9.2.6 - Synapses Flashcards
What happens when the impulse arrives at the synaptic knob?
Calcium channels open and calcium ions diffuses in
What is the name of the neurons that pass on an impulse before a synapse and receive an impulse?
Pre synaptic neuron
post synaptic neuron
What do synaptic vesicles do?
Move and fuse with the pre-synaptic membrane.
Neurotransmitrers are released into the synaptic cleft.
By what process does a neurotransmitter move across the synaptic cleft?
Diffusion
What do neurotransmitters do after they diffuse across the syanptic cleft?
Bind to specific protein receptors on the post-synaptic membrane.
After neurotransmitters bind to specific proteins on the post-synaptic neuron membrane, what happens next?
Sodium channels open and sodium ions diffuse in.
This causes an excitary post-synaptic potential to be set up.
What happens if there is a sufficient number of excitary post-synaptic potentials?
The positive charge caused by the influx of sodium ions exceeds the threshold level and an action potential will occur.
What is an inhibitory post-synaptic potential and how does it work?
A synaptic potential that makes a post-synaptic membrane less likely to generate an action potential.
Different ion channels open in the membrane allowing inward movement of negative ions so more negative than resting potential meaning an action potential is less likely to occur.
What are neurotransmitters broken down by?
Hydrolytic enzymes
What happens to neurotransmitters after they are broken down?
They move back across the cleft, back into the synaptic knob and they are recylcled.
What enzyme breaks down acetylcholine?
acteylcholinesterase
What is acetylcholine separated into?
Acetate and choline
Where is an adrenergic synapse found and what neurotransmitters are involved?
Symapthetic nervous system
Noradrenaline is neurotransmitter.
Where is the cholinergenic synapse found and what neurotransmitters are involved?
Parasympathetic nervous system.
Acetylcholine is neurotransmitter
Describe the effects of nicotine.
Mimics the effect of acteylcholine, binds to acetylcholine receptors.
Triggers action in post-synaptic neuron but receptors remain unresponsive for some time (hence not needing to constantly smoke)
triggers the release of dopamine
Can be lethal at high doses
Describe the effects of lidocaine.
Used as a local anaesthetic by dentists.
Blocks Na+ channels so prevents and action potential in sensory neurons.
Prevents heart arrythmias as it can prevent extra action potentials in pacemaker.
Describe the effects of cobra venom.
Bind reversibly to acetylcholine receptors and so prevents the transmission of impulses across synapses.
In low doses it can relax the muscles of the trachea which can save the life of people having an asthma attack.
