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NEUR 2610 > Chapter 4: How Neurons Use Electric Signals to Transmit Information > Flashcards

Chapter 4: How Neurons Use Electric Signals to Transmit Information Flashcards

1
Q

who speculated that electricity might be the messenger that spreads info thru the nervous system?

A

Stephen Gray

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2
Q

who discovered electrical stimulation?

A

Luigi Galvani

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3
Q

passage of an electrical current from the uninsulated tip of an electrode thru tissue, resulting in changes in the electrical activity of the tissue (muscle contraction)

A

electrical stimulation

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4
Q

who demonstrated that electrical stimulation of the neocortex causes movement?

A

Guastav Theodor Fritsch + Eduard Hitzig

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5
Q

who first (unethically) demonstrated that the brain of a conscious person could be stimulated electrically to produce movement of the body

A

Roberts Bartholow

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6
Q

who was the first to measure the brain’s electrical currents w/ a voltmeter

A

Richard Caton

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7
Q

graph of electrical activity from the brain, which is mainly composed of graded potentials from many neurons

A

electroencephalogram (EEG)

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8
Q

who proved that electrical messages in nerves is not the same as real electricity on a wire?

A

Hermann von Helmholtz

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9
Q

nerves conduct info at ___, whereas electricity flows along a wire about ___

A

30-40m/s; 1 million times faster

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10
Q

who’s idea was it that waves of chemical change travel along an axon to deliver a neuron’s message?

A

Julius Bernstein

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11
Q

the neurons of most animals are tiny, around ___ in diameter

A

1-20 micrometres

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12
Q

device that measures the strength of electrical voltage by recording the difference in electrical potential between 2 points

A

voltmeter

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13
Q

who first noticed that the North Atlantic squid Loligo vulgaris had giant axons?

A

J.Z. Young

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14
Q

how big are the North Atlantic squid Loligo vulgaris’ axons?

A

can be as large as 1mm in diameter

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15
Q

how does the North Atlantic squid propel itself?

A
  1. with fins
  2. by contracting its mantle to force water out (via stellate ganglion)
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16
Q

squid diagram

A

a. giant axon
b. mantle axons
c. stellate ganglion

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17
Q

who used the North Atlantic squid’s axons to determine the neuron’s ionically based electrical activity (Nobel Prize)?

A

Alan Hodgkin + Andrew Huxley

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18
Q

specialized device that serves as a sensitive voltmeter, registering changes in voltage over time

A

oscilloscope

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19
Q

the units used when recording the electrical charge from a nerve/neuron

A

millivolts + milliseconds

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20
Q

a microscopic insulated wire or a saltwater-filled glass tube whose uninsulated tip is used to stimulate or record from neurons

A

microelectrode

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21
Q

Hodgkin and Huxley learned that the ___ is a change in the concentration of specific ions across the cell membrane

A

nerve impulse

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22
Q

3 factors that influence the movement of anion/cations into or out of cells

A
  • diffusion
  • concentration gradient
  • voltage gradient
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23
Q

in a semipermeable membrane, one half will be positively charged and the other negative, and the voltage difference will be greatest ____

A

close to the membrane

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24
Q

at equilibrium, the differential concentration of the chloride ions on the 2 sides of the membrane produces ___

A

a difference in charge (voltage)

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25
Q

most biological membranes are ___ because ___

A

semipermeable; they have ion channels embedded

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26
Q

the inside of the membrane at rest has a charge of ___ relative to the extracellular side

A

-70mV

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27
Q

a store of potential energy is called the membrane’s ___

A

resting potential

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28
Q

4 charged particles that take part in producing the resting potential

A

ions of:
1. sodium (Na+)
2. potassium (K+)
3. chloride (Cl-)
4. large protein molecules (A-)

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29
Q

__ and __ ions are more concentrated in the intracellular fluid

A

protein (A-) and potassium (K+)

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30
Q

__ and __ ions are more concentrated in the extracellular fluid

A

sodium (Na+) and chloride (Cl-)

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31
Q

3 features that contribute to the cell membrane’s resting charge

A
  1. because the membrane is relatively impermeable to large molecules, the negatively charged proteins (A-) remain inside the cell
  2. ungated potassium + chloride channels allow potassium (K+) and chloride (Cl-) ions to pass more freely, but gates on sodium channels keep out positively charged sodium ions (Na+)
  3. Na+ – K+ pumps extrude Na+ from the intracellular fluid and inject K+
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32
Q

what creates the resting potential?

A

protein anions (A-) are manufactured inside the cell and have no channels to cross the membrane and leave the cell

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33
Q

why do potassium (K+) cations not balance out the charge of the protein anions inside the cell?

A

the potassium concentration is much higher inside the cell to try to balance this, but not all of them enter because of the potassium concentration gradient - they are drawn back out of the cell due to lower numbers outside

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34
Q

the sodium-potassium pump continually exchange __ intercellular sodium ions for ___ potassium ions

A

3; 2

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35
Q

___ ions are free to leave the cell thru their open channels, but ___ ions are slow to re-enter due to their closed channels

A

potassium; sodium

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36
Q

__ sodium ions reside on the outside of the axon membrane vs. the inside

A

10x as many

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37
Q

at equilibrium, there are about __ chloride ions outside the cell vs. inside

A

12x as many

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38
Q

small voltage fluctuation across the cell membrane

A

graded potentials

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39
Q

hyperpolarization is due to an efflux of ___, making the extracellular side more ___

A

K+; positive

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40
Q

depolarization is due to an influx of ___

A

Na+

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41
Q

graded potentials usually only last ___

A

a few milliseconds

42
Q

hyperpolarization + depolarization typically take place on the ___

A

soma membrane + dendrites

43
Q

3 channels that underlie graded potentials

A
  1. potassium channels: efflux of K+ = hyperpolarization
  2. chloride channels: influx of Cl- = hyperpolarization
  3. sodium channels: influx of Na+ = depolarization
44
Q

what indicates that potassium channels have a role in hyperpolarization?

A

the chemical tertaethylammonium (TEA), which blocks potassium channels, also blocks hyperpolarization

45
Q

what indicates the involvement of sodium channels in depolarization?

A

the chemical tetrodotoxin (TTX), which blocks sodium channels, also blocks depolarization

46
Q

large, brief reversal in an axon membrane’s polarity that lasts 1ms

A

action potential

47
Q

when is the action potential triggered?

A

when the cell membrane is depolarized to -50mV = threshold potential

48
Q

the action potential can trigger a total voltage change of ___, reaching as great as ___

A

100mV; +30mV

49
Q

gated protein channel that opens/closes only at specific membrane voltages

A

voltage-activated channels

50
Q

sequence of action for voltage-activated channels during an action potential

A
  1. cell membrane potential reaches -50mV, both sodium & potassium voltage-activated channels open
  2. voltage-activated sodium channels respond faster vs. potassium, so Na+ influx happens just before K+ efflux
  3. sodium channels have 2 gates, at +30mV one of them close - Na+ influx happens quickly
  4. potassium channels open slower and remain longer = reverses Na+ depolarization & even hyperpolarizes the membrane
51
Q

the state of an axon in the repolarizing period, during which a new action potential cannot be elicited because gate 2 of sodium channels (not voltage-activated) are closed

A

absolutely refractory

52
Q

the state of an axon in the later phase of an action potential, during which higher-intensity electrical current is required to produce another action potential & potassium channels are still open

A

relatively refractory

53
Q

voltage-activated sodium channels have _ gate(s) and voltage-activated potassium channels have _ gate(s)

A

2; 1

54
Q

propagation of an action potential on the membrane of an axon

A

nerve impulse

55
Q

the passing along of an action potential is similar to ___ because ___

A

the domino effect; there is no decrement in the magnitude

56
Q

refractory periods limit the frequency of action potentials to about one every ____

A

5 ms

57
Q

the max rate at which action potentials can occur is about ___

A

200 per second

58
Q

___ prevent the action potential from reversing direction and returning to its point of origin

A

refractory periods

59
Q

our largest axons are about ___ wide

A

30 micrometres

60
Q

the part of the axon that is not covered by myelin

A

nodes of Ranvier

61
Q

fast propagation of an action potential at successive nodes of Ranvier

A

saltatory conduction (leaping)

62
Q

2 important consequences myelin has for propagating action potentials

A
  1. propagation becomes energetically cheaper since action potentials regenerate only at the nodes of Ranvier, not along the axon’s entire length
  2. myelin improves the action potential’s conduction speed
63
Q

jumping from node to node ___ the rate at which an action potential can travel along an axon because ___

A

speeds; the current flowing within the axon beneath the myelin sheath travels very fast

64
Q

on larger, myelinated mammalian axons, nerve impulses can travel at a rate as high as ___

A

120 m/s

65
Q

on smaller, uninsulated axons, nerve impulses can travel only about ___

A

30 m/s

66
Q

in multiple sclerosis, the ___ is damaged, which ___

A

myelin formed by oligodendroglia; disrupts the affected neurons’ ability to propagate action potentials via saltatory conduction

67
Q

what is at the site of the loss of myelin in patches (MS)?

A

scarring and/or plaque

68
Q

who performed experiments on large motor neurons in the vertebrate spinal cord to answer how the neuron integrates such an enormous array of inputs into a nerve impulse?

A

John C. Eccles

69
Q

a spinal cord motor neuron has an extensive dendritic tree with as many as __ main branches that subdivide numerous times & are covered w/ ___

A

20; dendritic spines

70
Q

brief depolarization of a neuron membrane in response to stimulation, making the neuron more likely to produce an action potential

A

excitatory postsynaptic potentials (EPSPs)

71
Q

brief hyperpolarization of a neuron membrane in response to stimulation, making the neuron less likely to produce an action potential

A

inhibitory postsynaptic potentials (IPSPs)

72
Q

EPSPs are associated w/ the opening of ___ channels

A

sodium channels

73
Q

IPSPs are associated w/ the opening of ___ channels

A

potassium

74
Q

why is an action potential not produced on the motor neuron’s cell body membrane even when an EPSP is strong?

A

the cell body membrane of most neurons do not contain voltage-activated channels - must reach the initial segment

75
Q

area near where the axon meets the cell body that is rich in voltage-gated channels, which generate the action potential

A

initial segment

76
Q

addition of one graded potential to another that occur close in time

A

temporal summation

77
Q

addition of one graded potential to another that occur close in space

A

spatial summation

78
Q

the ___ always indicates the summed influences of multiple temporal and spatial inputs

A

cell body membrane

79
Q

if the threshold level is maintained for a long period, the action potentials will ___

A

follow one another in rapid succession as quickly as the gates on the voltage-activated channels can reset

80
Q

inputs that are ___ are usually much more influential than those occurring some distance away

A

close to the initial segment

81
Q

some cells in the developing hippocampus can produce additional action potentials called ___ when the cell would normally be refractory

A

giant depolarizing potentials

82
Q

giant depolarizing potentials aid in developing the brain’s ___

A

neural circuitry

83
Q

reverse movement of an action potential into the soma + dendritic field of a neuron; postulated to play a role in plastic changes that underlie learning

A

back propogation

84
Q

in some nonmammalian species, they might lack ___ and have ion channels that respond to ___ rather than voltage

A

dendritic branches; light

85
Q

the many differences among neurons suggest that the nervous system capitalizes on ___ to produce ___

A

structural/functional modifications; adaptive behaviour

86
Q

transgenic technique that combines genetics + light to excite or inhibit targeted cells in living tissue

A

optogenetics

87
Q

the light-activated ion channel channelrhodopsin-2 (ChR2) absorbs ___ light and opens briefly to allow the passage of __, exciting the cell via ___

A

blue; Na+ and K+; depolarization

88
Q

the light-activated ion channel halorhodopsin (NpHR) absorbs ___ light and pumps ___ into the cell, inhibiting the cell via ___

A

green-yellow; Cl-; hyperpolarization

89
Q

who used optogenetic techniques in mice to silence or activate neurons in the hypothalamus during stress?

A

Sterley

90
Q

the base of each hair on your arm is wrapped in ___. when you displace the hair, ___

A

a dendrite of a touch neuron; the encircling dendrite is stretched

91
Q

ion channel on a tactile sensory neuron that activates in response to stretching of the membrane, initiating a nerve impulse

A

stretch-activated channels

92
Q

an odorous molecule in the air that lands on an ___ and fits itself into a specially shaped compartment opens ___

A

olfactory receptor; chemical-activated ion channels

93
Q

amyotrophic lateral sclerosis (ALS) essentially means ___ and ___, primarily due to the death of ___

A

muscle weakness; hardening of the lateral spinal cord; spinal motor neurons

94
Q

the axon terminal contacts a specialized area of the muscle membrane called an ___, where the axon terminal releases the chemical transmitter ___

A

end plate; acetylcholine

95
Q

on a muscle, the receptor-ion complex that is activated by the release of the neurotransmitter acetylcholine from the terminal of a motor neuron

A

end plate

96
Q

2 steps of muscle contraction

A
  1. a motor neuron’s axon collaterals contact a muscle fibre end plane, then acetylcholine attaches to receptor sites on the end plate’s transmitter-activated channels, opening them
  2. these large membrane channels allow simultaneous influx of Na+ and efflux of K+, generating current sufficient to activate voltage-activated channels, triggering action potentials, causing the muscle to contract
96
Q

receptor complex that has both a receptor site for a chemical and a pore thru which ions can flow

A

transmitter-activated channels

97
Q

how is a transmitter-activated channel on an end plate different from the channels on axons + dendrites?

A
  • a single end plate channel is larger than 2 sodium AND 2 potassium channels combined
  • when its transmitter-activated channel opens, they allow both Na+ influx AND k+ efflux through the same pore
98
Q

in myasthenia gravis, the thymus, which produces antibodies that binds to viruses, makes antibodies that bind to the ___ on muscles, causing ___

A

acetylcholine receptors; weakness + fatigue

99
Q

how fast does an action potential travel along a squid’s axon?

A

25 m/s

100
Q

myasthenia gravis is an ___, and usually ___ with treatment

A

autoimmune disease; well controlled

NEUR 2610 (8 decks)

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