1. Topic 13 The Somatic Sensory System Lange Biology 463 - Neurobiology

2. Introduction Somatic Sensation –Enables body to feel, ache, chill –Responsible for touch and pain –Somatic sensory system: Different from other systems Receptors: Broadly distributed Responds to many kinds of stimuli

3. Touch Types and layers of skin –Hairy and glabrous (hairless - e.g., palms) –Epidermis (outer) and dermis (inner) Functions of skin –Protective –Prevents evaporation of body fluids –Provides direct contact with world Mechanoreceptors –Most somatosensory receptors are mechanoreceptors

4. Touch Mechanoreceptors Pacinian corpuscles Ruffini's endings Meissner's corpuscles Merkel's disks Krause end bulbs

5. Touch Mechanoreceptors –Small and large receptive fields

6. Touch Mechanoreceptors –Two-point discrimination Receptive field density Receptive field size

9. Touch Primary Afferent Axons –A  C –C fibers mediate pain and temperature –A  mediates touch sensations

10. Pain Perception Primary Afferents and Spinal mechanisms –First pain and second pain –Referred pain: Angina

11. Touch The Spinal cord –Spinal segments (30)- spinal nerves within 4 divisions of spinal cord

12. Touch The Spinal cord –Dermatomes- 1-to-1 correspondence with segments –Shingles

14. Touch Dorsal Column–Medial Lemniscal Pathway –Touch and proprioception

15. Touch Homuncular Mapping

16. Touch

17. Homuncular Mapping of a variety of mammals shows differences in distribution of sensory structures that relate to habitat and environmental success.

18. Temperature Thermoreceptors –Hot and cold receptors

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