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Physio > Graded Potentials And Action Potentials > Flashcards

Graded Potentials And Action Potentials Flashcards

1
Q

Signal transmission types

A

. Graded potentials

. Action potentials

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2
Q

Depolarization

A

. Membrane potential becomes less negative (inside of cell more positive)

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3
Q

Hyperpolarization

A

. Membrane potential becomes more negative (inside of cell more negative)

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4
Q

Repolarization

A

. Membrane potential returns toward resting membrane potential after a depolarization of hyperpolarization

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5
Q

Overshoot

A

. Reversal of polarity of membrane potential (inside of cell becomes positive compared to outside)

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6
Q

Voltage-gated channels

A

. Voltage sensor that causes channel to undergo conformational change when membrane potential is changed over specific range
. Opening of these initiates action potential (NOT graded)

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7
Q

Ligand-gated channels

A

. Chemically-gated
. Respond to binding of extracellular neurotransmitters to their receptors (receptor-operated channels) OR respond to intracellular second messengers
. Opening these generates graded potentials

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8
Q

Mechanosensitive channels

A

. Stretch-activated (respond to membrane deformation)
. Mediate pressure of touch and sensory inputs
. Stimulates graded potentials

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9
Q

Background channels

A

. Spontaneously open and close in absence of external stimulus
. Generate resting membrane potential

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10
Q

Postsynaptic potentials

A

. Occur at postsynaptic membrane of neuron-neuron synapse
. Stimulus is neurotransmitter released from presynaptic neuron
. Either excitatory or inhibitory

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11
Q

Excitatory postsynaptic potentials (EPSPs)

A

. Postsynaptic response to excitatory neurotransmitter opens mixed cation channels that carry Na and K
. Results in depolarization
. Brings membrane closer to hers hold for firing action potentials

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12
Q

Inhibitory postsynaptic potentials (IPSPs)

A

. Postsynaptic response to inhibitory neurotransmitter
. Opens K (or Cl) channels
. Causes hyperpolarization
. Takes cell further away from threshold for firing action potential

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13
Q

T/F Opening of K or Cl channels stabilize the cell at resting membrane potential without changing the resting membrane potential

A

T

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14
Q

End-plate potentials (EPPs)

A

. graded potentials
. Occur at motor end plate of neuromuscular junction
. Stimulus is neurotransmitter (Ach) released from motor nerve
. Caused by opening of mixed cation channel that allows Na and K to pass through

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15
Q

Receptor Potentials

A

. Graded potentials
. Occur at receptor of afferent (sensory) nerve
. Stimulus is physical (stretch, pressure)

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16
Q

The changes from resting membrane potential that don’t cause AP, the repolarization after removal of stimulus depends on _____

A

Changes in driving force that were set up by stimulus

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17
Q

When cell is hyperpolarized from resting potential, the driving force for K is ____

A

Reduced (membrane potential becomes nearer to Ek, driving force for Na influx inc.)

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18
Q

After removal of a stimulus, the return to resting potential is ____

A

Passive, based solely on driving forces and permeability for specific ions

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19
Q

In response to a depolarization from resting potential, the driving force for K ____ and driving force for Na ______

A

. K efflux increases

. Na influx decreases

20
Q

Graded potentials can be depolarizing or ____

A

. Hyperpolarizing

. Depends on currents involved

21
Q

Graded amplitude

A

. Magnitude of response (mV) varies w/ magnitude of stimulus

22
Q

Decrement also conduction

A

. Magnitude of potential change declines the further away from the stimulus site you get

23
Q

Action potentials

A

. Rapid, large changes in membrane potential

24
Q

Graded potentials have what relationship to action potentials?

A

Graded potentials have stimulus (trigger) for generation (firing) of AP

25
Q

Threshold potential

A

. Point when stimulus is just adequate to initiate AP 50% of the time
. Due to voltage-dependence of activation (opening) of Na channels responsible for initiating AP

26
Q

T/F Graded potentials and action potentials have a threshold potential

A

F, only AP has it

27
Q

AP relationship to distance

A

. AP does not decrease in amplitude over distance

. Propagated

28
Q

Absolute refractory period

A

. Period where AP can’t be elicited no matter how strong the stimulus

29
Q

Relative refractory period

A

. Period where another AP can be elicited only by greater than normal stimulus

30
Q

How is the shape of an AP determined?

A

. time-dependent changes in Na and K currents

31
Q

Voltage clamp technique

A

. Voltage can be set and help by investigator
. Clamping membrane potential above threshold for AP causes current to flow w/o change in membrane potential
. Allows investigation of current flowing at any membrane potential
. Looked at current in Na-containing, Na free, K-containing, and K free to see contributions of each ion

32
Q

Upstroke (depolarizing phase) of AP is caused by what kind of mechanism?

A

Positive feedback

. Opening of some Na channels causes depolarization which causes more Na channels to open

33
Q

Na vs K channel behavior during voltage clamp pulse

A

. Na does not remain high, but spontaneously decays (inactivated)
. K turns on more slowly but maintains during voltage pulse, do not exhibit inactivation

34
Q

Na channels exert what kind of feedback onto voltage-gated channels?

A

Positive feedback

35
Q

K channels exert what kind of feedback on voltage-gated ion channels?

A

Negative feedback

36
Q

Why doesn’t membrane potential ever reach Ena?

A

. Driving force for Na dec. as membrane potential approaches Ena
. Na decreases due to inactivation of Na channels
. K slowly starting to build

37
Q

What causes repolarization?

A

. Inactivation of Na (dec. inward positive current)

. Activation of K (inc. outward positive current)

38
Q

Afterhyperpolarization

A

. Mechanisms responsible for repolarization cause transient hyperpolarization
. Na channels don’t immediately recover from inactivation and K channels are slow to close upon repolarization
.

39
Q

Role of Na-K-ATPase

A

. Maintains resting membrane potential by maintaining concentration gradients needed for resorting membrane potential and AP

40
Q

Conduction of AP by local current flow

A

. Depolarization causes inside of cell to be positive in that region of axon
. In areas adjacent, the cell is still at rest w/ negative inside
. Current flow locally since opposite charges attract

41
Q

Saltatory conduction

A

. Axon covered w/ myelin sheath
. Gaps btw myelin (nodes of Ranvier) have fast Na channels and are the only areas that can generate AP
. AP in one node depolarizers the next node to threshold
. Areas in between don’t generate APs

42
Q

Saltatory conduction is a good mechanism because of what reasons?

A

. Faster conduction: process of depolarizing a node further away is faster than depolarizing adjacent areas (less intermediate steps)
. Energy efficient: process fo cintuinally generating APs require less energy in myelinated nn.

43
Q

What determines speed of conduction?

A

. Diameter of the fiber (larger fiber conducts faster)

. Presence of myelin (myelinated faster than unmyelinated

44
Q

Tubocurarine

A

. Neuromuscular blocking agent found in arrow poison
. Dec. EPP amplitude so it is insufficient to reach threshold for skeletal muscle APs
. Assists w/ intubation, setting fractures and dislocation
. Used to diagnose Myasthenia Gravis

45
Q

tetrodotoxin (TTX)

A

. found in puffer fish
. Voltage-gated Na channel inhibitor to inhibit upstroke of AP
. Causes loss of sensory and motor function

46
Q

Multiple sclerosis

A

. Attacks myelin of myelinated axons
. As myelin sheath degrades, scarring occurs giving symptoms
. AP conduction is adversely affected by demyelination

Physio (62 decks)

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