Neurotransmitters Flashcards
What are spines and what is their function?
- spines are found on dendrites of neurones
- they serve to increase the surface area to increase the amount of information coming into the neurone
Roughly how big are the synaptic gaps?
20-100nm
What are the 3 stages of synaptic transmission?
1) Biosynthesis, packaging and release of neurotransmitter
2) Receptor action
3) Inactivation
Name 3 animo acid transmitters.
- glutamate-the most important excitatory transmitter in the brain
- GABA-the most important inhibitory transmitter in the brain
- glycine- smallest AA, inhibitory transmitter, function mainly in the brain stem & spinal cord
Name 2 amine transmitters.
- noradrenaline (NA)- important part of the sympathetic, autonomic nervous system
- dopamine (DA)- important transmitter in the brain, involved in Parkinson’s disease
Name a neuropeptide.
-opioid peptides
Transmitter release requires an increase of what intracellularly?
-transmitter release requires increase in Ca concentration tip 200um
Tell me about synaptic vesicles.
- synaptic vesicles are filled with neurotransmitter and docked in the synaptic zone
- special proteins on the vesicle (and pre-synaptic membrane) enable fusion and exocytosis
Vesicular proteins are targets for what? Give examples.
- targets for neurotoxins
- Alpha latrotoxin (from black widow spider) stimulates transmitter (ACh) release to depletion - causes respiratory arrest
- Zn dependent endopeptidases inhibit transmitter release
e. g tetanus toxin causes paralysis
e. g Botulinum toxin produces by bacterium causes flaccid paralysis (most lethal toxin, 10^-12 grams would kill a mouse)-known as botox-paralyses skeletal muscles
Tell me about ion channel receptors and give examples of them at CNS & PNS
- fast response (msecs)
- mediate all fast excitatory and inhibitory transmission
- in CNS- glutamate, GABA
- in NMJ/PNS- ACh at nicotine receptors
Tell me about G-protein couples receptors and give examples of them at CNS & PNS
-slow response (sec/mins)
(-7 transmembrane segments)
-effectors may be enzymes (adenyl cyclase, phospholipase C) or channels (Ca or K)
-in CNS & PNS- ACh at muscarininc receptors, DA, NA, serotonin (5HT), neuropeptidases
What happens when GABA and glycine receptors are stimulated?
-influx of chlorine, leading to hyper polarisation
Tell me about the 2 types of glutamate receptors.
1) AMPA receptors
- majority of fast excitatory synapses
- rapid onset (open quickly), offset and desensitisation (if over stimulated)
- allow Na influx
2) NMDA receptors
- slow component of excitatory transmission
- serve as coincidence detectors (can’t activate on their own, need something else to depolarise the cell first) which underlie learning mechanisms
- allow Ca/Na influx
How is glutamate synthesised?
-glutamate is synthesised from glucose via TCA cycle & transamination
How is glutamate inactivated?
- uptake of glutamate into glial cells and enzymatically modified by glutamate synthetase to glutamine
- re-uptake of glutamate by exictatory amino acid transporters (EAATs) back into pre-synaptic neurone
