1. The Nervous System Chapter 11

2. Functions of the Nervous system I Sensory (input): Light Sound Touch Temperature Taste Smell Internal Chemical Pressure Stretch External Chemical

3. Functions of the Nervous system II Integration: Integration means making sense of sensory input. Analyzing stimuli based on experience, learning, emotion & instinct and reacting in a useful way (you hope). Motor (output): The response to the sensory input and subsequent integration. Sending signals to the muscles and other organs of the body instructing them how to respond to the stimuli.

4. The Basic Scheme

5. Organization of the Nervous system

6. The CNS compared with the PNS

7. Support Cells of the Nervous system the Central Nervous System Astrocytes Microglia Oligodendrocytes Ependymal Cells the Peripheral Nervous System Schwann Cells (a.k.a. Neurolemmocytes) Satellite Cells

8. Astrocytes & microglia Astrocytes & microglial cells protect the neurons of the CNS.

9. Astrocytes & microglia Functions of astrocytes: 1.Connect neurons to capillaries. This makes up the “blood-brain barrier”. 2.Maintain the the electrochemical environment Capture and recycle neurotransmitters Absorb and return K + and other ions. Connected to one another and capable of communicating via gap junctions. Function of microglial cells: 1.Dendritic macrophages that phagocytize microbes and necrotic (dead) tissue.

10. Ependymal Cells & oligodendrocytes

11. Functions: Ependymal Cells - Line the ventricles of the brain an central canal of the spinal cord. They aid in the circulation of cerebrospinal fluid (CSF). Oligodendrocytes - These cells have processes that wrap around the axons of neurons. This creates an insulation coating called a myelin sheath.

12. Schwann Cells & satellite cells These are the support cells in the peripheral nervous system. Schwann cells provide the myelin sheath for peripheral axons. Satellite cells serve a slightly similar function to astrocytes, supporting the cell bodies of peripheral neurons.

13. Neurons - the “action cells”

14. Characteristics of neurons Long-lived Generally last a life time with 90% are formed by the time you are 6 years old. The rest are produced when as you go through puberty. Amitotic Until recently it was thought that neurons didn’t regenerate at all! Some may but generally what you have at adulthood is all you get. High metabolic rate This means high oxygen demand and lots of mitochondria. Neurons also require glucose.

15. Myelin Myelin is a lipid-rich component of the cell membranes of Schwann cells and oligodendrocytes. It acts kind of like the insulation on an electrical wire.

16. Chemically gated ion channels

17. Voltage gated ion channels

18. A Resting Membrane Potential Because there is a higher concentration of Na + outside than there is K + inside. This leads to an electric charge or electric potential.

19. Relative ion concentrations Ions have differential permeability. The RMP is maintained by the pumping action of a Na + /K + pump, powered by ATP

20. Polarization (subthreshold) and hyperpolarization

21. A stimulus leads to a depolarization A change in ion concentrations leads to a reversal of the charge separation.

22. Ion flow in a neuron The depolarization spreads along the cell membrane by serial opening and closing of ion gates.

23. A graded potential Graded potentials are not “all-or- none”, like action potentials

24. The cycle of an Action Potential

25. Propagation of an Action Potential

28. Temporal summation

29. Anatomy of an Action Potential

30. Salutatory conduction

31. Different types of synapses

32. A Chemical Synapse

33. EPSPs & IPSPs

34. Integration: summation of potentials

35. Synthesis of Neurotransmitters

36. Mechanisms of Neurotransmitter activity

37. A Basic Neural Circuit

38. Type of neurons

39. Three structural classes of neurons Multipolar Most numerous Many dendrites Motor and association neurons Unipolar Second most numerous Rounded body with one process Somatic & general sensory neurons Bipolar Least common, found in special sensory organs

40. Comparison of neuron types

41. Functional categories of neurons

42. This is it for 231 Lecture Final at 10 am next Tuesday. Lab Practicals: Tuesday, 6/8 @ 2 pm Thursday, 6/10 @ 10 am.