For each variety of inhibition in the nervous system A–E, select the best option for its descrip-tion from the following list

A. Option 3 A form of inhibition in which activation of one neural group causes inhibition of neurones surrounding the activated group. This is seen in the neurones of the occipital cortex where central excitation reduces activity in surrounding neurones.

B. Option 5 A state where neurones in the brain and spinal cord are less excitable than normal. A general state of inhibition of excitability of the neurones in the CNS can be induced by general anaesthetic and other drugs that depress the central nervous system.

C. Option 2 Inhibition produced by release of transmitters that affect the membrane potential of efferent neurones. Here the inhibition of the post-synaptic membrane is caused by the action of pre-synaptic nerve terminals directly on the membrane of the post-synaptic cell body.

D. Option 1 Inhibition produced by the action of neurotransmitters on the terminal processes of afferent nerves. In this case nerve endings of afferent neurones release neurotransmitters close to the nerve endings of other neurones to modulate release of neurotransmitter from them.

E. Option 4 Inhibition of a conditioned reflex by an application of a new stimulus just before the application of the conditioned stimulus. Conditioned reflexes can be reinforced or inhibited by external stimuli given at about the same time as the conditioned stimulus.