lecture 6: neurotransmitters Flashcards
what are the essential components before a neurotransmitter is released?
- the dendrites detect the input
- the information propagates down the dendrite and is integrated in the soma
- the action potential is generated in the axon hillock
how big is the synaptic cleft?
the synaptic cleft is 20 -100 nm wide
how long down it take for one action potential to get from one cell to the next?
- it takes 2 milliseconds
- what is the overall mechanism of a neurotransmitter
- the action potential propagates along the membrane
- the voltage gated calcium channels open
- the Ca2+ enters the nerve terminal and the exocytosis of the NT starts
- the neurotransmitter diffuses across the gap and interacts with the receptors
- the transmitter is removed by being broken down by enzymes at the post synaptic synapse
the sodium potassium pump restores the membrane potential
what are the three classes of neurotransmitter?
- amino acids
- amines
- neuropeptides
when does integration happen and what does it do?
integration is when the neurone receives multiple transmitter influences which are integrated to produce diverse functional responses
what is essential for the release of neurotransmitters?
calcium is vital
the increase in Ca2+ is needed
how does rapid release neurotransmitter occur?
- the NT are either diced at the synapse or they are floating in the terminal region
- interaction between presynaptic membrane and vesicle proteins allowing the vesicle to be docked stably
- there are alpha helical structures which interact together to form a super helix
- this has made a stable complex of the vesicle at the synapse which is full of neurotransmitter
- the vesicle then awaits Ca2+ signal
- when it comes the complex undergoes a conformational change which drives the release of the transmitter into the synaptic cleft
what naturally occurring toxins have an effect on the synaptic vesicle proteins?
- Tetanus - inhibits transmitter release
- Botulinum - flaccid paralysis
- Alpha Latrotoxin -depletes NT
what are the three main steps of transmitter release?
- docking (vesicles on pre synaptic membrane)
- protein complex formation (between vesicle membrane and cytoplasmic protein)
- ATP and vesicle recycling
what is the nature of ion channel receptors?
- the response is fast
what are neurotransmitters at ion channel receptors at the CNS?
- glutamate
- GABA
what are neurotransmitters at ion channel receptors at the neuromuscular junction?
- acetylcholine
what is the nature of G protein coupled receptors?
- slow
what are neurotransmitters at G protein coupled receptors at the CNA and PNS?
- acetylchpline
- dopamine
- noradrenaline
- 5 - hydroxytryptamine
- neuropeptides