Sns

• Central nervous system (CNS)


  Brain and spinal cord
• Peripheral nervous system (PNS)

  Cranial and spinal nerves, have sensory (afferent) and motor (efferent) components, ganglia, sensory receptors, enteric plexuses

  
• Nervous system


  • Consists of the central nervous system (CNS) and the peripheral nervous system (PNS)

  
• Functions of the nervous system

  • Sensory function - senses changes in internal and external environment
  • Integrative function - analyse sensory information, store, make decisions
  • Motor function - respond to stimuli by initiating action
• Sensory (afferent) neurons


  Serve the sensory function of the nervous system
• Motor (efferent) neurons


  Serve the motor function of the nervous system
• Subdivisions of the PNS

  • Somatic nervous system (voluntary)
  • Autonomic nervous system (involuntary)
  • Enteric nervous system

  
• Spinal cord


  • Located within the vertebral column, protected by vertebrae, meninges, and cerebrospinal fluid
  • Divided into grey matter (cell bodies, association neurons, unmyelinated axons) and white matter (myelinated axons)

  
• Spinal cord input and output

  1. Sensory (dorsal) root conducts impulses into spinal cord

  2. Motor (ventral) root conducts impulses out to periphery
• Sensory fibre input to spinal cord

  • Terminate in specific sites according to fibre type, modality, and intensity
  • Synapse onto second order neurons that ascend to brain

  
• Spinal cord tracts


  • Bundles of axons with common origin or destination, carrying similar information
  • Sensory (ascending) tracts conduct impulses toward brain
  • Motor (descending) tracts conduct impulses down cord

  
• The human brain contains approximately 10,000,000,000,000 neurons and each could receive 200,000 synaptic events

  
• No 1:1 relationship between brain structure and function exists
• Principal parts of the brain

  • Brain stem
  • Diencephalon
  • Cerebrum
  • Cerebellum

  
• Brain stem


  • Most cranial nerves originate from it
  • Involved in basic needs like sleep, breathing, autonomic functions

  
• Cerebrum


  • Largest part of the brain
  • Cerebral cortex is grey matter
  • Cerebral white matter contains tracts connecting to other parts of nervous system
  • Two hemispheres connected by corpus callosum

  
• Cerebral lobes


  • Occipital
  • Parietal
  • Frontal
  • Temporal

  
• Cerebral functional areas


  • Sensory areas - reception and interpretation of sensory impulses
  • Motor areas - govern muscular movement
  • Association areas - complex integrative functions like memory, emotions, reasoning

  
• Phineas Gage, a US railroad worker in 1814, suffered personality changes after a brain injury