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A&P 2 > Electrophysiology of the Nerve Cell > Flashcards

Electrophysiology of the Nerve Cell Flashcards

1
Q

what does the CNS use as its myelinated neuron?

what does the PNS use?

A
  • oligodendrocyte:spit out meylin for more than 1 target neuron
  • Schwann cell: myelinate portion of 1 axon, spaces are nodes of ranvier
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2
Q

what are nongated ion channels important for. what kind of channel are they? are they always open?

A

important for establishment of resting potential
leak channel
always open

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3
Q

what are ligand-gated ion channels activated by? where are they located

A

nt binding

located at sites of synaptic contact (primarily dendritic spins, dendrites and somata)

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4
Q

what are voltage gated ion channels sensitive to? how are they at resting state? where are they predominantly on?

A

differences across membrane
typically closed in resting state
predominatly on axons and axon terminals

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5
Q

what is conductance

A

ease with which ions flow across membrane

-how readily can membrane conduct the ions across itslef

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6
Q

what is resistance

A
  • inverse of conductance

- measured in ohms

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7
Q

what is capacitance

A

membrane’s ability to store an electric charge

-kept apart= pot diff exists across

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8
Q

Na/K ATPase pump 3 Na out and 2 K in…how do they leak

A

Na leak in

K leak out

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9
Q

in most neurons, what is the trigger zone

A

axon hillock=> begin of axons

  • lacks organelles
  • high density Na/K channel => action in pot. originate after receiving adequate stimulus
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10
Q

what does the generation and propagation of action potential contain

A

high density of voltage-gated Na and K channels

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11
Q

when the membrane depolarizes, what channels open what does this cause?

A

Na channels open, results in further depolarization and more channels to open

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12
Q

at threshold, incoming Na exceeds outgoing K and there is…

A

explosive opening of remaning Na channels

-all or none event

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13
Q

what is depolarization in regards to na and k

what is repolarization

A
  • influx of Na

- outflux of K, K flows out

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14
Q

what is overshoot

A

membrane potentiial reverses, w/ the inside becoming positive

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15
Q

what is afterhyperpolarization

A

K channels remain open

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16
Q

what are the phases of action potential

A

resting level=> threshold => rising phase => overshoot => peak => repolarization => afterhyperpolarization

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17
Q

at steady state, how are K and Na related

A

K = + inside cell
Na= + outside
-not the same amount, there is more + outside than inside
-inside is negative relative to amount of change on the outside

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18
Q

in resting state, where is more negative

A

slightly more - inside

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19
Q

larger diamter axons have _____ cytoplasmic resistance thereby permitting ……

A

less

a greater flow of ions and faster actin potentials

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20
Q

in unmyelinated axons, what is electrotonic conductance

A

action potential in one axon segment depolarizes an adjacent section

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21
Q

in propagation of an action potential in a myelinated axon, saltatory conduction occurs, what is this

A

the initiation of an action potential in one node of ranvier depolarizes the next node. jumping action potential from one node to the next

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22
Q

wider diameter axons are faster bc why?

A

less resistance

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23
Q

what does inactivation of sodium channels do to axons

A

makes axons temporarily refractory (resistant) to the generation of action potentials

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24
Q

what are the phases of inactivation of sodium channels

A
  1. absoulte refractory period: the membrane cannot generate an AP bc many of the Na channels are inactivated
  2. relative refractory period: some Na channels are responsive, but the stiumuls strenght must be greater than before bc the threshold is temporarily higher bc not all Na channels are available. amp is slow bc some K channels remain open. AP not propagated
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25
Q

what does the refractory period for a given cell determine

A

its maximum action potential firing rate and the direction of action potential propagation

26
Q

what lead to excitatory postsynaptic potentials (EPSPs)?

what lead to inhibitory postsynaptic potential (IPSPs)?

A

depolarization, causes + movement

hperpolarization, cuases - movement

27
Q

what potential change did the incoming signal from axon onto dendritic spine/process/cell body have on post synaptic cell membrane potential for EPSP? what about IPSP?

A

closer to threshold

further away from threshold

28
Q

what is time constant

A

time required for the pot to decay to 37% of initial peak value
-single contact of axon on single point on target cell

29
Q

what is temporal summation

A

postsynaptic pot are added w/ time; synapses w/ a long time constant are more likely to summate
-takes longer for mem pot to come back from baseline

30
Q

what is short constant

A

short amount of time for mem to head back to resting pot

  • action pot are independent events
  • action towards depolarization
  • NO SUMMATION (adding)
31
Q

what is long constant

A

take longer for the induced pot change to come back to baseline

  • more likely to summate
  • pot change close enough to action pot triggered in axon hillock
  • SUMMATION SIGNAL
32
Q

what is a space constant

A

distance at which voltage change has fallen to 37% of its peak value.
-2 diff points of contact

33
Q

what is spatial summation

A

summation due to activation of several synapses located at different sites of contact; neurons w/ a long space constant are more likely to summate

34
Q

what is synaptotagmin

what does it bind to and wehre is that found?

A

calcium sensor is an integral vesicular membrane protein called synaptotagmin, which undergoes a conformational change
-SNARES, found on the vesicle and terminal that causes vesicles to dock and bind to the presynaptic terminal membrane

35
Q

how do tetanus and botulinum toxins exert their effects?

A

by disrupting the function of SNARES, preventing synaptic transmission

36
Q

in tetanus toxin pathogenesis, once the toxin enters the CNS, it diffuses to the terminals of inhibitory glycinergic and _____ neurons

A

GABA

37
Q

what class of nt are glutamate and aspartate (excitatory), GABA and glycine (inhibitory)

A

amino acids

38
Q

what is acetylcholine derived from

what is the rate limiting step

A

choline
availability of choline
-choline is taken back up by high-affinity sodium-dependent mech; ach itself is not taken up

39
Q

what are the cholinergic receptors

A

nicotinic -2 alpha, 1 beta, 1 gamma, 1 delta

muscarinic - 5 subtypes

40
Q

in nicotinic, which subunit binds to Ach to induce a conformational change?
what does nicotonic do?

A

alpha

increases Na and K conductance. K goes in, Na goes out

41
Q

what does muscarinic act through
what do receptors M1 and M3 binding do? what does this result in?
what does M2 binding do?

A
  • G protein
  • decrease K conductance which results in depolarization. (m3 = role in acc)
  • increases K conductance which results in hyperpolarization
42
Q

what is the rate limiting enzyme for the catecholamine L-Tyrosine?

A

tyrosine hydroxylase

43
Q

where is MAO, the catecholamin nt in

what is mao inhibitory

A

mit in pre and post synaptic terminals

mao inhibitory is an antidepressent, inhibits the reuptake of serotonin

44
Q

where is COMT, the catecholamine nt located in

A

postsynaptic cytoplasm of muscle and glands, and CNS glia and extracellular space

45
Q

the catecholamine receptor, dopamine has 5 subtypes:
D1-like (D1 and D5) is coupled with what?
D2-like (D2-4) is copuled w/ what

A

stimulatory G proteins

inhibitory G proteisn (on pre and post synaptic membranes)

46
Q

how many adrenergic receptors are thre

A

lots.

47
Q

how many receptor subtypes does serotonin have
what is it dependent on
what kind of mech does it have

A

14.

- sodium dependent, active uptake mech

48
Q

what are selective serotonin reuptake inhibitor (SSRI)

A

class of anti-depressants used to treat depression, anxiety disorders, and some personality disorders

49
Q

waht do astrocytes do for glutamate and aspartate

what does it convert glutamate to?

A

have high affinity, active transport mech that removes these from the synapse (in addition to neruonal removal)
-converts glutamate to glutamine, which enters neuron and is recycled back to glutamate by action of glutaminase

50
Q

some glutamate receptors are ….while others are……which are they the most of?

A

ionotropic (most are cationic) while others are metabotrpic

51
Q

activation of ionotropic receptors increases gNa and gCa, what type of receptor is this

A

NMDA

52
Q

activation of metabotropic receptors inhibits Ca channels and thus leads to what

A

presynaptic inhibition

53
Q

what do GABA and glycine hyperpolarize?
how do they produce IPSPs?
removed from cleft into what?

A

postsynaptic membrane

  • produce IPSPs by increasing Cl flux
  • presynaptic neuron and glia
54
Q

what is an increase in Cl conductance facilitated by

A

benzodiazepines, which are anti-anxiety drugs

55
Q 
what are neuropeptides removed from the synaptic cleft by?
what does this ensure? 
what are they degraded by? 
is there a recycling mech?
may modify what?
A
  • diffusion
  • longer action
  • proteases in the extracellular space
  • no, need to be replenished by a steady supply of -new vesicles from the soma
  • response of co-leased nt; modulator function
56
Q

what do opoids do?

what does substance P do?

A
  • control pain, enkephalins, endorphins, morphine

- pain transmission

57
Q

what is nitric oxide (membrane soluble) synthesized from

  • what kind of release is it?
  • why is it not packaged into vesicles
  • what kind of neurons
A

L-argine by nitric oxide synthase (NOS)

  • release is calcium dependent
  • not packaged into vesciles bc lipid soluble
  • nitrergic neurons
58
Q

what is the ligand for endocannabinoids (membran soluble membranes)?
what is it released by?
lipid soluble?

A

ligand for THC

  • released by the postsynaptic cell and act on presynaptic cell
  • yes
59
Q

what is the stimulus like for short term memory

what is the stiumuls like for long term memory

A
  • a single stimulus strenthes the synapse

- repeated stimulation causes kinases to move into the nucleus, leading to gene expression and growth of new synapses

60
Q

what is the functional basis of short and long term memory

A

cAMP responsive element binding protein 1 (CREB1) binds the cAMP response element, a DNA nucleotide sequence present in many cellular promoters.
-the binding of CREB stimulates transcription

A&P 2 (8 decks)

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