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22 spring: neurology > test 3: lecture 3 > Flashcards

test 3: lecture 3 Flashcards

1
Q

Electrical signals necessary for neural function are
mediated by the flow ___ through aqueous pores
in the nerve cell membrane

A

of ions (electrical activity)

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2
Q

Vm

A

membrane potential

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3
Q

charge difference across the plasma membrane

A

membrane potential

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4
Q

resting Vm is ___

A

-70 mV

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5
Q

Any positive change in the membrane potential

A

depolarization (inside of cell becomes more positive)

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6
Q

Any negative change in the membrane potential

A

hyperpolarization

(inside of the cell becomes more negative)

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7
Q

Na moving in or out would cause depolarization

A

Na moving in, the inside of the cell would become more positive

(depolarization = more + )

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8
Q

K moving in or out would cause hyperpolarization

A

K moving out

hyperpolarization= more negative

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9
Q

V= Current x resistance

A

ohms law

driving force is by membrane potential

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10
Q

the amount of ___(ion flux/flow through an open channel) is directly proportional to the voltage across the membrane, i.e. the electrical “gradient” or electrical driving force

A

current

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11
Q

___ dictates the amplitude of ion flux

A

membrane potential

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12
Q

electrochemical gradient is a combo of ___

A

electrical (membrane potential)

chemical (concentration gradient) forces

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13
Q

Equilibrium is achieved when the tendency of an ion to move down its ___ gradient is exactly counter-balanced by an opposing ___ gradient, resulting in no net ion flux.

A

concentration

electrical

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14
Q

primary intracellular cation is ___

A

potassium (positive charge K+)

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15
Q

primary extracellular cation

A

sodium (Na+)

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16
Q

primary intracellular anion

A

proteins (negative charge)

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17
Q

primary extracellular anion

A

Cl-

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18
Q

how is resting membrane potential maintained

A
  • Na+/K+ ATPase - Contributes only a small amount (~8-10mV) of the resting membrane potential
  • K+ “leak” channels - Relatively selective permeability of the plasma membrane to K+ (via “leak” channels) contributes MOST of the resting membrane potential (K+ will leave the cell)
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19
Q

Eion

A

equlibrium(reversal) potential

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20
Q

equilibrium potential

A

•Defined as the Membrane Potential** at which the direction of ion flow through a particular channel reverses direction. **Enables one to predict which direction ions will flow

  • Determined primarily by the intracellular and extracellular concentration of each ion.
  • Unique for each ion
  • Nernst Equation
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21
Q

Na/K pump

A

3 Na out

2 K in

(uses ATP)

helps maintain resting Vm at -70 → small amount 8-10 mV

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22
Q

How does Na/K pumps work to set up K leak channels

A

Na/K will pump 3 Na out, 2 K in (net loss of +1)

K channels will open- there is more K inside cell than out. K will move down concentration gradient and will move out of cell. inside of cell becomes more negative

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23
Q

most of resting Vm is from ___

A

the loss of K from the cell

(potassium leaves cell through channels due to concentration gradient set up by Na/K pumps)

24
Q

what happens to K at -120 mV?

at -70?

at +70?

A

will flow into the cell

out of cell slowly (small current)

out of cell quickly (large current)

25
Q

what does the chart tell you

A

what an ion will do at specific membrane potentials

wether it will go in or out of the cell and how fast it will leave or enter

26
Q

Very ___ cell interior is needed to pull K+ into the cell against outward concentration gradient

A

negative

27
Q

Very ___ cell interior is needed to push Na+ out of the cell against inward concentration gradient

A

positive

28
Q

____ is determined by ion distribution (concentration differences) across the plasma membrane and the permeability of the membrane to each ion at a given time.

A

Actual membrane potential

29
Q

•Direction of flow for a particular ion is determined by the relationship of its ___ to the actual membrane potential.

A

equilibrium potential

30
Q

•Ion current (flow) amplitude is also determined by Vm; the electrical driving force (___).

A

Ohm’s law

31
Q

____ is a very rapid change in membrane potential. It occurs when a “stimulation” of the nerve cell membrane depolarizes the membrane enough to allow voltage gated Na+ channels to open

A

An action potential

32
Q

what is the threshold for action potential?

A

(threshold ~ -50mV).

cell must depolarize (become more + to -50) then it will launch the action potential down the axon

33
Q

explain action potential graph

A

stimulus opens some Na channels

threshold at -50

voltage gated Na channels open (more + depolarization)

voltage gated K channels slowly open (more negative but not enough to cancel out rapid influx of Na- cell will continue to depolarize until peak at +40)

Na channels close (K channels still open cell becomes more negative and repolarization starts)

K channels close but slowly. Cell becomes too negative (hyperpolarization)

resting potential is fixed by Na/K pumps to get to -70 (refractory period)

34
Q

Depolarization occurs when ligand-gated nonselective ___ channels at the post-synaptic membrane generate small excitatory depolarizing stimuli.

A

cation (+ go into the cell, make more +, depolarization)

35
Q

how is threshold reached?

A
  • ligand-gated nonselective cation channels at the post-synaptic membrane generate small excitatory depolarizing stimuli. (cell becomes more +)
  • These signals allow Na+ to begin to pass into the cell, and the depolarization spreads to the axon hillock and initial segment where there are a large amount of voltage gated Na channels
36
Q

where does action potential start?

A

axon hillock and initial segment

37
Q

___ contains a high conc. of voltage-gated sodium channels.

A

initial segment

38
Q

EPSP

A

EPSP - Excitatory Post-Synaptic Potentials

(positive charges into the cell); graded potential (depolarization)

little + into the cell that try to get to threshold to trigger action potential

39
Q

IPSP

A

IPSP - Inhibitory Post-Synaptic Potentials

(negative charges into the cell); graded potential

small negative into the cell causing hyperpolarization (more negative) → further away from threshold

40
Q

if IPSP + EPSP = 50 mV what will happen

A

summation

inhibitory(hyperpolarization- more negative) + excitatory(depolarization more positive)

action potential

41
Q

temporal summation of PSP

A

multiple stimulus from same place add on top of each other

42
Q

spacial summation

A

stimulus from different areas will add together

43
Q

compare graded and action potentials

A
44
Q

how do voltage gated sodium channels work?

A

open at threshold

inactivation gate closes after specific time

membrane returns to resting, gate closes and inactivation gate moves out of the way

ready for next threshold

45
Q

absolute refractory period

A

Time immediately after action potential during which another AP cannot occur (due to Na+v channel inactivation and delay in K+v channel closing).

new action potential can not be triggered for specific time

46
Q

relative refractory period

A

period of time during the refractory period that another action potential can be sent if the stimulus was very big

cell not back to normal but Na channels reset so technically they could go again if they had to

47
Q

what can increase speed of action potential?

A

increase amount of voltage gated Na channels

increase diameter of the axon (decrease in resistance will increase current flow)

insulation (myelin)

48
Q

___ is made by schwann cells and acts as insulation

A

myelin

49
Q

how does myelin increase speed of action potential

A

gaps in myelin (nodes of ranvier) will make action potential jump from node to node (saltatory conduction)

50
Q

___ are regularly spaced gaps in the myelin sheath

A

nodes of ranvier

51
Q

jumping from node to node on an axon is called

A

saltatory conduction

•Saltatory conduction is metabolically efficient – ion movements limited to nodal regions (including Na+/K+ ATPase and K+ “leak channels”)

100x faster conduction velocities, necessary for rapid reflex

52
Q

why does axon myelination do

A

decreases cation leakage (prevents + from leaving axon therefore keeping the strength of the AP all the way down the axon (more downstream current)

myelin will also spread out the + and - charge → lower capacitance this will mean more + available down stream to continue AP

53
Q

how does myelin increase downstream current

A

prevent cation leakage

54
Q

what happens to capacitance with myelinated axon?

A

decreased capacitance because + and - farther apart

lower capacitance= more downstream current

55
Q

AP jumping from node to node

A

saltatory conductance

22 spring: neurology (26 decks)

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