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BIO108 - General Physiology > Lecture 5 - Membrane Potential > Flashcards

Lecture 5 - Membrane Potential Flashcards

1
Q
  • functional units of nervous system
  • receive, process and transnit infromation ot other cells
A

neurons

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2
Q

parts of neurons

A
  1. soma
  2. dendrites
  3. axons
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3
Q
  • body of a neuron
  • metabolic miantenance
A

soma

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4
Q

receptive surface that brings signals from other neurons toward the cell body

A

dendrites

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5
Q
  • conduct signals away from the cell
  • carry information for long distances with high fidelity and without loss
A

axons

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6
Q

detect sensory information from receptors

A

Afferent (sensory) neurons

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7
Q

carry impulses or motor commands to muscles and glands.

A

efferent (motor) neurons

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8
Q

located inside the central nervous system and are in between afferent and efferent neurons

A

Interneurons

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9
Q

Transmission of signals in a single neuron

A
  1. surface membrane innervated
  2. action potential initiation
  3. AP carried from spike-initiating zone to axon terminal
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10
Q

nerve impulse

A

action potential

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11
Q

corresponds to the site where action po- tentials are initiated

A

spike initiation zone (SIZ)

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12
Q
  • localized electrical gradient
  • electrical potential difference across cell membrane caused by different concentrations of K+, Na+, and Cl- ions
A

membrane potential

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13
Q

membrane potential of neurons is usually between

A

-60 to -80 mV

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14
Q

where are excess negative charges found

A

plasma membrane side

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15
Q

where are excess positive charges found

A

other side

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16
Q

membrane potential is the source of __ __ to move molecules across membranes

A

potential energy

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17
Q

how do excitable cells use changes in membrane potential

A

communication signals

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18
Q

membrane potential is critical for what?

A

coordinated movements of cells and organisms

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19
Q

what do every cell have

A

voltage or membrane potential

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20
Q

more concentrated within a cell

A

anions (negative)

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21
Q

more concentrated in the extracellular fluid

A

cations (positive)

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22
Q

factors affecting potential difference

A
  1. concentration gradient of ion
  2. membrane that is permeable to that ion
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23
Q

resting potential of unstimulated cell

A

-70mV

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24
Q

the magnitude of membrane potential __ until an equilibrium is reached

A

increases

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25
Q

equal numbers of anions and cations

A

electroneutral

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26
Q

as more potassium leaves the cell , what happens to the electrical force

A

increases to level that balance driving force from potassium concentration gradient

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27
Q

draw positive charges into the cell

A

excess negative charge inside

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28
Q

cations in membrane potential

A
  • K+
  • Na+
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29
Q

K+

A

principal intracellular cation

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30
Q

Na+

A

principal extracellular cation

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31
Q

anions in membrane potential

A
  • proteins, amino acids, sulfates, phosphate
  • Cl-
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32
Q

proteins, amino acids, sulfates, phosphate

A

prinicpal intracellular anions

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33
Q

Cl-

A

prinipal extracellular anion

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34
Q

concentraiton of K+ is greater inside the cell, wile concentration of Na+ is greater outside the cell

A

resting potential

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35
Q

use ATP to maintain K+ and Na+ gradients

A

sodium-potassium pump

36
Q

converts chemical potential to electrical potential

A

opening of ion channels

37
Q

what does the neuron at resting potential contain

A
  • many open K+ channels
  • fewer open Na+ channels
38
Q
  • allow ions to diffuse across the plasma membane
  • always open
A

non-gated ion channels

39
Q

can generate large changes in their membrane potential

A

excitable cells

40
Q

open or close in response to stimuli

A

gated ion channels

41
Q

Types of gated ion channels

A
  1. chemically-gated ion channels
  2. voltage-gated ion channels
42
Q

open or close in response to a chemical stimulus

A

chemically-gated ion channels (ligand-gated ioni channels)

43
Q

open or close in response to a change in membrane potential

A

voltage-gated ion channels

44
Q

changes in membrane potential

A

graded potentials

45
Q

graded potentials

A
  1. hyperpolarization
  2. depolarization
46
Q

membrane potential becomes more negative as gated K+ channels open and K+ diffuses out of the cell

A

hyperpolarization

47
Q

membrane potential becomes less negative as gated Na+ channels open and Na+ diffuses into the cell

A

depolarization

48
Q

all or nothing depolarization

A

action potential

49
Q

what is triggered if graded potentials sum to ~-55mV

A

action potential

50
Q

~-55mV of graded potential sum

A

threshold potential

51
Q

Two volted gates of Na+ channels

A
  1. closed activation
  2. open inactivation
52
Q

open rapidly in response to depolarization

A

closed activation gates

53
Q

close slowly in response to depolarization

A

open inactivation

54
Q

Five steps on action potential

A
  1. resting state
  2. depolarization
  3. rising phase of action potential
  4. falling phase of action potential
  5. undershoot
55
Q

what happens in depolarization

A
  • voltage-gated Na+ channels open first
  • Na+ flows into cell
56
Q

what happens in rising phase

A
  • threshold is crossed
  • membrane potential increases
57
Q

what happens in the falling phase

A
  • voltage-gated Na+ channels inactivate
  • voltage-gated K+ channels open
  • K+ flows out
58
Q

what happens during undershoot

A
  • membrane permeability to K+ is first higher than rest
  • voltage-gated K+ close
  • resting potential restored
59
Q
  • result of a temporary inactivation of Na+ channels
  • second action potential cannot be initiated
A

refractory period

60
Q

different period in changes in ion channels on membrane potential

A
  1. depolarizing stimulus
  2. absolute refractory period
  3. relative refractory period
61
Q

where is action potential repeatedly regenerated

A

along length of axon

62
Q

how is action potential generated

A

Na+ ions flow inward across membrane at one location

63
Q

rapid method by which nerve impulses move down a myelinated axon with excitation occurring only at nodes of Ranvier

A

Saltatory conduction

64
Q

where does excitation occur

A

nodes of Ranvier

65
Q

action potential travels directly from the presynaptic to the postsynaptic cells via gap junctions

A

electrical synapses

66
Q

how does electrical synapses travel from presynaptic to postsynaptic cells

A

via gap junctions

67
Q
  • information is transferred via the release of a neurotransmitter from one cell that is detected by an adjacent cell
  • more common than electrical synapses
A

chemical synapses

68
Q

region where neurons nearly touch and where nerve impulse is transferred

A

synapse

69
Q

small gap between neurons

A

synaptic cleft

70
Q

carries out transmission across a synapse

A

neurotransmitters

71
Q

what happens during transmission across a synapse by neurotransmitters

A
  1. sudden rise in calcium at end of one neuron
  2. stimulates synaptic vesicles to merge with presynaptic membrane
  3. neurotransmitter molecules released to synaptic cleft
72
Q

Three primary factors influencing impulse transmission

A
  1. axon diameter
  2. myelination
  3. temperature
73
Q

diameter of axon

A

typically around 1 micrometer

74
Q

formation of myelin sheath around nerve

A

myelination

75
Q

the lower the temperature, the __ the impulses move

A

slower

76
Q

what is affected by axon diameter and myelination

A

velocity of impulse propagation

77
Q

how fast the membrane ahead of the active regions is brought to threshold by the local-circuit current

A

conduction velocity of AP

78
Q

large axon diameter conduct __ due to less resistance

A

faster

79
Q

how far a change in voltage will spread

A

length constant

80
Q

greater the length constant the __ the conduction velocity of AP

A

faster

81
Q

evolutionary adaptation to increase the length constant of invertebrates

A

increase in axonal diameter

82
Q

evolutionary adaptation to increase the length constant of vertebrates

A

myelination

83
Q

composition of myelin sheath

A

layered glial cell membrane

84
Q

increase the transmembrane resistance and decrease the effective neuronal membrane capacitance

A

myelination

85
Q

by definition a material which is able to hold an electrical charge

A

Capacitance

86
Q

by definition is a measurement of the difficulty to pass an electric current through a materia

A

resistance

87
Q
  • where action potential is usually triggered
  • region of a neuron that controls the initiation of an electrical impulse based on the inputs from other neurons or the environment
A

axon hillock

BIO108 - General Physiology (9 decks)

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