Stimuli, nervous coordination and synpatic transmission exam qs

Question 1

In the nerve pathway in the diagram, synapses ensure that nerve impulses only travel
towards the muscle fibre.
Explain how.

Answer 1

Neurotransmitter only made in / stored in / released from pre-synaptic neurone;
2. (Neuro)receptors only on the post-synaptic membrane;

Question 2

Cannabinoid receptors are found in the pre-synaptic membrane of neuromuscular
junctions. When a cannabinoid binds to its receptor, it closes calcium ion channels.
Suggest how cannabinoids could prevent muscle contraction.

Answer 2

Prevents influx of calcium ions (into pre-synaptic membrane);
2. (Synaptic) vesicles don’t fuse with membrane
3. Neurotransmitter does not diffuse across synapse
4. No action potential

Question 3

Damage to the myelin sheaths of neurones can lead to problems controlling the contraction
of muscles.
Suggest one reason why.

Answer 3

Action potentials travel more slowly
muscles contract
slow(er)

Question 4

Cannabinoids include substances found in cannabis that can enter brain tissue. Scientists
are developing artificial cannabinoids that can enter neuromuscular junctions but cannot
enter brain tissue.
Suggest why these artificial cannabinoids would be better to use than cannabis when
treating someone with MS.

Answer 4

They won’t affect synapses in brain;
so only muscle affected

Question 5

The membrane potential at Q was the same whether medium or heavy pressure was
applied to the finger tip. Explain why

Answer 5

Threshold has been reached;
2. all or nothing principle.

Question 6

Morphine is a drug that has a similar structure to endorphins and can provide pain relief.
Explain how.

Answer 6

Morphine attaches to opioid receptors;
2. (More) dopamine released (to provide pain relief);