neurochemistry

• ionotropic receptors

  ionotropic - ligand gated

  • ion channels
  • in membranes
  • made up off subunits

  channel opens in response to binding of specific neurotransmitter

  Results in membrane:

  • Depolarisation = excitatory
  • Hyperpolarisation = inhibitory
  • Rapid response
• metabotropic receptors

  G protein coupled

  -   Single protein made up of 7 transmembrane domains – neurotransmitter binds to G protein causing it to open
• amino acid neurotransmitter

  (non essential)

  • glutamate
  • GABA
  • glycine
• amines (neurotransmitter)

  Monoamines:

  • Acetylcholine
  • Serotonin
  • Histamine Catecholamines:
  • Dopamine
  • Noradrenaline
  • Adrenaline
• purines (neurotransmitter)

  • adenosine
  • ATP
• neuropeptides (neurotransmitter)


  huge class
• amino acids

  make themselves

  
• Glutamate

  most common excitatory neurotransmitter in the brain cant cross the blood brain barrier

  synthesised in the presynaptic terminal

  can be taken back after being released

  • (glutamate-glutamine cycle) - involves astrocytes

  Can act on ionotropic and metabotropic
• GABA

  inhibitory neurotransmitter

  • made in presynaptic terminal
  • can be reused - taken up by GABA transporters
• GABA receptors

  GABAa - ligand-gated ion channel

  GABAb - protein coupled receptor

  GABAc - ligand gated ion channel

  GABAa and GABAc – ionotropic
• glycine

  inhibitory - main on in spinal cord

  only in ionotropic receptors

  • Glycine is a co-agonist with glutamate NMDA receptors
• Acetylcholine (ACh)

  primary neurotransmitter of PNS

  • primary NTM of neuromuscular junction
• ACh synthesis and uptake

  choline taken back up

  • reused to make ACh by binding with acetylCoA

  synthesis:

  • glucose
  • pyruvate
  • acetyl CoA
  • breaks down into acetyl and CoA
  • binds with choline to make acetylcholine
• ACh receptors

  Nicotinic - ionotropic

  • agonist = nicotine
  • antagonist = bungarotoxin

  Muscarinic receptors

  • agonist = muscarine
  • antagonist = atropine
• Serotonin

  cell bodies of neurones in raphe nucleus of brain stem

  • axons project to early every part of brain and spinal cord
  • multiple function e.e mood and sleep
• Histamine

  cell bodies of neurones in tuberomammillary nucleus of the posterior hypothalamus

  axons on all parts of brain

  promotes wakefulness
• Dopamine

  4 main dopamine pathways in the brain

  • mesolimbic pathway - major reward pathway
  • mesocortical pathway - executive functions
  • nigrostriatal pathway - movement
  • tuberoinfundibular pathway - prolactin secretion from pituitary gland
• Noradrenaline

  cell bodies of neurones in locus coeruleus of brain stem

  • axons project to nearly every part of brain and spinal cord
  • alertness, arousal, attention
  • Synthesised in neurones
  • Noradrenaline uptake into presynaptic terminal = NET
  • Metabotropic receptors = α and β
  • β blockers = heart conditions
  • β agonists e.g. salbutamol = asthma
• adrenaline


  Sympathetic nervous system triggers its release from adrenal glands

  Fight or flight response

  Synthesised in neurones only in medulla oblongata of the brain stem

  Adrenaline uptake into presynaptic terminal

  Binds to noradrenaline metabotropic receptors = α and β
• purines

  autonomic - excitatory cotransmitter

  • Cotransmitter with various other neurotransmitters in the brain e.g. glutamate, dopamine, serotonin