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BIOL1030 > Lecture 11 > Flashcards

Lecture 11 Flashcards

1
Q

what are neurons?

A

-nerve cells that transfer information within the body

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2
Q

what are the 2 types of signals neurons use to communicate?

A

-electrical signals
-chemical signals

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3
Q

what are the features of electrical signals?

A

-long distance
-mostly intracellular (within cells)

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4
Q

what are the features of chemical signals?

A

-short distance
-intercellular (outside/between cells)

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5
Q

what does interpreting signals involve?

A

-sorting complex sets of paths and connections

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6
Q

where does the processing of information take place?

A

-ganglia
-brain

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7
Q

what are ganglia?

A

-simple clusters of neurons

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8
Q

what is the brain?

A

-complex organization of neurons

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9
Q

what do neurons exemplify?

A

-the relationship between form and function that arises during evolution

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10
Q

where are most of the neurons organelles?

A

-cell body (soma)

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11
Q

what are the main parts of a neuron?

A

-body
-axon
-axon hillock
-dendrites
-synaptic terminals

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12
Q

what are dendrites?

A

-highly branched extensions that receive signals from other neurons

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13
Q

what is the axon?

A

-a longer extension that transmits signals to other cells at synapses

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14
Q

what is the axon hillcock?

A

-cone shaped base of an axon
-connects the axon to the cell body

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15
Q

what do synaptic terminals do?

A

-pass information across the synapse as chemical messengers
-chemical messengers are neurotransmitters

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16
Q

what is a synapse?

A

-junction between an axon and another cell

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17
Q

what is the basic path of where information is transmitted?

A

-from a presynaptic cell to a postsynaptic cell

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18
Q

what is a presynaptic cell?

A

-neuron

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19
Q

what is a postsynaptic cell?

A

-neuron
-muscle cell
-gland cell

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20
Q

what nourishes or insulates most neurons?

A

-glial cells

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21
Q

what are the 3 processes that the nervous system goes through to process information?

A

-sensory input
-integration
-motor output

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22
Q

what is the role of sensors?

A

-detect external stimuli and internal conditions
-transmit information along sensory neurons

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23
Q

where is sensory information sent? what occurs at this stage?

A

-the brain or ganglia
-interneurons integrate the information
-a motor output is created

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24
Q

how does the motor output leave the brain/ganglia? what does this output trigger?

A

-leaves via motor neurons
-triggers muscle or gland activity

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25
Q

what are the features of the central nervous system?

A

-includes the brain and nerve cord (spinal cord)
-where integration takes place

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26
Q

what are the features of the peripheral nervous system?

A

-includes everything else
-carries information in and out of the CNS

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27
Q

what do the bundled neurons of the PNS form?

A

-nerves

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28
Q

what is membrane potential?

A

-the voltage across a cell’s plasma membrane

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29
Q

what is voltage?

A

-difference in electrical charge

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30
Q

what is resting potential?

A

-the membrane potential of a neuron that is not sending signals

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31
Q

what do changes in membrane potential act as?

A

-signals
-transmitting and processing of information

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32
Q

what are the concentrations of ions in and out of a mammalian neuron at resting potential?

A

-[] of K+ is highest inside the cell
-[] of Na+ and Cl- is highest outside the cell

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33
Q

how are the K+ and Na+ gradients maintained? what do they represent?

A

-sodium-potassium pumps using ATP
-represent chemical potential energy

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34
Q

what converts chemical potential to electrical potential?

A

-the opening of ion channels in the plasma membrane

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35
Q

what are the relative amounts of open K+ and open Na+ channels in a neuron at resting potential?

A

-many open K+ channels
-few open Na+ channels

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36
Q

what results from the many open K+ channels?

A

-K+ is diffused out of the cell
-results in a buildup of negative charge and negatively charged proteins within the neuron
-act as a major source of membrane potential

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37
Q

at equilibrium what gradients are balanced?

A

-electrical and chemical

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38
Q

what is the equilibrium potential? what equation calculates this

A

-the membrane voltage for a particular ion at equilibrium
-nernst equation

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39
Q

is the equilibrium potential of K+ positive or negative? what about Na+

A

-K+ is negative
-Na+ is positive

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40
Q

what is known about the K+ and Na+ currents in a resting neuron? what about the resting potential?

A

-they are equal and opposite each other
-the resting potential across the membrane is steady

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41
Q

why do membrane potential changes occur?

A

-neurons contain gated ion channels
-they open or close in response to stimuli

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42
Q

who measures and how is membrane potential measured?

A

-electrophysiologists
-intracellular recording

43
Q

what does the resting membrane potential of a neuron depend on?

A

-the net movement of ions in and out of the cell

44
Q

what happens to the membrane when positive ions move in to cell (negative ions move out)? give an example.

A

-membrane becomes less polarized/depolarized
-Na+ channels open and Na+ moves in to the cell

45
Q

what happens to the membrane when positive ions move out of the cell (negative ions move in)? give an example.

A

-membrane becomes more polarized/hyperpolarized
-K+ channels open and K+ moves out of the cell

46
Q

what are graded potentials?

A

-changes in polarization where the magnitude of the change varies with the strength of the stimulus
-NOT NERVE SIGNALS

47
Q

what will graded potentials have an effect on?

A

-the generation of nerve signals

48
Q

what creates an action potential?

A

-a depolarization that shifts the membrane potential sufficiently
-massive change in membrane voltage

49
Q

what are features of action potentials?

A

-constant magnitude
-all or none
-transmit signals over long distances

50
Q

how do action potentials arise?

A

-some ion channels are voltage gated

51
Q

what does it mean for an ion channel to be voltage gated?

A

-open or close when the membrane potential passes a certain level

52
Q

what is the first stage of generating an action potential?

A

-most voltage gated sodium and potassium channels are closed
-at resting potential

53
Q

what is the third stage of generating an action potential?

A

-the threshold is crossed
-membrane potential increases

53
Q

what is the second stage of generating an action potential?

A

-voltage gated sodium channels open first
-sodium flows into the cell
-rising phase

54
Q

what is the fourth stage of generating an action potential?

A

-voltage gated sodium channels inactivate
-voltage gated potassium channels open
-potassium flows out of the cell
-falling phase

55
Q

what is the fifth stage of generating an action potential?

A

-membrane permeability to potassium is higher than at rest
-voltage gated potassium channels close
-resting potential is restored
-the undershoot

56
Q

what is the refractory period? what does it result from?

A

-period after an action potential where a second action potential cannot be initiated
-results from sodium channel inactivation

57
Q

where is an action potential usually generated?

A

-the axon hillock

58
Q

where do action potentials travel?

A

-toward the synaptic terminals
-only travels in one direction

59
Q

what happens to the neighbouring region of the axon membrane during action potential conduction?

A

-an electrical current depolarizes it

60
Q

what prevents the action potential from travelling backwards?

A

-inactivated sodium channels behind the depolarization zone

61
Q

what will increase the speed of an action potential?

A

-an increase in the axons diameter
-insulation

62
Q

what insulates axons in vertebrates?

A

-myelin sheath

63
Q

what forms the myelin sheath?

A

-glial cells
-oligodendrocytes in the CNS
-schwann cells in the PNS

64
Q

in which regions of the axon are action potentials formed? why here?

A

-nodes of ranvier
-voltage gated sodium channels are found here

65
Q

what are nodes of ranvier?

A

-gaps in the myelin sheath

66
Q

what saltatory conduction?

A

-the process that describes how action potentials skip from node to node

67
Q

what occurs at electrical synapses?

A

-electrical current flows from one neuron to another through gap junctions

68
Q

what occurs at chemical synapses?

A

-a chemical neurotransmitter carries information between neurons

69
Q

what type of synapses are most common?

A

-chemical synapses

70
Q

what is the pathway of the neurotransmitter from the presynaptic to postsynaptic?

A

-presynaptic neuron synthesizes and packages the neurotransmitter in synaptic vesicles
-neurotransmitter will diffuse across the synaptic cleft and be received by the postsynaptic cell

71
Q

where are synaptic vesicles located?

A

-in the synaptic terminal

72
Q

what causes the release of the neurotransmitter in order for it to be received by the postsynaptic cell?

A

-the action potential

73
Q

what does direct synaptic transmission involve?

A

-binding of neurotransmitters to ligand-gated ion channels in the postsynaptic cell

74
Q

what causes the generation of a postsynaptic potential?

A

-the neurotransmitter binding
-it will open ion channels

75
Q

what are the two categories of postsynaptic potentials?

A

-excitatory postsynaptic potentials (EPSPs)
-inhibitory postsynaptic potentials (IPSPs)

76
Q

what are excitatory postsynaptic potentials?

A

-depolarizations that bring the membrane potential toward the threshold

77
Q

what are inhibitory postsynaptic potentials?

A

-hyperpolarizations that bring the membrane potential farther from the threshold

78
Q

what is typical of most neurons to have on their dendrites and cell body?

A

-many synapses

79
Q

what will happen if a single EPSP is produced?

A

-nothing usually
-too small to trigger an action potential in the postsynaptic neuron

80
Q

what will happen if 2 EPSP’s are produced?

A

-if produced in rapid succession, an effect called temporal summation occurs

81
Q

what is the difference between temporal summation and spatial summation?

A

-temporal summation = same synapses on the same postsynaptic neuron in rapid succession
-spatial summation = different synapses on the same postsynaptic neuron produced simultaneously

82
Q

what will trigger an action potential in terms of EPSPs?

A

-a combination of EPSPs through spatial and temporal summation

83
Q

what will an IPSP do through summation?

A

-counter the effect of an EPSP

84
Q

what determines whether an axon hillock will reach threshold and generate an action potential?

A

-the summed effect of EPSPs and IPSPs

85
Q

how are neurotransmitters cleared from the synaptic cleft?

A

-inactivation by enzymatic hydrolysis
-recapture by the presynaptic neuron

86
Q

what can be said about a molecules shape?

A

-very important to its function
-determined by the position of its atoms valence orbitals

87
Q

what happens when a neurotransmitter binds to a receptor that is metatropic?

A

-movement of ion channels now depend on one or more metabolic steps
-activates a signal transduction pathway in the postsynaptic cell which involved a second messenger

88
Q

how do ligand-gated channels compare to second messenger systems?

A

-the effects of second messenger systems have a slower onset but last longer

89
Q

how many different receptors may a single neurotransmitter bind to?

A

-more than a dozen

90
Q

what two effects can neurotransmitters have on postsynaptic cells?

A

-excite postsynaptic cells
-inhibit postsynaptic cells

91
Q

what is acetylcholine?

A

-common neurotransmitter in vertebrates and invertebrates
-for muscle stimulation
-for memory formation
-for learning

92
Q

what are the two major classes of acetylcholine receptors in vertebrates?

A

-ligand gated receptor
-metabotropic receptor

93
Q

what toxins disrupt acetylcholine?

A

-nerve gas
-sarin
-botulism toxin (produced by certain bacteria)

94
Q

what are 4 classes of neurotransmitters?

A

-amino acids
-biogenic amines
-neuropeptides
-gases

95
Q

where are amino acid neurotransmitters active? what are some examples?

A

-active in the CNS + PNS
-ex: glutamate, GABA, Glycine (all active in the CNS)

96
Q

where are biogenic amines active? what are some examples?

A

-active in the CNS + PNS
-ex: epinephrine, norepinephrine, dopamine, serotonin

97
Q

what are neuropeptides? what are their key aspects?

A

-relatively short amino acid chains
-include substance P and endorphins (affect pain perception)

98
Q

what will bind to the same receptors as endorphins and act as painkillers?

A

-opiates

99
Q

what neurotransmitter gases are active in the PNS? what are their key aspects?

A

-nitric oxide (NO) + carbon monoxide (CO) (local regulators)
-NO is not stored in cytoplasmic vesicles, synthesized on demand
-broken down soon after production
-vertebrates synthesize small amounts of CO (deadly to inhale it normally)

100
Q

where are most neurotransmitters stored?

A

-cytoplasmic vesicles

101
Q

what does neuron organization and structure reflect?

A

-function in information transfer

102
Q

what establishes the resting membrane potential of a neuron?

A

-ion pumps + channels

103
Q

where do neurons communicate with each other?

A

-at synapses

BIOL1030 (11 decks)

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