lecture 9

• Neurotransmitters


  Chemicals that transmit signals between neurons

  
• Types of neurotransmitters


  • Acetylcholine
  • Histamine
  • Glutamate
  • GABA
  • Serotonin
  • Dopamine
  • Norepinephrine

  
• Synapse firing


  1. Signal being sent from presynaptic neuron attaches to neurotransmitter

  2. Neurotransmitter helps signal jump synaptic cleft

  3. Neurotransmitter attaches to receptor on postsynaptic neuron

  4. Cellular response carried out

  
• Role of calcium channels


  Depolarizing wave in presynaptic neuron reaches calcium ion channels, causing calcium to enter and release neurotransmitters, allowing depolarization to start in postsynaptic neuron
• Amino acids


  Building blocks (monomers) of proteins, bond together to form proteins, neurotransmitters are proteins
• Structure of amino acids

  • Amine group (NH3)
  • Carboxylic acid (COOH)
  • R-group
• Essential amino acids


  • 20 amino acids, 9 essential
• Amino acids required for key neurotransmitters

  • Histidine -> Histamine
  • Glutamate -> GABA
  • Tryptophan -> Serotonin
  • Tyrosine -> Dopamine -> Norepinephrine
  • Acetylcholine not directly from amino acid

  
• Excitatory neurotransmitters


  Encourage target cell to take action, located in basal ganglia, key role in peripheral nervous system (muscle contractions, hormone release, heartbeat, brain function, memory)

  
• Acetylcholine


  Too low causes memory/thinking issues, Alzheimer's, Huntington's; too high causes seizures, spasms, Parkinson's; obtained from choline in diet
• Histamine


  Made from histidine, excitatory, located in hypothalamus, high concentration in lungs, skin, blood vessels, GI tract, role in sleep, food, inflammation, allergic reactions, gastric acid

  
• GABA (gamma-aminobutyric acid)


  Made from glutamate, inhibitory, stops neurons from becoming overexcited, synthesized in nucleus accumbens, helps reduce fear, anxiety, stress
• GABA levels


  Too low causes anxiety, Huntington's disease; too high causes Parkinson's disease
• Serotonin


  Made from tryptophan, inhibitory, synthesized in pons, regulates mood, body temperature, sleep, appetite, blood clotting, circadian rhythm

  
• Serotonin levels


  Too low linked to anxiety, mood disorders, seasonal affective disorder; antidepressants increase serotonin levels

  
• Dopamine


  Made from tyrosine, excitatory/inhibitory/modulatory, synthesized in midbrain, "pleasure/reward" neurotransmitter, involved in memory, learning, behaviour, movement coordination, muscle movement, pleasure/addiction

  
• Dopamine levels


  Too high linked to schizophrenia; too low linked to depression, Parkinson's disease
• Norepinephrine


  Formulated from dopamine, precursor to epinephrine (adrenaline), excitatory, released from adrenal glands, involved in alertness, arousal, reaction time, mood, concentration

  
• Norepinephrine levels


  Too high seen in anxiety; too low implications in ADHD, depression, hypotension