General Senses
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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
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Classification of Receptors
Proprioceptors
Sense the position and movements of the
body
Located in muscles, tendons and joints
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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
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Classification of Receptors
Chemoreceptors
Odor, taste
Nociceptors
Tissue damage:trauma, ischemia
Photoreceptors
Respond to light
Only in the eyes
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The general sensory receptors
 Unencapsulated nerve endings
Free nerve endings
Thermoreceptors:cold and warm receptors
Nociceptors
Most abundant in epithelia and connective
tissues
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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
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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
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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
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Proprioceptors
 Muscle spindles
Monitor skeletal muscle length
Trigger stretch reflexes
 Golgi tendon
Monitors the degree of tension of a tendon
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Sensory receptors
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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
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Tests for general senses
 Relative density and location of receptors test
Temperature test
Touch test
Two-point discrimination test
Tactile localization test
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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
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