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Physiology I > Lecture 4: Graded And Action Potentials > Flashcards

Lecture 4: Graded And Action Potentials Flashcards

1
Q

What kind of signals are critical to nervous system and muscles

A

Electrical

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2
Q

Why use ion permeability changes and not hormones/cell-cell signaling in the brain

A

Faster = survival

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3
Q

Where are neurotransmitters released

A

Synaptic cleft

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4
Q

4 functional regions o neuron

A

-cell body
-dendrites
-axon
-presynaptic terminal

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5
Q

Cell body function

A

Make proteins to maintain neuron

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6
Q

Dendrites function

A

Receive signals from neighboring neurons and deliver across axon to next neuron

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7
Q

Axon function

A

Integrate signal from dendrites and transmit action potential along cell

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8
Q

Presynaptic terminal function

A

Signal adjacent cells

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9
Q

2 types of ion channels involved in graded and action potentials

A

-ligand gated
-voltage gated

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10
Q

Graded potential vs action potential

A

-action potential large depolarization over long distance
-graded potential amplitude depends on strength of stimulus, shorter distances

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11
Q

Step 1 of graded potential (3)

A

-resting membrane exposed to stimulus (i.e. neurotransmitter)
-opens chemically gated channels
-changes membrane potential (depolarization or hyperpolarization)

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12
Q

Step 2 of graded potential

A

-ions move through channel to produce current
-depolarizes/hyperpolarizes nearby regions of cell membrane
-change in potential is proportional to stimulus

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13
Q

Graded potentials can lead to

A

Action potentials

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14
Q

Repolarization definition

A

Return to resting potential after depolarization

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15
Q

2 types of postsynaptic potentials: graded potentials

A

-EPSP
-IPSP

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16
Q

EPSP

A

-excitatory postsynaptic potential
-right after depolarization

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17
Q

IPSP

A

-inhibitory postsynaptic potential
-right after hyperpolarization

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18
Q

Graded potential: threshold

A

Amount of graded potentials required to create an action potential

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19
Q

Where does integration of post-synaptic potentials occur

A

Initial segment of axon

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20
Q

Typical EPSP voltage and how long it lasts

A

0.5 mV
20 seconds

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21
Q

A typical neuron would need ________ to reach threshold

A

30

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22
Q

Temporal summation definition

A

Occurs when single synapse receives many EPSPs in short period of time

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23
Q

Spatial summation definition

A

Occurs when single synapse receives many EPSPs from many presynaptic cells

24
Q

Action potential features

A

-one way
-all or none
-signal propagates non decrementally

25
Q

“Signal propagates non decrementally” meaning

A

-impulse propagates along axon
-amplitude of impulse is maintained

26
Q

2 gates within voltage gated Na+ channels

A

-activation gate
-inactivation gate

27
Q

How many gates do voltage gated K+ channels have

A

1 (open OR closed)

28
Q

When are voltage gated channel gates triggered to respond

A

At threshold

29
Q

3 conformations of voltage gated Na+ channels

A

-resting
-activated
-inactivated

30
Q

Activated voltage gated Na+ channel at threshold: what happens

A

-Influx of Na+
-activation gate opens
-inactivation gate starts to close before equilibrium is reached

31
Q

K+ channels have a ________ opening while Na+ channels have a _________ opening (hint: timing)

A

Delayed, rapid

32
Q

Opening Na+ channels at threshold is what kind of feedback cycle

A

Positive

33
Q

Positive feedback cycle for opening Na+ channels at threshold

A

depolarization —> opening of some voltage gated Na+ channels —> influx of Na+ which further decreases membrane potential —> depolarization —> repeat

34
Q

2 types of refractory periods

A

-absolute
-relative

35
Q

Absolute refractory period: definition

A

-when no stimulus can elicit an action potential

36
Q

State of voltage gated Na+ channels during absolute refractory period

A

Inactivated

37
Q

Supranormal stimulus definition

A

Stimulus that elicits a stronger response than original stimulus

38
Q

Relative refractory period definition

A

Interval when supranormal stimulus is required to elicit action potential

39
Q

Importance of refractory period (2)

A

-ensures one way propagation
-limits frequency of an action potential to conserve energy and prevent seizures

40
Q

How does Hyperkalemia cause muscle paralysis

A

-depolarization of skeletal muscle = increased excitability
-spontaneous APs occur
-voltage gated Na+ channels inactivate
-cells unable to fire APs (exhausted)

41
Q

2 things that determine speed of conduction

A

-diameter of fiber
-myelination

42
Q

2 types of fibers (conduction)

A

-rapid
-slow

43
Q

How does diameter affect speed of conduction

A

Larger diameter = lower internal resistance for current flow = faster conduction

44
Q

Are rapid or slow fibers larger in diameter

A

Rapid

45
Q

Where are rapid fibers found

A

Motorneurons

46
Q

Where are slow fibers found

A

Internal organs

47
Q

How does myelination affect speed of conduction

A

-Decreases capacitance of axon
-restrict action potential generation to nodes of ranvier
-increases conduction velocity

48
Q

Diameter of myelinated vs unmyelinated axons

A

Larger in myelinated

49
Q

2 types of conduction

A

-contiguous
-saltatory

50
Q

Which type of conduction occurs in myelinated fibers

A

Saltatory

51
Q

Which type of conduction occurs in unmyelinated fibers

A

Contiguous

52
Q

Contiguous conduction definition

A

AP spreads along every portion of membrane

53
Q

Saltatory conduction definition

A

Impulse jumps over sections of fiber covered with insulating myelin

54
Q

Is contiguous or saltatory conduction faster (and by how much)

A

Saltatory, 50 times

55
Q

Degenerative myelopathy definition and clinical signs

A

-Progressive disease of spinal cord causing progressive paralysis
-begins with ataxia in hind limbs
-dog with wobble when walking, knuckle over or drag feet

56
Q

All or none principle: 2 conditions

A

-if stimulus exceeds threshold, AP will be initiated (AP is triggered or not)
-AP will always be same magnitude for particular axon no matter how large the stimulus

Physiology I (5 decks)

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