OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

How do neurotransmitters function at a synapse?

1. They repair damaged neurons

2. They enhance impulse speed directly

3. They diffuse across the gap and bind to receptors

4. They prevent impulses from traveling

The correct answer is: They diffuse across the gap and bind to receptors

Neurotransmitters play a crucial role in the functioning of synapses, which are the junctions between neurons. When a nerve impulse reaches the end of one neuron, neurotransmitters are released from vesicles into the synaptic cleft, which is the small gap between two neurons. The correct process occurs when these neurotransmitters diffuse across the synaptic cleft and bind to specific receptors on the surface of the adjacent neuron. This binding of neurotransmitters to receptors on the postsynaptic neuron can initiate a response in that neuron, such as generating a new nerve impulse. Each neurotransmitter has a specific receptor it binds to, which then triggers a cascade of cellular responses. This is essential for the transmission of signals in the nervous system, allowing communication between nerve cells. The other options do not accurately represent the function of neurotransmitters. Repairing damaged neurons and enhancing impulse speed directly do not occur through neurotransmitters, while preventing impulses from traveling contradicts the role of neurotransmitters as facilitators of signal transmission.