Chapter 24 Fluid, Electrolyte, and Acid-Base Balance

Normal pH values are limited to the range between

7.35-7.45

Physiological adjustments affecting fluid and electrolyte balance are mediated primarily by

ADH, aldosterone, ANP & BNP

Increasing or decreasing the rate of respiration can have a profound effect on the buffering capacity of body fluids by

lowering or raising the PCO2

Respiratory alkalosis develops when respiratory activity

lowers plasma PCO2 to below-normal levels

Chronic diarrhea causes a severe loss of bicarbonate ions resulting in

metabolic acidosis

The exchange between plasma and interstitial fluid is determined by the relationship between the

net hydrostatic and net colloid osmotic pressures

The force that tends to push water out of the plasma and into the interstitial fluid is the

net hydrostatic pressure

Secretion of aldosterone occurs in response to

a drop in plasma volume at the juxtaglomerular apparatus, a decline in filtrate osmotic concentration at the DCT, high potassium ion concentrations

In a protein buffer system, if the pH increases a carboxyl group (COOH) of an amino acid dissociates and releases

a hydrogen ion

As a result of the aging process, the ability to regulate pH through renal comensation declines due to

a reduction in the number of functional nephrons

The risk of respiratory acidosis in the elderly is increased due to

a reduction in vital capacity

When the production of hydrogen ions in your body is precisely offset by their loss, you are in

acid-base balance

The activity that occurs in the body to maintain calcium homeostasis occurs primarily in the

bone, digestive tract, kidneys

The hemoglobin buffer system helps prevent drastic alterations in pH when

the plasma PCO2 is rising or falling

The primary role of the carbonic acid-bicarbonate buffer system is in preventing pH changes caused by

the rising and falling of the plasma PCO2

Compensation for metabolic alkalosis involves

decreased pulmonary ventilation, increased loss of bicarbonates in the urine

Deviations outside of the normal pH range due to changes in hydrogen ion concentrations

disrupt the stability of cells membranes, alter protein structure, change the activities of important enzymes

Disorders that have the potential for disrupting pH balance in the body include

emphysema, renal failure, neural damage, CNS disease, heart failure, hypotension

All of the homeostatic mechanisms that monitor and adjust the composition of body fluids respond to changes in the

extracellular fluid

Sodium ions enter the ECF by crossing the digestive epithelium via

facilitated diffusion and active transport

When the amount of water you gain each day is equal to the amount you lose to the environment, you are in

fluid balance

If the ECF is hypertonic with respect to the ICF, water will move

from the cells into the ECF until osmotic equilibrium is restored

When pure water is consumed, the ECF becomes

hypotonic with respect to the ICF

Electrolyte balance primarily involves balancing the rates of absorption across the digestive tract with rates of loss at the

kidneys and swear glands

Important examples of organic acids found in the body are

lactic acid and ketone bodies

The most important factor affecting the pH in body tissues is

the PCO2

The concentration of potassium in the ECF is controlled by adjustments in the rate of active secretion

along the distal convoluted tubular and collecting system of the nephron

The rate of tubular secretion of potassium ions changes in response to

alterations in the potassium ion concentration in the ECF, changes in pH, aldosterone levels

The most common problems with electrolyte balance are caused by

an imbalance between sodium gains and losses

The most important factor affecting the pH in body tissues is

carbon dioxide concentration

The lungs contribute to pH regulation by their effects on the

carbonic acid-bicarbonate buffer system

Whenever the rate of sodium intake or output changes, there is a corresponding gain or loss of water that tends to

keep the sodium concentration constant

When a pulmonary response cannot reverse respiratory acidosis, the kidneys respond by

increasing the rate of hydrogen ion secretion into the filtrate

The body content of water or electrolytes will rise if

intake exceeds outflow

Extracellular fluids in the body consist of

interstitial fluid, blood plasma, lymph, cerebrospinal fluid, synovial fluid, serous fluids, aqueous humor, perilymph, endolymph

Nearly two-thirds of the total body water content is

intracellular fluid (ICF)

All water transport across cell membranes and epithelia occur passively, in response to

osmotic gradients and hydrostatic pressure

When water is lost but electrolytes are retained, the osmolarity of the ECF rises and osmosis then mvoes water

out of the ICF and into the ECF until isotonicity is reached

When carbon dioxide concentrations rise, additional hydrogen ions are produced and the

pH goes down

When the PCO2 increases and additional hydrogen ions and bicarbonate ions are released into the plasma, the

pH goes down, acidity rises

When an individual loses body water

plasma volume decreases and electrolyte concentrations rise

Important homeostatic adjustments occur in response to changes in

plasma volume or osmolarity

The most frequent cause of metabolic acidosis is

production of a large number of fixed or organic acids

The major causes of metabolic acidosis are

production of a large number of fixed or organic acids, impaired ability to excrete H+ at the kidneys, a severe bicarbonate loss

Atrial natriuretic peptide hormone

reduces thirst, blocks the release of ADH, blocks the release of aldosterone

The two important effects of increased release of ADH are

reduction of urinary water losses and stimulation of the thirst center

A mismatch between carbon dioxide generation in peripheral tissues and carbon dioxide excretion at the lungs is a

respiratory acid-base disorder

The condition that results when the respiratory system cannot eliminate all the carbon dioxide generated by peripheral tissues is

respiratory acidosis

Pulmonary and renal mechanisms support the buffer systems by

secreting or generating hydrogen ions, controlling the excretion of acids and bases, generating additional buffers when necessary

The renal response to acidosis is limited to

secretion of H+ and generation or reabsorption of HCO3

The principal ions in the ECF are

sodium, chloride, and bicarbonate

The principal ions in the ECF are

sodium, chloride, bicarbonate

Angiotensin II produces a coordinated elevation in the ECF volume by

stimulating thirst, causing the release of ADH, triggering the secretion of aldosterone