A heart cell can be modeled as a cylindrical shell thatis 100 mm long, with an outer diameter of 20.0 mm and a cell wall thicknessof 1.00 mm,. Potassium ions move acrossthe cell wall, depositing positive charge on the outer surface and leavinga net negative charge on the inner surface. During the so-called restingphase, the inside of the cell has a potential that is 90.0 mV lowerthan the potential on its outer surface. (a) If the net charge of the cellis zero, what is the magnitude of the total charge on either cell wallmembrane? Ignore edge effects and treat the cell as a very long cylinder.(b) What is the magnitude of the electric field just inside the cell wall?(c) In a subsequent depolarization event, sodium ions move throughchannels in the cell wall, so that the inner membrane becomes positivelycharged. At the end of this event, the inside of the cell has a potentialthat is 20.0 mV higher than the potential outside the cell. If we modelthis event by charge moving from the outer membrane to the innermembrane, what magnitude of charge moves across the cell wall duringthis event? (d) If this were done entirely by the motion of sodium ions,Na+, how many ions have moved?
A heart cell can be modeled as a cylindrical shell that
is 100 mm long, with an outer diameter of 20.0 mm and a cell wall thickness
of 1.00 mm,. Potassium ions move across
the cell wall, depositing positive charge on the outer surface and leaving
a net negative charge on the inner surface. During the so-called resting
phase, the inside of the cell has a potential that is 90.0 mV lower
than the potential on its outer surface. (a) If the net charge of the cell
is zero, what is the magnitude of the total charge on either cell wall
membrane? Ignore edge effects and treat the cell as a very long cylinder.
(b) What is the magnitude of the electric field just inside the cell wall?
(c) In a subsequent depolarization event, sodium ions move through
channels in the cell wall, so that the inner membrane becomes positively
charged. At the end of this event, the inside of the cell has a potential
that is 20.0 mV higher than the potential outside the cell. If we model
this event by charge moving from the outer membrane to the inner
membrane, what magnitude of charge moves across the cell wall during
this event? (d) If this were done entirely by the motion of sodium ions,
Na+, how many ions have moved?
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