Overview of the Nervous System

Oct 17, 2024

Nervous System Review - Part Two

Central Nervous System (CNS)

  • Brain: Cannot expand; pressure/bleeding can cause displacement, leading to problems.
  • Spinal Cord:
    • Length: 17-18 inches, from the first cervical to the second lumbar vertebrae.
    • Functions: Transmits sensory info to the brain and motor info from the brain; produces reflexes via 31 spinal nerves.
    • Injury: Sensitive to injury, often leading to severe and permanent damage.
    • Structure: Includes cervical, thoracic, lumbar, and sacral vertebrae.

Peripheral Nervous System (PNS)

  • Function: Carries information to/from the CNS.
  • Divisions:
    • Sensory Division: Somatic and visceral sensory.
    • Motor Division: Somatic and autonomic systems.
      • Autonomic System: Sympathetic (fight or flight) and parasympathetic (rest and digest).

Spinal Nerves

  • 31 pairs named after vertebrae (C2, C3, etc.).
    • Cervical: 8 pairs
    • Thoracic: 12 pairs
    • Lumbar: 5 pairs
    • Sacral: 5 pairs
    • Coccygeal: 1 pair
  • Each spinal nerve has specific body functions.

Cranial Nerves

  • 12 pairs carrying impulses to/from the brain.
    • Cranial Nerve 1 (Olfactory): Smell
    • Cranial Nerve 2 (Optic): Vision
    • Cranial Nerve 3 (Oculomotor): Pupil constriction
    • Cranial Nerve 4 (Trochlear): Down/medial eye movement
    • Cranial Nerve 5 (Trigeminal): Facial sensation, chewing
    • Cranial Nerve 6 (Abducens): Lateral eye movement
    • Cranial Nerve 7 (Facial): Taste, facial movements
    • Cranial Nerve 8 (Acoustic/Vestibulocochlear): Hearing, balance
    • Cranial Nerve 9 (Glossopharyngeal): Taste, throat movement
    • Cranial Nerve 10 (Vagus): Throat/organs function
    • Cranial Nerve 11 (Spinal Accessory): Shoulder/neck muscles
    • Cranial Nerve 12 (Hypoglossal): Tongue movement
  • Mnemonic to remember: "On old Olympus’s towering top a fin in German Witzelhop."

Autonomic Nervous System

  • Function: Maintains homeostasis.
  • Sympathetic: Activates fight or flight response (increases heart rate, blood pressure, etc.).
  • Parasympathetic: Restores after crisis (decreases heart rate, increases GI motility, etc.).

Effects of Aging on the Nervous System

  • Brain: Loss of weight and neurons, decreased blood flow and oxygen use.
  • Memory: Short-term memory affected more than long-term.
  • Learning: Slower speed but still possible.
  • Hypothalamus: Decreased ability to maintain body temperature.
  • Neuromuscular: Tremors, decreased fine motor coordination, reflexes, and reaction time.
  • Sensory: Decreased sense of touch, vision, hearing, and balance.

Prevention of Neurological Conditions

  • Lifestyle Changes:
    • Control hypertension/cholesterol through diet and exercise.
    • Avoid smoking and obesity.
  • Trauma Prevention:
    • Avoid alcohol/drugs, use seat belts, helmets, safe swimming practices.
    • Safe use of firearms, wear protective equipment.
  • Health Practices:
    • Treat ear/sinus infections promptly to prevent spread to the brain.
    • Practice safe sex to prevent STDs that can cause neurological changes (e.g., syphilis, HIV).
    • Address drug abuse, particularly IV drug use.