Rod cells are more numerous than cone cells. The two divisions of the autonomic nervous system, the parasympathetic and sympathetic, are usually regulated in opposite directions by sensory stimuli. The sympathetic system initiates sexual arousal. The brainstem controls the autonomic nervous system. The autonomic nervous system controls the activity of smooth and cardiac muscles rather than skeletal muscles.
Gonadotrophins come only from the pituitary.
The loudness of a sound is encoded in the frequency of action potentials in the afferent nerve. An adult has more neurons than an infant. Activation of a synapse just prior to an action potential in the postsynaptic cell strengthens that synapse. The hippocampus is needed for memory. Grey matter contains cell bodies of neurons.