Nerves 3
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What is the threshold potential?
About -55mV
What will happen when the membrane potential hits -55mV?
An action potential will be fired
What is a generator potential?
A graded potential occurring at sensory nerves
What is an EPSP?
A generator potential that will depolarise the cell
What is a IPSP?
A generator potential that will hyperpolarise the cell
What is the graded potential between a motor neurone and a muscle called?
End plate
What is the function of graded potentials?
To decide whether or not the stimulus is great enough for a response
4 examples of graded potentials
• Generator • Post synaptic • Endplate • Pacemaker
4 key properties of graded potentials
• Excitatory • Non-propegating • Decremental • Local
Why are graded potentials decremental?
The current leaks out of the cell as it travels down it
What is shown by the amplitude of a graded potential?
Signal intensity
How can graded potentials generate an IPSP?
• Opening Cl channels on the post synaptic neurone
How are fast IPSP’s generated?
• Opening ionotropic Cl channels
How are slow IPSP’s generated?
• By binding to g-protein coupled receptors that open potassium channels causing K to leave the cell
What 2 neurotransmitters will trigger an IPSP?
• Glycine - GABA
How are fast EPSP’s generated?
• Opening Na/K channels
How are slow EPSP’s generated?
• Blocking potassium channels that cause potassium to leave the cell
What is meant by the fact that graded potentials can summate?
• Two excitatory/inhibitory signals can add to each other
What is temporal summation?
Input from the same stimulus add up to each other (turning on a tap, turning it off, then turning it back on again)
What is spatial summation?
2 different stimuli add to each other (turning on 2 taps at the same time)
What is synaptic integration?
• All inputs taken into consideration - Action potential decided
Why do synapses nearer the axon hillock have a better chance of generating an AP?
• Decremental aspect • Have to travel less distance so less signal is lost • Axon hillock is what decided to fire an AP