Receptors are sense organs that receive stimuli.
On the basis of their location in body receptors are of following types -
1. Extero receptor - Located at or near the body surface.
2. Proprio receptor - Detect changes in position of limbs, muscle length and are located in muscles, tendons and joints. On earthquake first of all affected.
3. Viscero receptor - Entero receptors detect pain in viscera, degree of stretching of blood vessel's wall and movment in digestive tract.
On the basis of type of stimuli they receive, receptors are of following types -
1. MECHANICAL RECEPTORS - Respond to mechanical changes.
(i) Thigmo receptors or Tango receptors - For touch. Missner's corpuscles, Markel's disc & tectile corpuscles.
(ii) Algesi receptors - For pain. Free nerve endings are more.
(iii) Pacinian corpuscles or Baro receptor - For pressure, deeply placed in dermis.
(iv) Stato receptor - Respond to gravity.
(v) Phonoreceptor - Respond to sound waves.
(vi) Rheo receptor - Respond to water current e.g. in fishes.
2. THERMO RECEPTOR - End bulb of krausie or frigido receptor for cold. End bulb of Ruffini or callorie receptor for heat.
3. CHEMO RECEPTOR - Gustatory receptors are for taste. Olfactory receptors are for smell.
4. GALVANO RECEPTOR - Electro receptor. Respond to electric current in surrounding water e.g. in some fishes.
5. PHOTO RECEPTOR - Respond to light e.g. Eyes.