1 / 57

Descartes View

Descartes View. K&W 4-1. Luigi Galvani (1737-1798). Electrified Frogs. Luigi Galvani Frog legs attached to wire in market Electrical storm made legs move Early idea of electrical properties of nervous system. Electrical Stimulation. K&W 4-2. Neural Communication.

frederique
Download Presentation

Descartes View

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Descartes View K&W 4-1

  2. Luigi Galvani (1737-1798)

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

  4. Electrical Stimulation K&W 4-2

  5. Neural Communication

  6. 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 K&W 4-4

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

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

  9. Squid and axon K&W 4-5

  10. Microelectrodes KW 4-7

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

  12. Reversal of charges K&W 4-15

  13. Ions

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

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

  16. Ions of the axon KW 4-10

  17. Resting Cell Recording KW 4-10

  18. Resting Cell Charges KW 4-10

  19. Depolarization A Graded Potential KW 4-11

  20. Hyperpolarization KW 4-11 A Graded Potential

  21. Axons get polarized K&W 4-11

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

  23. Fig. 2-17, p. 43

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

  25. Fig. 2-15, p. 39

  26. Neural Communication

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

  28. Falling dominos K&W p. 131

  29. Ion flow K&W 4-15

  30. 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

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

  32. End of segment one

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

  34. 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

  35. Nodes of Ranvier K&W 4-16

  36. Saltatory conduction K&W 4-17

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

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

  39. Firing Line

  40. Threshold

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

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

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

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

  45. Temporal EPSP KW 4-19 top

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

  47. Spatial EPSP KW 4-19

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

  49. 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

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

More Related