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Spinal Cord

Spinal Cord. & Nerves. Ch 13. The Spinal Cord. cranial nerves- 12 pr. spinal nerves- 31 pr. Peripheral Nervous System. white matter. grey matter. dorsal root. pia mater. arachnoid. ventral root. spinal nerves. dura mater. The Spinal Cord. vertebra. spinal cord. spinal nerve.

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Spinal Cord

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  1. Spinal Cord & Nerves Ch 13

  2. The Spinal Cord

  3. cranial nerves- 12 pr spinal nerves- 31 pr Peripheral Nervous System

  4. white matter grey matter dorsal root pia mater arachnoid ventral root spinal nerves dura mater The Spinal Cord

  5. vertebra spinal cord spinal nerve The Spinal Cord

  6. sensory pathway motor pathway Nerve Pathways into the Spinal Cord

  7. synapses Neuron-To-Neuron Transmission

  8. Spinal Nerves

  9. Spinal Cord

  10. Spinal Nerves

  11. Spinal Nerves

  12. Cervical Plexus • Formed by ventral rami of C1–C4 • Innervates skin and muscles of the neck, ear, back of head, and shoulders • Phrenic nerve • Major motor and sensory nerve of the diaphragm (receives fibers from C3–C5)

  13. Cervical Plexus

  14. Brachial Plexus • Formed by ventral rami of C5–C8 and T1 (and often C4 and T2) • It gives rise to the nerves that innervate the upper limb • Major branches of this plexus: • Roots—five ventral rami (C5–T1) • Trunks—upper, middle, and lower • Divisions—anterior and posterior • Cords—lateral, medial, and posterior

  15. Brachial Plexus Roots (ventral rami): C4 Dorsal scapular C5 Nerve to subclavius C6 Suprascapular Upper Posterior divisions C7 Trunks Middle C8 Lateral Lower Cords T1 Posterior Long thoracic Medial pectoral Medial Lateral pectoral Axillary Upper subscapular Musculo- cutaneous Lower subscapular Thoracodorsal Radial Medial cutaneous nerves of the arm and forearm Median Ulnar (a) Roots (rami C5 – T1), trunks, divisions, and cords Posterior divisions Roots Anterior divisions Trunks Figure 13.9 (a)

  16. Brachial Plexus: Nerves • Axillary—innervates the deltoid, teres minor, and skin and joint capsule of the shoulder • Musculocutaneous—innervates the biceps brachii and brachialis and skin of lateral forearm • Median—innervates the skin, most flexors and pronators in the forearm, and some intrinsic muscles of the hand • Ulnar—supplies the flexor carpi ulnaris, part of the flexor digitorum profundus, most intrinsic muscles of the hand, and skin of medial aspect of hand • Radial—innervates essentially all extensor muscles, supinators, and posterior skin of limb

  17. Axillary nerve Anterior divisions Posterior divisions Trunks Roots Humerus Radial nerve Musculocutaneous nerve Ulna Radius Ulnar nerve Median nerve Radial nerve (superficial branch) Dorsal branch of ulnar nerve Superficial branch of ulnar nerve Digital branch of ulnar nerve Muscular branch Median nerve Digital branch (c) The major nerves of the upper limb Figure 13.9 (c)

  18. Thoracic Nerves • T3-T12 • 11 intercostal nerve • 1 subcostal nerve

  19. Lumbar Plexus • Arises from L1–L4 • Innervates the thigh, abdominal wall, and psoas muscle • Femoral nerve—innervates quadriceps and skin of anterior thigh and medial surface of leg • Obturator nerve—passes through obturator foramen to innervate adductor muscles

  20. Lumbar Plexus

  21. Sacral Plexus • Arises from L4–S4 • Serves the buttock, lower limb, pelvic structures, and perineum • Sciatic nerve • Longest and thickest nerve of the body • Innervates the hamstring muscles, adductor magnus, and most muscles in the leg and foot • Composed of two nerves: tibial and common fibular

  22. Sacral Plexus

  23. Functional Divisions of the Peripheral Nervous System Afferent Division • Sensory (advances) neuron – goes toward CNS Efferent Division • Motor (exits) neuron- leaves CNS • Somatic Nervous System • Autonomic Nervous System

  24. sensory neuron motor neuron stretch receptor interneuron motor neuron patellar ligament Spinal Reflex Arc

  25. 1 Quadriceps strongly contracts. Golgi tendon organs are activated. Interneurons Quadriceps (extensors) Spinal cord Golgi tendon organ Hamstrings (flexors) + Excitatory synapse – Inhibitory synapse Figure 13.18, step 1

  26. 2 1 Afferent fibers synapse with interneurons in the spinal cord. Quadriceps strongly contracts. Golgi tendon organs are activated. Interneurons Quadriceps (extensors) Spinal cord Golgi tendon organ Hamstrings (flexors) + Excitatory synapse – Inhibitory synapse Figure 13.18, step 2

  27. 2 1 Afferent fibers synapse with interneurons in the spinal cord. Quadriceps strongly contracts. Golgi tendon organs are activated. Interneurons Quadriceps (extensors) Spinal cord Golgi tendon organ Hamstrings (flexors) 3a Efferent impulses to muscle with stretched tendon are damped. Muscle relaxes, reducing tension. + Excitatory synapse – Inhibitory synapse Figure 13.18, step 3a

  28. 2 1 Afferent fibers synapse with interneurons in the spinal cord. Quadriceps strongly contracts. Golgi tendon organs are activated. Interneurons Quadriceps (extensors) Spinal cord Golgi tendon organ Hamstrings (flexors) 3b 3a Efferent impulses to antagonist muscle cause it to contract. Efferent impulses to muscle with stretched tendon are damped. Muscle relaxes, reducing tension. + Excitatory synapse – Inhibitory synapse Figure 13.18, step 3b

  29. Reflex Arc • Sensory receptor • Sensory neuron • Integration center • Motor neuron • Effector- part of body that responds to a motor nerve impulse

  30. INQUIRY • What is a reflex? • Damage of the spinal cord above C3 can result in_____? • In which portion of the spinal cord do the interneurons lie? • What kind of peripheral nerve fiber carries motor impulses outward to smooth muscles and glands of internal organs?

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