How drugs affect us

• Central nervous system


  Spinal chord & brain

  
• Ximena Nelson: 'THE BRAIN is wider than the sky,

  For, put them side by side,

  The one the other will include

  With ease, and you beside.'
• Spinal chord


  • Emanates from hole at base of the skull
  • Enclosed within vertebral column
  • Paired nerves
  • White matter: contains ascending & descending tracts (bundles of nerve fibres, the 'nerves' of the CNS)
  • Grey matter: dorsal (toward the back) & ventral 'horns'
  • Dorsal horn has cell bodies of interneurons on which afferent neurons end
  • Ventral horn has cell bodies of efferent motor neurons to skeletal muscle

  
• Spinal nerves


  1. Connect to the spinal chord via dorsal & ventral roots

  2. Afferent fibres (incoming signals) are in the dorsal root

  3. Efferent fibres in the ventral root

  4. The roots join to form the spinal nerve

  
• Cranial and spinal nerves

  Constitute the basis of the PNS

  
• Spinal chord


  • Transmits information to & from the brain
  • Integrates afferent and efferent input to produce responses without involving the brain: spinal reflexes
• The brain is wider than the sky
• Regions of vertebrate brain


  • Brain stem
  • Cerebellum
  • Forebrain

  
• Brain stem


  • Coordinates balance & subconscious movement
• Cerebellum


  • Continuous with spinal chord: controls breathing & circulation
• Forebrain


  • Sophisticated neural functions (language, awareness)
  • Homeostasis

  
• Functional areas of cerebral cortex

  • Initial visual processing
  • Sound processing
  • Voluntary motor action
  • Speech
  • Higher mental functions
  • Receiving & processing sensory input (position, cold, pain): 'somatosensory' (body feelings)

  
• Cerebrum


  • Composed of basal nuclei & convoluted cerebral cortex
  • Divided into left & right hemispheres
  • Connected via corpus callosum (300 million axons between hemispheres)
  • Functional areas do not work in isolation! CNS is about integration

  
• Explicit (declarative) memory


  Needs conscious thought, but can be long-term
• Implicit memory


  Skills, habits, & conditioning are stored in older parts of the brain

  
• Memory storage


  Explicit memory for people, objects, places, tacks, and events is stored in the prefrontal cortex, is then converted to long-term memories in the hippocampus & finally stored in the cortical areas [that process] the senses

  
• The test is hard because the part of the brain that handles language has conflicting tasks: verbalising the colour of the written words while ignoring the meaning of words representing colours
• P/Ice/crystal meth


  A derivative of amphetamine
• Methamphetamine


  Chemical name
• Effects of meth on the brain


  • Short term: changes in brain chemistry, behaviour
  • Long term: changes in brain structure, behaviour
• Brain areas affected by meth & E


  • Thought
  • Mood
  • Emotional memory
  • Aggression
  • Appetite
  • Thirst
• Synapses


  Neurotransmitter pathways in the brain

  
• Synapses


  • Voluntary motor action
  • Vocalisation
  • Higher mental functions
• Transporters


  The role of transporters
• Transporters are affected by ecstasy and meth
• NET: noradrenaline/norepininephrine (re-uptake) transporter; DAT: dopamine transporter; SERT: serotonin transporter
• Acute effects of Meth, E


  • Elevated mood during, depression-like feelings, anxiety, irritability after
• Serotonin in monkey neocortex

  Reduced 2 weeks and 7 years after meth administration
• Long-term effects of meth


  • Changes in brain structure and behaviour
  • Serotonin reduction
  • Serotonin metabolite reduced
  • Serotonin transporter reduction
  • Terminals degenerate
• Meth causes neuronal degeneration
• Opioid-induced respiratory depression (OIRD)


  Due to many effects on the PNS & CNS
• Effects of opioids on breathing


  • Respiratory rate depression
  • Abnormal respiratory pattern
• Antagonism eliminates rate depression by fentanyl, but the abnormal pattern characteristic of opioids persists
• Respiratory rate following saline & morphine is reduced in control mice vs. mice following opioid receptor blocked neurons
• Emily Dickinson: 'THE BRAIN is wider than the sky,

  For, put them side by side,

  The one the other will include

  With ease, and you beside.'
• Reality is a construct of the brain
• The diagonal lines are parallel
• The radiating lines influence our perception of the parallel lines
• The vertical zigzag patterns disrupt our horizontal perception
• The squares appear distorted by the background patterns