nerve impulses ms answers

Question 1

Explain how a resting potential is maintained across the axon membrane in
a neurone.

Answer 1

higher conc of potassium inside
higher conc of sodium outside
memerbane more permeable to potassium ions
sodium ions actively transported out
potassium in

Question 2

A scientist investigated the effect of inhibitors on neurones. She added a
respiratory inhibitor to a neurone. The resting potential of the neurone
changed from –70 mV to 0 mV.
Explain why.

Answer 2

less ATP produced
less active transport
electrochemical gradient not maintained
so no net movement of sodium and potassium ions

Question 3

Describe the sequence of events involved in transmission across a cholinergic
synapse.

Answer 3

Depolarisation of presynaptic membrane
Calcium channels open and calcium ions enter
causing synaptic vesicles fuse with
presynaptic membrane and release
acetylcholine
Acetylcholine diffuses across synaptic cleft
attaches to receptors on the postsynaptic membrane;
Sodium ions enter (postsynaptic neurone) leading to depolarisation;

Question 4

Use your knowledge of how myosin and actin interact to suggest how the
myosin molecule moves the mitochondrion towards the presynaptic
membrane.

Answer 4

Myosin head attaches to actin performs
powerstroke;
pulls mitochondria along the actin;
next myosin head attaches to actin
performs powerstroke

Question 5

Suggest and explain one advantage of the movement of mitochondria
towards the presynaptic membrane when nerve impulses arrive at the
synapse.

Answer 5

Mitochondria supply additional ATP
for active transport of ions