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Monet: The Bridge at Argenteuil

Monet: The Bridge at Argenteuil. The Spinal Cord. Not Just an Passive Conduit!. Spinal Cord. Extends from foramen magnum to L2 Central Gray matter (association neurons/processes) and peripheral white matter (myelinated nerves)

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Monet: The Bridge at Argenteuil

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  1. Monet: The Bridge at Argenteuil

  2. The Spinal Cord Not Just an Passive Conduit!

  3. Spinal Cord • Extends from foramen magnum to L2 • Central Gray matter (association neurons/processes) and peripheral white matter (myelinated nerves) • Gray matter shaped like “H” with posterior, anterior and lateral horns

  4. Posterior: Sensory Neurons, Association Neurons (reflexes) • Anterior: Motor Neurons • Lateral: Sympathetic Autonomic Motor Neurons • Nerve Pathways: groups of ascending and descending nerve axons within white tissue of cord.

  5. Nerve Pathways • Names tell function (first part = origin) • i.e Spinothalamic: originates in spinal cord and terminates in thalamus • Ascending Patways: 2-3 neurons in sequence • Somatic (motor) nerves are in 2 locations :

  6. Motor Nerves • Lower motor neurons: located in spinal gray matter or brainstem • Axons extend to muscles • Upper motor neurons: Motor Cortex, Cerebellum, or Brainstem: Descend to medulla, cross to opposite side of cord and connect to lower neurons

  7. Cerebrospinal Fluid • bathes brain and spinal cord (flows) providing protection • Produced by Choroid Plexus in brain: Capillary/Ependymal structure surrounding ventricles • Chemicals can get into this fluid & influence brain activity • i.e. altitude incr. CO2 & H+ in CSF, this stimulates the hypothalamus to incr. breathing & incr. urineoutput.

  8. Assignment: • Read: 211-217 and 202-203 (Reflexes and Neuronal Circuits) • First Exam will be the week of Sept. 18 (Either Weds/Friday) • The Exam will cover the Nervous System: Chapter 8

  9. The Spinal Cord Anatomy and Reflexes

  10. Spinal Cord: Coloring Guide • As the spinal cord exits the skull, it is continuous with the medulla: Color the “cervical segment” Red (AC: C1-C8) • Note: At the Cervical Enlargement, nerves exit to serve the upper limbs

  11. Color Guide: • The second segment is the Thoracic Segment:Color Blue (AT: T1-T12) • The final segment to be colored is the Lumbar Segment:Color Green (AL: L1-L5)* • Note: The Lumbar enlargement serves the lower limbs (A2)

  12. Spinal Cord Cross Section: • Note: Nerves exit between adjacent vertebrae via the intervertebral foramen • The spinal nerves exiting the cord are bundles of both ascending and descending nerve fibers: Color Purple (D)

  13. Spinal Nerves: • Nerves extending from the ventral aspect of the spinal cord are called the ventral root:Color red (C2) • These are descending motor nerves • Nerves extending from the dorsal spinal cord are the dorsal root:Color blue (C1) • These are ascending sensory nerves

  14. Gray Matter: Color Green (B) • Dorsal (Posterior) Horn: Think “Dorsal root” – Sensory neurons and association neurons • Ventral (Anterior) Horn: Think “Ventral root” – motor neurons • Lateral Horn: Sympathetic neurons (more later!)

  15. ! Reflex Activity • What happens when you accidentally touch your hand to a hot stove? • Do you sit and think? NO! • You withdraw your hand almost before you even realize it’s fried!

  16. To CNS Stimulus! Response! • The sensory signal is sent directly to the spinal column • It crosses association neurons-motor neurons, which initiate an immediate response • sensory info is also sent to CNS (but response has already begun)

  17. The “Reflex Arc” • Sensory receptor • Afferent Neuron • Association Neurons • Efferent (motor) Neuron • Effector Organ (Skeletal or Smooth)

  18. Cranial and Spinal Nerves • Cranial Nerves: 12 pairs (right and left) originating from brainstem (10) and cerebrum (2) • Afferent and/or Efferent: • Somatic • Parasympathetic • Names/Roman Numeral designations (Vagus: X)

  19. Interesting Cranial Nerves • Trigeminal (V): Both sensory and motor • Senses: facial skin, teeth and dentists love to dismantle this nerve! • Motor: Well, you know how fun it is to leave the dentist with this one deadened!

  20. Another interesting one… • Vagus (X): Sensory to airways, viscera; Motor to the smooth muscle of the airways, and PSNS to the heart/lung/gut etc. • Vagus From “vagabond” to wonder • Vagal Tone: seen in well trained athletes with very low heart rates

  21. Spinal Nerves: • 31 pairs exit intervertebral foramen • After exit: Join to become “Plexus” • Afferent and Efferent: • Somatic and Autonomic

  22. Interesting Spinal Nerves: • Phrenic Nerve: Originating from the cervical plexus, innervates the diaphragm muscle (BREATHING • The “wind knocked out of me”… • Hiccups after heart surgery • Predict question: page223?

  23. Radial and Ulnar Nerves • Radial: “Crutch paralysis” • Ulnar: Ever hit your “Funny Bone”? It’s not a bone at all – but the ulnar nerve!

  24. Peripheral Nervous System: • Definition: Neurons and processes found outside the central nervous system – Includes: • All Sensory Neurons (Afferent) • Axons from motor neurons (somatic efferent) • Autonomic Motor neurons: preganlionic axons and all postganlions

  25. Begin Reviewing Nervous System: • Summary (Page 228-230) • Check your understanding by reviewing the topics covered up to Peripheral Nervous System • Be able to answer Content Review Questions: (1-10, 12-17, 20-24)

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