Heroin is a drug acting on the nervous system. Pain receptors are present in the skin. These receptors send impulses along sensory neurones to the spinal cord. Fig. 3.1 shows the synapses between sensory neurone A and a relay neurone, and sensory neurone B and a relay neurone, in the spinal cord. Fig. 3.2 provides an enlarged view of the synapse between sensory neurone A and the relay neurone.
(a)[2]
Define what is meant by the term drug.
(b)[4]
Describe how impulses pass across the synapse.
(c)[2]
Suggest how the structure of a synapse makes impulses travel in only one direction.
(d)[3]
Explain how heroin affects synapse function.
(e)[3]
List three stimuli, other than pain, that humans can detect.
Worked solution & mark scheme
This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: “any chemical / substance that is taken into the body” …