15.6 - Synaptic Transmission Flashcards
What is a cholinegeric synpase?
One in which neurotransmitter is a chemical called acetlycholine
What is acetlycholine made up of?
Acetly (more precisely ethanoic acid)
and
choline
Where are cholinergic synapses common in?
Vertabrates
Occur in the CNS and neuromuscular junctions (junctions between neurones and muscles)
What does each receptor portein bind to?
Specifically to a neurotransmitter
Specific complementary shape
What are some neurotransmitters are?
- Some neurotransmitters and receptors are excitatory - lead to a new action potential in postsynaptic neurone
- Some are inhibitory that make it less likely for an action potential created in postsynaptic neurone
What are the two ways drugs can act on synpases?
- Stimulate the nervius system by creating more action potential in postsynaptic neurone
- They inhibit the nervous system by creating fewer action potentials in post synaptic neurone
How do drugs stimulate nervous system by creating more action potentials in post synaptic neurone?
A drug may do this thing by mimicking a neurotransmitter
This stimulate the release of more neurotransmitter or inhibiting an enzyme that breaks down the neuro transmitter
The outcome is to enhance the body’s response to impulses passed along the post synaptic neurone
e.g neurone transmit impulse from sound receptor, person perceive sound to be louder
How do drugs inhibit the nervous system by creating ewer action potentials in the postsynaptic neurone?
A drug may do this by inhibiting the release of neurotransmitter or blocking the receptor on sodium/potassium ion channels on post synaptic neurone
Outcome is to reduce the impulses passed aling the postsynaptic neurone
In this case, neurone transmit impulses from sound receptor , a person will percieve the sound as being quieter
What effect of drug on synpase depend on type of neurotransmitter
e.g
drug will inhibit the action of excitatory neurotransmitter will reduce the particular effect
but
drug that inhibit the inhibitory neurotrnsmitter will enhance the effect
What do endorphoins (neurotransmitter used in sensory nerve pathways - pain pathway) act as?
They block the sensation of pain
Drugs such as morphonine and codenine bind to specific receptors in the brain used by endorphins and mimic effects of endorphins
Suggest what is the likely effect of drugs like morphonine and codeine on body and explain the effect
- They will reduce the pain
- They act as endorphins by binding to receptors and therefore prevent action potential created in the neurone of pain pathway
How does seretonin act?
It is a neurotransmitter and involved in the regulation of sleep and certain emotional state
Reduced activity of neurones that release serotonins is thought to be cause of clinical depression
Prozac is an antidepressant drug that affects serotonin in synaptic cleft
Suggest a way that the drug Prozac might affect serotonin within the synaptic cleft
Proazac might prevent the elimination of serotonin from synaptic cleft
Explain how the effect of Prozac being an effective antidepressant?
By increasing the concentration of serotonin in synaptic cleft
It is actively is increased
reducing depression which is caused by reduced serotonin activity
What is GABA?
Neurotransmitter that inhibits the formation of action potentials which binds to post synaptic neurone
Valium is a drug that enhances the binding of GABA to receptors
Suggest the likely effect of Valium of the nerve pathway that causes muscle contractions
Valium increases the inhibitory effects of GABA so therefore there is fewer action potentials on the nerve pathway that causes the muscle to contract
Epilespy can be the result of the increase of activity of neurones in brain due to insufficient GABA
An enzyme breaks fown GABA on post synaptic membrane
A drug called Vigabatrin has a molecular structure similar to GABA and can be used to treat epilespy
Suggest a way Viagbatrin might be effective in treating epilespy
The molecular structure of Vigabatrin is similar to GABA so competitive inhibitor to compete for active stie of enzyme that breaks down GABA
As less GABA broken down by enzyme, more avaliable to inhinbit activity
OR
Viagatbtrin bind to GABA receptor on neurone membrane and mimic action
Instructions of synaptic transmission
- The arrival of action potential at the end of presynpatic neurone causes calcium ions protein channels to open and enter synaptic knob by facilitated diffusion
- Influx of calcium ions into presynaptic neurone causes synaptic fuses with presynaptic membrane releasing acetlycholine in synaptic cleft
- Acetlycholine molecules diffuse across the cleft - diffusion pathway is short
- Then binds to the receptor sits on sodium ion protein channel
- Causes the sodium ion protein channel to open allowing Na+ rapidly diffuse in
- Influx of sodium ions generate a new action potential in post synaptic neurone
Instructions of synaptic transmission to recycle
- Acetlycholine hydrolses into choline and ethanoic acid (acetly)
- This diffuses this back across synaptic cleft to presynaptic neurone (=recycling)
- Recycling the choline and ethanoic acid , the rapid breakdown of acetlycholine also prevents it from continously generating a new action potential in postsynaptic neurone - discrete transfer
- ATP is released by mitochondria to combine choline and ethanoic acid into acetlycholine
- This is stored in synaptic vesicle for future
- Sodium ion protein channels close for absence of acetlycholine
