help Resting membrane potential Action potential Depolarization Repolarization H
ID: 57119 • Letter: H
Question
help Resting membrane potential Action potential Depolarization Repolarization Hyperpolarization Synaptic vesicles Neurotransmitter Excitatory neurotransmitter Inhibitory neurotransmitter Absolute refractory period Relative refractory period Draw the diagram to show the membrane potential changes that occur when an action potential is triggered. Mark the threshold potential, depolarization, replolarization and hyperpolarization phases Explain the permeability of the membrane with respect to Na+ and K+ ions in these phases. Explain the conformation of the the Na+ and K+ channels in the three phases httPs://www.voutube.com/watch?v=7EvhsOewnH4 Action potentialExplanation / Answer
Resting membrane potential :- potential of membrane at rest i.e. equivalent to -70mV.
Action potential:- Increase in electrical membrane potential for a very short duration of time following immediate decrease. Action potential is equivalent to 40mV for axon membrane
Depolarisation:- loss of polarisation in the membrane is called as depolarisation. Normally the inside of membrane is negative in comparison to outside. Depolarisation makes this membrane less negative.
Repolarisation: Return of polarisation in membrane is called as repolatisation. It can also be said that return of membrane to the normal -ve value as before.
Hyperpolarisation:- Increase in stimulus in such a way that it inhibits action potential is called as hyperpolarisation. It is reverse of depolarisation. This occurs when sodium channels are unable to open.
syanaptic vesicles :- Also known as neurotransmitter vesicle. It is a small vesicle present in first axon, which releases neurotransmitter at the site of synapse in response to change in voltage gated calcium channels.
neurotransmitter:- A chemical (signal) released at the site of synapse, which aids in paracrine signalling.
Excitory neurotransmitter:- stimulates the nerve impulse eg: dopamine. They stimulate the brain.
Inhibitory neurotransmitter:- which inhibits the nerve impulse eg- GABA and dopamine. They do not stimulate the brain and calms it down.
Absolute refractory period: During depolarisation K+ channels are opened and Na+ channels are closed. Throeugh these K+ channels , K+ keeps on entering the cell until resting membrane potential is achieved. At this time, depolarisation is impossible , because sodium channels are closed. This time period during which sodium channels will remain close is known as absolute refractory period. During this time period, nerve impulse cannot be stimulated no matter how much high stimulus is given.
Relative refractory period: After repolarisation, there is a period when nerve impulse can be stimulated if greater than normal stimulus is given. This period is the relative refractory period.
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