HLTH1004 Week 6(CNS)

• Central Nervous System (CNS)

  Comprised of the brain and the spinal cord
• Central Nervous System (CNS)

  • Functionally divided into the autonomic and somatic nervous system
• Brain


  Main function is to synthesise and respond to information from the body in order to maintain homeostasis
• Some functions are lateralised to one side of the brain, including some parts of language</b>
• Neurons


  The communicating elements of the CNS
• Sensory data


  Information about the conditions inside +/or outside the body
• Motor commands


  Control or adjust the peripheral organs (e.g. Skeletal muscles)
• Brain


  Controls the intelligence, memory, learning and emotion for each individual
• Structures of the Central Nervous System (CNS)

  • Brain and spinal cord
  • Neural tissue (neurons and glial cells)
  • Blood vessels
  • Connective tissues that protect and support
  • Skull
  • Meninges
  • Blood brain barrier
• Meninges


  Protective layers surrounding the brain
• Blood brain barrier


  Barrier that is selective, but not absolute, allowing certain nutrients to move by facilitated diffusion while denying metabolic wastes, proteins, toxins, most drugs, small nonessential amino acids, and K+
• Blood brain barrier is absent in some areas, such as vomiting center and hypothalamus, to monitor chemical composition and temperature of blood
• Regions of the adult brain

  • Cerebral hemispheres
  • Diencephalon
  • Cerebellum
  • Brain stem (midbrain, pons, medulla oblongata)

  
• Ventricles


  Fluid-filled chambers continuous to one another and to central canal of spinal cord, filled with cerebrospinal fluid (CSF) and lined by ependymal cells
• Ventricles of the brain

  • Lateral ventricles
  • Third ventricle
  • Fourth ventricle
• Lateral ventricles are paired, large C-shaped chambers located deep in each hemisphere, separated from one another by a membranous septum and connected to the third ventricle via interventricular foramen
• Third ventricle lies in diencephalon and is connected to the fourth ventricle via cerebral aqueduct
• Fourth ventricle lies in hindbrain and is continuous with central canal of spinal cord, with three openings connecting it to subarachnoid space surrounding brain
• Cerebral hemispheres


  Form superior part of brain, account for 83% of brain mass, divided into five lobes by sulci, gyri, and fissures
• Grey matter


  Neuron cell bodies and short non-myelinated neurons
• White matter


  Mostly myelinated axons (with some non-myelinated axons)
• Homunculus


  How the body is represented in the brain

  
• 90% of humans have left-sided cerebral dominance, usually resulting in right-handedness
• Cerebral cortex


  Thin (2–4 mm) superficial layer of grey matter, site of conscious mind including awareness, sensory perception, voluntary motor initiation, communication, memory storage, and understanding
• Traumatic brain injury (TBI)


  Form of brain injury caused by sudden damage to the brain, including open head injuries from penetrating objects and closed head injuries from blows to the head
• Cerebrovascular accidents (CVAs)


  Also referred to as "strokes", caused by ischemia (tissue deprived of blood supply) leading to death of brain tissue, which can result in hemiplegia (paralysis on one side) or sensory and speech deficits
• Spinal cord


  Consists of the cervical, thoracic, lumbar and sacral segments, with 31 pairs of spinal nerves originating from dorsal root ganglia
• Gray matter of spinal cord


  Contains neuron cell bodies and short nonmyelinated neurons
• White matter of spinal cord

  Contains mostly myelinated axons (with some nonmyelinated axons) allowing communication between parts of spinal cord and between spinal cord and brain
• Ascending pathways


  Pathways conducting sensory information upward through a chain of three neurons: first-order sensory, second-order interneuron, and third-order neuron extending to somatosensory cortex
• Main ascending sensory pathways

  • Dorsal column-medial lemniscal pathways (touch, vibration)
  • Spinothalamic pathways (pain, temperature, coarse touch, pressure)
  • Spinocerebellar tracts (muscle tendon or stretch)
• Descending pathways


  Deliver efferent impulses from brain to spinal cord, including direct pyramidal pathways and indirect multineuronal pathways regulating axial muscles, coarse limb movements, and head/neck/eye movements
• Major descending pathways


  • Pyramidal (lateral and ventral corticospinal) pathways
  • Reticulospinal and vestibulospinal tracts
  • Rubrospinal tracts
  • Tectospinal tracts