Neurotransmitters Flashcards
(34 cards)
What is a neurotransmitter?
A chemical that is used to transmit information from the presynaptic neuron to the postsynaptic neuron
What is the criteria for neutrality
- Chemical synthesised presynpatically
- Electrical stimulation leads to the release of the chemical
- Chemical produces physiological effect - switches on neuron or not
- Terminate activity
What is dales law?
If a particular neurotransmitter is released by one of a neurons synaptic endings, the same chemical is releases at all synaptic ending of that neuron - but the dendritic field can receive signals from multiple transmitters
Where are the neurotranmitters kept?
In a vesicle, there is a set amount of neurotransmitter, which is docked at the synaptic membrane
What does depolarisation of the presynaptic neuron lead to?
The opening of calcium channels
What do vesicles fuse with?
The synaptic membrane and releases the NT - vesicles detach from the docking zone
How are neurotransmitters released?
Depolarisation - leads to opening of calcium channels
Vesicles fuse with the synaptic membrane, releasing neurotransmitter. this detaches from the docking zone
Where do neurotransmitter bind?
To the receptors on the post-synaptic membrane, which affects the activity of the post synaptic cell
What are thy types of receptors?
Ionotropic receptor
Metabotropic receptor
What is an ionotropic receptor?
Looks like a donut, composed of subunits, different parts making them up
Fast transmission - ion movement leads to an immediate change in the postsynaptic cell
What is a metabotropic receptor?
Activates an internal second messenger system that goes on to affect the functioning of the post-synaptic cells
Steps of a metabotropic receptor
- Neurotransmitter binds to receptor and activates the G-protein
- G protein splits and activates other enzymes
- The breakdown of GTP turns of G protein activity
- Series of chemical reaction leads to amplification of signal - second messenger system
What are the types of fast transmission?
Excitatory - ion channel opens, movement of positive ions into the neuron, causing depolarisation. Excitatory post synaptic potential
Inhibitory - ion channel opens, movement of negative ions into the neuron, hyper polarisation, inhibitory post synaptic potential
What does amplification refer too?
With metabotropic receptors, you activate one receptor to start with, which causes a chain in events - activating G protein, stimulating adenylyl cyclase to convert ATP to cAMP - cAMP activates protein kinase A
The proteins are slow, take more time and steps but the effects are bigger
What does neurotransmitter deactivation mean?
The neurotransmitter needs to be deactivated after use to remove them from the synaptic cleft - something has to stop it from not having too much signalling
What is a deactivating enzyme?
It is on the post synaptic neuron, breaks down neurotransmitter, degrades them so not very useful
What are the classes of neurotransmitters?
Amino acids - glutamate, gaba Monoamines - dopamine etc Soluble gases Acetlycholine Neuropeptide - pain modulating- endorphins
Where do you get amino acids from?
Your diet
What is glutamate?
The major fast excitatory neurotransmitter in the CNS
Very widespread
All neurons have glutamate, otherwise they aren’t turned on
Activates different types of receptors: mGluR, NMDA, AMPA, Kainate
What happens with glutamate in normal neuronal transmission?
Presynaptic release of glutamate - postsynaptic activation of AMPA receptors - influx of Na - depolarisation - EPSP
What is glutamate involved in?
Learning and memory
How are EPSP’s boosted?
Spatial summation - if you get 3 excitatory inputs at once on the axon, get a bigger depolarisation
Temperal summation - if the signals come in at different times through one axon in summation, enhancement in depolarisation
What is neural integration?
The way that EPSP’s are boosted
What is GABA?
Gamma aminobutyric acid
Major inhibitory neurotransmitter
Activates an ionotropic receptor (GabaA) which opens a chloride channel, leading to hyper polarisation IPSP
