when does a synaptic signal end

A

when the neurotransmitter is broken down by enzymes or taken back into presynaptic cell for reuse

28
Q

where does the cell bod of a postsynaptic neuron receive input from

A

can be hundreds or thousands of synaptic terminals

29
Q

is a single EPSP strong enough to trigger an action potential in a postsynaptic neuron?

A

no - too small

30
Q

summation

A

ind. postsynaptic potentials can combine to produce larger potential

31
Q

temporal summation

A

if 2 EPSPs are produced in rapid succession

32
Q

spatial summation

A

EPSPs produced nearly simultaneously by different synapses on the same postsynaptic neuron add together

33
Q

what can trigger an action potential

A

combination of EPSPs through spatial and temporal summation

34
Q

how can an IPSP counter the effect of an EPSP?

A

through summation

35
Q

what does the summed effect of EPSPs and IPSPs determine

A

whether an axon hillock will reach threshold and generate an action potential

36
Q

after a response is triggered, what does the chemical synapse do

A

return to its resting state
- neurotransmitter molecules cleared from synaptic cleft

37
Q

nerve gas sarin

A

tiggers paralysis and death due to inhibition of the enzyme that breaks down the neurotransmitter controlling skeletal muscles

38
Q

metabotropic

A

movement of ions through a channel depends on one or more metabolic steps
- can be metabotropic receptor on postsynaptic membrane

39
Q

what happens when a neurotransmitter binds to a metabotropic receptor

A
  • activates signal transduction pathway in postsynaptic cell involving a second messenger
  • leads to amplification where many channels are opened/closed in response
40
Q

types of receptors for neurotransmitters

A

inotropic and metabotropic

41
Q

how many receptors can a single neurotransmitter bind to

A

can be more than a dozen
- can excite postsynaptic cells expressing one receptor and inhibit postsynaptic cells expressing a different receptor

42
Q

acetylcholine

A

common neurotransmitter in vertebrates and invertebrates

43
Q

what is acetylcholine involved in

A
  • muscle stimulation
  • memory formation
  • learning
44
Q

2 major classes of acetylcholine receptors in vertebrates:

A
  1. ligand gated
  2. metabotropic
45
Q

what can disrupt acetylcholine neurotransmission

A

number of toxins
- like nerve gas sarin and botulism toxin produced by certain bacteria

46
Q

how many known neurotransmitters are there

A

over 100

47
Q

4 classes of neurotransmitters

A
  1. amino acids
  2. biogenic amines
  3. neuropeptides
  4. gases
48
Q

glutamate

A

one of several amino acids that can act as a neurotransmitter (vertebrates and invertebrates)

49
Q

glycine

A

acts as inhibitory synapses in parts of CNS outside the brain

50
Q

gamma-aminobutyric acid (GABA)

A

neurotransmitter at most inhibitory synapses in the brain

51
Q

biogenic amines include:

A
  • norepinephrine
  • epinephrine
  • dopamine
  • serotonin
52
Q

what do biogenic amines do

A

central role in number of nervous system disorders

53
Q

Parkinson’s disease

A

associated with lack of dopamine in brain

54
Q

neuropeptides

A

relatively short chains of amino acids that also function as neurotransmitters

55
Q

what do neuropeptides include

A
  • substance P
  • endorphins
  • both affect perception of pain
56
Q

opiates

A

bind to same receptors as endorphins and can be used as painkillers

57
Q

nitric oxide (NO)

A

local regulators in PNS

58
Q

where is NO stores

A
  • not stored in cytoplasmic vesicles like most neurotransmitters
  • synthesized on demand
59
Q

when can NO be broken down?

A

within a few seconds of production

60
Q

can CO be used as a neurotransmitter?

A

yes - body makes it in small amounts

Biology II (43 decks)

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