Mucles And Nerves

Question 1

Explain the role of cholinesterase in the synapse

Answer 1

• Splits ACh into acetate and choline
• stops continuous depolarisation of postsynaptic membrane
• choline recycled into presynaptic neurone

Question 2

Suggest ways in which a toxin acting at cholinergic synapses may cause muscle paralysis

Answer 2

Toxin may bind to receptors on postsynaptic membrane
So stops ACh/ inhibits depolarisation/ no action potentials/ Na+ channels stay shut
Stops recycling of ACh by presynaptic neurone
Inhibits acetyl cholinesterase

Question 3

Outline the roles of Calcium ions in synapses

Answer 3

Enter presynaptic neurone
Cause vesicles containing ACh to fuse with presynaptic membrane
ACh released into synaptic cleft/ exocytosis

Question 4

Outline the roles of synapses in the nervous system

Answer 4

Ensure one-way transmission
Filter out infrequent impulses/ temporal summation
Allow interconnection of nerve pathways
Or spatial summation/ convergence of impulses
Memory/ learning
Can have an inhibitory effect too