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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
Q

Synaptic transmission

A

action potential is passed from one neuron to another at synaptic contacts

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26
Q

More permeability to potassium

A

resting potential of the neuron will be lesser than -60mV, about -86mV

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27
Q

More permeability to sodium

A

the resting potential will be greater than -60 mV (+64 mV)

28
Q

Hyperpolarization

A

goes past resting potential

29
Q

Depolarization

A

becoming more positive

30
Q

Repolarization

A

becoming more negative

31
Q

Steps of action potential

A
  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
Q

Passive conduction (graded potentials)

A

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
Q

Refractory period

A

makes sure depolarization doesn’t flow backwards along the axon

34
Q

How does action potential maintain its amplitude?

A

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
Q

What factors increase AP conduction velocity?

A

Increasing diameter of axon = decreases friction = increases flow

insulting the axon with myelin = decreases leakage out of axon

36
Q

Saltatory conduction

A

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
Q

Multiple sclerosis

A

varied clinical presentation caused by demyelination and inflammation of axonal pathways in the CNS

38
Q

Electrical synapses

A

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
Q

Steps of chemical synapse

A
  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
Q

Ligan gated ion channels

A

Neurotransmitter binds, channel opens, ions flow across membrane.

Allows for multiple different types of ions to flow across the membrane

41
Q

G-protein-coupled receptors

A

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
Q

Excitatory postsynaptic potentials

A

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
Q

Inhibitory postsynaptic potentials

A

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
Q

Temporal summation

A

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
Q

Spatial summation

A

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
Q

Synaptic plasticity

A

strength of synaptic connections between neurons is dynamic

can produce short-term or long-term changes with different underlying mechanisms

47
Q

Short term synaptic plasticity

A

either facilitation or depression

affects the amount of neurotransmitter being released from presynaptic terminals in response to an action potential

48
Q

Synaptic facilitation

A

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
Q

Synaptic depression

A

causes neurotransmitter release to decline during sustained synaptic activity

decrease of vesicles available to release NT
decrease strength of synapse

50
Q

Habituation plasticity

A

process that causes the animal to become less responsive to repeated occurrences of a stimulus

ex: smells slowly decrease over time

shorter effects

51
Q

Sensitization plasticity

A

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
Q

What causes gill withdrawal?

A
  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
Q

Repeated stimulation of the siphon results in habituation. Which synaptic change occurs during habituation?

A

the synapse between the sensory and motor neurons is depressed

54
Q

What structure can be found exclusively at an electrical synapse?

A

connexon

55
Q

What occurs during habituation at a cellular level?

A

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
Q

What occurs during sensitization at a cellular level? (short term)

A

recruits additional neurons

57
Q

What occurs during sensitization at a cellular level? (long term)

A

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
Q

Long-term potentiation

A

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
Q

Long-term depression

A

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
Q

Trisynaptic pathway

A

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
Q

Why is the trisynaptic pathway important?

A

gives evidence for LTD and LTP
LTP has been shown to occur throughout the circuit

62
Q

NMDA receptors

A

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
Q

AMPA receptor

A

just need NT to bind to allow Na into the postsynaptic

only allows sodium into the postsynaptic neuron

64
Q

LTP and AMPA

A

LTP causes more AMPA receptors

more AMPA receptors increases sensitivity to glutamate, which means its easier to produce an AP

65
Q

LTP and NMDA

A

LTP does NOT cause more NMDA receptors

NMDA is important for LTP inductions and not LTP expression

66
Q

LTD and AMPA

A

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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