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The Nervous System

This article provides an overview of the spinal nerves, including their anatomy, distribution, and role in the autonomic nervous system. It discusses the spinal nerve plexuses, major peripheral nerves, and differences between the somatic and autonomic nervous systems. Additionally, it explores the anatomy and functioning of the sympathetic and parasympathetic divisions of the autonomic nervous system. Development aspects of the nervous system are also mentioned.

shirleyramsey
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The Nervous System

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  1. The Nervous System

  2. PNS: Spinal Nerves • There is a pair of spinal nerves at the level of each vertebrae for a total of 31 pairs • Formed by the combination of the ventral and dorsal roots of the spinal cord • Named for the region from which they arise

  3. PNS: Spinal Nerves Figure 7.25a

  4. PNS: Anatomy of Spinal Nerves • Spinal nerves divide soon after leaving the spinal cord • Dorsal rami—serve the skin and muscles of the posterior trunk • Ventral rami—form a complex of networks (plexus) for the anterior

  5. PNS: The Spinal Nerves Figure 7.25b

  6. PNS: Spinal Nerve Plexuses Table 7.2 (1 of 2)

  7. PNS: Spinal Nerve Plexuses Table 7.2 (2 of 2)

  8. PNS: Major Peripheral Nerves Figure 7.26a

  9. PNS: Distribution of Major Nerves Figure 7.26b

  10. PNS: Distribution of Major Nerves Figure 7.26c

  11. PNS: Autonomic Nervous System • Motor subdivision of the PNS • Consists only of motor nerves • Also known as the involuntary nervous system • Regulates activities of cardiac and smooth muscles and glands • Two subdivisions • Sympathetic division • Parasympathetic division

  12. PNS: Differences Between Somatic and Autonomic Nervous Systems • Nerves • Somatic: one motor neuron • Autonomic: preganglionic and postganglionic nerves • Effector organs • Somatic: skeletal muscle • Autonomic: smooth muscle, cardiac muscle, and glands

  13. PNS: Differences Between Somatic and Autonomic Nervous Systems • Neurotransmitters • Somatic: always use acetylcholine • Autonomic: use acetylcholine, epinephrine, or norepinephrine

  14. PNS: Comparison of Somatic and Autonomic Nervous Systems Figure 7.27

  15. PNS: Anatomy of the Sympathetic Division • Originates from T1 through L2 • Ganglia are at the sympathetic trunk (near the spinal cord) • Short pre-ganglionic neuron and long post-ganglionic neuron transmit impulse from CNS to the effector • Norepinephrine and epinephrine are neurotransmitters to the effector organs

  16. PNS: Anatomy of the Autonomic Nervous System Figure 7.28

  17. PNS: Sympathetic Pathways Figure 7.29

  18. PNS: Anatomy of the Parasympathetic Division • Originates from the brain stem and S1 through S4 • Terminal ganglia are at the effector organs • Always uses acetylcholine as a neurotransmitter

  19. PNS: Autonomic Functioning • Sympathetic—“fight or flight” • Response to unusual stimulus • Takes over to increase activities • Remember as the “E” division • Exercise, excitement, emergency, and embarrassment

  20. PNS: Autonomic Functioning • Parasympathetic—“housekeeping” activites • Conserves energy • Maintains daily necessary body functions • Remember as the “D” division • digestion, defecation, and diuresis

  21. Effects of the Sympathetic and Parasympathetic Divisions of the ANS Table 7.3 (1 of 2)

  22. Effects of the Sympathetic and Parasympathetic Divisions of the ANS Table 7.3 (2 of 2)

  23. Development Aspects of the Nervous System • The nervous system is formed during the first month of embryonic development • Any maternal infection can have extremely harmful effects • The hypothalamus is one of the last areas of the brain to develop

  24. Development Aspects of the Nervous System • No more neurons are formed after birth, but growth and maturation continues for several years • The brain reaches maximum weight as a young adult

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