1. Human Anatomy Nervous System Introduction

2. Functions • Communication and control between various organs of the body • To detect changes in the environment and respond to them • To maintain homeostasis • Homeostasis is the condition by which internal physiological conditions remain constant despite changes in the environment.

3. Overview of the Nervous System • Two anatomical subdivisions • Central nervous system (CNS) • Brain • Spinal cord • Peripheral nervous system (PNS) • 12 pair of cranial nerves • 31 pair of spinal nerves • Autonomic nervous system (ANS) • Runs with the CNS and PNS

4. A. The Neuron • The nerve cell • Basic functional unit of the nervous system • Capable of generating and transmitting electrical activity

5. The Neuron

6. The Neuron

7. Structure of the Neuron 1 2 4 3

8. Structure of the Neuron • Dendrites – numerous and short, conveys electrical impulse to rest of neuron

9. Structure of the Neuron 2. Cell Body – contains typical organelles of most cells

10. Structure of the Neuron 3. Axon – single and long, conveys electrical impulses away from cell body

11. Structure of the Neuron • Synapse – a communication junction between a neuron and another cell

12. Chemical Synapse • When electrical impulse reaches terminal part of axon, chemicals called neurotransmitters are released into synaptic cleft (space between the 2 cells) • Neurotransmitter causes second cell to become active i.e., muscle contraction, gland secretion, neuron activation

13. Synapse

14. Synapse

15. Neuromuscular Junction (NMJ) Muscle fiber

16. B. Neuroglia • Support cells of the nervous system

17. Neuroglia -- CNS • Microglia – small, mobile, remove cell debris, wastes and pathogens • Astrocytes – maintain blood-brain barrier • Oligodendrocytes – myelinate CNS axons

18. Microglia

19. Astrocytes

20. Astrocytes • The astrocytes help to form the blood-brain barrier • Prevents harmful materials in the blood from reaching the brain

21. Oligodendrocytes

22. Oligodendrocytes • Associated with axons of neurons found in CNS (brain and spinal cord) • Wrap themselves around axon in “jellyroll” fashion • Produce myelin which is a lipid that serves as an insulator to electrical currents (see saltatory conduction)

23. Oligodendrocyte Node of Ranvier

24. Development of Oligodendrocyte

25. Development of Oligodendrocyte

26. Saltatory Conduction • Occurs only on myelinated axons • Myelin is a fatty substance that insulates from electrical activity • Electrical activity jumps from node to node rather than traveling the entire length of the axon • Faster than non-myelinated axons • 100m/sec vs 1m/sec

27. Saltatory Conduction Electrical current jumps from node to node

28. Myelinated vs Non-myelinated

29. Neuroglia -- PNS • Schwann cell • Same structure and function as oligodendrocyte except in PNS

30. Schwann Cell

31. Summary of Neuroglia • CNS – microglia, astrocytes and oligodendrocytes • PNS – Schwann cells (neurolemma cells)

32. Nerve and Axon Regeneration • Schwann cells and oligodendrocytes

33. Nerve Regeneration

34. Nerve Regeneration

35. Nerve Regeneration

36. Amyotrophic lateral sclerosis (ALS)Lou Gehrig disease • Affects neurons in CNS • Causes weakened skeletal muscles • Does not affect sensory abilities • Fatal • Steven Hawking

37. Multiple Sclerosis (MS) • Progressive demyelination of CNS neurons • This causes scarring (sclerosis) of neurons • Disrupts conduction of nerve impulses • Affects both muscles and sensory • Occurs mainly 18-40 yo • Progression is slow • Read entirety of p.435