General Senses

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

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

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

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

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

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

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

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

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

Sensory receptors

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

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

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