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    Can any one summaries whats happens during reasting portential and action potential. Plus how is the axon deploarised?????

    Becuase the books are have sumtimes seems so confusing what they write.

    Thanx
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    Ok so it goes a little something like this.
    At resting potential the axon is at -70mV
    3 Sodium ions are pumped out of the axon as 2 Potassium ions are pumped in. This produces a potential voltage across the membrane.
    When a nerve impulse is required, the pump stops
    Some sodium channels open, which allows an influx of sodium ions back into the axon. This naturally raises the potential difference across the membrane to -40mV
    As soon as the potential difference reaches -40mV, (which is called the threshold value) this triggers the opening of more sodium channels causing an even greater influx of sodium ions. If the impulse is not great enough to reach -40mV then nothing will happen.
    But in the event that it does, then the influx of more sodium ions will lead to an increase in voltage of +40mV across the membrane
    Once +40mV is reaches, sodium channels close, K channels open and the pump starts working again.
    This process will 'overshoot' which is called hyperpolarisation when the potential difference drops to -75mV
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    A resting potential is maintained by the sodium-potassium pump. Sodium ions are actively pumped out of the membrane and potassium ions are pumped into the membrane to achieve a resting potential of -65mv (quite sure thats right??)
    For the action potential the parts you should mention in the exam are:
    1) Action potential arrives at Synaptic knob
    2) Causes calcium channels to open. Allows an influx of Ca2+ which depolarises the membrane.
    3) Vesicles containing ACh move and fuse to the pre-synaptic membrane by exocytosis.
    4) ACh released and diffuses across synaptic cleft where it binds to receptors on post-synaptic membrane called Acetyl cholinesterase.
    5) New action potential develops and ACh recycled.
    Sorry, just realised, my explantion is transmission of impulse at synapse. Hope i helps
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    'receptors on post-synaptic membrane called Acetyl cholinesterase?'

    So your saying that the receptors on the post-synaptic membrane are really enzymes that catalyse the hydrolysis of the actylcholine???
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    depends if its a parasympathetic nerve or not

    remember parasympathetic = acetyl choline
    sympathetic = noradrenaline.
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    (Original post by Revenged)
    'receptors on post-synaptic membrane called Acetyl cholinesterase?'

    So your saying that the receptors on the post-synaptic membrane are really enzymes that catalyse the hydrolysis of the actylcholine???
    Nah, I don't think that's right. The receptors don't do anything but respond to the presence of the neurotransmitter. The acetyl cholinesterase is a different molecule altogether.
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    acetylcholinesterase breaks down acetylcholine in synaptic cleft i think so that action potentials dont keep on happening.
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    The resting potential is maintained by the sodium potassium pump. A stimulus is converted to an electrical impulse by a receptor cell. This causes the voltage gated channels to open and sodium ions to flood in until inside of the axon reaches +40mv. (depolarisation). Then this causes the sodium ions to close and the potassium ions to open. They flood in and repolarise the axon at the point. Does that help, if not i have some more notes
    xx
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    cheers, endeavour... i didn't think it sounded right
 
 
 
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