Lecture 23: The Synapse Flashcards
What is a synapse?
The junction between nerve cells where a nerve impulse is transferred from one neurone to another.
What are the two types of synapse?
Electrical and Chemical.
What’s the difference between electrical and chemical synapses?
Electrical synapses are linked by gap junctions and are very fast. Chemical synapses are linked by a chemical neurotransmitter and are slower than electrical. Speeds can vary.
Is a NMJ a chemical or electrical synapse?
Chemical, releases acetylcholine.
What are the 5 key components of the pre-synaptic side of a synapse?
- Axon Terminal / Bouton
- Vesicles
- Cytoskeleton
- Mitochondria
- Voltage gated Ca2+ channels
What is the gap in synapse called?
The synaptic cleft.
What are the 3 key features of the post-synaptic side of the synapse?
- Neurotransmitter receptors
- These allow Na+ or Ca2+ entry to depolarise cell.
- Often appears as thick membrane called PSD (post synaptic density)
What is the concentration of Ca2+ in the ECF?
2-2.5mM
What are the 7 steps of signal transmission across a chemical synapse?
- Action potential propagates down axon to pre-synaptic bouton.
- Pre-synaptic bouton is depolarised - Ca2+ channels open.
- Ca2+ ions trigger the release of the neurotransmitter from vesicles.
- Neurotransmitter released into synaptic cleft.
- Neurotransmitter binds to specific receptors on post PSD.
- Na+ channels open causing local depolarisation of post synaptic cell.
- Net depolarisation followed by repolarisation (EPSP)
What does EPSP stand for?
Excitatory Post Synaptic Potential.
Match the following terms:
Depolarisation, Hyperpolarisation, Inhibitory, Excitatory.
Depolarisation - Excitatory
Hyperpolarisation - Inhibitory
How is a synapse ‘switched off’.
Excess neurotransmitter released into the synaptic cleft, eg. ACh @ NMJ.
Excess neurotransmitter must be removed by:
a) degradation
b) reuptake into the bouton
c) reuptake into glia
REMOVAL REQUIRES ATP.
How does Novichok (Новичо́к) work?
It inhibits ACh degradation, ACh accumulate at the synapse and causes convulsions and constant contractions which can stop the heart and other important organs.
