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Human Anatomy

The nervous system is essential for communication and control within the body, allowing us to detect and respond to environmental changes while maintaining homeostasis. This overview delves into its two anatomical subdivisions: the central nervous system (CNS), comprised of the brain and spinal cord, and the peripheral nervous system (PNS), inclusive of cranial and spinal nerves. It also covers neurons—the fundamental units of the nervous system—detailed synaptic communication, neuroglia's support role, and key disorders like amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS).

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Human Anatomy

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  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

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