Sensory Receptor Classification

Free Nerve Ending

Unencapsulated dendrites of sensory neurons; detect pain; a type of nociceptor

Encapsulated Nerve Endings

Sensory receptor cells surrounded by a specialized capsule (e.g., Meissner's corpuscles, Pacinian corpuscles)

Specialized Receptor Cells

Distinct receptor cells (e.g., hair cells of the inner ear, photoreceptors of the retina)

Nociceptors

Sensory neurons that sense pain; stimuli can be chemical, mechanical, or temperature-based; have free nerve endings

Exteroceptors

Receptors near a stimulus in the external environment (e.g., somatosensory receptors in the skin)

Interoceptors

Receptors that interpret stimuli from internal organs and tissues (e.g., receptors sensing increased blood pressure in the aorta or carotid sinus)

Proprioceptors

Receptors near moving parts of the body (e.g., muscles, joints) that interpret the positions of tissues as they move

Chemoreceptors

Respond to chemical stimuli; basis for olfaction (smell) and gustation (taste)

Osmoreceptors

A type of chemoreceptor related to fluid balance

Mechanoreceptors

Respond to mechanical stimuli; basis for most aspects of somatosensation, audition, and equilibrium

Thermoreceptors

Respond to temperature changes

Photoreceptors

Sensitive to light energy; located in the retina (rods and cones)