Sensory Receptor Classification: By Stimulus, Location, Function, and Adaptation

Sensory receptors are categorized by multiple criteria:

A. By Stimulus Type

• Mechanoreceptors – touch, pressure, vibration, stretch.
• Thermoreceptors – heat, cold.
• Photoreceptors – light (vision).
• Chemoreceptors – taste, smell, blood chemistry.
• Nociceptors – pain (tissue damage, extreme temps).

B. By Location

• Exteroceptors – body surface (skin).
• Interoceptors – internal organs (blood pressure, O₂).
• Proprioceptors – muscles, tendons, joints (position sense).

C. By Function

• Sensory receptors – transduce stimuli to neural signals.
• Transducers – convert energy forms (e.g., light → electrical).
• Receptors (molecular) – bind ligands (hormones, neurotransmitters).
• Ion channels – gate ion flow, altering membrane potential.

D. By Adaptation Rate

• Rapidly adapting – phasic response (e.g., Pacinian corpuscles).
• Slowly adapting – tonic response (e.g., muscle spindles).

Receptors may belong to multiple categories. This framework aids understanding of sensory processing.