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The Nervous System Part: 3

The Nervous System Part: 3. Ms. Herrera. Spinal Cord. Extends from the foramen magnum of the skull to the first or second lumbar vertebra Comprised of 31 pairs of spinal nerves 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal

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The Nervous System Part: 3

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  1. The Nervous SystemPart: 3 Ms. Herrera

  2. Spinal Cord • Extends from the foramen magnum of the skull to the first or second lumbar vertebra • Comprised of 31 pairs of spinal nerves • 8 cervical • 12 thoracic • 5 lumbar • 5 sacral • 1 coccygeal • Extends from the foramen magnum of the skull to the first or second lumbar vertebra

  3. Spinal Cord Anatomy • Internal gray matter is mostly cell bodies • Dorsal (posterior) horns • Anterior (ventral) horns • Gray matter surrounds the central canal • Central canal is filled with cerebrospinal fluid • Exterior white mater—conduction tracts • Dorsal Column: contains sensory (afferent) tracts • Lateral & Ventral Column: Contains both ascending and descending (motor: efferent tracts)

  4. Peripheral Nervous System (PNS) • Comprised of nerves and ganglia (neuronal cell bodies) that are outside the CNS • Mixed nerves • Both sensory and motor fibers • All spinal nerves are mixed • Sensory (afferent) nerves • Carry impulses toward the CNS • Found in sensory structures • Motor (efferent) nerves • Carry impulses away from the CNS • Arise in CSN and include nerves from Somatic and Autonomic division

  5. Peripheral Nervous System (PNS) • Cranial Nerves • There are a total of 12 that are identified by name and number • Mostly serve the head and neck • Most are mixed nerves, but three are sensory only

  6. 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

  7. PNS: 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

  8. PNS: Spinal Nerves

  9. PNS: Autonomic Nervous System • A.K.A. involuntary nervous system • Motor subdivision of the PNS • Consists only of motor nerves • Actions: • Regulates activities of cardiac and smooth muscles and glands • Two subdivisions • Sympathetic division • Parasympathetic division

  10. PNS: Differences Between Somatic and Autonomic Nervous Systems Somatic Autonomic • Nerves • one motor neuron • Effector organs • skeletal muscle • Neurotransmitters • always use acetylcholine • Nerves • preganglionic and postganglionic nerves • Effector organs • smooth muscle, cardiac muscle, and glands • Neurotransmitters • use acetylcholine, epinephrine, or norepinephrine

  11. Anatomy of the Autonomic Nervous System

  12. PNS: Autonomic Functioning Sympathetic Parasympathetic • A.K.A. “fight-or-flight” response • Response to unusual stimulus • Takes over to increase activities • Release acetycholine • Remember as the “E” division • Exercise, excitement, emergency, and embarrassment • “housekeeping” activities • Conserves energy • Maintains daily necessary body functions • Release norepinephrine • Remember as the “D” division • digestion, defecation, and diuresis

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