1. General Senses

2. Classification of Receptors
By origin of the stimuli
Exteroceptors
Senses stimuli external to the body
Found close to the body surface
Touch, cutaneous pain, vision, hearing, smell,etc
Interoceptors (visceroceptors)
Reacts to stimuli arising form within the body
Visceral pain, nausea, stretch, pressure

3. Classification of Receptors
Proprioceptors
Sense the position and movements of the body
Located in muscles, tendons and joints

4. Classification of Receptors
According to the type of stimuli
Thermoreceptors
Mechanoreceptors
Physical deformation:vibration, touch, pressure, stretch, tension
Also hearing, balance
Located in skin, viscera, joints

5. Classification of Receptors
Chemoreceptors
Odor, taste
Nociceptors
Tissue damage:trauma, ischemia
Photoreceptors
Respond to light
Only in the eyes

6. The general sensory receptors
Unencapsulated nerve endings
Free nerve endings
Thermoreceptors:cold and warm receptors
Nociceptors
Most abundant in epithelia and connective tissues

7. The general sensory receptors
Tactile (Merkel) discs
Light touch
Sense texture, shapes, edges
Merkel discs:merkel cell+nerve ending
Located in the stratum basale of the epidermis
Hair receptors (peritrichial endings)
Sense hair movement
Quick adaptation

8. The general sensory receptors
Encapsulated nerve endings
Tactile corpuscle (Meissner)
Located in the dermal papilla in sensitive hairless areas
Light touch and texture
Krause end bulbs
Similar to tactile
Located in mucous membranes

9. The general sensory receptors
Pacinian corpuscles
Deep pressure, stretch, tickle, vibration
Deep in the dermis and mainly found in the hands, genital, feet, breast, and some visceras
Ruffini corpuscles
Deep pressure, stretching of the skin, joint movements
Located in the dermis, subcutaneous, ligaments, tendons and joint capsules

10. Proprioceptors Muscle spindles Monitor skeletal muscle length
Trigger stretch reflexes
Golgi tendon
Monitors the degree of tension of a tendon

11. Sensory receptors

12. Receptor physiology
Stimulus is identified by the area of the brain’s sensory cortex
Four cutaneous sensations recognized
Tactile, heat, cold and pain
They cluster in certain areas
Punctuate distribution

13. Tests for general senses
Relative density and location of receptors test
Temperature test
Touch test
Two-point discrimination test
Tactile localization test

14. Tests for general senses
Adaptation test
For touch
For temperature
Negative afterimage
Referred pain
Pain is perceived in one area but the painful stimulus comes from another area
Angina pectoris, heart burn, phantom limb pain