Neurotransmitters Flashcards
What are the features of synaptic transmission
Plasticity Rapid timescale Adaptability Diversity Learning and memory
What occurs at the dendrites and axons in relationship to communication
Dendrites - information reception
Axon - transfer of AP and communication between cells via neurotransmitter release
What occurs in the soma in relation to communication
Integration
How long does it take for an impulse to travel to the next neuron
2ms
What are the specialised structures of neurotransmission
presynaptic nerve ending/terminal GAP that has high resistance to electrical charge Postsynaptic region (dendrite or cell soma)
What is the size of GAP
20-100nm
What are the 3 stages of synaptic transmission
- Biosynthesis, packaging and release
- Receptor action
- Inactivation
What is the most important amino acid for neurotransmitters
Glutamic acid found in GABA
Describe the activation of a CNS synapse
- Membrane depolarises
- Calcium channels open
- Calcium influx into the cell
- Vesicles fuse with the membrane
- Exocytosis of neurotransmitter
How fast is synaptic transmission
200 microseconds
what is the intracellular increase in calcium
200 micromolars
How many molecules per synaptic vesicle
4000-10,000
What does the release of transmitter require
Docked transmitter containing vesicles on the presynaptic membrane
Protein complex formation between vesicle, membrane and cytoplasmic proteins to enable both vesicle docking and a rapid response to calcium entry
ATP and vesicle recycling
What contributes to rapid release
Synaptic vesicles are filled with the neurotransmitter and are docked in the synaptic zone “primed”
Calcium entry activated a calcium sensor in the protein complex
Interaction between synaptic vesicle and synaptic membrane proteins
Give 3 examples neurotoxins that target vesicular proteins
tetanus toxin causes paralysis
Botulinum toxin toxin causes flaccid paralysis
Alpha latroxin from the black widow spider stimulates transmitter release to depletion
Describe the ion channel receptor
Fast - micro-milliseconds (ms)
Mediates all fast an excitatory and inhibitory transmission
CNS: glutamate,GABA
NMJ: Ach
Describe the G-protein coupled receptor
Slow - s/min
Effectors may be enzymes (Adenyl cyclase) or channels (e.g. Ca2+ or K+)
CNS/PNS: ACh, dopamine etc.
Give examples of the ion channel receptor
Nicotinic cholinergic receptors (nAChR)
Glutamate (GLUR)
GABA (GABAR)
Glycine (GlyR) receptor
Describe an excitatory ion channel receptor
Glutamate
causes an influx of sodium to increase membrane potential
Describe an inhibitory ion channel receptor
GABA
hyper polarises the membrane to produce a negative potential to inhibit action potentials
What are the 2 types of glutamate receptor
AMPA and NMDA
Which type of glutamate receptor is the majority of fast excitatory synapses
AMPA
Which type of glutamate receptor is the majority of slow excitatory synapses
NMDA
How does calcium modify AMPA receptors
Calcium modifies the AMPA receptors potentiating the AMPA receptor response and activates protein synthesis which modifies synapse formation
