4. Neuromuscular Junction

Question 1

Where are the cell bodies of motor neurons located?

Answer 1

Ventral horn

Question 2

What happens when acetylcholine binds to receptor sites on a motor end plate?

Answer 2

1. Binding triggers opening of Na+ channels
2. Ion movements depolarise the motor end plate, generating an end plate potential
3. Flow of current brings the adjacent area to the threshold
4. Action potential is initiated and sent through muscle

Question 3

Where is ACh produced?

Answer 3

Pre-synaptic terminal

Question 4

What is ACh produced by?

Answer 4

Enzyme: choline acetyltransferase

Question 5

What is used to make ACh?

Answer 5

Acetyl Co-A and choline

Question 6

What is the resting end plate potential for muscle?

Answer 6

-80mV

Question 7

What type of receptor does ACh bind to?

Answer 7

Nicotinic

Question 8

What does acetylcholinesterase do?

Answer 8

Breaks down ACH
Causes Na+ channels to close
Field is cleared for a new input

Question 9

How does curare paralyse skeletal muscle?

Answer 9

Inhibits binding of ACh

Used during anaesthesia

Question 10

How is paralysis of skeletal muscle treated?

Answer 10

Acetylcholinesterase inhibitors

Question 11

How does botox block the release of ACh?

Answer 11

Cleaves synaptic proteins required for vesicle release

Question 12

What is myasthenia gravis?

Answer 12

Immune system attacks the motor end plate ACh receptor
Causes muscle contraction and weakness
Treated with AChE inhibitor