Nerves and the Neuromuscular Junction

Question 1

Label the Neurone

Answer 1

Question 2

What happens during the absolute refractory period of an action potential?

Answer 2

No further action potentials can be stimulated

Question 3

What happens dring the relative refractory period?

Answer 3

If the stimulus is strong enough then you could get another action potential produced

Question 4

What happens during depolarisation?

Answer 4

The sodium channels open and sodium ions flood into the neurone until there is the same amount on each side of the membrane which causes the potential across the membrane to become positive (+30mV)

Question 5

What happens during repolarisation?

Answer 5

The postassium channels open and potassium floods out of the neurone causing the membrane potential to become negative again but as these are slow to close hyperpolarisation occurs

Question 6

What is hyperpolarisation?

Answer 6

The membrane potential is lower than the resting potential and so it’s harder to stimulate another action potential at this stage

Question 7

Fill in the missing labels

Answer 7

Question 8

fill in the labels

Answer 8

Question 9

Describe stages 1 and 2 on this diagram

Answer 9

1. an action potential arrives at the presynaptic neurone and causes the membrane to depolarise and this causes calcium ions to enter the presynaptic terminal
2. The calcium ions cause rthe vesicles contain acetylcholine to move to the presynaptic membrane and bind with it

Question 10

Describe stage 3 on this diagram

Answer 10

• Acetylcholine to discharged into the synaptic cleft by exocytosis
• Calcium ions are pumped out of the presynaptic terminal and the exocytosis stops
• The released ACh diffuses across the synaptioc cleft and binds to ACh receptors on the post synaptic membrane which are gated channels and causes the gates to open

Question 11

Describe depolarisation and its importance on muscle contraction at a neuromuscular junction

Answer 11

• Sodium ions move acorss the post synaptic membrane causing depolarisation
• This is a graded potential so once it reaches more than -60mV a muscle action potential will be propagated across the sarcolemma

Question 12

Describe stage 4 on this diagram

Answer 12

• Acetylcholine is removed from the synaptic cleft by being broken down by acetylcholinesterase
• It’s broken down into acetate and choline
• Choline is reabsorbed into the presynaptic terminal and is recycled by having more acetate added to it
• the acetate diffuses away