CBSE Class 10 Answered

Receptors are biological transducers that convert energy from both external and internal environments into electrical impulses. Receptors are connected to the central nervous system by afferent nerve fibres.

Chemical receptors, or chemoreceptors, are sensitive to substances taken into the mouth (taste or gustatory receptors), inhaled through the nose (smell or olfactory receptors), or found in the body itself (detectors of glucose or of acid-base balance in the blood). Receptors of the skin are classified as thermoreceptors, mechanoreceptors, and nociceptors.

Thermoreceptors are of two types, warmth and cold. Warmth fibres are excited by rising temperature and inhibited by falling temperature, and cold fibres respond in the opposite manner.

Mechanoreceptors are also of several different types. Examples - Sensory nerve terminals around the base of hairs are activated by very slight movement of the hair. The Pacinian corpuscles, elaborate structures found in the skin of the fingers and in other organs, are layers of fluid-filled membranes forming structures just visible to the naked eye at the terminals of axons.

Nociceptors are sensitive to stimulation that is noxious, or likely to damage the tissues of the body.