QUESTION 5 Which of the following conditions MUST exist for a neuron to be at a
ID: 3507783 • Letter: Q
Question
QUESTION 5
Which of the following conditions MUST exist for a neuron to be at a resting membrane potential:
The diffusive and electrical forces for each ion must be balanced.
There must be a net outward flow of current.
The number of positive charges on the inside of the membrane must be equal to the number of positive charges on the outside of the membrane.
The intracellular and extracellular solutions must be electrically neutral.
All of the above
a.The diffusive and electrical forces for each ion must be balanced.
b.There must be a net outward flow of current.
c.The number of positive charges on the inside of the membrane must be equal to the number of positive charges on the outside of the membrane.
d.The intracellular and extracellular solutions must be electrically neutral.
e.All of the above
Explanation / Answer
e. All the above
There is no measurable charge excess in any side of the membrane. So, although there is an electric potential across the membrane due to charge separation, there is no actual measurable difference in the global concentration of positive and negative ions across the membrane (as it is estimated below), that is, there is no actual measurable charge excess on either side. That occurs because the effect of charge on electrochemical potential is hugely greater than the effect of concentration so an undetectable change in concentration creates a great change in electric potential.
Potassium ions can move across the membrane in both directions but by the purely statistical process that arises from the higher concentration of potassium ions inside the cell, there will be more potassium ions moving out of the cell. Because there is a higher concentration of potassium ions inside the cells, their random molecular motion is more likely to encounter the permeability pore (ion channel) that is the case for the potassium ions that are outside and at a lower concentration. An internal K+ is simply "more likely" to leave the cell than an extracellular K+ is to enter it.
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