Water & The Major Minerals

Chapter 12

Water & the Body Fluids

• Water – Makes up 60% (3/5) of adult’s body weight.• Higher for children

– Makes up 75% (3/4) of lean muscle.• 25% (1/4) of fat

– Males have more water (more lean muscle)• Females, the elderly, obese have less

Water & the Body Fluids

• Water in body fluids:– Carries nutrients & waste products through the body.– Maintains structure of large molecules.– Participates in metabolic reactions.– Serves as a solvent so substances can participate in

metabolic reactions.– Acts as a lubricant & cushion around joints, inside eyes,

in the spinal cord, & as amniotic sac during pregnancy.– Aids in regulation of body temperature.– Maintains blood volume.

Water Balance & Recommended Intakes

• Fluid inside cell – Intracellular fluid

• Fluid outside cell– Extracellular fluid

• Interstitial fluid– Fluid surrounding cells

• Composition between the two differs.

• Composition in each remains constant under normal conditions.

Water Balance & Recommended Intakes

• Water intake– Influenced by thirst & satiety

Sensed by hypothalamus & nerves.

Water Balance

– Dehydration : loss of water & loss not replaced.• Symptoms:

– Water intoxication (rare) : excessive water consumption, may result due to a kidney disorder which reduces the amount of urine produced.• Symptoms

• Hyponatremia

Water Balance

Water Balance

• Water Sources– Nearly all foods contain

water – Water is produced

during cellular respiration & during condensation reactions.

Water Balances

• Water losses– Body must excrete a

minimum of 500 mL (~ 2 cups) of urine a day.• Reason

– Water is also lost• As sweat• From lungs as vapor• In feces

– Average daily losses

Water Balance

• Water Recommendations– Water needs vary depending on diet, environmental

conditions, activity, & humidity.– Sometimes expressed in proportion to amount of

energy expended under average environmental conditions.• For a person that expends 2000 kcal a day, the amount is 2 –

3 L (8 – 12 cups).– Agrees with AI for total amount set by DRI.

• If physically active or a hot day, a person will probably need more.

Water Balance

• Water Recommendations (continued)– Any beverage can meet fluid needs.• Caffeinated beverages

– Caffeine acts as a diuretic.» Causes more water to be lost.

– People can consume it to meet daily fluid needs, however.

• Alcohol– Acts as a diuretic.– Should not be used to meet daily fluid needs.

Water Balance

• Health Effects of Water– Protection against

– Hard or Soft Water makes a difference

Water Balance

• Bottled water – people may think its better & safer.– Not necessarily true in US.

• Distilled water– Has all minerals removed.

• Natural water– Comes from spring or well– Mineral content may not be changed.

• Mineral water– Comes from spring or well– Contains more minerals.

• Minerals give it unique taste.

– Usually has higher sodium content.

Blood Volume & Blood Pressure

• Kidneys are major control for homeostasis of body fluids.– Kidneys regulate blood volume which influences

blood pressure.– Kidneys reabsorb needed substances.– Kidneys excrete metabolic wastes with some

water.

Nephron (p. 387)

Blood Volume & Blood Pressure

• ADH (antidiuretic hormone)– Released

– Action

Blood Volume Regulation (p. 388)

Blood Volume & Blood Pressure

• Renin

• Angiotensin

• Aldosterone

Fluid & Electrolyte Balance

• Dissociation of Salt in Water– Mineral salts dissociates (separates) into ions

when dissolved in water.• Ions -

– Positive ions called cations.– Negative ions called anions.

• Electrolytes – salts that dissolve in water & dissociate into ions.• conduct electrical currents.

Fluid & Electrolyte Balance

• Dissociation of Salt in Water (continued)– Electrolyte

• Balance

• Major extracellular ions

• Major intracellular ions

Fluid & Electrolyte Balance

• Electrolytes attract water– Water has net charge of

zero.– Water is polar molecule

• Hydrogen

• Oxygen

Fluid & Electrolyte Balance

• Water Follows Electrolytes– Water moves across cell membranes when

electrolytes move across.– Osmosis

– Osmotic pressure

Osmosis (p. 391)

Fluid & Electrolyte Balance

• Proteins Regulate Flow of Fluids & Ions– Sodium –Potassium Pump (protein)• Regulates

• Regulation of Fluid & Electrolyte Balance– GI tract & Kidneys regulate• GI tract

• Kidneys

Fluid & Electrolyte Imbalances

• Different Solutes Lost by Different Routes– Solutes lost due to vomiting, sweating, bleeding or

diarrhea• Sodium and chloride

– Adrenal gland tumor• Oversecretion of aldosterone• Kidneys may excrete too much potassim.

– Uncontrolled diabetes• Excretion of glucose

Fluid & Electrolyte Imbalances

• Replacing Lost Fluids & Electrolytes– Normal replacement of lost fluids• Drink water

– Severe cases• ORT (oral rehydration therapy)

Acid – Base Balance

• Ions also regulate acidity of fluids.• pH of body (7.35- 7.45) must be maintained

otherwise life threatening situations result.– Examples

• Acidity is determine by H+

• 3 system defend against pH fluctuations

Acid-Base Balance

• Systems to prevent pH fluctuations– 1. Regulations by Buffers

– 2. Regulation in the Lungs• Raising & slowing

respiration rate

– 3.Regulation in Kidneys• Reabsorb or excreting

bicarbonate.

The Minerals - Overview

• Inorganic– Retain chemical identity– Remain in body until excreted– Can’t be changed into anything else– Can’t be destroyed by heat, air, acid, or mixing.

• Body’s Handling of Minerals

The Minerals - Overview

• Variable Bioavailability– Binders• Found in some foods.

– Prevent mineral absorption» Phytates» Oxalates

Sodium

• Sodium Roles in body– Maintains normal fluid electrolyte balance– Assists in nerve impulse conduction– Assists in muscle contraction

• Sodium & Hypertension

Sodium

• Sodium & Bone Loss– Calcium excretion increased with high salt intake.

– See in summary: p. 397

Chloride

• Chloride Roles in Body– Maintains normal fluid & electrolyte balance.– Part of HCL – Necessary for proper digestion

Potassium

• Potassium Roles in Body– Maintains normal fluid & electrolyte balance.– Assists in may reactions.– Supports cell integrity– Assists in nerve impulse conduction.– Aids in muscle contraction.

• Potassium & Hypertension

Calcium

• Calcium Roles in Body– Mineralization of bones & teeth.– Involved in muscle contraction & relaxation.– Important in nerve functions, blood clotting, blood

pressure.

Calcium

• Calcium in bones– As bones form, calcium forms hydroxyapatite on

matrix of collagen.• As mineralization continues, bones become denser &

stronger.

– Bones constantly remodeled.• Bones gain & lose minerals • Children gain more than they lose.

– Teeth • Formed in similar pattern, but they are not bone.• Fluoride hardens & stabilizes the crystals of teeth

Calcium

• Calcium in body fluids– Extracellular fluids• Helps maintain blood pressure

– Reason

• Also participates in blood clotting.

– Intracellular fluids• Binds to proteins and activates them

– Proteins participate in

Calcium

• Calcium & Disease Prevention– May protect against hypertension.

• Calcium & Obesity– May help maintain a healthy body weight.

Calcium

• Calcium balance– Involves hormones &

vitamin D.– 3 organs respond

whenever blood calcium levels rise or fall.• Intestines, bones, kidneys • Note figure 12 -12, p. 401

– Calcium rigor– Calcium tetany

Calcium

• Calcium absorption– Factors to enhance absorption

• Acidity of stomach keeps Ca soluble.• Vitamin D helps to make the calcium binding protein needed for

absorption.

– Factors that inhibit absorption (many that enhance also inhibit)• Lack of stomach acid• Vitamin D deficiency• High phosphorus intake• Phytates• Oxalates

Calcium

• Calcium in Milk– Calcium most abundant in milk– Consequences of drinking too little milk.

• Calcium in other foods– Tofu– Almonds– Broccoli

Calcium

• Calcium Deficiency– Stunted growth in children– Osteoporosis in adults

• Toxicity Symptoms– Constipation– Risk of kidney stones– Interference with absorption of other minerals.

Phosphorus

• Phosphorus Roles in Body– Mineralization of bones & teeth– Part of every cell– Important in genetic material– Part of phospholipids– Used in energy transfer & in buffer systems

• Phosphorus Deficiency– Muscular weaaakness– Bone pain

Magnesium

• Roles in Body– Bone mineralizaiton– Building of proteins– Enyme action– Muscular contraction– Nerve impulse conduction

• Deficiency– Weakness– confusion

Sulfate

• Part of proteins• Stabilizes protein shape– Disulfide bridges