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Block 1: Neuroscience > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

Action Potential?

A

Rapid + transient change in the membrane potential (Vm) of a cell (ex. neuron)

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2
Q

Basis of electrical signaling in body?

A

Action Potential

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3
Q

Action Potentials usually initiate at?

A

Axon Hillock

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4
Q

Action Potentials are propagated by?

A

Voltage-Gated Ion Channels along the axon

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5
Q

Action Potential is an _____ phenomenon?

A

“All-or-Nothing”

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6
Q

AP will NOT fire if Vm is?

A

Under threshold

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7
Q

Minimum depolarization needed to?

A

Fire AP

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8
Q

S4 segment senses change in?

A

Voltage

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9
Q

“Voltage Sensors” with Ion Selectivity?

A

1) Na+ Channel
2) K+ Channel (Tetramer)

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10
Q

Voltage-Gated Na+ Channels?

A

3 Conformational States (Open, Inactivated, Closed)

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11
Q

Activation of the voltage-gated Na+ channels leads to?

A

Increased flow of ions and depolarization

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12
Q

Inactivation of the voltage-gated Na+ channels leads to?

A

Stops the flow of ions and leads to repolarization

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13
Q

Voltage-Gated K+ Channels?

A

1) Depolarization triggers opening of voltage-gated K+ channels
2) K+ ions rush OUT OF cell
3) Transient efflux (high Pk) leads to Hyperpolarization

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14
Q

Depolarization triggers?

A

Opening of Voltage-Gated K+ channels

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15
Q

Hyperpolarization is built in defense against?

A

Hyperexcitability (Negative feedback decreases probability of activating more channels)

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16
Q

Na+ and K+ Channel Synchrony?

A

1) Rapid activation of Na+ channels causes depolarization
2) Na+ channel inactivation STOPS depolarization
3) Slower activation of K+ channels contributes to depolarization and eventual hyperpolarization

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17
Q

Propagation?

A

Movement down axon

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18
Q

Non-Propagated Depolarization?

A

Spreads passively through local current flow (“Electronic Conduction”)

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19
Q

Depolarization attenuates as it?

A

Moves down axon

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20
Q

Peak membrane potential during an AP remains?

A

Consistently depolarized

21
Q

AP propagation takes?

A

Time (to charge membrane)

22
Q

Myelination increases?

A

Conduction velocity

23
Q

Depolarization decreases as it?

A

Moves down axon

24
Q

Propagated Depolarization (Concept 1)?

A

Depolarization attenuates as it moves down axon

25
Q

Propagated Depolarization (Concept 1) is caused by?

A

1) Membrane Resistance (Rm)
2) Interaxonal Resistance (Ri)

26
Q

Membrane Resistance?

A

Barricade on cell surface that is preventing passive flow of ions out

27
Q

Interaxonal Resistance?

A

Resistance inside axon (“like traffic”)

28
Q

Length Constant?

A

Distance it takes to reach 37% of Vmax

29
Q

Length Constant is directly proportional to?

A

Rm

30
Q

Length Constant is inversely proportional to?

A

Ri

31
Q

Propagated Depolarization (Concept 2)?

A

Peak membrane potential along an axon during an AP remains consistently depolarized

32
Q

Propagated Depolarization (Concept 2) is caused by?

A

Refractory Periods

33
Q

Refractory Periods keep it?

A

Moving down the axon

34
Q

Absolute Refractory Period?

A

A 2nd Ap can NOT fire
(Na+ channels can not be reactivated) (either in open or inactivated state)

35
Q

Relative Refractory Period?

A

A much greater depolarization required for an AP to fire (Active K+ channels hyperpolarizing the cell)

36
Q

Propagated Depolarization (Concept 3)?

A

AP propagation takes time (time is needed for the membrane to charge as the AP moves along the axon)

37
Q

Time needed to charge membrane = ?

A

Rate limiting event of AP propagation

38
Q

Time Constant?

A

Time it takes for the change in Vm to reach 63% of its final value

39
Q

Time Constant is directly proportional to?

A

Rm

40
Q

Time Constant is directly proportional to?

A

Cm

41
Q

Greater the size of the axon?

A

Greater the time it takes for the membrane to charge

42
Q

Capacitance?

A

Ability for something to hold a charge

43
Q

Propagated Depolarization (Concept 4)?

A

Myelination increases the conduction velocity by:
1) Increasing Rm –> Increases length constant
2) Decreasing Cm –> Decreases time constant

44
Q

Myelination increase = ?

A

Membrane Resistance will increase

45
Q

Saltatory Conduction?

A

Propagation of APs along myelinated axons from 1 node of Ranvier to the next node

46
Q

Multiple Sclerosis?

A

An autoimmune, degenerative disease of axon demyelination

47
Q

MS increases?

A

Passive current flow

48
Q

MS decreases?

A

AP conduction velocity

49
Q

MS results in?

A

Muscle Functions being messed up

Block 1: Neuroscience (15 decks)

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