9's before baes
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When DDT binds to a sodium ion channel, the channel remains open all the time. Use this information to suggest how DDT kills insects

The markscheme says:
1. Neurones remain depolarised;
2. So no action potentials / no impulse transmission.

But wouldn't action potentials continue to be triggered because the threshold is being reached like with how drugs can bind to the postsynaptic membrane of NMJ causing sodium ions to continuously move in and depolarise the membrane so action potentials are triggered continuosly?
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MO0NCHILDRM
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(Original post by 9's before baes)
When DDT binds to a sodium ion channel, the channel remains open all the time. Use this information to suggest how DDT kills insects

The markscheme says:
1. Neurones remain depolarised;
2. So no action potentials / no impulse transmission.

But wouldn't action potentials continue to be triggered because the threshold is being reached like with how drugs can bind to the postsynaptic membrane of NMJ causing sodium ions to continuously move in and depolarise the membrane so action potentials are triggered continuosly?
no ,after an action potential,the neurone membrane becomes hyperpolarised or depolarised whichever fits the ms best (more negative inside than at rest),to generate a new action poetntial it needs to repolarise itself which wont happen if sodium ions just keep dffusing in because theyll just make the potential difference more positive as theyre positive ions, the sodium ion channels close during a period called a "refractory " period which also prevents the action potential moving backwards or two action potentials meeting and so on, in order for this period to happen the sodium ion channels need to remain closed so they dont move along the axon and let the neurone go back to its resting potential, ddt causes them to never close meaning no new action potential will be generated

in summary, for an action potential to happen again since it itself happens because of the chasnge in the potential difference, the neurone needs to go back to its resting potential which is -60mV, if sodium ion channels remain open this resting potential difference can not be achieved since it is achieved with a certain balance of the sodium and potassium ion channels

to translate what the markscheme is saying, "the neurone remains depolarised and is not repolarised to its resting action potential therefore a new action potential can not be achieved"

whether the threshold is reached or not doesnt really matter if the neurone isnt at its resting potential in the beginning
Last edited by MO0NCHILDRM; 1 month ago
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9's before baes
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(Original post by MO0NCHILDRM)
no ,after an action potential,the neurone membrane becomes hyperpolarised or depolarised whichever fits the ms best (more negative inside than at rest),to generate a new action poetntial it needs to repolarise itself which wont happen if sodium ions just keep dffusing in because theyll just make the potential difference more positive as theyre positive ions, the sodium ion channels close during a period called a "refractory " period which also prevents the action potential moving backwards or two action potentials meeting and so on, in order for this period to happen the sodium ion channels need to remain closed so they dont move along the axon and let the neurone go back to its resting potential, ddt causes them to never close meaning no new action potential will be generated

in summary, for an action potential to happen again since it itself happens because of the chasnge in the potential difference, the neurone needs to go back to its resting potential which is -60mV, if sodium ion channels remain open this resting potential difference can not be achieved since it is achieved with a certain balance of the sodium and potassium ion channels

to translate what the markscheme is saying, "the neurone remains depolarised and is not repolarised to its resting action potential therefore a new action potential can not be achieved"

whether the threshold is reached or not doesnt really matter if the neurone isnt at its resting potential in the beginning
right, thank you so much
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