Interactive Summaries

Chapter 12: Water and Major Minerals

Water: The Essential Ingredient for Life

Overall, water makes up of your weight. Leaner people have proportionality water because muscle tissue is water by weight, while adipose tissue is water. Water in your body contains numerous dissolved minerals called electrolytes. The body maintains its electrolyte balance through the intake and excretion of water and the movement of ions. Positively charged ions are known as . One of the main positively charged ions is . Negatively charged ions are known as . One of the main negatively charged ions is . About of body water is in the intracellular fluid and is in extracellular fluid. The major components of extracellular fluid are interstitial fluid and . To maintain the balance of sodium and potassium, all cell membranes incorporate sodium-potassium pumps that actively pump sodium out of the cell while allowing potassium back in. If solutes are more concentrated on one side of a semipermeable membrane than the other then .


People who eat foods high in potassium may find it helps to . The highest amounts of potassium can be found in the intercellular fluid within . Central nervous system potassium levels must remain constant even in the face of falling levels in the muscles and blood. Although food manufacturers often add to processed foods, they do not routinely add potassium. If a person's diet is rich in that substance they may not meet the minimum potassium recommendations. A balanced, healthy diet supplies between milligrams of potassium per day. Hypokalemia (low blood potassium) results from potassium depletion most commonly caused by . A person with is most at risk for potassium deficiency. Others at risk are athletes and people doing physical labor in high temperatures because they have high water losses due to excessive sweating. Symptoms include muscle weakness, loss of appetite, and confusion. Excess potassium can slow and eventually stop the heart.


Our bodies contain more calcium than any other mineral, about of our total body weight. Ninety-nine percent of calcium is contained in . Bone is made of cells and an extracellular matrix. Two types of cells continually remodel our bones by building them up and tearing them down. first secrete the collagen protein matrix that forms the initial framework for new bone. break down bone simultaneously releasing calcium and phosphate, which enter the bloodstream. It is thought that we achieve peak bone mass around age . But our bones change in response to our activities. Elderly individuals can strengthen and rebuild their bones by performing exercise.

Calcium is a key factor in normal transmission of nerve impulses. The movement of calcium into nerve cells triggers the release of at the junction between nerves. Blood cannot without calcium. Calcium levels rarely fall low enough to significantly impair this function of blood.

The three hormones that regulate calcium levels in the blood are calcitriol, calcitonin and . Inadequate calcium intakes, high sodium intakes, excess caffeine intake, and other diurectics can affect calcium balance by increasing . A person could have hypocalcemia if they experience . A person could have hypercalcemia if they suffer from .

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