Explain the structures and steps involved in the coordination of the reflex action. (6 marks)

To score full marks in this question the student should provide:'Scientifically relevant facts, events or processes are identified and given in detail to form an accurate account.' (Level 2: 4-6 marks)The student needs to consider the receptor, the neurones and the effector in the correct sequence.
Model answer: Receptors can detect stimuli such as pressure or heat, which causes the generation of electrical signals. The impulses then travel through the sensory neurone towards the spinal cord. The signal changes from being electrical impulses to becoming chemical neurotransmitters when encountering the synapses at the spinal cord. These neurotransmitters stimulate an electrical impulse when they reach the end of the synapse and the beginning of a neurone. The first synapse is between the sensory neurone and relay neurone, and the second is between the relay neurone and motor neurone. The motor neurone carries out the electrical signal to an effector such as a limb muscle, the eye lid muscles or glands, causing them either contract (i.e muscles) or secrete chemicals (i.e. glands) in response to the stimulus.