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KNES 251 (Motor Control) > Action Potential Propagation, Synaptic Transmission, Neuromuscular Junctions > Flashcards

Action Potential Propagation, Synaptic Transmission, Neuromuscular Junctions Flashcards

Lectures 5/6

1
Q

How do action potentials spread down the axon?

A

Wave-like motion as neighboring molecules diffuse (causing action potentials)

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2
Q

Fun fact on invertebrates

A

very few of their axons are myelinated

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3
Q

Why don’t action potentials travel in both directions?

A

On the “back side” of an action potential the sodium channels are INACTIVE

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4
Q

Why do we notice a decrease in voltage at neighboring axon locations?

A

Charges diffuse passively along axon (looses “umph” as it goes)

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5
Q

Which is faster passive diffusion or active current flow?

A

Passive diffusion!

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6
Q

Axon length constant

A

lambda- (about 1-2mm) is how far down the axon it takes for the voltage to decay to 37% of its original amplitude

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7
Q

Is passive diffusion sufficient for the action potential to travel fully down the axon?

A

No! It wouldn’t make it to the end for most

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8
Q

Describe the Nodes of Ranvier

A

-voltage gated Na+ and K+ channels
-no myelin here
-action potential regenerated here

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9
Q

Where does the diffusion of action potentials occur?

A

In myelinated areas

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10
Q

Def: saltatory conduction

A

-fast/slow/fast/slow
-action potential “jumps” down axon from one Node of Ranvier to the next

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11
Q

Do the action potentials move quicker at the Nodes of Ranvier or through the myelin?

A

Through the myelin, by diffusion

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12
Q

Which neurons conduct faster- myelinated or unmyelinated?

A

Myelinated, b/c regenerated at each node

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13
Q

Where are neurotransmitters stored?

A

In vesicles in the axon

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14
Q

What happens when an action potential invades the presynaptic terminal and causes depolarization?

A

Voltage-gated Ca2+ channels open

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15
Q

What does Ca2+ do in synaptic transmission?

A

-causes vesicles (containing neurotransmitters) to fuse with membrane
-leading to exocytosis (burst out)

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16
Q

Following exocytosis what happens to the released neurotransmitter?

A

It diffuses across the synaptic cleft and binds to receptor molecules on the post-synaptic membrane

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17
Q

For case purposes: lets say the release of the neurotransmitter (glutamate) into the synaptic cleft binds to receptor molecules… does that mean glutamate will be the molecule entering the post-synaptic cell?

A

Not necessarily, may open sodium gates

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18
Q

Do neurotransmitters only open postsynaptic channels?

A

No, they can close channels as well

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19
Q

How does the postsynaptic current (influx of ions into cell) change the excitability of the cell?

A

The ions cause excitatory or inhibitory potential

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20
Q

What happens to any neurotransmitters left in the synaptic cleft?

A

Removed by glial cells (support neurons) or degraded by enzymes

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21
Q

Synaptic cleft

A

-small space bwtn presynaptic (axon) and postsynaptic (dendrite)

22
Q

Def: dendritic spines

A

-contact points on the postsynaptic neuron
-small projections of cell membrane

23
Q

When do omega formations occur?

A

-when Ca2+ enters and synaptic vesicles fuse to membrane (to release contents)

24
Q

What is a quanta?

A

-unit of measurement
-meant to describe the amount of NT in one vesicle

25
Q

What is the purpose of having various proteins?

A

-complex structure/function
-create, load, and release synaptic vesicles

26
Q

What is the budding process?

A

-recycling of synaptic vesicles

27
Q

Once Ca2+ causes exocytosis what happens to the presynaptic vesicles?

A

-fuse with membrane
-pull in HRP from outside cell (endocytosis)
-axon notices
-this temporary vesicle joins up with endosome

28
Q

What is the endosome?

A

-Large vesicle made up of vesicle membrane
-collects/reforms vesicles

29
Q

Why are tracer molecules like (HRP) necessary for budding?

A

-recognizable by endosome

30
Q

How are SNARE complexes activated?

A

entry of Ca2+ into the presynaptic terminal

31
Q

What is the purpose of SNARE proteins?

A

-aid in the release of neurotransmitters
-help bind to membrane (“dock”), then tear vesicle

32
Q

Name the four most common local anesthetics

A

Procaine, lidocaine, novocaine, cocaine

33
Q

What are local anesthetics used for?

A

-used to block action potentials from being sent to CNS (NO PAIN!!)

34
Q

How do local anesthetics (procaine, lidocaine, novocaine, cocaine) work?

A

bind with and block Na+ channels (no depolarization)

35
Q

describe how reversible antagonists work

A

they eventually unbind (from Na+ channels) and the anesthetic wears off… like at dentist

36
Q

Tetrodotoxin (TTX)

A

-blocks Na+ channels IRREVERSIBLY
-puffer fish and some other poisonous creatures synthesize TTX as a protective mechanism

37
Q

What is TTX and what would happen if too many channels are blocked?

A

Tetrodotoxin- won’t unbind for Na+, so if too many blocked (OVERDOSE! and death from asphyxiation)

38
Q

Fugu

A

-puffer fish prepared by highly certified Japanese chefs (tightly regulated)

39
Q

glutamatergic synapse

A

-most common excitatory synapse in nervous system
-glutamate released from presynaptic membrane
-open channels that allow Na+ to flow into postsynaptic membrane (make neuron more positive)

40
Q

Neurons store _______ of neurotransmitter(s)

A

one type

41
Q

Neurons receive _______ of neurotransmitter(s)

A

various kinds

42
Q

GABAergic synapse

A

-most common inhibitory synapse
-GABA released
-open Cl- channels (make neuron more negative)

43
Q

EPSP

A

-excitatory postsynaptic potential
-make more positive

44
Q

IPSP

A

-inhibitory postsynaptic potential
-make more negative

45
Q

How are action potentials initiated in the postsynaptic neuron?

A

The postsynaptic currents sum together, if threshold is reached - BAM! - action potential

46
Q

Which cells receive the most action potential inputs?

A

Purkinje cells (cerebellum)… hundreds of thousands

47
Q

Which cells receive a lot of action potentials?

A

Pyramidal cells (cerebral cortex)… tens of thousands

48
Q

Where are alpha motor neurons located?

A

ventral horn of spinal cord

49
Q

What do alpha motor neurons connect to?

A

-their axons connect to a group of muscle fibres

50
Q

How do Acetylcholine (ACh) receptors work?

A

-both K+ and Na+ can flow through, but more Na+ enters than K+ leaves
-NET: depolarization (more positive)

51
Q
A

KNES 251 (Motor Control) (13 decks)

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