Calculated Normal Conditions E K millivolts 61 log10 Kout K

Calculated Normal Conditions:

E K+ (millivolts) = 61 log10 ([K+]out /[K+]in)

E K+ (millivolts) = 61 log10 ([4.0 mM]out /[150 mM]in)

E K+ (millivolts) = 61 log10 (0.0266666667)

E K+ (millivolts) = -96.01590733 mV = -96 mV

Calculated Elaina’s Conditions:

E K+ (millivolts) = 61 log10 ([K+]out /[K+]in)

E K+ (millivolts) = 61 log10 ([6.2 mM]out /[150 mM]in)

E K+ (millivolts) = 61 log10 (0.0413333333)

E K+ (millivolts) = -84.405567374 mV = -84 mV

Question:

a.) Et represents the threshold membrane potential for action potential production and is about 15 millivolts more depolarized than Erest. If the value for Et in Elaina is numerically identical to that of a normal patient, what would be the effect of Elaina’s change in resting membrane potential on the amount of depolarization required to produce an action potential?

b.) Can this change (the difference between the resting membrane potential and threshold) explain any of Elaina’s symptoms? If so, state which ones and explain why.

Table 1-A Partial List ofElaina\'s VitalSigns Elaina Normal Vitals Blood Pressure 126/84 (Hypertension) 90-120 Pulse Rate 105 bpm (Tachycardia) 60-100 bpm 98.6 F 98.8 °F Temperature Table 2-A Partial List ofResults from Elaina\'sBlood Work Elaina Normal Measurment White Blood Cell Count 7,800 cells/mms 4500-10,500 cells/mm Sodium (mM) 135-145 142 3.5-5.2 6.2 Potassium (mM) 59-174 Triiodothyronine (T)(ng/dL) 11.2 Tetraiodothyronine or thyroxine(T) (ng/dL 7.3 4.5-12 Thyroid stimulation Hormone ITSH) (ng/dL 1.8 0.3-3.0

Solution

According to the given measurement levels, Elaina is hyperkalemic i.e. increased level of potassium. Increase potassium levels decrease the voltage difference across the membrane due to which the resting membrane becomes less negative and lower threashold is required to induce depolarization. Thus, hyperkalemia induces depolarization.

Similarly, hyperkalemia induces frequent depolarizations in cardiac cells which increases the pulse rate resulting in a tachychardia.