Week 2- Part 2- Neurotransmitter types. Flashcards
What do many psychoactive drugs do?
How much steps go under what defines a NT?
Exert their effects by influencing specific neurotransmitter systems.
4 steps.
What defines a NT- step 1:
Where is it stored and synthesised?
What will you find inside presynaptic neurons?
What are NT synthesised from precursors?
What do enzymes do?
In the presynaptic neuron- released at synapses.
Enzymes and precursors required to synthesize the substance.
Molecules- things you might get from your diet.
Convert them into one molecule then another then eventually into the finished product.
What defines a NT- step 2:
Where is it present?
How is it released?
What kind of process is NT release?
In the presynaptic terminal.
In amounts sufficient to exert a defined action on the postsynaptic neuron or effector organ.
Calcium dependent.
Continuation from what defines a NT- step 2:
Explain how.
What is a vesicle fusion?
AP arrive at the synaptic buttons- depolarization caused by APs trigger the opening of voltage gated calcium channels- positively charged calcium channels rush into the presynaptic terminal - triggers vesicle fusion- release NTs molecules into the synapse.
Fusion of synaptic fusion with the cell membrane.
Continuation from what defines a NT- step 2:
How can you test this in a lab?
Stick calcium into a neuron and see if it releases the substance you think is a neurotransmitter.
What defines a NT- step 3:
How can it be administered?
What happens when it is administered like this?
Should this administration have an effect?
Exogenously in reasonable concentrations- to neurons.
It mimics the action of the endogenous transmitter (for example, it activates the same ion channels or second-messenger pathway in the postsynaptic cell).
Yes- like trigger APs.
Continuation from what defines a NT- step 3:
What is present in the postsynaptic cell?
How can this be shown through?
How is it exactly done?
Specific receptors for the substance are present.
Imaging techniques- High-resolution histological- show that specific receptors are present in the postsynaptic membrane.
By radioactively labelling NT molecules- see where they actually bind- to find where receptors are in the postsynaptic membrane.
Continuation from what defines a NT- step 3:
What can agonists do?
What can sometimes happen?
What can antagonists do?
What can be agonists or antagonists?
Agonists can enhance the effect of the neurotransmitter.
They mimic it therefore having the same effect.
Antagonists block the effects of the neurotransmitter- like getting into a receptor and stopping the NT getting in there and doing something.
Many psychoactive drugs- are agonists or antagonists- of specific NTs.
What defines a NT- step 4:
What exists?
What kind of enzymes are there?
What kind of pumps are there?
A specific mechanism for removing the substance from the synaptic cleft- when its job has been done.
Enzymes that degrade the substance.
Pumps that move the substance (or its metabolites) back into the presynaptic neuron (i.e. reuptake pumps).
Contrasting NTs and hormones- NTs:
Do NTs travel over long or short distances?
What do they bind to and over what distance?
What might happen?
NTs act over tiny distances- i.e. across the synapse.
Bind to postsynaptic receptors over short distance (20-40 nm) from the point of release.
May diffuse over slightly longer distances to neighbouring cells (e.g. 100s of nm).
Continuation from contrasting NTs and hormones- hormones:
What do hormones typically influence?
What are hormones released into?
How do they travel?
But what can happen?
Target cells far away from the hormone-secreting cell.
Bloodstream.
Considerable distances to target tissues (e.g. no more than a metre)- e.g. if something is travelling from a gland in your head to an organ lower down in your body, it has to travel a long distance.
A substance can act as a neurotransmitter in one region of the brain while serving as a hormone elsewhere.
What is one things NTs are split into?
What are these further split into?
Give examples of Small molecule NT.
Give examples of monoamines.
Give examples of amino acid NTs.
Small molecule NTs.
Monoamines (biogenic amines) + Amino acid NTs.
Acetycholine + ATP and its by products.
Two families- catecholamines + indoleamines.
Catecholamines- Dopamine, norepinephrine and epinephrine.
Indoleamines- Serotonin + melatonin.
Glumata, GABA and 6 others.
What else are NTs split into?
Give some examples.
What is another thing NTs can be split into?
Give some examples.
Neuropeptides- Large molecule NTs.
Endogenous opiates (endorphins), substance P, cholecystokinin, insulin, vasopressin, oxytocin and more than 40 others.
Gaseous NTs.
Nitric oxide + carbon monoxide (might have a biological function).
Give examples of two things which have similar molecular structures.
What are peptides NTs?
What are they way bigger than?
What are endorphins?
Dopamine + noradrenaline.
Strings of amino acids to form peptide molecules, protein molecules.
Small molecules NTs.
Strings of amino acids- forming large peptides molecules.
Acetylcholine:
What is it?
Where is it a major neurotransmitter?
What kinds of muscle?
Small neurotransmitter molecule.
In the autonomic nervous system and at neuromuscular junctions (activates muscles)- It releases byneurons which activate muscles.
Not just skeletal muscle but also smooth muscle controlled by the autonomic nervous system (e.g. vasodilation).
