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Topic 6
Synapses and Neuromuscular junction
| Term | Definition |
|---|---|
| What is a synapse | These are gaps between the end of the axon and neurone and the dendrite of another one |
| How are action potential transmitted | They are transmitted through nerurotransmitters that diffuse across the synapse |
| Functions of the synapse Step 1 | An action potential arrives at the synaptic knob leads to opening of Ca2+ channels and diffuses into synaptic knob |
| Step 2 | Vesicles containing neruotransmitters move towards and fuse with the presynaptic membrane. Neurotransmitters is released to the synaptic cleft |
| Step 3 | Neurotransmitters diffuse down the concentration gradient across the synaptic cleft to post synaptic membrane neurotransmitters bind by complementary shape to receptors on the surface of the post synaptic membrane |
| Step 4 | Na+ ion channels on the post synaptic membrane open and Na+ diffuse in if enough neurotransmitter then enough Na+ diffuse in above threshold and post synaptic neuron becomes depolarised |
| Step 5 | Nerurotransmitters is degraded and released fom the receptor the Na+ channel close and the post synaptic neurone can re establish resting potenital the neurotransmitter is transported back into the presynaptic neurone where it is recycled |
| What is Summation | This is the rapid build up of neurotransmitters in the synapse to help generate action potential by two methods spatial or temporal summation. |
| why is this needed | This is needed because some action potentials do not result in sufficient concentrations of neurotransmitters being released to generate a new action potential |
| What is spatial summation | Many different neurones collective trigger a new action potential by combining the neuro transmitter they release to exceed the threshold value |
| What is Temporal summation | One neurone releases neurotransmitter repeatedly over a short period of time to add up enough to exceed threshold value |
| What do inhibitory synapses cause | These causes chloride ions to move into the post synaptic neurone and potassium ions to move out |
| How does hyperpolarisation occur | Due to combined effect of negative ions moving in and positive ions moving out |
| Where does the neruomuscular junction occur | This occurs between the motor neruone and a muscle very similar to the synaptic junction |
Created by:
yHya