Exercises: Synapse, Neurotransmitters and Drugs

Define the term synapse. Name the three main parts of a chemical synapse and state the role of a neurotransmitter.

Name the neurotransmitter released at neuromuscular junctions and describe two ways in which neurotransmitter activity at a synapse can be ended after it has acted.

State the roles of dopamine and endorphins in the body and name one lifestyle activity that can increase the release of each.

Describe, in correct order, the events at a chemical synapse from the arrival of an action potential at the presynaptic terminal to the generation of a new impulse in the postsynaptic neuron. Include the roles of calcium ions, vesicles and receptors.

Selective serotonin reuptake inhibitors (SSRIs) are prescribed for depression.

1. a) Explain what is meant by reuptake.

1. b) Explain how an SSRI increases the effect of serotonin in the synapse.

1. c) Suggest why the drug may take several weeks to show its full effect.

Cocaine blocks dopamine reuptake transporters on presynaptic neurones.

1. a) Explain the effect on dopamine concentration in the synaptic cleft.

1. b) Explain why repeated use can lead to tolerance and dependence.

1. c) Name two health or social supports available in Ireland for someone with a drug dependence.

Botulinum toxin prevents the release of acetylcholine from presynaptic terminals, while organophosphate pesticides inhibit acetylcholinesterase.

1. a) Explain the effect of each on skeletal muscle.

1. b) Explain why one causes flaccid paralysis and the other sustained contraction.

1. c) Discuss why farm workers handling organophosphates in Ireland must use protective equipment.

In Parkinson's disease, dopamine-producing neurones in the brain degenerate. Patients are treated with L-dopa, a precursor of dopamine that crosses the blood–brain barrier, whereas dopamine itself does not.

1. a) Explain why dopamine cannot be given directly.

1. b) Describe the symptoms expected and link them to loss of dopamine at synapses.

1. c) Evaluate the long-term effectiveness of this treatment given that neurones continue to die.

Opioid drugs such as morphine bind to the same receptors as endorphins.

1. a) Explain how opioids relieve pain.

1. b) Explain why the body reduces its own endorphin production and receptor number with prolonged use, and how this causes withdrawal symptoms.

1. c) Discuss the benefits and risks of prescribing opioids, and evaluate natural alternatives such as exercise for managing mild pain.