Practical 1

Question 1

Direct muscle stimulation on skeletal muscle leads to

Answer 1

Opening of voltage-gated Na+ channels

Question 2

Why doesn’t Atropine have an effect on the response of ACh on skeletal muscle but Tubocurarine does?

Answer 2

Atropine blocks muscarinic receptors and skeletal muscle uses nicotinic receptors

Question 3

Effect of neostigmine on tubocurarine response

Answer 3

Neostigmine (AChE inhibitor) enhances synaptic levels of ACh which out-competes tubocurarine for binding to nicotinic receptors

Question 4

Tetrodotoxin

Answer 4

Voltage-operated Na+ channel blocker

Question 5

Suxamethonium

Answer 5

Agonist that stimulates nicotinic ACh receptors. As it repetitively stimulate is, it produces a ‘depolarising block’ at the skeletal NMJ preventing repolarisation. Skeletal muscle relaxant. Long lasting.

Question 6

Why does adding neostigmine to suxamethonium make it worst?

Answer 6

Neostigmine is a AChE inhibitor and hence increase ACh conc. The increase in ACh perpetuates the maintained stimulation of nicotinic receptors responsible for the muscle relaxation.