1. Somatosensory Systems cutaneous proprioceptive

2. Adequate Stimuli Thermal (infrared radiation, contact) Touch (light touch, pressure, vibration) Pain and Itch (chemical, thermal, mechanical) Proprioception (mechanical; stretch or pressure)

3. epicritic location vibration texture shape protopathic pain temperature itch and tickle Cutaneous subsystems

4. Epricritic, or non-pain Somatosensation

6. Meissner’sMerkel’s Pacinian Riffini’s Free nerve ending 60 hz vibration Stretch 200 hz vibration Pressure Pain

7. As in the retina, receptive fields vary in size. Smaller receptive fields = greater acuity two-point discrimination

8. Center-surround organization of cutaneous receptive fields results in lateral inhibition, as in retina Serves to enhance contrast

9. Protopathic, or pain Somatosensation

10. Free nerve endings that respond to: mechanical stimuli thermal stimuli chemical stimuli, or all three (polymodal receptors) Pain Receptors Called Nociceptors

11. Free nerve endings of unmyelinated C fibers or thinly myelinated A δ fibers

13. Cutaneous classified by conduction velocity Proprioceptive classified by axon diameter

16. SubstanceEffect Potassiumactivation Bradykininactivation Histamineactivation Prostaglandinssensitization Substance Psensitization

17. Gate control theory of pain control

18. Referred Pain

21. CN V and VII

22. Parallel Processing in the Somatosensory System Lemniscal System (non-pain; epicritic) Extralemniscal System (pain; protopathic) Spinothalamic pathways Neospinothalamic Paleospinothalamic Spinomesencephalic

26. Neospinothalamic PaleospinothalamicSpinomesencephalic

27. Neospinothalamic Pathway

28. Paleospinothalamic Pathway

29. Spinomesencephalic Pathway

30. Descending control of pain

34. Sensory System Summary 1. Sensory systems detect change over space (lateral inhibition to enhance 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)