1. Neuro I Or: What makes me do that Voodoo that I Do so Well!

2. Neurons and More Neurons The root of it all…...

3. The Brain Responsible for all behavior Sensation – Sensory (Afferent) Neurons Movement – Motor (Efferent) Neurons Integration of info – Interneurons

4. The Brain Donald Hebb Proposed that the brain is not merely a mass of tissue – but a highly integrated series of structures that perform specific functions cell assemblies

5. Cell Assemblies Groups of connected neurons that perform certain functions

6. Cell Assemblies: The Neuron A specialized cell that receives, processes and/or transmits information – Modulatory Characteristics

7. Modulatory Characteristics Depolarize – Make a neighbor more likely to be active Hyperpolarize – Make a neighbor less likely to fire Change the dynamics of a receptor – Make it less receptive to a signal (NT) Affect synthesis, movement and release of NT to another neuron Moduation

8. Neuronal Structure Spinal Motor Neuron

9. Variations on a Theme Golgi Type II (Cortex) Basket Cell (Cerebellum)

10. Sensory Neurons Bipolar (Vision) Unipolar (Pain/Touch)

11. Neuronal Structure Spinal Motor Neuron

12. Soma Contains the nucleus and machinery – Life Processes

13. Neuronal Structure: Dendrites Spinal Motor Neuron

14. Dendrites (Tree) Highly Aborized Receive “messages” from other neurons – Some have dendritic “spines” Input sites – Separated from neighbor by a synapse (space) Caveat: They can transmit signals as well

15. Dendritic Spines

16. Neuronal Structure: Axon Spinal Motor Neuron

17. The Axon Tube-like structure – Micrometers to meters – Covered by the “Myelin Sheath” Axon

18. The Axon Tube-like structure – Carries a signal from the soma to the terminal buttons Signal = Action Potential (AP) (electrical/chemical event) Axon

19. Myelin Sheath

20. Surrounds many (but not all) axons Formed by Oligodendrocytes (CNS) and Schwann Cells (PNS) There are gaps between adjacent cells – Several micrometers – Called “Nodes of Ranvier” – Internode region

21. Neuronal Structure: Terminal Buttons Spinal Motor Neuron

22. Terminal Buttons Found at the end of the axon – When an AP reaches the terminal Release chemical into the synapse –Neurotransmitter (NT)

23. Neurotransmitters This Info can be excitatory or inhibitory to a neighboring neuron

24. Cell Assemblies

25. Signaling in the Neuron

26. Electrical Potentials Most work done with the Giant Squid Axon – Neurons work by electrical and chemical activity

27. Electrical Potential Inside is more negative than the outside -70 mv Membrane resting potential

28. Ions Molecules that have given up or taken on an electron – Gives the molecule a charge – Some move more readily across the membrane then others Dependent on circumstances

29. Ion Distribution

30. Ion Concentrations 1:1354040Cl- ------ 400A- 1:25100.4Ca++ 1:946050Na++ 40:110400K+ RATIOOUTSIDEINSIDEION The number is not as important as the ratio

31. Ion Concentration More positive charge on the outside then on the inside of the neuron

32. The Active Neuron

35. The Action Potential (AP) Its hard to know what’s going on Difficult to isolate ions – Everything is occurring at once – The charge is changing Impacts ion movement

37. Reaching Threshold Excitatory Input (Depolarization) – Causes the influx of positive ions (Na+) into the cell by opening Na+ channels Voltage gated channels –Great variety in threshold level – If enough positive charge comes in The threshold is reached –More NA+ channels open –Making the cell more positive –All or none

39. Caveat Takes many excitatory inputs to reach thresholds – Temporal summation – Spatial summation

40. Repolarization After time – The Na+ channels automatically close – K+ channels begin to open K+ leaves the cell carrying with it the positive charge –Repolarization

42. Overshoot Too much K+ leaves causing the cell to be hyperpolarized

44. Back to Resting State The Na+/K+ pump restores the normal ion concentrations and distributions

47. Axonal Conduction This measurement takes place at one point on the giant squid axon – The signal must travel distances to reach its destination

48. Signal Decrement Weak depolarization = loss of signal

49. AP Propagation Strong depolarization = strong signal

50. Neuronal Structure Spinal Motor Neuron AXON HILLOCK

51. Axon Hillock Has a high concentration of low threshold Na+ Channels – Very sensitive to changes in ion movement – Activation results in a autocataclysmic response All Or none

53. Neuronal Structure Spinal Motor Neuron AXON HILLOCK

54. Myelin Sheath Act as an insulator – Prevents things from moving in and out of the cell Including Ions

55. Oligodendrocytes

56. Nodes of Ranvier

57. Gaps in the sheath High concentration of Na+ channels – Reenergizes the signal so it can reach the axon terminal

59. Neuron: Axon Terminal

60. Axon Terminal: Synaptic Vesicles

61. Synaptic Transmission

62. Cell Assemblies

63. Synaptic Transmission: Caveat

64. In conclusion: Neurons are good. They excite or inhibit. They produce 1 neurotransmitter (in mammals). Transmission is essential. Neuromodulators can change everything (more on that later)