Nervous System: Spinal Cord and Nerves

  1. Spinal Cord
    • Information highway between brain and body.
    • Extends through vertebral canal from foramen magnum to L1
    • Each pair of spinal nerves receives sensory information and issues motor signals to muscles and glands
    • Spinal cord is part of the central nervous system, while nerves are part of the peripheral nervous system
  2. Functions of the Spinal Cord
    • Conduction: Pass information between brain and nerves
    • Locomotion: Repetitive, coordinated actions of muscle groups
    • Reflexes: Involuntary responses to stimuli
  3. Anatomy of the Spinal Cord
    • 31 pairs of spinal nerves among the cervical, thoracic, lumbar, and sacral regions
    • Cervical and lumbar enlargements
    • Medullary cone tapers at the end
    • Cauda Equina: (Horse's Tail) L2-S5 nerves
  4. Meninges
    Fibrous Layers covering spinal cord like the Dura Mater, Arachnoid Mater, and Pia Mater
  5. Dura Mater
    Tough membrane made of collagen
  6. Arachnoid Mater
    Squamous epithelial cells create loose mesh of fibers filled with cerebral spino fluid
  7. Pia Mater
    Delicate membrane
  8. Spina Bifida
    • Failure of vertebral arch to close covering of spinal cord
    • Often causes paralysis below affected area
    • Folic acid as part of a healthy diet (before conception) drastically decreases risk
  9. Gray Matter
    Neuron cell bodies
  10. White Matter
    Myelinated axons
  11. Cuneate Fasciculus
    • or Dorsal Column-medial Lemniscus Pathway
    • Carries touch, movement, and limb position information up the spinal cord to the brain
  12. Decussation
    Crossing over to other side of brain
  13. Spinothalamic Tract
    Carries pain and temperature information up spinal cord to the brain
  14. Corticospinal Tract
    Carries planned movement information to motor neurons in spinal cord
  15. Nerves
    • Bundles of axons
    • Epineurium covers nerves, perineurium surrounds a bundle of nerves (fascicle), endoneurium surrounds individual axons
    • Blood vessels penetrate perineurium
  16. Ganglia in Peripheral Nervous System
    • Cluster of neuron cell bodies in PNS
    • Dorsal root ganglion is cluster of sensory neuron cell bodies
  17. Spinal Nerves
    • 31 Pairs
    • Mixed with sensory and motor neurons
  18. Spinal Nerves Connection with Spinal Cord
    • Dorsal root is sensory input
    • Ventral root is motor output
  19. Dorsal Root
    Sensory neuron entry into spinal cord
  20. Ventral Root
    Motor neuron exit from spinal cord
  21. Dorsal Ramus
    Muscles and joints on dorsal surface
  22. Ventral Ramus
    Muscles and joints of trunk and limbs
  23. Nerve Plexi
    • Ventral rami branch and come together to form 5 nerve plexi
    • Cervical in the neck: C1-C5 (neck and diaphragm)
    • Brachial in armpit: C5-T1 (arm and some of shoulder and neck)
    • Lumbar in lower back: L1-L4 (abdominal wall, anterior thigh, and genitalia)
    • Sacral in pelvis: L4-S4 (lower trunk and legs)
    • Coccygeal: S4-S5
  24. Cervical Plexus
    • Sensory: ear, chin, neck, shoulder, anterior chest
    • Motor: diaphragm
  25. Lumbar Plexus
    Sensory and motor for lower abdomen, anterior thigh
  26. Sacral and Coccygeal Plexi
    Sensory and motor for remainder of leg (posterior thigh, distal portion), foot, genitals, and gluteal region
  27. Sciatica
    Sciatic nerve gets pinched and pain from sciatica radiates from the buttock down the leg and can travel as far as the feet and toes
  28. Poliomyelitis
    • Virus that can enter CNS and destroy motor neurons
    • Muscle weakness and paralysis
  29. Amyotropic Lateral Sclerosis
    Degeneration of motor neurons, which leads to muscle weakness and paralysis
  30. Dermatome/Myotome
    • Each nerve sends and receives information to and from a band of the body
    • There's lots of overlap between adjacent nerves
    • Total loss of sensation requires 3 adjacent nerves to be damaged
  31. Shingles (Herpes Zoster)
    • Chicken pox virus remains dormant in dorsal root ganglia for life
    • Can become active in one dorsal root ganglion in older adults
    • Only parts of the body receiving input from that nerve are affected
  32. Reflexes
    • Require sensory input
    • Occur very quickly
    • Involuntary
    • Stereotyped
  33. Sensory Part of Reflex: Muscle Spindle
    • Muscle spindle sensory fibers fire action potentials when muscle is stretched
    • This causes motor neurons to induce muscle contraction
  34. Flexor and Crossed-Extension Reflex
    • Pain receptor stimulation can induce flexor reflex
    • Allows withdrawal from painful stimulus
    • Crossed-extension reflex does opposite in other leg
    • Prevents falling on face
  35. Golgi Tendon Organ Reflexes
    • GTO sensory fibers fire action potentials when muscle contracts
    • This stops motor neuron from firing so that muscle won't contract further
  36. What does the Sympathetic Nervous System Increase?
    Alertness, heart rate, blood pressure, pulmonary air flow, blood glucose, blood from to muscles
  37. What does the Sympathetic Nervous System Decrease?
    Blood flow to skin and digestive tract, reproductive processes, and immune system funtions
  38. Parasympathetic Nervous System
    • Complementary of sympathetic NS
    • Digestion and reproductive processes occur
    • Heart rate, blood pressure etc. decreases
Card Set
Nervous System: Spinal Cord and Nerves
Nervous System