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| Question | Answer |
| Chemical 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 |
| Events in synaptic transmission | 1. 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 |
| What 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 |
| Reduced vesicle release; investigated by Katz | Reduced 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 |
| Knee jerk reflex example | 1. 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 |
| EPSPs and IPSPs | EPSPs- 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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