The Nervous System

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  • The nervous system
    • The peripheral nervous system (PNS)
      • Somatic nervous system
        • Uses sensory nerve cells to convey sensation from skeletal or voluntary muscles, the skin and the sense organs.
        • Uses motor nerve cells to initiate skeletal muscle contraction voluntarily
      • Visceral nervous system
        • Conveys sensory information from visceral organs e.g. heart, lungs, kidneys
        • Autonomic nervous system used to initiate muscle contraction in this system
        • Information received as deeper sensations e.g. internal pain and bladder fullness
      • Autonomic nervous system
        • Parasympathetic nervous system
          • Maintains body function at rest, and restores body function after sympathetic nervous system activity
        • Sympathetic nervous system
          • Initiates activities associated with emergency and stress e.g. increased BP/ heart rate and increased blood sugar conc.
    • The central nervous system (CNS)
      • The spinal cord
        • Runs from the neck down to the base of the back
        • Is protected by the bones in the vertebral column
      • The brain
        • Where higher cognitive functions e.g. memory, thought and emotion, take place.
        • Takes up nearly all of the space in the skull
  • The major centre for nervous system control
  • Approx. 10^12 neurons in an adult human
  • CNS  is nourished and maintained by the circulation of cerebrospinal fluid- a clear watery fluid with similar constituents to blood (minus red blood cells)
  • Nerve cells lying outside the CNS
  • Essential in allowing the CNS and the periphery of the body to communicate.
  • Associated with involuntary actions
  • Associated with voluntary actions
  • Made up of motor nerves from the CNS that either excite (contract) or inhibit (relax) smooth muscle
  • Not under voluntary control. Associated with blood vessels, glands, bladder and the respiratory system.
  • Can excite or inhibit cardiac muscle
  • The two systems work complementar to each other
  • Most visceral organs are innervated by both limbs of the autonomic nervous system


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