Fibrillation is a coronary event in which rapid, uncoordinated twitching of small muscle fibers in the heart replaces the normal rhythmic contraction, causing the heart to stop pumping blood. Without...

Fibrillation is a coronary event in which rapid, uncoordinated twitching of small muscle fibers in the heart replaces the normal rhythmic contraction, causing the heart to stop pumping blood. Without rapid intervention, fibrillation may result in brain damage or even cardiac arrest, also known as a heart attack. During fibrillation, 10% of the ability to restart the heart is lost every minute A defibrillator is an electronic device that delivers an electric shock to the fibrillating heart to restore the normal rhythm. A common type is the capacitive-discharge defibrillator, which uses a capacitor to store and quickly deliver charge to a patient. The charge delivered to the heart as an electric shock can sometimes restore the heart’s normal electrical activity and beating. A fully charged capacitor is switched on at t = 0 so that the current out of the defibrillator is:

Assuming that the capacitor cannot be charged while it is being discharged, how long will it take for the capacitor to be 99% discharged? Assume that the capacitor has 0.080 C of charge at t = 0.

Consider a cell during the depolarization and repolarization phases. A system is defined such that it includes a patch of the membrane measuring 1mm2 and the interior of the cell directly below this patch. During the depolarization phase, which lasts 0.1 ms, sodium ions are estimated to flow into the neuron at a rate of 7.8 1015ions/(cm2.s). During the repolarization phase, which lasts 0.2 ms, potassium ions are estimated to flow out of the neuron at a rate of 4.5 1015ions/(cm2.s). After both phases, what is the accumulation of positive charge inside the cell?