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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
“Signal propagates non decrementally” meaning
-impulse propagates along axon -amplitude of impulse is maintained
26
2 gates within voltage gated Na+ channels
-activation gate -inactivation gate
27
How many gates do voltage gated K+ channels have
1 (open OR closed)
28
When are voltage gated channel gates triggered to respond
At threshold
29
3 conformations of voltage gated Na+ channels
-resting -activated -inactivated
30
Activated voltage gated Na+ channel at threshold: what happens
-Influx of Na+ -activation gate opens -inactivation gate starts to close before equilibrium is reached
31
K+ channels have a ________ opening while Na+ channels have a _________ opening (hint: timing)
Delayed, rapid
32
Opening Na+ channels at threshold is what kind of feedback cycle
Positive
33
Positive feedback cycle for opening Na+ channels at threshold
depolarization —> opening of some voltage gated Na+ channels —> influx of Na+ which further decreases membrane potential —> depolarization —> repeat
34
2 types of refractory periods
-absolute -relative
35
Absolute refractory period: definition
-when no stimulus can elicit an action potential
36
State of voltage gated Na+ channels during absolute refractory period
Inactivated
37
Supranormal stimulus definition
Stimulus that elicits a stronger response than original stimulus
38
Relative refractory period definition
Interval when supranormal stimulus is required to elicit action potential
39
Importance of refractory period (2)
-ensures one way propagation -limits frequency of an action potential to conserve energy and prevent seizures
40
How does Hyperkalemia cause muscle paralysis
-depolarization of skeletal muscle = increased excitability -spontaneous APs occur -voltage gated Na+ channels inactivate -cells unable to fire APs (exhausted)
41
2 things that determine speed of conduction
-diameter of fiber -myelination
42
2 types of fibers (conduction)
-rapid -slow
43
How does diameter affect speed of conduction
Larger diameter = lower internal resistance for current flow = faster conduction
44
Are rapid or slow fibers larger in diameter
Rapid
45
Where are rapid fibers found
Motorneurons
46
Where are slow fibers found
Internal organs
47
How does myelination affect speed of conduction
-Decreases capacitance of axon -restrict action potential generation to nodes of ranvier -increases conduction velocity
48
Diameter of myelinated vs unmyelinated axons
Larger in myelinated
49
2 types of conduction
-contiguous -saltatory
50
Which type of conduction occurs in myelinated fibers
Saltatory
51
Which type of conduction occurs in unmyelinated fibers
Contiguous
52
Contiguous conduction definition
AP spreads along every portion of membrane
53
Saltatory conduction definition
Impulse jumps over sections of fiber covered with insulating myelin
54
Is contiguous or saltatory conduction faster (and by how much)
Saltatory, 50 times
55
Degenerative myelopathy definition and clinical signs
-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
All or none principle: 2 conditions
-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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