16.10: Potassium
- Page ID
- 58184
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Potassium shares many functions with sodium and chloride, except potassium predominates in intracellular fluid, whereas sodium and chloride predominate in extracellular fluid. Potassium thus regulates the amount of fluid within cells, and also participates in cell metabolism. Potassium is particularly noted for its role in conducting electrical impulses—especially in the heart. Either a deficiency or an excess of potassium can disturb the rhythm of the heart beat.
Figure 16-9: Electrolytes sodium and chloride are in fluids outside of cells; potassium is in fluids within cells.
Potassium is an essential part of all living cells—both animal and plant. Since potassium is found in the intracellular water, more water in the cell (as when there’s less fat in the cell) means more potassium. So it is that lean cuts of meat contain more potassium than fatty cuts. Fruits and vegetables are also especially rich in potassium.
Although a high sodium intake is seen as the main culprit in salt-sensitive high blood pressure, a diet rich in potassium is thought to have a protective effect. It may be a matter of combination: a low potassium diet (one sparse in fruits and vegetables) is often a high-salt diet.
Like sodium and chloride, potassium is readily absorbed from the intestine, and its main route of excretion is the urine. Potassium deficiencies great enough to cause symptoms are unusual. Deficiency symptoms include loss of appetite, weakness, nervous disorders, and heartbeat irregularities.
The usual cause of a deficiency is excessive potassium losses, either through the digestive tract (as in cases of prolonged diarrhea or vomiting, or laxative abuse) or through the urine (due to the prolonged use of diuretics, or some kidney diseases). Those with bulimia, the eating disorder characterized by a continual cycle of binge eating followed by induced vomiting (discussed in Chap. 3), can be at particular risk when both laxatives and diuretics are abused.
As is the case with the other electrolytes, potassium toxicity is also uncommon under ordinary conditions, since excesses are readily excreted in the urine. Kidney diseases can, however, interfere with the process. One major concern with respect to potassium toxicity is that it can cause the heart to stop beating. A potassium-rich solution is, in fact, used in lethal injections for carrying out capital punishment.