State the effector in this reflex arc. 

With reference to the experiments on habituation, state the effect of repeated stimulation on the level of neurotransmitter in the synapses.

With reference to the withdrawal of the siphon in Aplysia californica, explain the concept of summation.

Amphetamines act on synapses that use dopamine as a neurotransmitter by increasing the release of dopamine into the synaptic cleft. Outline the effect this would have on human synaptic transmission.

muscle «that retracts gill»

less neurotransmitters/dopamine are released «to the synaptic cleft by presynaptic interneurons»

a. summation is the sum of all depolarization impulses/neurotransmitters released in the synapse/synaptic cleft of the effector/motor neuron 

b. in control more excitatory than inhibitory so effect would be excitatory 

c. less of each in habituated so not enough to produce action potential in the effector/motor neuron

a. amphetamines are stimulants 

b. increases the release of dopamine in the presynaptic neuron 

c. blocks reuptake by presynaptic neuron 

d. more dopamine in the synaptic cleft 

e. increased binding on / transmission by the postsynaptic neuron