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Animal Physiology > Exam 2: Ch 5 Notes > Flashcards

Exam 2: Ch 5 Notes Flashcards

1
Q

what is a neuron

A

specialized cell that communicates via electrical activity

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2
Q

how does the nervous system work

A

input –> dendrite –> soma processing –> output –> synapse

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3
Q

is shape (morphology) important

A

yes

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4
Q

can inputs be excitatory or inhibitory?

A

yes

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5
Q

graded potential

A

vary in size

generated by inputs

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6
Q

action potential

A

invariant in size in a particular neuron

all or none

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7
Q

what do glia do and how many are there

A

support neuronal function

10x more than neurons

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8
Q

functions of glia

A

regulate extracellular ion concentrations, regulate neurotransmitter concentration

buffer reactive oxygen species

metabolic support, insulation

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9
Q

astrocytes

A

glia that are more numerous in the brain

fills paces between neurons

influence neurite growth, survival, and function

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10
Q

resting potential

A

inside the cell its negative -45mV to –80mV

maintained at all times by concentration gradient of K through leak channels

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11
Q

passive membrane properties

A

resistance

capacitance

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12
Q

what is gating

A

a stimulus that opens the gate (channel etc)

voltage or transmitter gated

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13
Q

what is responsible for passive/active electrical membrane properties

A

channels w/ gating and selectivity

leak channels open at rest (K+)

voltage-gated Na, K, Ca channels move ions down [ ] gradient

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14
Q

resistance is related to …

A

channels

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15
Q

capacitance is related to

A

insulating nonpolar lipid tails and conducting polar lipid heads

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16
Q

how do resistance and capacitance work

A

when voltage is applied, current goes to the capacitor b/c there is no resistance

resistance inc as charge builds, and current goes to a resistor

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17
Q

2 driving forces of resting potential

A

[ ] gradient

electrical driving force

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18
Q

what is equilibrium potential

A

[ ] driving force is equal and opposite to the electrical driving force

no net movement of charge

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19
Q

at resting potential what channels are not open in a neuron

A

voltage-gated

NT-gated

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20
Q

at resting potential what channels are open in a neuron

A

mostly K+ leak (flows out due to [ ] gradient, mostly neg resting pot)

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21
Q

at resting pot is the [ ] gradient changed by K+ leak channels?

A

no, only takes a few diffusing K+ ions to set up inside neg resting pot

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22
Q

what is essential to maintaining [ ] gradient of Na+ high out and K+ high in

A

Na/K ATPase of 3 Na out/2 K in per 1 ATP

Na leaks in so must be pumped out to keep [Na] in cell low

ouabain tipped arrow can kill a hippo

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23
Q

what is the nernst equation used for

A

calculate exact value of equilibrium potential for a single ion in mV

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24
Q

what does nernst equation depend on

A

temp (K)

charge of ion (pos or neg)

[ ]s of each ion of either side of the membrane

25
Q

nernst equation formula

A

Ek = (RT/zF) ln ( [ion out] / [ion in] )

Ek = voltage

z = charge of ion

26
Q

in squid giant axon Ek+ = -93 mV and ENa = 56 mV… which one “wins”?

A

depends on permeability of membrane to each ion

cell resting pot is ~ -70 mV so K+ contributes more than Na+

this is due to large K+ conductance and small Na+ conductance (many K+ leaks channels and only a few Na+ leak channels)

27
Q

nernst potential indicates which ions are involved in…

A

resting potential

membrane potential

28
Q

action potentials change the ______ of the membrane

A

permeability

29
Q

what is the Goldman equation used for

A

calculate the voltage contributions of multiple ion species to equilibrium potential

30
Q

what does goldman equation depend on

A

[ ] gradient of each ion

permeability (P) of the membrane to each ion

31
Q

3 things to maintain resting potential

A

[ ] gradients

mechanism to maintain gradients (Na/K ATPase)

selective permeability`

32
Q

if theres a smaller [ ] gradient then there is a _____ driving force and less _____ resting potenetial

A

smaller, negative

33
Q

permeability of K and Na at rest

A

K high

Na low

34
Q

electrical driving force on ion equation

A

E = Vm - E(ion)

ex. if cell is at -70 mV and ENa = 62 then E = 132 mV

35
Q

6 properties of an action potential

A

all or none

same size all the time (1 exception)

regenerative above threshold (pos reinforcement loop)

go above 0 mV

post-AP hyperpolarization

refractory period

36
Q

when an input depolarizes a cell what happens in general

A

voltage-gated Na channels open (changes conductance) and the voltage changes

if input depolarizes above threshold you get an AP

if input does not reach threshold there is no AP

37
Q

what is the positive feedback loop of reaching threshold

A

depol –> open voltage-gated Na channels –> Na in –> depol

38
Q

which voltage-gated channels are faster to open

A

Na+ conductance is rapid

K+ conductance has a slower onset (slower to open)

due to chem. properties

39
Q

what is AP shape dictated by

A

channel properties

Na looks normal

Ca looks like a plateau

40
Q

at rest, leak channels maintain…

A

rising phase: voltage gated Na

falling phase: voltage gated K

41
Q

full cycle of depol

A

input –> open voltage gated Na and Na moves in —1 ms—> voltage-gated Na channels inactivated and no Na moves —back to —–> -60mV due to K+ channels —–> Na channels close and cell ready to be depol again

42
Q

what causes voltage-gated Na channel inactivation

A

absolute refractory period during AP

43
Q

inward current makes a _______ inflection

A

downward

44
Q

outward current makes an _______ inflection

A

upward

45
Q

what does measuring AP current look like

A

initial inward current from Na ions

later outward current from K ions

46
Q

if sustained stimulus

A

rapidly adapting —> only fires at change

slowly adapting —> continuous fiing

47
Q

fugu sushi (pufferfish)

A

tetrodotoxin TTX blocks voltage-gated Na channels

blue ringed octopus

california newt

48
Q

lidocaine blocks…

A

Na channels (dentists)

49
Q

what if double stimulus

A

2nd AP smaller than the 1st if the stimulus is during the relative refractory period

K channels still open

not all Na channels have closed, still some inactivated

50
Q

squid giant axon (giant diameter) voltage clamping hypothesis

A

Na+ drives depol to cause AP

made artificial seawater w/o Na+

51
Q

squid giant axon voltage clamping experiment results

A

rising phase of AP driven by inward Na current

falling phase of AP driven by outward K+ current

Na open fast

K open with lag/delay

52
Q

squid giant axon voltage clamping experiment

A

stimulation electrode passes current to hold cell at 60 mV —> channels open —> current flows —-> voltage clamp measures current —> plays same current back to cell

53
Q

voltage gated ion channels respond to ________

A

depol

54
Q

are Na channels ion specific?

A

yes

voltage sensor

activation gate

ball + chain mechanism

55
Q

ion specificity

A

dimensions

charge at mouth

selectivity filter lining the channel

ions lose H2O of dehydration and interact w/ charges inside channel

56
Q

Patch clamping

A

voltage clamp a patch of membrane

single channel

neurons and channels

57
Q

problem with patch clamping neurons

A

multiple types

express protein in an artificial bilayer or cell w/o channel (frog oocyte)

58
Q

K channel structure

A

each gene codes for a subunit (4)

59
Q

na channel structure

A

all 4 subunits are the same and coded for by the same gene

Animal Physiology (26 decks)

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