Transmission across a synapse

Question 1

What is a cholinergic synapse?

Answer 1

A synapse where the neurotransmitter is acetylcholine

Question 2

What is acetylcholine made of?

Answer 2

Acetyl (ethanoic acid) and choline

Question 3

Where are cholinergic synapses commonly found?

Answer 3

In the central nervous system and at neuromuscular junctions in vertebrates

Question 4

How do neurotransmitters bind to receptors on the postsynaptic neurone?

Answer 4

The receptor proteins have a specific complementary shape to the neurotransmitter

Question 5

Why are there many different types of neurotransmitters and receptors?

Answer 5

Different neurotransmitters and receptors allow for specific communication across synapses, as each receptor has a complementary shape to its neurotransmitter

Question 6

What determines whether a neurotransmitter is excitatory or inhibitory?

Answer 6

The specific receptor to which the neurotransmitter binds determines whether it triggers or inhibits an action potential

Question 7

What is the function of inhibitory neurotransmitters?

Answer 7

They decrease the likelihood of an action potential by causing hyperpolarisation of the postsynaptic membrane

Question 7

What is the function of excitatory neurotransmitters?

Answer 7

They increase the likelihood of an action potential in the postsynaptic neurone

Question 8

How do drugs affect synapses?

Answer 8

Drugs act on synapses in two main ways, either enhancing or inhibiting synaptic transmission

Question 9

How can drugs stimulate the nervous system?
How can drugs inhibit the nervous system?

Answer 9

By increasing the number of action potentials in the postsynaptic neurone

By reducing the number of action potentials in the postsynaptic neurone

Question 9

What are three ways in which drugs can stimulate the nervous system?

Answer 9

1. Mimicking a neurotransmitter to activate receptors
2. Stimulating the release of more neurotransmitter
3. Inhibiting the enzyme that breaks down neurotransmitters, prolonging their effect

Question 10

What is the overall effect of drugs that stimulate the nervous system?
What is the overall effect of drugs that inhibit the nervous system?

Answer 10

They enhance the body’s response to stimuli e.g. making sound louder or more quieter

Question 11

What are two ways in which drugs can inhibit the nervous system?

Answer 11

1. Inhibiting the release of neurotransmitters
2. Blocking receptors on sodium/potassium ion. channels, preventing repolarisation

Question 12

Endorphins are neurotransmitters used by certain sensory nerve pathways, especially pain pathways. Endorphins block the sensation of pain. Drugs such as morphine and codeine bind to specific receptors in the brain used by endorphins and so mimic the effects of endorphins.

1) Suggest the likely effects of drugs like morphine and codeine on the body
2) Explain how the effect you suggest might be brought about

Answer 12

1. Drugs like morphine and codeine would likely enhance the effects of endorphins, by blocking high sensations of pain
2. They act like endorphins by binding to the receptors and therefore preventing action potentials being created in the neurones of the pain pathways

Question 13

Serotonin is a neurotransmitter involved in the regulation of sleep and certain emotional states. Reduced activity of the neurones that release serotonin is thought to be one cause of clinical depression. Prozac is an antidepressant drug that affects serotonin within synaptic clefts.

3)Suggest a way that the drug Prozac might affect serotonin within synaptic clefts

4)Explain how the effect you suggest makes Prozac an effective antidepressant

Answer 13

3. Prozac might prevent the elimination of serotonin from the synaptic cleft
4. By increasing the concentration of serotonin the synaptic cleft, its activity is increased, reducing depression, which is cause by reduced serotonin activity