A+P Ch. 16: Water, Electrolyte, & Acid-Base Balance

What percent of the human’s body water is inside the cells (intracellular fluid)?

Two-thirds (63%)

What percent of the human’s body water is outside the cells (extracellular fluid)?

One-third (37%)

What is the largest part of extracellular fluid?

Interstitial fluid

What is interstitial fluid?

Fluid between the cells

Where is interstitial fluid also found?

Blood plasm & lymph

What is a small amount of fluid in the extracellular fluid?

Transcellular fluid

What is transcellular fluid formed by?

Secretions of epithelial cells

What does transcellular fluid include?

Eye fluids (humors) & cerebrospinal fluid

What do body fluids differ in?

Amounts of dissolved substances, especially electrolytes

What is extracellular fluid high in?

Na+ & Cl-

What is intracellular fluid high in?

K+

What are the total amount of ions outside of the cell about equal to?

The total amount of ions inside the cells

What does the about equal amount of ions inside & outside of the cells keep same?

Amount of water in cells

What is an important homeostatic function to maintain the proper levels of?

Ions (salts)

What is the hydrostatic pressure like in capillaries at the arteriole end?

High

What does high hydrostatic pressure on the arteriole end do?

Pushes water out of the plasma

What does the plasma have high levels of?

Proteins (mostly albumin)

What does the plasma with high levels of proteins create?

High osmotic pressure

Where does water come back into the plasma?

Venous end

Where is some water lost?

At the capillaries

What collects this lost water & returns it to the blood?

Lymph vessels

What are the body’s means of gaining water?

Drinking fluids, food, & metabolism (aerobic respiration)

What are the body’s ways of losing water?

Sweat, feces, across skin & lungs, & urine

What do homeostatic processes keep balanced?

Water input & output

What is water balance regulated by?

Central nervous system & kidneys

What is water balance coordinated with?

Salt balance & maintenance of blood pressure

What does higher body water increase?

Blood pressure

What does lower body water decrease?

Blood pressure

How does the hypothalamus measure body water?

By measuring osmotic pressure

What does high osmotic pressure mean?

Low body water

What direction can the hypothalamus regulate water output?

Either

What does the hypothalamus alter the level of to regulate the water output?

ADH

What is ADH secreted by?

Posterior pituitary gland

What happens when ADH is increased?

Water will be retained & urine will be concentrated

What happens when ADH is decreased?

Water will be lost & urine will be dilute

What happens when osmotic pressure rises?

Cells shrink

What happens when ECF osmotic pressure falls?

Cells swell

What is the term used for an accumulation of water in the tissues?

Edema

What causes edema?

Low plasma proteins, blocked lymph vessels, leaky veins, & inflammation

What is one example of blocked lymph vessels that keeps water from being returned to blood?

Elephantiasis (caused by parasitic worm)

What balances are also regulated?

Electrolyte

What is one way that sodium ions are regulated?

Renin-angiotensin system

What causes renin production by JG cells?

Low blood pressure or high filtrate osmolarity

What does the renin production eventually lead to?

Angiotensin II production & aldosterone released by adrenal cortex

What does aldosterone cause in the renal tubules?

Increase reabsorption (conversation) of Na+ ions & release (loss) of potassium ions (K+)

What can high K+ in the blood act directly on?

Adrenal cortex

What does aldosterone result in?

Increased water retention & blood pressure

What ion is under tight regulation in the plasma?

Calcium (Ca++)

Where is Ca++ stored?

Bone

What is the main control of Ca++ levels in the plasma by?

Parathyroid hormones (PTH)

Where does PTH cause reabsorption of Ca++?

Bone & kidney tubules

What does PTH cause production of?

Active form of vitamin D (calcitriol)

What does calcitriol helps absorb from the intestines?

Ca++

Where are most of the hydrogen ions from?

Metabolic processes

What does aerobic respiration form?

Carbonic acid

What does anaerobic respiration form?

Lactic acid

What does the breakdown of fats yield?

Ketone bodies

What are substances that stabilize pH of a solution?

Buffers

What helps minimize pH changes to body fluids?

Buffers

What are the three major buffering systems?

Bicarbonate system, phosphate system, & protein system

What together keeps the pH in balance?

The three major buffering systems

What in the blood causes the addition of H+ ions to the plasma?

CO₂

What is constantly being acidified?

Blood

How does the body remove CO₂?

Respiratory systemW

What do receptors in the brainstem measure?

H+ of the fluids in the brain

What do the receptors trigger when H+ is too high?

Increased breathing rate & depth, which leads to more CO₂ being excreted

What do high protein diets cause?

H+ production

What can increase tubular secretion of H+?

Kidneys

What is the pH’s narrow range in the plasma?

7.35-7.45

What is low plasma pH called?

Acidosis

What is high plasma pH called?

Alkalosis

What is a lowering of plasma pH due to breathing issues (low rate & depth of breathing)?

Respiratory acidosis

What is a lowering of plasma pH due to a metabolic issue?

Metabolic acidosis

What are the two common causes for metabolic acidosis?

Kidney failure & diabetes mellitus

What digestive issues can also cause acidosis?

Diarrhea & vomiting

What results from hyperventilation?

Respiratory alkalosis

What happens when factors other than breathing result in higher plasma pH, such as vomiting?

Metabolic alkalosis

What can raise plasma pH?

Antacids