2. Spinal Cord and Spinal Nerves

3. Spinal Cord and Spinal Nerves
Chapter 13
Spinal Cord and Spinal Nerves

4. Spinal Cord Extends from foramen magnum to second lumbar vertebra
Segmented
Cervical
Thoracic
Lumbar
Sacral
Gives rise to 31 pairs of spinal nerves
Not uniform in diameter throughout length

5. Meninges Connective tissue membranes surrounding spinal cord and brain
Dura mater
Arachnoid mater
Pia mater
Spaces
Epidural: Anesthesia injected
Subdural: Serous fluid
Subarachnoid: CSF

6. Cross Section of Spinal Cord

7. Cross Section of Spinal Cord
Gray matter
Neuron cell cell bodies, dendrites, axons
Horns
Posterior (dorsal)
Anterior (ventral)
Lateral
Commissures
Gray: Central canal
White
White matter
Myelinated axons forming nerve tracts
Fissure and sulcus
Three columns or funiculi
Ventral
Dorsal
Lateral

8. Reflex Arc
Basic functional unit of nervous system and simplest portion capable of receiving stimulus and producing response
Components
Sensory receptor
Sensory neuron
Interneurons
Motor neuron
Effector organ

9. Stretch Reflex
Muscles contract in response to a stretching force applied to them

10. Golgi Tendon Reflex
Prevents contracting muscles from applying excessive tension to tendons

11. Withdrawal Reflex
Function is to remove a body limb or other part from a painful stimulus

12. Withdrawal Reflex with Reciprocal Innervation
Causes relaxation of extensors muscle when flexor muscles contract

13. Withdrawal Reflex with Crossed Extensor Reflex
When a withdrawal reflex is initiated in one lower limb, the crossed extensor reflex causes extension of opposite lower limb

14. Peripheral Nerves Consist of Axon bundles Schwann cells
Connective tissue
Endoneurium
Perineurium: Surrounds axon groups to form fascicles
Epineurium

15. Spinal Nerves

16. Dermatomal Map
Skin area supplied with sensory innervation by spinal nerves

17. Cervical Plexus C1-C4 Phrenic nerve
From C3-C5 cervical and brachial plexus
Innervate diaphragm

18. Brachial Plexus C5-T1 Major nerves Axillary Radial Musculocutaneous
Ulnar
Median

19. Axillary Nerve

20. Radial Nerve

21. Musculocutaneous Nerve

22. Ulnar Nerve

23. Median Nerve

24. Lumbosacral Plexus

25. Obturator Nerve

26. Femoral Nerve

27. Tibial Nerve

28. Fibular Nerve

29. PNS Disorders General disorders Infections
Anesthesia: Loss of sensation
Hyperesthesia: Increased sensitivity to pain, pressure, light
Paresthesia: Tingling, prickling, burning
Neuralgia: Nerve inflammation causing stabbing pain
Sciatica: Pain radiating down back of thigh and leg
Infections
Herpes: Skin lesions
Shingles or herpes zoster: Adult disease of chickenpox
Poliomyelitis: Infantile paralysis
Genetic and autoimmune disorders
Myasthenia gravis: Results in fatigue and muscular weakness due to inadequate ACh receptors