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BIO 238 > Nerves Part 2 > Flashcards

Nerves Part 2 Flashcards

1
Q

what are the 4 functional segments of a neuron and what part of the neuron makes up each

A
  1. receptive segment (dendrite + cell body)
  2. initial segment (axon hillock)
  3. conductive segment ( axon)
  4. transmissive segment (synapse)
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2
Q

what is the resting membrane potential of a neuron

A

-70mV

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3
Q

what 2 things cause the RMP of a neuron

A
  1. Na/K pump moves more + ions out

2. a lot of K+ ions move out through the leak channels

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4
Q

what does it mean for the membrane of a neuron to be polarized

A

the outside of the membrane has a net + charge and the inside has net - charge

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5
Q

what does the receptive segment do

A

it receives stimuli (input)

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6
Q

why doesn’t the receptive segment have an action potential

A

it doesn’t have Na+ voltage-gated channels

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7
Q

events of receptive segment

A

stimulation –> chem-gated channels open –> graded potentials are generated

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8
Q

what does the initial segment do

A

it is the trigger zone;

graded potentials are processed and action potentials are initiated

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9
Q

what does the conductive segment do

A

propagates action potentials

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10
Q

what does the transmissive segment do

A

signal is transmitted to another cell;
arriving AP causes release of a neurotransmitter that will have an excitatory or inhibitory effect on a neuron, muscle, or gland

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11
Q

what kind of proteins does the receptive segment have

A

chem-gated channels for cations, K+, Cl-

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12
Q

what kind of proteins does the initial segment have

A

volt-gated Na+ and K+ channels

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13
Q

what kind of proteins does the conductive segment have

A

volt-gated Na+ and K+ channels

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14
Q

what kind of proteins does the transmissive segment have

A

volt-gated Ca^2+ channels and pumps

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15
Q

what can stimulate a neuron

A

release of neurotransmitters, pressure, stretch

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16
Q

what 3 steps happen to membrane as a result of stimulation

A
  1. specific chem-gated ion channels (Na+, K+, Cl-) with in the receptive segment open temporarily
  2. ions flow through the membrane down the concentration gradient
  3. the RMP is slightly altered to a graded potential
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17
Q

what is a graded potential

A

a small, short change from RMP where cell becomes slightly more pos or neg; depends on strength of stimulation

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18
Q

what is meant by local potential

A

graded potential weakens with distance along the membrane

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19
Q

what is postsynaptic potential

A

graded potentials that occur in the postsynaptic neuron

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20
Q

exitatory postsynaptic potential

A

if a neurotransmitter increases the membrane (by letting in Na+) and brings it closer to threshold

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21
Q

inhibitory postsynaptic potential

A

if neurotransmitter decreases the membrane (by letting Cl- in or K+ out) and takes it farther away from threshold

22
Q

what is summation of graded potentials

A

process by which all EPSPs and IPSPs get added together

23
Q

synaptic integration

A

the net result of EPSPs and IPSPs

24
Q

threshold value

A

minimum voltage to change to open volt-gated channel (-55mV)

25
Q

what happens to polarity if threshold value is reached

A

temporary reversal of polarity across plasma membrane –> inside becomes more pos, then returns to RMP

26
Q

what is the “all or none” law

A

if threshold is reached AP is sent; if threshold not reached, no AP sent

27
Q

what are the 2 processes involved in the propagation of AP

A

depolarization and repolarization

28
Q

what is depolarization

A

membrane potential becoming less negative

29
Q

what structure does depolarization and what is the goal

A

voltage-gated Na+ channels;

to spread the action potential

30
Q

what is the process of depolarization

A
  1. volt-gated Na+ channels open rapidly for a short period of time when threshold is reached
  2. rapid entry of Na+ makes inside more pos
  3. volt-gated Na+ channels inactivate
31
Q

what is the nerve signal (or nerve impulse)

A

the consecutive opening of volt-gated Na+ channels along the axon toward the synaptic knob (the domino effect that propagates the signal)

32
Q

what is repolarization

A

the reestablishment of RMP

33
Q

what is structure is repolarization done by and what is the goal

A

volt-gated K+ channels;

to return the membrane to RMP after AP passes

34
Q

what is the process of repolarization

A
  1. volt-gated K+ channels open for a short period of time when threshold of +30mV is reached
  2. exit of K+ makes the inside of axon negative (-70mV)
35
Q

hyperpolarization

A

the volt-gated K+ channels close too slowly and the membrane becomes too negative so the Na/K pump has to get it back to -70 mV

36
Q

refractory period

A

brief time after the initiation of the AP

37
Q

relative refractory period

A

AP is possible but with greater stimulation (the neuron is still hyperpolarized)

38
Q

absolute refractory period

A

no amount of stimulus is able to generate a 2nd AP (Na+ channels are inactivated)

39
Q

what 2 factors affect velocity of a nerve signal

A
  1. diameter of axon (larger = faster)

2. myelination of axon (myelination = faster)

40
Q

continuous conduction

A

occurs in unmyelinated axons and involves sequential opening of Na+ and K+ channels

41
Q

saltatory contraction

A

occurs in myelinated axons and involves AP only at neurofibril nodes

42
Q

converging circuit

A

input that converges at a single postsynaptic neuron

43
Q

diverging circuit

A

spreads info from one presynaptic neuron to several postsynaptic neurons

44
Q

what are the steps of the transmissive segment

A
  1. arrival of AP to the synaptic knob triggers opening of volt-gated Ca^2+ channels
  2. movement of Ca^2+ in
  3. synaptic vesicles release neurotran. into synaptic cleft
  4. neurotran diffuse across the cleft and bind to receptors on the postsynaptic cell
  5. postsynaptic cell (neuron, or muscle, or gland) is stimulated
45
Q

neurotransmitters

A

various organic compounds produced in nerve cells in order to transmit a signal that can be excitatory or inhibitory

46
Q

acetylcholine

A

neurotransmitter that excites skeletal muscle cells but inhibits cardiac muscle

47
Q

norepinephrine

A

released during stress, increases heart rate but decreases digestion

48
Q

what are the 2 ways to eliminate neurotransmitters after release

A

degredation of reuptake

49
Q

degredation

A

chemical inactivation in the synaptic cleft

50
Q

reuptake

A

reuptake into the presynaptic neuron to be reused

BIO 238 (8 decks)

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