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4 Neuroscience > L1 Action Potential > Flashcards

L1 Action Potential Flashcards

1
Q

Basic functions of neuron

A

to integrate and relay info from other neurons in a neural circuit

about 86 billion in one body

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2
Q

Basic structure of neuron

A

Body
Axon
Dendrites
Myelin sheaths
Axon terminal

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3
Q

Interneurons

A

located in spinal cord
local circuit neurons, relatively short axons
connect brain regions

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4
Q

Projection neurons

A

extend to distant targets, both afferent (sensory/towards NS) and efferent (motor/away NS)

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5
Q

Glial cells

A

-supportive functions for neurons, not transmitting electrical signals
-maintains ionic environment
-modulates the rate myelin sheath
-controls the uptake and metabolism of neurotransmitters
-providing scaffold for neural development
-recovery from neural injury
-connects. brain and immune system
-facilitates flow of interstitial fluid in sleep

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6
Q

Types of glial cells

A

astrocytes
oligodendrocytes
microglial

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7
Q

Astrocytes

A

only in central NS
starlike appearance

maintain chemical environment, forms blood-brain barrier, secrete substances that form new synaptic connections

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8
Q

Oligodendrocytes

A

lay down myelin for CNS
stem cells can generate new ones after injury

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9
Q

Schwann Cells

A

lay down myelin for PNS
stem cells can generate new ones after injury

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10
Q

Microglial cells

A

-derived primarily from hematopoietic precursor cells
-similar to macrophages
-remove cellular debris, secrete signaling molecules that modulate inflammation

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11
Q

Glial stem cells

A

not a lot known about the importance of glial cells

retain the capacity to generate new precursor cells

2 types include astrocytes (ventricles) and oligodendrocytes (white matter)

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12
Q

Afferent neurons

A

sensory, entering CNS

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13
Q

Efferent neurons

A

motor, exiting CNS

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14
Q

Reflex circuit (knee-jerk)

A
  1. Hammer tap, stretches sensory receptors in extensor muscles
  2. Sensory neuron synapses on motor neuron and spinal interneurons
  3. Interneuron synapse inhibits motor neuron to flexor muscles
  4. Motor neuron synapses on extensor muscle fibers, contraction
  5. Flexor muscle relaxes b/c of interneuron
  6. Leg extends
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15
Q

Extracellular recording

A

electrode is placed near the nerve cell of interest to detect activity

used for detecting temporal patterns of action potential activity

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16
Q

Intracellular recording

A

electrode is placed inside the cell of interest to detect activity

can detect the smaller graded changes in electrical potential that trigger action potentials

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17
Q

Action potential

A

electrical signal that transiently reverses the negative resting potential and makes the transmembrane potential positive

all or nothing changes

self-regenerating wave of electrical activity

comes from ion fluxes

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18
Q

Resting membrane potential

A

neurons at rest generate negative potential
-60mV
more potassium inside the cell, more sodium/calcium/chloride outside the cell

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19
Q

Why are electrical potentials generated across the membranes of neurons?

A
  1. there are differences in concentrations of specific ions across nerve cell membranes
  2. membranes are selectively permeable to some of these ions
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20
Q

Active transporters

A

-actively move selected ions against concentration gradient
-create ion concentration gradient

steps: ion binds, ion transported across membrane

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21
Q

Ion channels

A

allow ions to diffuse down concentration gradient
are selectively permeable to certain ions

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22
Q

Types of potentials

A

receptor potentials
synaptic potential
action potential

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23
Q

Receptor potential

A

sensory neurons
due to the activation of sensory neurons by external stimuli (light, sound, heat).

neuron responds to touch with a receptor
potential that changes the resting potential for a fraction of a second

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24
Q

Synaptic potential

A

brief changes in resting potential

allow transmission of information from one neuron to another and produce very brief change in resting potential. These serve as means of exchanging info in CNS and PNS

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25
Synaptic transmission
action potential is passed from one neuron to another at synaptic contacts
26
More permeability to potassium
resting potential of the neuron will be lesser than -60mV, about -86mV
27
More permeability to sodium
the resting potential will be greater than -60 mV (+64 mV)
28
Hyperpolarization
goes past resting potential
29
Depolarization
becoming more positive
30
Repolarization
becoming more negative
31
Steps of action potential
1. Begin at resting potential (-60mV) 2. Stimulus pushes the membrane potential to threshold potential (-50mV) 3. Na+ channels open, rapidly depolarizing the membrane potential (+40mV) 4. Potassium channel opens, repolarizing the membrane 5. Delay in close, causes hyperpolarization (-70mV). 6. Potassium channels close
32
Passive conduction (graded potentials)
the electrical signal "leaks" across the membrane, causing a change in membrane potential down the axon causes a slight change farther down the axon, eventually dies out the farther it moves away from the initial stimulus/beginning of axon action potential needs both passive and active conduction to spread
33
Refractory period
makes sure depolarization doesn't flow backwards along the axon
34
How does action potential maintain its amplitude?
same idea as positive feedback loop activating voltage dependent on Na+. membrane potential depolarization leads to more Na+ conductance, more Na+ entry, further depolarization
35
What factors increase AP conduction velocity?
Increasing diameter of axon = decreases friction = increases flow insulting the axon with myelin = decreases leakage out of axon
36
Saltatory conduction
process of action potential propagation during which current flows across the neuronal membrane only at nodes of raniver action potentials are jumping from one node to the next, allowing for non-continuous depolarization, in myelinated axons
37
Multiple sclerosis
varied clinical presentation caused by demyelination and inflammation of axonal pathways in the CNS
38
Electrical synapses
minority in the human system typically instant, can be bidirectional breathing neurons are an example current flow occurs at gap junctions, which contain connexon channels which allow for passive electrical flow
39
Steps of chemical synapse
1. Neurotransmitter is synthesized and stored in vesicles 2. AP occurs 3. AP causes CA channels to open, CA flows in 4. CA causes vesicles to fuse with presynaptic membrane, NT is released into synaptic cleft 5. Transmitter binds to receptor molecule which causes either inhibitory or excitatory response in post synaptic cell
40
Ligan gated ion channels
Neurotransmitter binds, channel opens, ions flow across membrane. Allows for multiple different types of ions to flow across the membrane
41
G-protein-coupled receptors
Neurotransmitter binds, g-protein is activated, g protein subunits or messengers modulate ion channels, ion channel opens, ions flow across membrane modulate ion channels
42
Excitatory postsynaptic potentials
an EPP leads to depolarization in the postsynaptic cell via a reversal potential that is more positive than the resting membrane potential glutamate is an example increases the likelihood of an action potential occurring in the postsynaptic neuron
43
Inhibitory postsynaptic potentials
an EPP that leads to hyperpolarization in the postsynaptic cell via a reversal potential that is more negative than the resting membrane potential decrease the likelihood of an AP occurring in the postsynaptic neuron example of GABA
44
Temporal summation
across multiple presynaptic spikes occur close enough in time to combine and trigger an AP at axon hillock kid saying mom over and over again
45
Spatial summation
across multiple presynaptic terminals applied at the same time, in different areas, cumulative effect on membrane potential multiple kids saying mom around the house at the same time
46
Synaptic plasticity
strength of synaptic connections between neurons is dynamic can produce short-term or long-term changes with different underlying mechanisms
47
Short term synaptic plasticity
either facilitation or depression affects the amount of neurotransmitter being released from presynaptic terminals in response to an action potential
48
Synaptic facilitation
rapid increase in synaptic strength that occurs when two ore more APs fire at the presynaptic terminal within a few miliseconds of each other allows for calcium buildup
49
Synaptic depression
causes neurotransmitter release to decline during sustained synaptic activity decrease of vesicles available to release NT decrease strength of synapse
50
Habituation plasticity
process that causes the animal to become less responsive to repeated occurrences of a stimulus ex: smells slowly decrease over time shorter effects
51
Sensitization plasticity
process that allows an animal to generalize an aversive response elicited by a noxious stimulus to a variety of other non-noxious stimuli dogs w/shock collar; pairing a shock w/fence longer effects
52
What causes gill withdrawal?
1. Touching the siphon --> activates sensory neurons 2. form excitatory synapses that release glutamate onto respective interneurons, and motor neurons 3. motor neuron release ACh, exciting the gill muscle pain is conveyed by the modulatory interneuron
53
Repeated stimulation of the siphon results in habituation. Which synaptic change occurs during habituation?
the synapse between the sensory and motor neurons is depressed
54
What structure can be found exclusively at an electrical synapse?
connexon
55
What occurs during habituation at a cellular level?
transmission at the glutamatergic synapse (between sensory and motor) is depressed there is a decrease in the number of vesicles available for release, causing a decreased transmission from presynaptic to postsynaptic
56
What occurs during sensitization at a cellular level? (short term)
recruits additional neurons
57
What occurs during sensitization at a cellular level? (long term)
changed gene expression 1. interneurons will release serotonin, which binds to the G-protein and stimulates production of cAMP. 2. cAMP binds to protein kinase A, which blocks K+ from leaving the cell 3. Prolonged AP causes more CA+ channels to be opened, which causes more release of neurotransmitters, more motor neuron activity
58
Long-term potentiation
long-lasting increase in synaptic strength high frequency stimulus if you want to cause a chain reaction, you have to at least provide a weak stimulation to the following synapse changes occur if stimulation is less than 100ms apart
59
Long-term depression
long-lasting decrease in synaptic strength incorrect sequencing of events can lead to LTD no changes occur/LTD occurs if the stimulation or firing is greater than 100ms apart from each other
60
Trisynaptic pathway
1.Neurons in entorhinal cortex 2.travels to synapse on granule cell layer of dentate gyrus 3. Granule cells give rise to mossy fibers, which synapse on CA 3 cells 4. CA3 cells lead to fibers that leave the hippocampal formation adn schaffer fibers 5. CA1/schaffer fibers leave hippocampus and project to subiculum 6. cells from the subiculum proect back to the entorhinal cortex, completes the loop
61
Why is the trisynaptic pathway important?
gives evidence for LTD and LTP LTP has been shown to occur throughout the circuit
62
NMDA receptors
having a molecule of magnesium blocking the channel need HIGH frequency to dispel the Mg2+ allows both Ca and Na into the cell, which creates LTP along the post-synaptic neuron ultimately not needed, but more receptors = greater stimulus = LTP
63
AMPA receptor
just need NT to bind to allow Na into the postsynaptic only allows sodium into the postsynaptic neuron
64
LTP and AMPA
LTP causes more AMPA receptors more AMPA receptors increases sensitivity to glutamate, which means its easier to produce an AP
65
LTP and NMDA
LTP does NOT cause more NMDA receptors NMDA is important for LTP inductions and not LTP expression
66
LTD and AMPA
when post synaptic neurons aren't being stimulated, the cell begins to internalize/destroy the AMPA receptors it does not need

4 Neuroscience (9 decks)

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