1. The Skin Example Skin Receptors: Free nerve ending; Pacinian corpuscles; Ruffini endings; Hair follicle ending; Meissner corpuscle; Merkel’s disk Light touch Pressure Vibration Temperature Pain Hair movement

2. The Skin Example Skin Receptors: Free nerve ending; Pacinian corpuscles; Ruffini endings; Hair follicle ending; Meissner corpuscle; Merkel’s disk

3. Different types of skin receptors

4. Spinal Cord

5. Monosynaptic Reflex Disynaptic Reflex 1. Sensory neurons 2. Neurons in the spinal cord 3. Motor neurons which control muscle contraction

6. Why does the reflex occur before perception takes place? Answer: The sensation of heat reaches our perception only after the reflexive withdrawal took place, because the somatosensory information can travel very quickly to the spinal cord and then back down to the motor neurons, whereas it takes a longer time for this information to reach the higher areas of the brain, where it yields to perception.

7. SKIN Spinal Cord  Brain BRAIN

8. Somatosensory pathway

9. Spinal Cord  Brain Cerebral Cortex Thalamus Medulla Note crossing! Spinal Cord

10. The Thalamus: Anatomy

11. The thalamus: Functions The major role of thalamus is to gate and otherwise modulate the flow of sensory information to cortex.

12. The Thalamus: Functions The thalamus also play an important role in regulating states of sleep and wakefulness.

13. Sensory processing hierarchy ThalamusCortexSensor

14. Sensory processing is different areas of the brain

15. The full somatosensory pathway Touch on left finger Heat on right finger

16. The “Homunculus” The cortical representation of sensory information is not uniform, but emphasizes certain sensory parts of the body, such as the lips and fingers.

17. Somatosensory - Brain CNS preserves the peripheral body map. Amount of CNS tissue is proportional to the distribution of peripheral receptors.

18. Homunculus: Other Animals

19. Brain Mapping Finding out what each part of the brain does

20. Brain Areas are Specialized for Different Functions

21. Demo: how many picks? Use a fork for the following experiment. Gently pressure your neighbor’s fingertip with 1, 2, or 3 of the fork’s picks. Can he tell (without looking) how many picks are touching his fingertip? Now do the same on other body area, such as inside the arm, on the legs, on the lips, or on the back of the body. Can you still tell how many picks? Where?

22. Somatosensory discrimination varies throughout the body surface

23. Somatosensory - Brain | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | ?

24. Somatosensory - Brain | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | SiteThreshold Distance Fingers2-3 mm Upper Lip5 mm Cheek6 mm Nose7 mm Palm10 mm Forehead15 mm Foot20 mm Belly30 mm Forearm35 mm Upper arm39 mm Back39 mm Shoulder41 mm Thigh42 mm Calf45 mm Influence of: Ice Distraction Sound

25. Pain! Gate Control Theory

26. Proprioception ? 123123