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Sensory receptors classified by stimulus type
Mechanoreceptors: respond to touch, pressure, vibration, stretch, and itch
thermoreceptors: sensitive to change in tempertature
photoreceptors: respond to light energy (retina)
chemoreceptors: responds to chemicals (smell, taste, changes in body chemistry)
nociceptors: respond to pain causing stimuli
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snesory receptors classified by location
- 1. Exteroceptors: respond to stimuli arising outside the body
- - most special sense ograns
- 2. Interoceptros
- -respond to stiumuli arising in internal viscera and blood vessels
- -sensitive to chemical changes, tissue stretch, and temp changes
- 3. Proprioceptors
- -respond to stretch in skeletal muscles, tendons, joints, ligaments, and connective tissue cvering bones and muscles
- -inform brain of bodys movments
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Unencapsulated dendritic endings
- 1. thermoreceptors
- 2. nociceptors
- 3. light touch receptors
- -Merkel discs (deep layers of epidermis)
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encapsulated dendritic endings
*All are mechanoreceptors*
1. Meissner's corpuscles: discriminative touch (dermal papillae)
2. Picinian (lamellated) corpuscles: deep pressure and vibration (dermis and subcutaneous tissue)
3. Ruffini endings: deep continuous pressure (dermis, subcutaneous tissue, and joint capsules)
4. Muscle spindles: muscle stretch (perimesium of muscle tissue)
5. Goldi tendon organs: stretch in tendons
6. Joint kinesthetic receptors - stretch in articular capsules
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Aspects of sensory perception
perceptual detection: ability to detect a stimulus (Requires summation of impulses)
magnitude estimation: intensity is coded in the frequency of impulses
spatial discrimintation: identifying the site of pattern of the stimulus (studied by 2 point discrimination test)
feature abstraction: indentification of more complex aspects and several stimulus properties
quality discrimination: the ability to identify submodalities of a sensation (sweet vs sour)
pattern recognization : recognition of familiar or significnat patterns in stimuli (like the melody in a piece of music)
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Regeneration of nerve fibers
- 1. the axon becomes fragmented at the injury site
- -Walerian degeneration
2. macrophages clean out the dead axon distal to the injurt
3. axon sprouts, or filaments, grow through a regeneration tube formed by schwann cells
4. the axon regenerates and a new myelin sheath forms
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Hiltons law
- •Hilton’s law: Any nerve
- serving a muscle that produces movement at a joint also innervates the joint
- and the skin over the joint
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