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PSYCH 275 > Chapter 4: Neurons Use Electrical Signals to Transmit Information > Flashcards

Chapter 4: Neurons Use Electrical Signals to Transmit Information Flashcards

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1
Q

Electrographic Seizures

A

abnormal rhythmic neuronal discharges, may be recorded by an electroencephalogram

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2
Q

Electrical Stimulation

A

passage of an electrical current from the uninsulated tip of an electrode through tissue, resulting in changes in the electrical activity of the tissue

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3
Q

Voltmeter

A

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

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4
Q

Electroencephalogram (EEG)

A

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

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5
Q

Oscilloscope

A

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

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6
Q

Microelectrode

A

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

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7
Q

Diffusion

A

movement of ions from an area of higher concentration to an area of lower concentration through random motion

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8
Q

Concentration Gradient

A

difference in the relative abundance of a substance among regions of a container, allows the substance to diffuse from an area of higher concentration to an area of low concentration

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9
Q

Voltage Gradient

A

difference in charge between two regions that allows a flow of current if two regions are connected

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10
Q

What is the behavioral response to stimulation?

A

how do our nerve detect a stimulus (sensory) and inform the brain about it?

how does the brain decide what response should be made?

how does the brain command muscles to move to produce a behavioral response?

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11
Q

What is electricity?

A

a flow of electrons from a body that contains a higher charge (more electrons) to a body that contains a lower charge (fewer electrons)

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12
Q

What is electrical potential?

A

the ability to do work using stored electrical energy

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13
Q

What are volts?

A

difference of charge between the positive and negative poles

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14
Q

What is the relationship between electricity and biological tissue?

A

if it contains an electrical charge, this charge can be recorded

if it’s sensitive to an electrical charge, the tissue can be stimulated

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15
Q

What is the negative pole?

A

the source of electrons, higher charge

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16
Q

What is the positive pole?

A

location to which electrons flow, lower charge

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17
Q

Who was Galvani?

A

eighteenth century

electrical current applied to a dissected nerve induced a twitch in the muscle connected to the nerve, electricity flows along the nerve

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18
Q

What is electrical stimulation?

A

passing an electrical current from the tip of an electrode through brain tissue, resulting in changes in the electrical activity of the tissue

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19
Q

Who were Fritsch and Hitzig?

A

mid-nineteenth century

electrical stimulation of the neocortex causes movement (arms and legs)

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20
Q

What was Bartholow’s study from 1874?

A

first report of human brain stimulation

passed an insulated needle into the left posterior lobe so that the non-insulated portion rested entirely in the substance of the brain

the reference was placed in conduct with dura mater

when the circuit was closed, muscular contraction in the right upper and lower extremities ensued

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21
Q

What was Richard Caton’s study?

A

first attempt to measure electrical currents of the brain using a voltmeter and electrodes on the skull

noticed fluctuations in the voltmeter

early evidence that neurons send electrical messages

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22
Q

What is an electroencephalogram?

A

graph that records electrical activity through the skull or from the brain and represents graded potentials of many neurons

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23
Q

What was von Helmholtz’s experiment?

A

nineteenth century

stimulated brain nerve to calculate the information speed

flow of information in the nervous system is too slow to be a flow of electricity

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24
Q

What was Julius Berstein’s experiment?

A

1886

must be neuronal chemistry (based on ions) that produce electrical charges

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25
Q

How do tools measure neuron’s electrical activity?

A

when a single axon is stimulated, it produces a wave of excitation

if an electrode is connected to a voltmeter it can detect a change in electrical charge on that axon’s membrane as the wave passes

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26
Q

What is a volt?

A

a measure of a difference in electrical potential

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27
Q

What is a voltmeter?

A

a device that measures the difference in electrical potential between two bodies

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28
Q

Why was the giant axon of a squid studied?

A

much larger in a diameter than human axons

humans: 1 to 20 micrometers, squid: up to 1 millimeter

easier subject of experiments

used to discover the neuron’s ionically based activity

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29
Q

What are waves of information?

A

neurons can convey information as a wave, induced by stimulation on the cell body, that travels down the axon to its terminal

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30
Q

What is an oscilloscope?

A

a device that served as a sensitive voltmeter

used to record voltage changes on an axon

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31
Q

What are microelectrodes?

A

a set of electrodes small enough to place on or in and axon (1 mm in size)

can be used to measure a neuron’s electrical activity and deliver an electrical current to a single neuron (stimulation)

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32
Q

What are cations?

A

positively charged ions

examples: sodium (Na+), potassium (K+)

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33
Q

What are anions?

A

negatively charged ions

examples: chloride (Cl-), protein molecules (A-)

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34
Q

What is diffusion?

A

movement of ions from an area of higher concentration to an area of lower concentration through random motion

results in dynamic equilibrium

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35
Q

What is a concentration gradient?

A

relative abundance of substance in space

differences in concentration of a substances allow the substance to diffuse from an area of higher concentration to an area of lower concentration

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36
Q

What is a voltage gradient?

A

difference in charge between two regions that allows a flow of current if the two regions are connected

opposite charges attract

similar charges repel

ions will move down a voltage gradient from an area of higher charge to an area of lower charge

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37
Q

What is equilibrium?

A

at equilibrium, the concentration gradient is equal to the voltage gradient

efflux (outflow) of chloride ions down the chloride concentration gradient is counteracted by the influx (inward flow) of chloride ions down the chloride voltage gradient

equilibrium occurs when the concentration gradient of chloride ions on the right side of the beaker is balanced by the voltage gradient of chloride ions on the left

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38
Q

Resting Potential

A

electrical charge across the insulating cell membrane in the absence of stimulation, a store of potential energy produced by a greater negative charge on the intracellular side relative to the extracellular side

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39
Q

Graded Potentials

A

small voltage fluctuation across the cell emebrane

40
Q

Hyperpolarizations

A

increase in electrical charge across a membrane, usually due to inward flow of chloride or sodium ions or the outward flow of potassium ions

41
Q

Depolarization

A

decrease in electrical charge across a membrane, usually due to the inward flow of sodium ions

42
Q

Action Potential

A

large brief reversal in the polarity of an axon membrane

43
Q

Threshold Potential

A

voltage on a neuronal membrane at which an action potential is triggered by the opening of sodium and potassium voltage-activated channels, about -50 mV relative to extracellular surround, also called the threshold limit

44
Q

Voltage-Activated Channels

A

gated potential channel that opens or closes only at specific membrane voltages

45
Q

Absolutely Refractory

A

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

46
Q

Relatively Refractory

A

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, a phase during which potassium channels are still open

47
Q

Nerve Impluse

A

propagation of an action potential on the membrane of an axon

48
Q

Node of Ranvier

A

the part of an axon that is not covered by myelin

49
Q

Saltatory Conduction

A

fast propagation of an action potential at successive nodes of Ranvier, saltatory means “leaping”

50
Q

Multiple Sclerosis (MS)

A

nervous system disorder resulting from the loss of myelin around axons in the CNS

51
Q

Autoimmune Disease

A

illness resulting from the loss of the immune system’s ability to discriminate between foreign pathogens in the body and the body itself, abnormal immune response by the body against substances and tissues normally present in the body

52
Q

What is the resting potential?

A

electrical charge across a cell membrane in the absence of stimulation

a store of negative energy on the intracellular side relative to the extracellular side

the inside of the membrane at rest is -70 mV relative to the extracellular side

four charged particles take part in producing the resting potential

Na+ and Cl- in higher concentration outside the cell

K+ and A- in higher concentration inside the cell

53
Q

How is the resting potential maintained?

A
  1. Because the membrane is relatively impermeable to large molecules the negatively charged proteins (A-) remain inside the cell
  2. Ungated potassium and chloride channels allow potassium and chloride ions to pass freely, but gates on sodium channels keep out positively charged sodium ions
  3. Na+ K+ pump forces out Na+ from the intracellular fluid and inject K+
54
Q

What is the electrical makeup of the inside of the cell?

A

large proteins anions are manufactured inside cells

no membrane channels are large enough to allow these proteins to leave

cells accumulate positively charged potassium ions to balance out the negative protein anion charge

concentration gradient keeps potassium influx limited

residual potassium ions outside the membrane contribute to the charge across membrane

55
Q

What is the electrical makeup of the outside of the cell?

A

sodium ions are kept out

the difference in concentrations of sodium contributes to the membrane’s resting potential

gates on the sodium ion channels are ordinarily closed, blocking the entry of most sodium ions

when sodium leaks into neuron (influx), sodium-potassium pumps regulate sodium and potassium flow, sodium ions are kept out

chloride ions move in and out of the cell through open channels

the equilibrium point is approx. the same as the membrane’s resting potential, and so chloride ions ordinarily contribute little to the resting potential

56
Q

What are graded potentials?

A

if the concentration of any on the ions across the unstimulated cell membrane changes, the membrane voltage changes

these graded potentials are small voltage fluctuations across the cell membrane

57
Q

What is hyperpolarization?

A

increase electrical charge across a membrane (more negative)

usually due to the inward flow of chloride ions or outward flow of potassium ions

58
Q

What is depolarization?

A

decrease in electrical charge across a membrane (more positive)

usually due to an influx of sodium

59
Q

How does blocking channels affect the body?

A

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

it can be lethal because it’s toxin impedes the electrical activity of neurons

60
Q

What is an action potential?

A

large, brief reversal in polarity of an axon

lasts approximately 1 millisecond

voltage across membrane suddenly reverses

intracellular side more positive relative to extracellular side

61
Q

How do action potentials occur?

A

voltage-activated ion channels: gated protein channels that open or close only a specific membrane voltages

sodium and potassium: closed at membrane’s resting potential, voltage-activated channels selectively open at -50 mV

combined flow of Na+ and K+ –> action potential

62
Q

What is the threshold potential?

A

voltage at which an action potential is triggered

about -50 mV relative to extracellular surround

Na+ and K+ voltage-activated channels are attuned to the threshold voltage of -50mV

cell membrane changes to -50 mV = both types of channels open to allow ion flow across the membrane

after a process of depolarization, the membrane potential reverses and return to its resting potential

63
Q

What is the role of voltage-activated ion channels in action potentials?

A
  1. When threshold voltage is met, voltage activated channels open briefly, K+ and Na+ channels open
  2. Sodium channels respond quicker than potassium, voltage change due to Na+ influx takes places before voltage change due to K+ efflux
  3. Sodium channels have two gates, once the membrane depolarizes to about +30 mV, one of the gates closes, Na+ influx begins quickly and ends quickly
  4. The potassium channels open more slowly than the sodium channels and they remain open longer, the efflux of K+ reverses the depolarization produced by Na+ influx and even hyperpolarizes the membrane
64
Q

What is the absolute refractory period?

A

the state of an axon in the depolarization or repolarization period, during which a new action potential cannot (usually) be elicited

65
Q

What is the relative refractory period?

A

during hyperpolarization, an action potential can only occur with a stronger electrical stimulus (more intense second stimulation)

66
Q

What is a nerve impulse?

A

propagation of an action potential on the membrane of an axon

voltage change from one AP triggers neighboring voltage-activated channels

size and shape of action potential remain constant along the axon (all-or-none law)

67
Q

What is the relationship between refractory periods and nerve action?

A

although an action potential can travel in either direction on an axon, refractory periods prevent it from reversing direction

refractory periods produce a single discrete impulse that travels away from the point of initial stimulation

when an action potential begins near the cell body, it usually travels down the axon to the terminals

68
Q

What is myelin?

A

produced by oligodendroglia in the CNS and Schwann cells in the PNS

speeds up neural impulse

69
Q

What are the nodes of Ranvier?

A

part of an axon that is covered by myelin

packed with voltage-activated channels

enables saltatory conduction: flow of energy, AP jumps from node to node

70
Q

What is the relationship between myelin and action potential propagation?

A

propagation is energetically cheaper since action potentials regenerate at the nodes of ranvier

myelin improves conduction speed, action potential in unmyelinated axons have higher metabolic costs

nodes of ranvier are spaced ideally for salutatory conduction

71
Q

What is multiple sclerosis?

A

myelin is damaged

disrupts the functioning of neurons: sensory loss, difficulty moving, fatigue

sudden symptomology

72
Q

Excitatory Postsynaptic Potential (EPSP)

A

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

73
Q

Inhibitory Postsynaptic Potential (IPSP)

A

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

74
Q

Initial Segment

A

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

75
Q

Temporal Summation

A

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

76
Q

What is spatial summation?

A

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

77
Q

What is back propagation?

A

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

78
Q

Optogenetics

A

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

79
Q

Stretch-Activated Channel

A

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

80
Q

End Plate

A

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

81
Q

Transmitter-Activated Channel

A

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

82
Q

How do neurons integrate information?

A

through dendritic spines, a neuron can establish more than 50,000 connections to other neurons

nerve impulses traveling from other neurons bombard the receiving neuron with excitatory and inhibitory inputs

the cell body, which lies between the dendritic tree and its axon, can receive inputs from many other neurons

how does rthe neuron integrate this enormous array of inputs into a nerve impulse?

83
Q

What are excitatory postsynaptic potentials (EPSP)?

A

brief depolarization of a neuron membrane in response to stimulation

depolarized neuron is more likely to produce an action potential

are associated with the opening of sodium channels, allows influx of Na+

84
Q

What are inhibitory postsynaptic potentials (IPSP)?

A

brief hyperpolarization of a neuron membrane in response to stimulation

hyperpolarized neuron is less likely to produce an action potential

associated with the opening of potassium channels (efflux of K+) or with the opening of chloride channels (influx of Cl-)

85
Q

What is temporal summation?

A

pulses that occur at approximately the same time on a membrane are summed

86
Q

What is spatial summation?

A

pulses that occur at approximately the same place on a membrane are summed

87
Q

What is the summation of inputs?

A

a neuron sums all inputs that are close in time and space

it provides an indication of the summed influenced of multiple inputs

if the summed ionic inputs exceed the threshold (approximately -50mV) at the axon hillock, and action potential will be initiated

88
Q

What is the role of ions in summation?

A

the influx of sodium ions accompanying one EPSP is added to the influx of sodium ions accompanying a second EPSP if the two occur close together in time and space

the same is true regarding effluxes of potassium ions

the neuron “analyzes” its inputs before deciding what to do

89
Q

What is the axon hillock?

A

junction of cell body and axon

rich in voltage-activated channels

where EPSPs and IPSPs are integrated

where action potentials are initiated (usually)

90
Q

What is back propagation?

A

reverse movement of an action potential from the axon hillock into the dendritic field

signals the dendritic field that the neuron is sending an action potential over its axon

may play a role in plastic changes in the neurons that underlie learning

91
Q

How does sensory stimuli produce action potentials?

A

we receive information about the world in various ways

neurons related to these diverse receptors all have ion channels on their cell membranes

these ion channels initiate the chain of events that produces a nerve impulse

92
Q

How does the sense of touch work?

A

each hair on our body allows us to detect the slightest displacement

dendrite of a touch neuron is wrapped around the base of each hair

hair displacement opens stretch-activated channels on the dendrite’s membrane

when channels open, they allow an influx of Na+ ions sufficient to depolarize the dendrite to its threshold level

93
Q

How do nerve impulses produce movement?

A

spinal motor neurons send nerve impulses to synapses on muscle cells

axon of each motor neuron makes one or more synapses with target muscle

end plate: part of the muscle membrane that is contacted by the axon terminal

94
Q

How does acetylcholine work?

A

chemical transmitter that the axon terminal releases at the muscle end plate

attaches to transmitter-activated channels

channels open, allowing Na+ and K+ ions across the muscle membrane to depolarize the muscle to the threshold

muscles then generate action potentials to contract

95
Q

What are muscle contractions?

A

when a motor neuron’s axon collaterals contact a muscle fiber end plate

acetylcholine attaches to receptor sites on the end plate’s transmitter-activated channels, opening them

these large membrane channels allow simultaneous influx of Na+ and efflux of K+

triggers action potentials

causes the muscle to contract

PSYCH 275 (11 decks)

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