Bio – week six (neurochemistry) – Flashcards

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pre -synaptic cells
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sends the message
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post-synaptic cells
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receive the message
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what happens at the end of a neuron
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vesicles containing neurotransmitters are dumped into the synapse - this has an effect on the post-synaptic cell - inhibitory decreases the likelihood of post synaptic cell firing, and excitatory increases the likelihood of post-synaptic cell firing
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what chemicals are responsible for the communication between neurons?
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neurotransmitters
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what are the benefits of chemical communication?
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can change the signal from excitation to inhibition have flexibility about the signal given off can be affected by other chemicals in the body can allow selectivity - can prevent certain receptive cells many weak signals can add up to make a response
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what triggers an action potential in the post-synaptic membrane?
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vesicles full of neurotransmitters are held in the axon terminal and when the action potential reaches the end of the axon it triggers calcium channels to open - influx of calcium ions in axon terminal = vesicles will merge with the membrane - releases neurotransmitters into the synaptic cleft
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what does the neurotransmitter do next?
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the neurotransmitter will bind to a complementary receptor site on the post-synaptic membrane (lock and key - some require another chemical in order to bind) binding of the neurotransmitter causes a shape change in the ligand/transmitter gated ion - open/closes the ion channel = affects the flow of ions through it if it allows negative ions in = further hyper-polarises (away from action potential) if it allows positive ions in = depolarises the cell towards the excitation threshold happens at many different places and IT IS THE SUMMATION OF -VE/+VE THAT LEADS TO AN ACTION POTENTIAL
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temporal summation
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multiple pre-synaptic neurons releasing neurotransmitters onto the same post-synaptic membrane - if they're close enough in time
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spatial summation
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multiple pre-synaptic neurons releasing neurotransmitters onto the same post-synaptic membrane - if they're close enough spatially + in time
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acetylcholine (ACH)
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released at the junction between nerves and muscles - makes muscles contract
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serotonin
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involved in the mechanism of sleep, mood and arousal
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GABA
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inhibitory transmitter of CNS
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glutamate
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excitatory transmitter in the brain crucial in learning + memory
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norepinephrine
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helps control arousal level influences wakefulness, learning and memory
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dopamine
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influences movement, emotion and motivation
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how does a direct neurotransmitter work?
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binds directly to the ion channel can cause change in shape of channel - affects ion flow can be positive or negative
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how does an indirect neurotransmitter work?
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binds to another protein on the cell membrane causes changes inside the cell - affects ion channels
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how does an agonist drug work?
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enhances the neurotransmitters effect: mimics the neurotransmitter increases release of neurotransmitter counteracts clean up enzymes blocks the re-uptake
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how do antagonist drugs work?
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impedes the neurotransmitters effect: blocks the release of neurotransmitters can block them from binding
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where can drugs work?
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at synthesis, release, the receptor, turnover or re-uptake
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how does alcohol affect the brain?
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GABA normally binds to receptors and allows in some -ve ions - reducing the cells likelihood to fire - alcohol will also bind and keep the channels open for longer - more inhibition
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how does cannabis affect the brain?
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indirect affect on GABA neurons - less inhibition of dopamine neurons = more dopamine is released = more firing in those cells - these cells are linked in a reward circuit which is normally inhibited by GABA cells but cannabis stops this inhibition
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what is the blood brain barrier?
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layer of tightly joined cells that surround the blood vessels in the brain - large molecules can not get through the tight junctions in the capillary wall - acts as a filter - stops most things from getting through
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how can dopamine be administered?
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it can't cross the blood brain barrier but l-dopa can and then a chemical reaction can convert this into dopamine
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