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Biomedical Science 2 > Neuromuscular Junctions > Flashcards

Neuromuscular Junctions Flashcards

1
Q

NMJ are..

A

stable throughout life but are also dynamic. They can ressurrect themselves in response to injury

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2
Q

By the end of the life cycle of NMJ it is found that mainly 1 neuron…

A

can supply and bind to many effector muscles

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3
Q

Sprouting is where

A

One neuron binds and attaches to another muscle

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4
Q

The neuron consists of….

A

the soma, the axon and finally the synapse.

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5
Q

Motor neuron disease is a process where

A

synaptic connections degenerate. It hits the NMJ’s then goes to the motor neurons in the spinal cords to degrade

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6
Q

the cytoplasmic volume of the axon and the synaptic terminals exceeds…

A

the volume of the somato-dendritic compartment . by thousands of fold

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7
Q

neuromuscular junctions trigger and sustain…

A

muscle contractile force. A higher frequency will produce a tetanus unlike a 1Hz frequency

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8
Q

axons break up across the neuron and those branches end up at…

A

Neuromuscular Junctions

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9
Q

Motor units are intermingled and vary in size

A

by 5-10 fold

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10
Q

The NMJ comprises of 4 cell types…

A
  1. Kranocytes
  2. Axon
  3. Terminal Schwann cell
  4. Muscle fibre
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11
Q

The motor nerve terminal contains

A

Mitochondria and smooth synaptic vesicles

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12
Q

Excitation contraction coupling occurs when

A

acetylcholine binds to the receptors on the motor end plate. This causes …..

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13
Q

Steps of Motor neuron formation are as follows

A

(attach pic)

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14
Q

Acetylcholine receptors cluster

A

when a nerve terminal binds to a muscle and agrin influences the receptors to be positioned there

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15
Q

Motor Neurone death is a normal part…

A

of prenatal development

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16
Q

Neonatal muscles are polyneuronally…

A

innervated

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17
Q

Synapse elimination involves

A

progressive retraction and takeover of NMJ

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18
Q

in rodents, polyinnervation is eliminated by…

A

2-4 weeks

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19
Q

Neurones retract some of their neurones while…

A

stabilising others

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20
Q

Motor unit sizes can be estimated from…

A

isometric forces

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21
Q

Motor units size decreases…

A

postnatally

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22
Q

Synapse elimination is part of…

A

post natal development

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23
Q

synaptic elimination is likely to be

A

a competitive factor which causes it to happen

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24
Q

Laser ablation of one input leads to…

A

takeover by the other

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25
Q

There is evidence which shows competition and programmed withdrawal in terms of

A

synaptic elimination

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26
Q

Synapse elimination is influenced by

A

activity

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27
Q

Activity dependent rewiring may depend on competition for

A

neurotrophic factors.

28
Q

Single action potential produces muscle

A

contraction

29
Q

Synaptic activity can be recorded with…

A

intracellular microelectrodes

30
Q

Action potentials are triggered when

A

end plate potentials cross the firing threshold

31
Q

NMJ’s reliably trigger and sustain

A

muscle contractile force

32
Q

During depolarisation of nerve terminal, voltage gated sodium channel allow current to flow in which lead to activation of

A

voltage gated calcium channels

33
Q

When calcium enters the cell, it increases the chances

A

of synaptic vesicles releasing neurotransmitter

34
Q

The potassium channels which are later activated after depolarisation are designed to…

A

repolarise the membrane

35
Q

Acetylcholine receptors associate and aggregate with…

A

scaffold proteins

36
Q

Ach receptor are

A

ligand gated ion channels

37
Q

The more acetylcholine receptors are activated…

A

the higher the current (epc)

38
Q

Acetylcholinesterase is found at

A

the neuromuscular junction

39
Q

Acetylcholine is broken down to

A

choline and acetate. Choline is reabsorbed back.

40
Q

Acetylcholinesterases increases

A

The EPP amplitude

41
Q

hemicholinium inhibits…

A

the uptake of choline

42
Q

botulinium blocks the

A

exocytosis of acetylcholine

43
Q

Neuromuscular synaptic strength is determined by

A

number of vesicles contains neurotransmitter released from motor nerve terminals (quantal content) and the magnitude of each vesicles effect on motor end plates

44
Q

Quantal analysis equation is

A

m=n x p (m=quant. of transmitter released) (n=number of vesicles available) (p= probability of vesicle exocytosis)

45
Q

sprouting helps by

A

adding a neuronal junction to a damaged NMJ/neuron

46
Q

myasthenia refers to

A

muscle weakness

47
Q

Symptoms of myasthenia Gravis include…

A

double vision in all directions, see attach pic

48
Q

By using edrophonium on a person with myasthenia gravis….

A

symptoms dramatically improve

49
Q

Mysathenia Gravis and LEMS are

A

autoimmune diseases which cause the destruction of some acetylcholine channels or calcium channels

50
Q

A decrease in the sensitivity of the acetylcholine receptors result in

A

more acetylcholine being released

51
Q

detubucurarine is a

A

competitive inhibitor of acetylcholine

52
Q

to increase the likelihood of acetylcholine channels opening,

A

increase levels of anticholinesterase

53
Q

Anticholinesterases prolong

A

end plate potentials and end plate currents

54
Q

Omethoate induces µCTX-resistant hypercontractions localised to NMJs

A

This causes NMJ hypercontractions and are associated with muscle necrosis and synaptic degeneration

55
Q

Nerve damage triggers

A

wallerian degeneration

56
Q

Within 6-15 h of nerve damage.,..

A

synaptic vesicles are degraded

57
Q

Within 24 of nerve damage,,,

A

remnants of terminal has been engulfed by schwann cell

58
Q

Wallerian degeneration results from activation of

the SARM-1 gene by

A

a) toxic accumulation of a substrate for the NAD synthetic enzyme NMNAT;
b) depletion of NAD

59
Q

The WldS gene mutation substitutes for loss of

NMNAT a8er denervation

A

preventing SARM1 activation

60
Q

Kranocytes first spread out from NMJs

A

making contact to axons which still supply NMJ’s

61
Q

Schwann cells are able to…

A

form bridges between intact and denervated NMJ’s

62
Q

Reinnervation is accompanied by

A

recovery of muscle force

63
Q

“ALS” comprises a spectrum of syndromes

A

attach slide pic

64
Q

90-95 % of ALS cases are

A

sporadic

65
Q

Challenges to ALS research includes

A

prevent motor neurones dying, promote compensation by surviving motor neurons, replace and regenerate lost motor neurones

66
Q

one potential treatment for ALS could be

A

Stem cells

67
Q

In a trial, a mice was rescued from MND,

A

via SARM 1 inactivation

Biomedical Science 2 (4 decks)

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