2. K&W 4-1 Descartes View

3. Luigi Galvani (1737-1798)

4. Electrified Frogs Luigi Galvani Frog legs attached to wire in market Electrical storm made legs move Early idea of electrical properties of nervous system

5. Electrical Stimulation K&W 4-2

6. Neural Communication

7. K&W 4-4 The journey of nerve message As message passes along the nerve, Electrode indicates a shift from negative to positive and then back to negative again

8. Neural Communication Cell body end of axon Direction of neural impulse: toward axon terminals

9. Hodgkin and Huxley Two Cambridge profs and a squid get together (1939)

10. Squid and axon K&W 4-5

11. Microelectrodes KW 4-7

12. Recording from an axon K&W 4-6

13. Reversal of charges K&W 4-15

14. Ions

15. Ions on the move K&W 4-8 Concentration gradient: move from area of higher concentration to area of lower concentration

16. Ions meet a barrier K&W 4-9 No pores = No movement of ions With pores, ions can move. Charge develops Electrical Gradient: opposite charges attract (+ --) like charges repel (+ +)

17. Ions of the axon KW 4-10

18. Resting Cell Recording KW 4-10

19. Resting Cell Charges KW 4-10

20. Depolarization KW 4-11 A Graded Potential

21. Hyperpolarization KW 4-11 A Graded Potential

22. Axons get polarized K&W 4-11

23. When an action potential occurs, Na+ and K+ work together KW 4-13

24. Fig. 2-17, p. 43

25. Phases of the action potential K&W 4-14

26. Fig. 2-15, p. 39

27. Neural Communication

28. Reversal of Charges Cell body end of axon Direction of neural impulse: toward axon terminals

29. Falling dominos K&W p. 131

30. Ion flow K&W 4-15

31. Properties of Action Potentials All or none: fires completely or not at all Self-propagates: recreates itself Does not degrade: doesn’t lose power Full strength to the end of axon Axon can be any length

32. Analogies for Action Potentials Band of Fire moving down tube Ring sliding down a string Doing “the wave” in stadium

33. End of segment one

34. Naked Neurons Neurons without myelin sheath Slower Shorter Can’t carry messages long distances What does myelin sheath provide?

35. Louis-Antoine Ranvier French physician discoverer of the myelin sheath. 1835-1922 In 1878 he discovered myelin and the famous nodes which received his name

36. Nodes of Ranvier K&W 4-16

37. Saltatory conduction K&W 4-17

38. Multiple Sclerosis Jacqueline Du Pre 1945-1987 MS diagnosis in 1971 Hilary and Jackie (1998 movie)

39. Neuronal Integration To fire or not to fire, that is the question All or none principle: all or nothing at all Why important?

40. Firing Line

41. Threshold

42. Sherrington Sir Charles Scott Sherrington (1857-1952) Withdrawal reflex Principle of summation Nobel prize in medicine 1932

43. Withdrawal Reflex in Dogs One mild pinch between toes  no response Two pinches quickly in same spot  withdraw paw Temporal Summation Temporal = over time

44. Paw reflex: part 2 One mild pinch in one location  no response Two pinches in different locations  withdraw paw Spatial Summation Spatial = over space

45. Temporal: one location KW 4-19 Excitatory Postsynaptic Potential Presynaptic cell Postsynaptic cell synapse

46. Temporal EPSP KW 4-19 top

47. Spatial: more than one location K&W 4-20

48. Spatial EPSP KW 4-19

49. Importance of EPSP Excite cells Bring about activity Sensation felt Muscle moved

50. Excitation must be balanced Nervous system can’t run on just excitation Sometimes better not to respond Role on inhibition Calm down the nervous system

51. Role of Inhibition Provides break for the nervous system Lowers activity levels Keeps the brain from over-excitation, as in epilepsy

52. EPSP vs IPSP

53. Temporal IPSP KW 4-19

54. Temporal Combos

55. Spatial Combos

56. A cell decides to fire K&W 4-21 Democracy of Cells

57. Emotional Arousal Autonomic nervous system controls physiological arousal Sympathetic division (arousing) Pupils dilate Decreases Perspires Increases Accelerates Inhibits Secrete stress hormones Parasympathetic division (calming) Pupils contract Increases Dries Decreases Slows Activates Decreases secretion of stress hormones EYES SALIVATION SKIN RESPIRATION HEART DIGESTION ADRENAL GLANDS

58. Control over heart Sympathetic  excites Parasympathetic  inhibits Work together to control heart