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Lecture 11- synapses and chemical transmission
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- 1Chemical synapses- Synapses are specialised junctions between nerve cells that allow the passage of charge from nerve cell to nerve cell.
- Where cells do not have synapses they are often joined by jab junctions, when one cell is excited the current automatically flows to the other gap junction
- The neuromuscular junctions are the synapse between nerve and muscle
- vesicles of neurotransmitter release contents on AP, ach travels across synaptic cleft and binds to specific receptors on pots-synaptic membrane - 2Events in synaptic transmission1. Presynaptic action potential
2. Depolarisation of synaptic terminal
3. Opening of voltage gated calcium channels
4. Ca+ entry, fusion of vesicles with membrane
5. Transmitter release (& then reuptake degregation)
6. (@ the neuromuscular junction): Ach receptor actived cation channels open (+ions)
7. This activates sodium and potassium channels to open up further along the nerve - 3What if the post-synaptic response is subthreshold?Sub threshold= NO action potential; signal decreases with distance along the muscle
Supre-threshold= action potential is triggered - 4Reduced vesicle release; investigated by KatzReduced vesicle release can be due to;
- low calcium
- high magnesium
- curarae (posion)
* Subthreshold events are called 'end plate potentials' and can add up (summate) to reach threshold and trigger an AP.
* Minature end plate potentials summate to form end plate potentials which summate to form an action potential.
- Minature end plate potentials (MEPPs) vary in size and occur at rando.; caused by the spontaneous release of vesicles EG knee jerk reflex - 5Knee jerk reflex example1. Patella hit w/hammer, causing tendon to tense and muscle to stretch
2. Muscle spindle causes effects in the spinal cord, which regulate response:
- polarisation of extensor muscle and depolarisation of flexor muscle result in them being contracted at the same time, causing the knee jerk response - 6EPSPs and IPSPsEPSPs- excitatory postsynaptic potentials
IPSPs, add to generate depolarisation
IPSPs- Inhibitory postsynaptic potential, add to generate hyperpolarisation. Result in less APs being fired, reducing their frequency.
- They are sub-threshold events that determine if a neurone will reach threshold to fire an AP
- They add to cancel one another out
- Temporal and spatial summation summate to determine or not if an AP is fired.
'what matters is the balance between the 2'
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- Descripción
- Cell bio and neuroscience synapses and chemical transmission
- Creado por
- Rose P
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