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Chapter 7d. The Nervous System

Chapter 7d. The Nervous System. PNS: Spinal Nerves. There is a pair of spinal nerves at the level of each vertebrae for a total of 31 pairs Spinal nerves are formed by the combination of the ventral and dorsal roots of the spinal cord

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Chapter 7d. The Nervous System

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  1. Chapter 7d.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 • Spinal nerves are formed by the combination of the ventral and dorsal roots of the spinal cord • Spinal nerves are named for the region from which they arise

  3. PNS: Spinal Nerves Figure 7.22a

  4. Anatomy of Spinal Nerves • Spinal nerves divide soon after leaving the spinal cord • Only 1/2” long • Dorsal rami – serve the skin and muscles of the posterior trunk • Ventral rami – forms a complex of networks (plexus) for the anterior & limbs Figure 7.22b

  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: Distribution of Major Peripheral Nerves of the Upper and Lower Limbs Figure 7.26a

  9. PNS: Distribution of Major Peripheral Nerves of the Upper and Lower Limbs Figure 7.26b

  10. PNS: Distribution of Major Peripheral Nerves of the Upper and Lower Limbs Figure 7.26c

  11. Rami contain motor & sensory fibers • Damage to spinal nerve causes loss of sensation & paralysis • Plexus – complex network of nerves

  12. PNS: Autonomic Nervous System (ANS) • The involuntary branch of the nervous system • Regulates activities of cardiac & smooth muscles & glands • Maintains homeostasis • Motor subvision of the PNS • Consists of only motor nerves • Divided into two divisions • Sympathetic division • Parasympathetic division

  13. PNS: Differences Between Somatic and Autonomic Nervous Systems • Nerves • Somatic – one motor neuron (nerves controlling skeletal muscles) • Cell body in CNS; axon in spinal nerves extend to muscle • Autonomic – preganglionic and postganglionic nerves • 2 motor nerves: 1st in brain or cord (preganglionic), • 2nd is outside CNS (postganglionic), extends to organ it serves

  14. Differences Between Somatic and Autonomic Nervous Systems • Effector organs • Somatic – skeletal muscle • Autonomic – smooth muscle, cardiac muscle, and glands • Neurotransmitters • Somatic – always use acetylcholine • Autonomic – use acetylcholine, epinephrine, or norepinephrine

  15. Comparison of Somatic and Autonomic Nervous Systems Figure 7.24

  16. Autonomic divided into: • Sympathetic – mobilizes body during extreme situations • Parasympathetic – allows us to unwind & conserve energy

  17. 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 postganglionic neuron transmit impulse from CNS to the effector • Norepinephrine and epinephrine are neurotransmitters to the effector organs

  18. PNS: Anatomy of the Autonomic Nervous System Figure 7.25

  19. PNS: Sympathetic Pathways Figure 7.26

  20. 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

  21. 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

  22. Increased heart rate, deep breathing, cold-sweaty skin, dilated eyes, increased BP, increased blood glucose • Dilation of skeletal blood vessels to run faster • Blood away from digestive organs to serve heart, brain muscles • Type A personality – excessive sympathetic nervous system stimulation

  23. PNS: Autonomic Functioning • Parasympathetic – “housekeeping” activities • When at rest • Conserves energy • Maintains daily necessary body functions • Conserve body energy so you can digest • Why you relax after a meal • Remember as the “D” division • digestion, defecation, and diuresis • Both sympathetic & parasympathetic systems work continuously

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

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

  26. 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 • Rubella causes deafness and other CNS problems • Cerebral palsy is possibly caused by a decrease in oxygen

  27. Other problems with the CNS: Hydrocephaly and Anencephaly – failure of cerebrum to develop • Spina bifida – vertebrae form incompletely • The hypothalamus is one of the last areas of the brain to develop • Why premature newborns can’t control body heat

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

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