Chapter 26 - Fluid, Electrolyte, and Acid-Base Balance.

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What is the body water content of Infants?

73% or more water (low body fat, low bone mass).

What is the body water content of adult males?

~60% water.

What is the body water content of females?

~50% water (higher fat content, less skeletal muscle mass).

What does water content decline too in old age?

~45%.

What do each fluid compartment have?

A distinctine pattern of electrolytes.

What are the distinctive pattern of electrolytes in ECF?

Major Cation: Na+, Major anion: Cl- (chloride).

What are the distinctive pattern of electrolytes in ICF?

Low Na+ and Cl-. Major Cation: K+, Major anion: HPO42- (hydrogen phosphate).

What in extra- and intracellular fluids are nearly opposites?

Sodium and potassium concentrations.

Why are sodium and potassium nealry opposite in ECF and ICF?

Reflects the activity of cellular ATP- dependent sodium -potassium pumps.

What is the driving force for water intake?

Thirst.

What are the hypothalamic thirst center osmoreceptors stimulated by?

Declined plasma osmolality of 2 - 3%, Angiotension II or Baroreceptor input, Dry Mouth, Substantial decrease in blood volume or pressure.

What creates inhibition of thirst center?

Drinking water.

What are the inhibitory feedback signals of water intake?

Relief of dry mouth, activation of stomach and intestinal stretch receptors.

What is Obligatory water losses?

Insensible water loss from lungs and skin, feces, and minimum daily sensible water loss of 500 ml in urine to excrete wastes.

What is water reabsorption in collection ducts proportional too?

ADH release.

What does decreased ADH lead too?

Dilute urine and decrease volume of body fluids.

What does increased ADH lead too?

Concentrated urine.

What do Hypothalamic osmoreceptors trigger or inhibit?

ADH release.

What other facts may trigger ADH release via large changes in blood volume or pressure?

Fever, sweating, vomiting, dirrhea, blood loss, and traumatic burns.

What is a Negative Fluid Balance: Dehydration?

ECF water loss due to hemmorrpahge severe burns, prologned vomiting or diarrhea, profuse sweating, water deprivation, diurectic abuse.

What are the signs and symptoms of Dehydration?

Thirst, dry flushed skin, oliguria (decreased production of urine).

What can dehydration lead too?

Weight loss, fever, mental confusion, hypovolemic shock, and loss of electrolytes.

What is Hypotonic Hydration?

Cellular overhydration, or water intoxication.

When does Hypotonic Hydration occur?

With renal insufficiency or rapid water ingestion.

What happens if the ECF is diluted?

Hyponatremia (no enough sodium in the body fluids outside the cells).

What does Hyponatremia lead too?

Net osmosis into tissue cells.

What does net osmosis into tissue cells lead too?

Swelling of cells.

What does swelling of cells lead too?

Severe metabolic disturbancea such as nausea, vomiting, muscular cramping, cerebral edema - possible death.

What is Edema?

Atypical accumulation of IF fluid - tissue swelling.

What is Edema due too?

Anything that increases flow of fluids out of the blood or hinders its return - high blood pressure, capillary permeability (usually due to inflammatory chemicals), incompletant venous valves, localized blood vessel blockage, congestive heart failure, hypertension, high blood volume.

What does Edema result from?

Protein malnutrition, liver disease, or glomerulonephritis.

What does hindered fluid return occur with in Edema?

An imbalance in colloid osmotic pressures - hypoporteinemia (decreased plasma proteins).

How can blocked (or surgically removed) lymph vessesl result in Edema?

Cause leaked proteins to accumulate in IF, increased colloid osmotic pressure of IF draws fluid from the blood, results in low blood pressure and severly imparied circulation.

What are Electroylytes?

Salts, acids and bases.

What does Electrolyte balance usually refer too?

Only salt balance.

What are salts important for?

Neuromuscular excitability, secretory activity, membrane permeability, controlling fluid movements.

What do sodium salts account for in solutes of the ECF?

90 - 95%.

What is the single most abundant cation in ECF?

Sodium.

What is the only cation exerting significant osmotic pressure?

Sodium.

How is Na+ moved?

Pumped out against its electrochemical gradiant and leaks into cells.

How is Na+ reabsorbed?

65% in proximal tubules, 25% is reclaimed in loops of henle.

What does Aldosterone do?

Active reabsorption of remaining Na+.

What follows Na+ if ADH is present?

Water.

What is the main trigger for aldosterone release?

Renin-angiotensin.

What secretes renin-angiotensin?

JGA (Justaglomerular apparatus).

What does JGA secrete Renin in response too?

Sympathetic nervous system stimulation - decreased filtrate osmolality, decrease stretch due to low blood pressure.

What does renin do to angiotensin II?

Catalyzes it, which prompts aldosterone release from the adrenal cortex.

What can also trigger the release of Aldosterone?

Elevated K+ levels in the ECF.

How long does it take for Aldosterone to take effect?

Slowly - hours to days.

What is ANP released by?

Atrial cells in response to stretch and high blood pressure.

What are the effects of ANP?

Decreases blood pressure and blood volume. Decreases ADH, Renin and Aldosterone production. Increases excretion of Na+ and water. Promotes vasodilation directly and also by decreasing production of angitensin II.

What is Calcium ion Ca2+ in ECF important for?

Neuromuscular excitability, blood clotting, cell membrane permeability, secretory activities.

What is Hypocalcemia?

Increased excitability and muscle tetany.

What is Hypercalcermia?

Inhibits neurons and muscle cells, may cause heart arrhythmias.

What is Calcium balance controlled by?

Parathyroid hormone (PTH) and calcitonin.

How does PTH promote increase in calcium level?

Targets Bones, Small Intestine, and Kidneys.

What does PTH do to bones?

Activates osetoclases to break down bone matrix.

What does PTH do to Small Intestines?

Enhances intestinal absorption of calcium (indirect through vitamin D).

What does PTH do to Kidneys?

Enhances calcium reabsorption and decreases phosphate reabsorption.

What does Calcium reabsorption go hand in hand with?

Phosphate excretion.

What inhibits PTH secretion?

High or normal ECF calcium levels.

What does inhibited PTH secretion result in?

Release of calcium from bone is inhibited, larger amounts of calcium are lost in feces are urine, more phosphate is retained.

What does pH affect?

All functional proteins and biochemical reactions.

What is the normal pH of Arterial Blood?

7.4.

What is the normal pH of Venous Blood and Iterstitial fluid?

7.35.

What is the normal pH of ICF?

7.0.

What is the pH in Alkolosis or Alalemia?

Arterial blood pH > 7.45.

What is the pH in Acidosis or Acidemia (physiological acidosis)?

Arterial pH < 7.35.

What is H+ produced by?

Metabolism. - Phosphoric acid from breakdown of phosphorous containing proteins, lactic acid from anaerobic respiration of glucose, fatty acids and ketone bodies from fat metabolism, H+ liberated with C02 is converted to HC03 in blood.

What is the concentration of hydrogen ions regulated by?

Chemical buffer systems, respiratory centers, and renal mechanisms.

What is the Chemical Buffer Systems?

Rapid; first line of defense.

What is the Respiratory centers (brain stem)?

Act within 1 - 3 min.

What is the Renal Mechanism?

Most potent, but requires hours to days to effect pH changes.

What do Strong acids do to pH?

Dissociate completely in water; dramatically affects.

What do Weak Acids do to pH?

Dissociate partially in water; are efficient are prevent changes.

What do Strong Bases do to pH?

Dissociate easily in water; quickly tie up H+.

What do Weak bases do to pH?

Accept H+ more slowly.

What is a Chemical Buffer?

System of one or more compounds that act to resist pH changes when strong acid or base is added.

What is Bicarbonate Buffer System?

Mixture of H2C03 (weak acid) [carbonic acid] and salts of HC03- (e.g., NaHC03, a weak base) [sodium bicarbonate]. Buffers ICF and ECF.

What is the only important ECF buffer?

Bicarbonate Buffer.

What happens to bicarbonate buffer system if a strong acid is added?

Bicarbonate ties up Hydrogen and froms carbonic acid. pH of solution decerases only slightly.

What happens if a strong base is added to Bicarbonate buffer system?

Causes Carbonic Acid to dissociate and donate Hydrogen, pH of the solution rises only slightly.

What is the Phosphate Buffer System?

Nearly identical to Bicarbonate buffer.

What are the components of Phosphate Buffer System?

Sodium salts of Dihydrogen phosphate (H2P04-) [weak acid], Monohydrogen phosphate (HP042-) [weak base].

What is an effective buffer in urine and ICF where phosphate concentrations are high?

Phosphate Buffer System.

What are the most plentiful and powerful buffers?

Intracellular proteins.

What are protein molecules?

Amphorteric (can function as both a weak acid and a weak base).

What happens when pH rises?

Organic acid of Carboxyl groups (COOH) [weak acids] release H+.

What happens with pH falls?

Amino groups (NH2) [weak bases] bind H+.

What do Lungs eliminate?

Volatile carbonic acid by eliminating C02.

What do Kidneys eliminate?

Other fixed metabolic acids (phosphoric, uric, lactic acids, and ketones) and prevent metabolic acidosis.

What are the ultimate acid-base regulatory organs?

The Kidneys.

What are the most important renal mechanisms?

Conserving (reabsoring) or generating new HC03-, Excreting HC03-.

What is generating or reabsoring one HC03- the same as?

Losing one H+.

What is excreting one HC03- the same as?

Gaining one H+.

What is Respiratory Acidosis?

Most common cause of acid-base imbalance. Occurs when a person breathes shallowly, or gas exchange is hampered by diseases such as pneumonia, cystic fibrosis, or emphysema. - HYPOVENTILATION.

What is Respiratory Alkalosis?

Hyperventiation! Can occur from stress, anxiety, panic attack, bleeding, heart or lung disorder, infection.

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