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The Spinal Cord & Peripheral Nervous System

The Spinal Cord & Peripheral Nervous System. Lesson 7. Horns. Dorsal. Ventral. Spinal Cord. Dorsal root ganglion (DRG) Sensory input Ventral root Motor output Caudal spinal cord Cauda equina ~. Spinal Cord Tracts. Major descending & ascending tracts Motor 1. corticospinal tract

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The Spinal Cord & Peripheral Nervous System

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  1. The Spinal Cord & PeripheralNervous System Lesson 7

  2. Horns Dorsal Ventral

  3. Spinal Cord • Dorsal root ganglion (DRG) • Sensory input • Ventral root • Motor output • Caudal spinal cord • Cauda equina ~

  4. Spinal Cord Tracts • Major descending & ascending tracts • Motor • 1. corticospinal tract • distal muscles • only descending tract with overt effects • 1a. Rubrospinal tract • Red nucleus to spinal cord ~

  5. Spinal Cord Tracts • Sensory • 2. Dorsal column-medial lemniscal tract • touch, vibration, & proprioception • axons ascend ipsilaterally • synapse then decussate at medulla • 3. Spinothalamic tract (anterolateral) • pain & temperature • decussate at SC entry level • ascends contralaterally ~

  6. Spinothalamic path Corticospinal tract Medulla Dorsal column-medial lemniscal path

  7. Dorsal Ventral Spinal Cord

  8. Peripheral N. S. • Cranial Nerves - 12 pair • Spinal Nerves - 31 pair • Somatic Division • Sensory info • Body Movement • Autonomic division - Homeostasis • regulation ~

  9. Cranial Nerves • From ventral surface • numbered anterior  posterior • Sensory, motor, or mixed • Mnemonic ~

  10. On Old Olympus’s Towering Top A Famous Vocal German Viewed Some Hops Oh Oh Oh To Touch And Feel Very Green Vegetables A H I II III IV V VI VII VIII IX X XI XII Olfactory Optic Oculomotor Trochlear Trigeminal Abducens Facial Vestibulococlear Glossopharangeal Vagus Accessory (Spinal) Hypoglossal

  11. Spinal Nerves • 1 pair for each vertebral segment • 8 pr. cervical (C1-C8) • 12 pr. thoracic (T1-T12) • 5 pr. lumbar (L1-L5) • 5 pr. sacral (S1-S5) • 1 pr coccygeal ~

  12. Spinal Nerves • Thoracic nerves relatively small • back & ribs • Cervical, lumbar, & sacral: large nerves • rest of the body • All Interconnect • after leaving vertebral canal • form 4 major plexuses • cervical, brachial, lumbar, sacral~

  13. Somatic Nervous System • Sensory input • receptors  DRG  dorsal SC • Dorsal column-medial lemniscal pathway • Spinolthalamic tract • Motor output • Lateral SC  ventral horns  muscles • Corticospinal tract • Rubrospinal tract ~

  14. Dermatomes • Sensory innervation • each spinal nerve has receptive field • Overlap at distal branches • redundancy • retain some sensation even if a complete spinal nerve destroyed ~

  15. The Lateral Pathway Somatic N.S.: Motor Output • Voluntary movement • distal limbs • 2 tracts • Corticospinal tract • about 1 million axons • Rubrospinal tract • small part of pathway ~

  16. Motor N.S. • Striate muscle • uninterrupted neuron • a motor neuron • nerve-dependent • Excitatory only at neuroeffector synapse • NT is acetylcholine (ACh) • cholinergic • Nicotine = direct agonist (AG) • Curare = direct antagonist (ANT) ~

  17. Somatic Motor N. S. Effector Motor Neuron ACh Spinal Cord

  18. Autonomic N. S. • Homeostasis • Effectors • Smooth Muscle • Cardiac Muscle • Glands ~

  19. Autonomic Subdivisions • Not nerve-dependent • Sympathetic • Emergency, flight/fight • Parasympathetic • Conservation / vegetative ~

  20. Preganglionic neuron Postganglionic neuron Ganglion Autonomic N. S.: General Features Effector

  21. Autonomic N. S.: General Features Effector ACh • Ganglionic synapse: Nicotinic (nACh) • different than neuromuscular • Neuroeffector junction • Sympathetic: Norepinephrine • Parasympathetic: nACh & mACh ~

  22. Sympathetic vs. Parasympathetic • Sympathetic • ganglia near spinal cord • interconnected  active together • long-lasting effects • Parasympathetic • ganglia near effector • discrete  active independently • transient effects • Antagonistic regulation ~

  23. Effector Responses Effector SympatheticParasympathetic Heart Respiration  GI  Immune system  Iris (radial)(sphincter) Sweat glands no input Adrenal glands no input~

  24. Pre- Post- Smooth muscle Glands NE Adrenal Glands Parasympathetic Sympathetic ACh

  25. Sympathetic Arousal Syndrome • Fight or flight situations • Diffuse sympathetic activation • Adrenal glands • releases NE into blood • maintains sympathetic arousal • Parasympathetic rebound • antagonistic regulation ~

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