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From Flashcardlet > BMS 108 Ch. 07 Nervous System Part 2 > Flashcards

BMS 108 Ch. 07 Nervous System Part 2 Flashcards

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0
Q

Does an AP ever vary in amplitude?

A

No, it’s always +30mV

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1
Q

Action Potentials are _____________, once threshold is reached, there is no going back!

A

All-or-nothing

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2
Q

If AP can’t increase amplitude, how does it increase intensity?

A

by increasing frequency of APs

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3
Q

What is a refractory period?

A

A period following an action potential, where another action potential cannot be produced.

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4
Q

What are the two types of refractory periods?

A

Absolute and relative refractory periods

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5
Q

What is absolute refractory period? Why?

A

membrane cannot produce another AP; Na+ ion channels are inactivated (plugged)

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6
Q

What is a relative refractory period? Why?

A

Takes a much stronger stimulus to fire another AP (unlikely to happen); Some Na+ channels are inactivated and many VG K+ channels are still open.

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7
Q

AP uses _______ ________ to travel down an axon.

A

cable properties

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8
Q

If membrane potential is subthreshold, current leaks out as it travels through the cytoplasm, down the axon. What is this model called?

A

leaky hose model

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9
Q

Resistance ___________ as axon diameter ___________.

A

decreases; increases

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10
Q

Describe the conduction of an unmyelinated axon.

A
  • After axon hillock reaches threshold and fires AP, its Na+ influx depolarizes ADJACENT regions to threshold.
  • Which generates a new AP (processes propagates down the axon)
  • Refractory period causes the AP to travel one direction only
  • Conduction is relatively slow
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11
Q

Describe the conduction in a myelinated axon.

A
  • Ions can’t flow across myelinated membrane (no leaky hose; increases efficiency and speed by controlling ion direction)
  • APs occur ONLY at Nodes of Ranvier (VG Na+ channels only open at Nodes of Ranvier)
  • Current from AP at 1 node can depolarize next node to threshold (fast because APs skip from node to node
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12
Q

How do neurons communicate?

A

Synaptic transmission

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13
Q

What is a synapse?

A

A functional connection between a neuron (presynaptic) and another cell (postsynaptic).

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14
Q

What are the two types of synapses?

A

Chemical and electrical

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15
Q

What chemical do chemical synapses use to communicate?

A

neurotransmitters

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16
Q

Where are you likely to find electrical synapses?

A

in gap junctions (heart, smooth muscle)

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17
Q

How does an electrical synapse work?

A

Depolarization flows from one cell to another through channels called gap junctions.

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18
Q

The _______ ______ separates the _________ ________ (aka axon terminal) of presynaptic to postsynaptic cell.

A

synaptic cleft; terminal bouton

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19
Q

Neurotransmitters are inside ______ _______.

A

synaptic vesicles

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20
Q

Vesicles fuse with the terminal bouton’s membrane, releasing neurotransmitters by _____________.

A

exocytosis

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21
Q

What ion is the trigger for exocytosis of neurotransmitter?

A

Ca++

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22
Q

How does Ca++ come into the terminal bouton?

A

Via voltage-gated Ca++ channels

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23
Q

An action potential is required for _________ __________.

A

neurotransmitter release

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24
Q

Why do APs travel dow to the terminal bouton?

A
  • to depolarize the bouton
  • which opens the voltage-gated Ca++ channels
  • Ca++ travels into the bouton down its concentration gradient
  • Ca++ triggers exocytosis of neurotransmitter
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25
Q

What determines the frequency of an AP?

A

Refractory period

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26
Q

Neurotransmitter diffuses across the synaptic cleft and binds to ________ on the postsynaptic membrane (dendrites).

A

receptors (proteins)

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27
Q

These postsynaptic protein receptors are often chemically regulated, ________ _______ ion channels.

A

Ligand-gated

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28
Q

Ligand-gated ion channels that lead to DEPOLARIZATION cause _____ ______ ______ ______.

A

Excitatory Postsynaptic Potentials (EPSPs)

29
Q

Ligand-gated ion channels that lead to HYPERPOLARIZATION cause _____ ______ ______ ______.

A

Inhibitory Postsynaptic Potentials (IPSPs)

30
Q

EPSPs

  • the postsynaptic cell gets more ________ (depolarization).
  • moves _______ threshold
  • close _____ channels
  • open _____ & _____ channels
A

positive
toward
K+
Ca++; Na+

31
Q

IPSPs

  • the postsynaptic cell gets more ________ (hyperpolarization).
  • moves _______ threshold
  • open _____ & _____ channels
A

negative
away from
K+; Cl-

32
Q

EPSPs and IPSPs ______ and may trigger voltage-gated channels in the postsynaptic cell.

A

summate

33
Q

If membrane potential reaches threshold at the ______ ________, a new _____ ______ is generated.

A

axon hillock; action potential

34
Q

Why is the action potential created at the axon hillock?

A

The axon hillock has many voltage-gated Na+ channels necessary for an action potential.

35
Q

Unlike APs, EPSPs are ______ in amplitude.

A

graded

36
Q

What are cable properties?

A

signal decrements (decreases) with time and distance.

37
Q

What spatial summation?

A

Takes place when EPSPs from different synapses occur in postsynaptic cell at the same time.

38
Q

What is temporal summation?

A

Occurs because EPSPs that occur closely in time can sum before they fade.

39
Q

Are EPSPs and IPSPs influenced by cable properties, spatial summation and temporal summation?

A

yes

40
Q

How is synaptic inhibition accomplished?

A

by hyperpolarization

41
Q

What is involved in postsynaptic inhibition?

A
  • results from opening of VG Cl- channels and K+ channels
  • IPSPs change the MP away from threshold (more negative)
  • IPSPs dampen EPSPs (summation) which make it harder to reach threshold
42
Q

What is a neurotransmitter?

A

A chemical that is released from the presynaptic terminal bouton and binds to receptors on the postsynaptic cell.

43
Q

What are the changes in the postsynaptic cell that can result from the release of neurotransmitter?

A

EPSP
IPSP
muscle contraction
hormone release

44
Q

What is the most widely used neurotransmitter?

A

Acetylcholine (ACh)

45
Q

Acetylcholine (ACh) is used in the brain and all __________ ______.

A

neuromuscular junctions

46
Q

ACh has __________ and _________ receptor subtypes.

A

nicotinic (excitatory); muscarinic (variable)

47
Q

ACh in the synaptic cleft is broken down by _____________.

A

Acetylcholinesterase (AChE)

48
Q

The nicotinic ACh channel is a ________-_________ receptor channel.

A

ligand-gated

49
Q

nAChR is formed by ___ polypeptide subunits, which is a quatranary level protein.

A

5

50
Q

nAChR receptors are found at _______ ________.

A

neuromuscular junctions

51
Q

NAChR receptors open when ____ _____ bind.

A

2; ACh

52
Q

What are the effects on the postsynaptic cell when nAChR receptors open?

A
  • Permits diffusion of Na+ into and K+ out of the cell
  • Inward flow of Na+ dominates
  • EPSPs are produced
53
Q

mAChR receptors are both _______-________ and ___ _________-_________.

A

ligand-gated; g protein-coupled

54
Q

the mAChR receptor is not part of the ______ ________.

A

ion channel

55
Q

How many protein subunits form a mAChR?

A

1

56
Q

What are the effects of an ACh binding to mAChR?

A
  • activates an ion channel indirectly through G proteins (2nd messenger system)
  • either opens K+ channels (hyperpolarization) or closes them (depolarization)
  • this is why the effects are variable
57
Q

What is an agonist?

A
  • a chemical that mimics the action of a neurotransmitter
  • basis of pharmacology
  • receptors are named for agonists (nAChR = nicotine)
58
Q

What is an antagonist?

A
  • a chemical that blocks the action of a neurotransmitter

- e.g. curane - prevents ACh from binding to nAChR without activating it

59
Q

What are three monoamine neurotransmitters?

A
  1. Serotonin
  2. Norepinepherine
  3. Dopamine
60
Q

Serotonin is derived from _______.

A

tryptophan

61
Q

Norepinephrine and dopamine are derived from ________ and called __________.

A

tyrosine; catecholamines

62
Q

After release, monoamines are mostly inactivated by _________ __________ and broken down by _________ ________.

A

presynaptic reuptake; monoamine oxidase (MAO)

63
Q

MAO inhibitors are ______________.

A

antidepressants

64
Q

How does a MAO inhibitor work as an antidepressant?

A

MAO breaks down monoamine neurotransmitter, so inhibiting MAO means that more monoamine NT stays in the synaptic cleft longer.

65
Q

Like muscarinic acetylcholine receptors, monoamine NT receptors activate a ____ ______ _______ to open/close ion channels.

A

2nd messenger system

66
Q

What does serotonin affect?

A

mood, behavior, appetite and cerebral circulation

67
Q

What drug is structurally similar to serotonin?

A

LSD

68
Q

What are antidepressants that specifically block the reuptake of serotonin called?

A

Serotonin specific reuptake inhibitors (SSRIs)

e.g. Prozac, Zoloft, Paxil, Luvox

69
Q

SSRIs use the same mechanism as _______ ________, however, they are serotonin specific.

A

MAO inhibitors

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