Neuromuscular Junction

Question 1

What is the main neurotransmitter in the NMJ?

Answer 1

Acetylcholine

Question 2

What neurones release ACh?

Answer 2

Lower/alpha/somatic motor neurones

Question 3

Why does the NMJ fold?

Answer 3

To increase surface area

Question 4

What is transmitter release dependent on?

Answer 4

Calcium

Question 5

What does ACh binding to nicotinic receptor do?

Answer 5

Triggers end plate potential in muscle cell

Question 6

What breaks ACh down?

Answer 6

Acetylcholinesterase

Question 7

What are the products of the breaking down of ACh?

Answer 7

Acetyl CoA and choline

Question 8

What must neurotransmitters do at first to be released?

Answer 8

Must fuse with presynaptic cell membrane
Must dock at active zones of the presynaptic membrane
Then primed to fuse with the presynaptic membrane

Question 9

What coordinates the Docking/Priming/Fusion?

Answer 9

SNARE proteins

Question 10

What does SNARE stand for?

Answer 10

Soluble n-etylmaleimide sensitive factor attachment protein receptor

Question 11

Name the v snare proteins.

Answer 11

Synaptobrevin
Synaptotagmin

Question 12

Name the t snare proteins.

Answer 12

Syntaxin
SNAP 25

Question 13

What is transmitter release directly related to?

Answer 13

Pre-synaptic uptake of Ca++ by the neurone

Question 14

What does Ca++ bind to?

Answer 14

Synaptotagmin

Question 15

What does the Ca++ step allow?

Answer 15

Fusion of the vesicle to the presynaptic membrane and exocytosis

Question 16

What can be retrieved from the postsynaptic membrane and recycled?

Answer 16

Synaptic vesicles

Question 17

How do the SNARE proteins function?

Answer 17

Action potential has arrived at the nerve terminal
T snares form a complex
Synaptobrevin begins to join with syntaxin and SNAP 25 complex and 3 snares wind round each other bringing the vesicle and the nerve terminal closer together
Ca++ binding to synaptotagmin causing fusion of vesicle and release of ACh into synaptic cleft
ATP required disassemble SNARE porteins
Vesicle recycled

Question 18

What do the small amounts of ACh cause in a resting neurone?

Answer 18

Tiny depolarisations - minature end plate potential

Question 19

What causes End plate potentials?

Answer 19

Release of ACh from many different vesicles - quantal release of neurotransmitter

Question 20

What are the two theories for vesicle recycling?

Answer 20

Kiss and run
Fusion and collapse

Question 21

How does ACh release lead to a muscle action potential?

Answer 21

Binding of ACh to nicotinic receptors allows simultaneous flow of Na+ and K+ through the receptor (acts as ion channel - ligand gated ion channels)
Movement of ions lead to generation of EPP

Question 22

What increases the amplitude of the end plate potential?

Answer 22

More ACh

Question 23

What will lead to an action potential in the muscle?

Answer 23

Summation of end plate potentials

Question 24

What disease decreases the number of functioning ACh receptors?

Answer 24

Myasthenia Gravis

Question 25

Name an anticholinesterase.

Answer 25

Neostigmine

Question 26

When is AChE sinisterly used and how does it work?

Answer 26

Nerve gases lead to ACh not being degraded prolonging muscle stimulation

Question 27

What does a decreased release of ACh lead to?

Answer 27

Impaired synaptic transmission - botulism

Question 28

What causes decreased interaction between ACh and ACh receptors?

Answer 28

Curare