Biophysics of the sensory systems

Abstract

Multicellular organisms, especially the higher animals, are stimulated by the environment through sensory systems; specialized organ systems which transmit information from the environment to the brain. We traditionally speak of them as the five senses: vision, hearing, olfaction, taste, and touch. But they, in fact, include more. Sensations of pain and temperature, and even sensations of hunger and thirst can be thought of as being evoked by sensory detectors. We can, in general, classify sensory detectors as follows. First, there are the special senses of vision and hearing involving the highly specialized organ systems of the eye and ear. These are called teleceptors, receiving information from distant objects. Second, we have the chemical receptors, those receptors that are excited by chemical stimulation; olfaction and taste belong to this group. Third, somatic receptors are those responsible for the sensations of the body, namely touch, pressure, pain, and temperature. Finally, there are the visceral receptors that keep the brain informed about conditions inside the body and are responsible for the sensations of hunger, thirst, and the urge to discharge.