Medical Application
Applied Science: BTEC Level 3 National Extended Diploma, topic 1.5.12
Excitatory Drugs
Many drugs affect nervous transmission at synapses. Excitatory drugs stimulate the nervous system producing more action potentials on the post-synaptic membrane. Excitatory drugs could:
Mimic neurotransmitters
- Drugs with a similar shape to neurotransmitters can mimic their function.
- The drug can bind to receptors on the postsynaptic membrane to produce an action potential.
- These drugs are called agonists.
- E.g. Nicotine can bind to nicotinic cholinergic receptors in the brain to mimic acetylcholine.
Inhibit enzymes
- Drugs can bind to enzymes to prevent the breakdown of a neurotransmitter.
- The neurotransmitter would continue to generate an action potential in the postsynaptic membrane.
- E.g. Nerve gas inhibits acetylcholinesterase and stops the breakdown of acetylcholine. This causes loss of muscle control.
Release of neurotransmitters
- Drugs can cause presynaptic neurones to release neurotransmitters.
- More neurotransmitters will activate more receptors and an action potential is more likely to be created.
Inhibitory Drugs
Many drugs affect nervous transmission at synapses. Inhibitory drugs inhibit the nervous system so that fewer action potentials are produced. Inhibitory drugs could:
Block calcium ion channels
- Drugs can block calcium ion channels in the presynaptic membrane.
- Blocking calcium ion channels would prevent the release of neurotransmitters from the presynaptic neurone.
- E.g. Alcohol.
Block receptors
- Drugs can block receptors on the postsynaptic membrane.
- If the receptors are blocked, neurotransmitters cannot bind and an action potential is not generated in the postsynaptic neurone.
- These drugs are called antagonists.
- E.g. Curare blocks nicotinic cholinergic receptors causing muscle paralysis.
Test yourself on Medical Application
Which of these are NOT a way excitatory drugs can affect synaptic transmission?
How do inhibitory drugs inhibit the nervous system?
Which of the following statements about inhibitory drugs are true?
Which of the following are NOT mechanisms of inhibitory drugs?