Lecture 11 Flashcards
(104 cards)
1
Q
what are neurons?
A
-nerve cells that transfer information within the body
2
Q
what are the 2 types of signals neurons use to communicate?
A
-electrical signals
-chemical signals
3
Q
what are the features of electrical signals?
A
-long distance
-mostly intracellular (within cells)
4
Q
what are the features of chemical signals?
A
-short distance
-intercellular (outside/between cells)
5
Q
what does interpreting signals involve?
A
-sorting complex sets of paths and connections
6
Q
where does the processing of information take place?
A
-ganglia
-brain
7
Q
what are ganglia?
A
-simple clusters of neurons
8
Q
what is the brain?
A
-complex organization of neurons
9
Q
what do neurons exemplify?
A
-the relationship between form and function that arises during evolution
10
Q
where are most of the neurons organelles?
A
-cell body (soma)
11
Q
what are the main parts of a neuron?
A
-body
-axon
-axon hillock
-dendrites
-synaptic terminals
12
Q
what are dendrites?
A
-highly branched extensions that receive signals from other neurons
13
Q
what is the axon?
A
-a longer extension that transmits signals to other cells at synapses
14
Q
what is the axon hillcock?
A
-cone shaped base of an axon
-connects the axon to the cell body
15
Q
what do synaptic terminals do?
A
-pass information across the synapse as chemical messengers
-chemical messengers are neurotransmitters
16
Q
what is a synapse?
A
-junction between an axon and another cell
17
Q
what is the basic path of where information is transmitted?
A
-from a presynaptic cell to a postsynaptic cell
18
Q
what is a presynaptic cell?
A
-neuron
19
Q
what is a postsynaptic cell?
A
-neuron
-muscle cell
-gland cell
20
Q
what nourishes or insulates most neurons?
A
-glial cells
21
Q
what are the 3 processes that the nervous system goes through to process information?
A
-sensory input
-integration
-motor output
22
Q
what is the role of sensors?
A
-detect external stimuli and internal conditions
-transmit information along sensory neurons
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
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
25
what are the features of the central nervous system?
-includes the brain and nerve cord (spinal cord)
-where integration takes place
26
what are the features of the peripheral nervous system?
-includes everything else
-carries information in and out of the CNS
27
what do the bundled neurons of the PNS form?
-nerves
28
what is membrane potential?
-the voltage across a cell's plasma membrane
29
what is voltage?
-difference in electrical charge
30
what is resting potential?
-the membrane potential of a neuron that is not sending signals
31
what do changes in membrane potential act as?
-signals
-transmitting and processing of information
32
what are the concentrations of ions in and out of a mammalian neuron at resting potential?
-[] of K+ is highest inside the cell
-[] of Na+ and Cl- is highest outside the cell
33
how are the K+ and Na+ gradients maintained? what do they represent?
-sodium-potassium pumps using ATP
-represent chemical potential energy
34
what converts chemical potential to electrical potential?
-the opening of ion channels in the plasma membrane
35
what are the relative amounts of open K+ and open Na+ channels in a neuron at resting potential?
-many open K+ channels
-few open Na+ channels
36
what results from the many open K+ channels?
-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
37
at equilibrium what gradients are balanced?
-electrical and chemical
38
what is the equilibrium potential? what equation calculates this
-the membrane voltage for a particular ion at equilibrium
-nernst equation
39
is the equilibrium potential of K+ positive or negative? what about Na+
-K+ is negative
-Na+ is positive
40
what is known about the K+ and Na+ currents in a resting neuron? what about the resting potential?
-they are equal and opposite each other
-the resting potential across the membrane is steady
41
why do membrane potential changes occur?
-neurons contain gated ion channels
-they open or close in response to stimuli
42
who measures and how is membrane potential measured?
-electrophysiologists
-intracellular recording
43
what does the resting membrane potential of a neuron depend on?
-the net movement of ions in and out of the cell
44
what happens to the membrane when positive ions move in to cell (negative ions move out)? give an example.
-membrane becomes less polarized/depolarized
-Na+ channels open and Na+ moves in to the cell
45
what happens to the membrane when positive ions move out of the cell (negative ions move in)? give an example.
-membrane becomes more polarized/hyperpolarized
-K+ channels open and K+ moves out of the cell
46
what are graded potentials?
-changes in polarization where the magnitude of the change varies with the strength of the stimulus
-NOT NERVE SIGNALS
47
what will graded potentials have an effect on?
-the generation of nerve signals
48
what creates an action potential?
-a depolarization that shifts the membrane potential sufficiently
-massive change in membrane voltage
49
what are features of action potentials?
-constant magnitude
-all or none
-transmit signals over long distances
50
how do action potentials arise?
-some ion channels are voltage gated
51
what does it mean for an ion channel to be voltage gated?
-open or close when the membrane potential passes a certain level
52
what is the first stage of generating an action potential?
-most voltage gated sodium and potassium channels are closed
-at resting potential
53
what is the third stage of generating an action potential?
-the threshold is crossed
-membrane potential increases
53
what is the second stage of generating an action potential?
-voltage gated sodium channels open first
-sodium flows into the cell
-rising phase
54
what is the fourth stage of generating an action potential?
-voltage gated sodium channels inactivate
-voltage gated potassium channels open
-potassium flows out of the cell
-falling phase
55
what is the fifth stage of generating an action potential?
-membrane permeability to potassium is higher than at rest
-voltage gated potassium channels close
-resting potential is restored
-the undershoot
56
what is the refractory period? what does it result from?
-period after an action potential where a second action potential cannot be initiated
-results from sodium channel inactivation
57
where is an action potential usually generated?
-the axon hillock
58
where do action potentials travel?
-toward the synaptic terminals
-only travels in one direction
59
what happens to the neighbouring region of the axon membrane during action potential conduction?
-an electrical current depolarizes it
60
what prevents the action potential from travelling backwards?
-inactivated sodium channels behind the depolarization zone
61
what will increase the speed of an action potential?
-an increase in the axons diameter
-insulation
62
what insulates axons in vertebrates?
-myelin sheath
63
what forms the myelin sheath?
-glial cells
-oligodendrocytes in the CNS
-schwann cells in the PNS
64
in which regions of the axon are action potentials formed? why here?
-nodes of ranvier
-voltage gated sodium channels are found here
65
what are nodes of ranvier?
-gaps in the myelin sheath
66
what saltatory conduction?
-the process that describes how action potentials skip from node to node
67
what occurs at electrical synapses?
-electrical current flows from one neuron to another through gap junctions
68
what occurs at chemical synapses?
-a chemical neurotransmitter carries information between neurons
69
what type of synapses are most common?
-chemical synapses
70
what is the pathway of the neurotransmitter from the presynaptic to postsynaptic?
-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
where are synaptic vesicles located?
-in the synaptic terminal
72
what causes the release of the neurotransmitter in order for it to be received by the postsynaptic cell?
-the action potential
73
what does direct synaptic transmission involve?
-binding of neurotransmitters to ligand-gated ion channels in the postsynaptic cell
74
what causes the generation of a postsynaptic potential?
-the neurotransmitter binding
-it will open ion channels
75
what are the two categories of postsynaptic potentials?
-excitatory postsynaptic potentials (EPSPs)
-inhibitory postsynaptic potentials (IPSPs)
76
what are excitatory postsynaptic potentials?
-depolarizations that bring the membrane potential toward the threshold
77
what are inhibitory postsynaptic potentials?
-hyperpolarizations that bring the membrane potential farther from the threshold
78
what is typical of most neurons to have on their dendrites and cell body?
-many synapses
79
what will happen if a single EPSP is produced?
-nothing usually
-too small to trigger an action potential in the postsynaptic neuron
80
what will happen if 2 EPSP's are produced?
-if produced in rapid succession, an effect called temporal summation occurs
81
what is the difference between temporal summation and spatial summation?
-temporal summation = same synapses on the same postsynaptic neuron in rapid succession
-spatial summation = different synapses on the same postsynaptic neuron produced simultaneously
82
what will trigger an action potential in terms of EPSPs?
-a combination of EPSPs through spatial and temporal summation
83
what will an IPSP do through summation?
-counter the effect of an EPSP
84
what determines whether an axon hillock will reach threshold and generate an action potential?
-the summed effect of EPSPs and IPSPs
85
how are neurotransmitters cleared from the synaptic cleft?
-inactivation by enzymatic hydrolysis
-recapture by the presynaptic neuron
86
what can be said about a molecules shape?
-very important to its function
-determined by the position of its atoms valence orbitals
87
what happens when a neurotransmitter binds to a receptor that is metatropic?
-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
how do ligand-gated channels compare to second messenger systems?
-the effects of second messenger systems have a slower onset but last longer
89
how many different receptors may a single neurotransmitter bind to?
-more than a dozen
90
what two effects can neurotransmitters have on postsynaptic cells?
-excite postsynaptic cells
-inhibit postsynaptic cells
91
what is acetylcholine?
-common neurotransmitter in vertebrates and invertebrates
-for muscle stimulation
-for memory formation
-for learning
92
what are the two major classes of acetylcholine receptors in vertebrates?
-ligand gated receptor
-metabotropic receptor
93
what toxins disrupt acetylcholine?
-nerve gas
-sarin
-botulism toxin (produced by certain bacteria)
94
what are 4 classes of neurotransmitters?
-amino acids
-biogenic amines
-neuropeptides
-gases
95
where are amino acid neurotransmitters active? what are some examples?
-active in the CNS + PNS
-ex: glutamate, GABA, Glycine (all active in the CNS)
96
where are biogenic amines active? what are some examples?
-active in the CNS + PNS
-ex: epinephrine, norepinephrine, dopamine, serotonin
97
what are neuropeptides? what are their key aspects?
-relatively short amino acid chains
-include substance P and endorphins (affect pain perception)
98
what will bind to the same receptors as endorphins and act as painkillers?
-opiates
99
what neurotransmitter gases are active in the PNS? what are their key aspects?
-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
where are most neurotransmitters stored?
-cytoplasmic vesicles
101
what does neuron organization and structure reflect?
-function in information transfer
102
what establishes the resting membrane potential of a neuron?
-ion pumps + channels
103
where do neurons communicate with each other?
-at synapses
