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the nervous sytem (The synapse (electrical (3nm) or chemical (20nm)…
the nervous sytem
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Neurone is excitable, so can change it's resting potential. Membrane is more negative inside, so it's polarised.
At rest, voltage gated sodium ion channel is closed, potassium ions are pumped in through voltage gated potassium channel. Potassium channels are open and K+ ions diffuse out.
Action potential- Voltage gated sodium channels to open. Na+ ions diffuse in rapidly down the concentration gradient. Charge rapidly goes from -70 to +40 (depolarisation) sodium channels close. Potassium channels open and k+ ions diffuse out, more k+ ions diffuse out than Na+ in, so hyperpolarisation takes place. Sodium-potassium pump pumps k+ ions in and Na+ ions out.
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Absolute refractory period, once sodium channels are inactivated they can't be opened again until resting potential is re-established.
If the intensity of a stimulus is below the threshold value, no action potential is initiated.
Higher temperature increases nerve impulses. Larger dimeters of axon increases nerve impulses. Myelination increase nerve impulses.
Drug effect on synapses
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Some drugs mimic neurotransmitters. they aren't hydrolysed so continue to initiate impulses. some prevent breakdown of acetylcholine.
Psychoactive drugs act on the CNS by affecting different neurotransmitters or receptors, altering function and behaviour etc...
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Nerve nets
Simple type of nervous system, no brain, ganglion cells and sensory cells.
Regenerate quickly, simple pattern, no myelin, slow conduction
Reflex arc, rapid, automatic response resulting from a stimulus.
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