Most sensory nerves do not spontaneously generate action potentials. The senses of taste and smell are functionally similar, using similar transduction mechanisms. Hair cells of the inner ear are used to provide information about head position and acceleration. Each cone cell contains three different types of photosin that absorb red, green, and blue light, respectively. Photoreceptors are most dense near the fovea.
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.