sensory systems 1. visual 2. auditory 3. somatosensory 4. gustatory 5. olfactory acoustic vestibular...
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Sensory Systems
1. Visual
2. Auditory
3. Somatosensory
4. Gustatory
5. Olfactory
acousticvestibular
cutaneousproprioceptive
chemical (flavor)
Distal senses
Proximal senses
Adequate Stimuli for Somatosensation
Thermal (infrared radiation, contact)
Touch (light touch, pressure, vibration)
Pain and Itch (chemical, thermal, mechanical)
Proprioception (mechanical; stretch or pressure)
epicriticlocationvibrationtextureshape
protopathicpaintemperatureitch and tickle
Cutaneoussubsystems
Meissner’s Merkel’s
Pacinian Ruffini’s Free nerve ending
60 hz vibration
Stretch200 hz vibration
Pressure
Pain
As in the retina, receptive fields vary in size.
Smaller receptive fields = greater acuitytwo-point discrimination
Center-surround organization of cutaneousreceptive fields results in lateral inhibition.
Serves to enhance contrast
Free nerve endings that respond to:
•mechanical stimuli•thermal stimuli•chemical stimuli, or •all three
(polymodal receptors)
Pain Receptors
Called Nociceptors
Substance Effect
Potassium activation Bradykinin activation Histamine activation Prostaglandins sensitization Substance P sensitization
Gate control theory ofpain control
Transcutaneous electrical nerve stimulation may act via gate control
Parallel Processing in theSomatosensory System
Lemniscal System (non-pain;epicritic)
Extralemniscal System (pain;protopathic)Spinothalamic pathways
NeospinothalamicPaleospinothalamic
Spinomesencephalic
Sensory System Summary
1. Sensory systems detect change
over space (lateral inhibition toenhance contrast)
over time (rapidly adapting)
2. Detect “features”
4. Parallel pathways
5. Hierarchical processing
6. Topographical organization
7. Non-uniform receptive fields
8. Extreme sensitivity, wide dynamic range
9. Non-linear response
3. Structures are laminated (cells in layers)
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