Synaptic transmission (cells of NS) Flashcards
What are the 2 types of synapses?
- Chemical
- Electrical
What is an electricl synapse like?
- Has gap junctions where APs move thru
- Creates a coupling potential in the post synaptic neurone
What moves through gap junctions?
Ions move through gap juntions to produce AP
What theory do electrical synapses fit well with?
The Retisular theory (Golgi)
What is the inferior olive?
Group of neurones in the medulla oblongata that is involved in motor coordination
- Brain stem nucleus
- Movement
- Neurones form electrical synapses with eahc other to synchronise activity of networks
What are astrocytes?
- Inter-connected via gap junctions to form syncytia
- Ca+ signalling
What are the 2 components involved in electrical synapses?
- Inferior olive
- Atrocytes
Explain the stages of transmission at a chemical synapse:
- NT molecules are synthesised & packaged in vesicles
- An AP arrives at the presynaptic terminal
- Voltage gated Ca2+ channels open, Ca2+ enters
- Rise in Ca2+ triggers fusion of synaptic vesicles w the prsynaptic membrane
- Transmittter molecules diffuse across the synaptic cleft & bind to specific receptors on the postsynaptic cell
- Bound receptors activate postsynaptic cell
- A NT breaks down, is taken up by the presynaptic terminal or other cells or diffuses away from synapse
Rewatch lecture on slide 8 about vesicle docking
Apparently calcium is very important for this
What theory do chemical synapses fit well with?
The neurone doctrine (Cajal)
Sherrington coined the term synapse
Where are chemical synapses a prevalent mode of synaptic communication?
In the vertabrate central & peripheral nervous system
Give an example of a chemical synapse:
Neuromuscular junction
Summarise chemical synapses:
- Neurotransmitters
- Exocytosis and posy synaptic receptors
- One way
- Slow
- Prevalent neurone junctions in the NS
Summarise electrical synapses:
- Ions
- Gap junctions
- Two way
- Fast
- Neurone junction in certain areas of the NS & gap junctions connect astrocytes in syncytia
Who conducted the reaserch into chemical synapses?
Otto Loewi (1921)
Used a perfused frog heart
What was the process that Otto Loewi used when researching chemical synapses?
(Using the perfused frog heart)
- Stimulated the atached Vagus nerve
- Rapidly slowed the HR of the first heart
- Delay slowed heartbeat of 2nd perfused heart, not directly attached to Vagus nerve
- Conclusion: chemical released into the solution that inhibits heartbeat
Chemical later found to be ACh
What did Henry Dale study in 1936?
He studied chemical transmission at the neuromuscular junction
What are neuromuscular junctions also known as?
Motor end plates
What are neuromuscular junctions (NMJ)?
They are specialised chemical synapses between motor neurones axon terminal & muscle fibre
What is a motor unit?
A group of muscle fibres innervated by a single neurone
What are the agonists/antagonist that can work on the NMJ?
- Eserine = agonist
- Tubocurarine = antagonist
What does eserine do at the NMJ?
- Blocks acetylcholinesterase
- Prevents the breakdown
This increases the action of ACH
What does tubocuranine do at the NMJ?
- Nicotinic receptor antagonist
- Prevents action of ACh (blocks the action of ACh)
What is the process of synaptic transmission at the NMJ?
1 - An AP arrives at the presynaptic terminal & causes voltage-gated Ca2+ channels in the presynaptic membrane to open
2 - Ca2+ ions enter the presynaptic terminal & initiate the release of the NT ACh from synaptic vesicles
3 - ACh is released into the synaptic cleft by exocytosis
4 - ACh diffuses across the synaptic cleft & binds to ligend-gated Na+ channels on the postsynaptic membrane
5 - Ligand-gated Na+ channels open & Na+ enters postsynaptic cell causing the postsynaptic membrane to depolarise –> if depolarisation passes threshold, an AP is generated along the postsynaptic membrane
Process contiunes with ACh reuptake (on another flashcard)
