- Created by: 11APhillips
- Created on: 31-12-19 11:58
- Synapses connect neurons to form large circuits, there are 10^15 neurons
- They can undergo two types of changes:
- Short term - Used for signalling
- Long term - Used for learning and memory
- This is a type of synapse where the current flows from one neuron to another through a gap junction.
- The membranes are only 3.5 nanometers apart.
- They are comprised of two hemi-channels called connexons.
- Connexons have six subunits called connexins.
- A connexin has four membrane spanning domains.
- They allow for faithful transmission/high speed transmission and bidirectional signalling, but they have limited flexibility as they are faithful conveyors of signal.
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- Otto Loewi showed the importance of chemical synapses by taking synaptic fluid from a frog vagua nerve and putting it into a recipient heart; the fluid caused the heart rate to slow.
The Nicotinic acetylcholine receptor
- It has 2 alpha, 1 beta and 1 gamma subunit.
- A twisting response upon acetylcholine binding opens the channel.
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Post synaptic responses
- A postsynaptic depolarisaion is called an excitatory postsynaptic potential (EPSP).
- In muscle, the same thing is called an end plate potential
- We know that the two major players are Na and K through studying the reversal potential.
- You can determine this by recording the post synaptic potential against a control membrane potential
- You start at -70mV and evoke a response and then increase the potential stepwise; the point at which no ion flow occurs is the reversal potential.
- In inhibitory synapses, the result of stimulation is hyperpolarisation, which called an inhibitory postsynaptic potential (IPSP).
- There may also be an influx of Cl-.
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