Ch. 27: Fluid, Electrolytes, Acid Homeostasis Flashcards
What are osmoreceptors and their function?
-osmoreceptors are specialised cells in the hypothalamus
-respond to changes in extracellular tonicity (ECF [Na+])
-effectively controls the distribution of water between ICF and ECF
What do baroreceptors do?
Where are high pressure baroreceptors located and inputs info via what pathway?
What do they respond to?
-provide input to the hypothalamus, mediate change by ADH secretion
-high pressure baroreceptors (located in the carotid sinus) input to the hypothalamus via adrenergic pathways
-respond to changes in mean arterial blood pressure.
What mechanisms maintain fluid balance?
Osmorecptors and baroreceptors
What is the range of normal vs dehydrated plasma osmolality?
260-280 hydrated
>290 dehydrated
Why does dehydration develop? What does water do to reach osmotic equilibrium? What happens when fluid imbalance continues?
Develops when water losses outpace water gains
Water loss from ECF increases osmotic concentration in ECF
Water moves from ICF to ECF to reach osmotic equilibrium
If fluid imbalance continues, loss of water from ICF produces severe thirst, dryness, wrinkling of skin
What disorder can dehydration lead to and describe what the disorder is
Hypovolemia: a state of low extracellular fluid volume, generally secondary to combined sodium and water loss
What is hypovolemia shock? What are symptoms?
The most severe form of hypovolemia, characterized by tachycardia, cold, clammy extremities, cyanosis, low urine output (less than 15 ml/hr)
What treatment does hypovolemia shock need?
Rapid treatment with isotonic fluid boluses and assessment and treatment
What are symptoms of different percentages of lost body weight of dehydration? (3)
1-2%: dry and sticky mouth, thirst, fatigue
3-4%: dry mouth, impaired physical performance, reduction in urine
5-6%: difficulty in concentrating, headache
What are the pounds needed to be lost to determine whether someone is severely, moderately, or mildly dehydrated?
mild: A woman who weighs 120 lost 5 lbs
moderate: A man who weighs 90 lost 15 lbs
severe: A woman who weighs 140 lost 20 lbs
What is hypervolemia vs hypovolemia?
Hypervolemia: excess fluid volume
Hypovolemia: decreased fluid volume
Does hypervolemia and hypovolemia inhibit or stimulate?
Hypervolemia: inhibits
Hypovolemia: stimulates
What does hypervolemia inhibit or stimulate ? What does it contribute to?
Inhibits
ADH release
Aldosterone
Thirst
Contributes to: increased urination of dilute urine
What does hypovolemia stimulate or inhibit? What does it contribute to?
Stimulates
Thirst
ADH release
Aldosterone
Contributes to: decreased urination of concentrated urine
What causes the cells of the body to shrink or swell and what does not cause it to shrink or swell.
-Changes in osmolarity of the ECF (as with dehydration/over hydration) can cause the cells of the body to shrink
-When ECF is isotonic to cells of the body, they do not shrink or swell.
What is osmolarity? Which type of solutions have low osmolarity or high osmolarity?
Osmolarity describes the total solute concentration of a solution
-Solutions with a low solute concentration have a low osmolarity
-Those with a high osmolarity have a high solute concentration.
What is intracellular fluid, extracellular fluid, and interstitial fluid? What do they include?
Intracellular fluid: The liquid found inside cells (ICF is 2/3 of fluid, cytosol)
Interstitial fluid: A solution that surrounds the cells also called tissue fluid (lymph plasma, CSF, aqueous humor)
Extracellular fluid: all body fluid outside of cells (ISF, blood plasma, CSF, lymph, aqueous humor)
Is water percentage higher in females or males and their percentage?
Water is higher in males (60%) and female are (50%)
What are some examples of electrolytes that are cations and anions and non electrolytes?
Cations (+): sodium, potassium, calcium, magnesium
Anions (-): chloride, bicarbonate , phosphate, sulfate
Non-electrolyte: glucose, urea, dextrose
Water moves from which osmolarity to which?
Water moves from the side of the membrane with lower osmolarity (more water) to the side with higher osmolarity (less water).
What is hypotonic solution?
ECF has a lower osmolarity than the fluid inside the cell; water enters the cell.
What is hypertonic solution?
ECF has a higher osmolarity than the fluid inside the cell; water leaves the cell.
What is isotonic solution?
ECF has the same osmolarity as the cell; there will be no net movement of water into or out of the cell.
What is osmosis?
The movement of water molecules from high water concentration to a lower water concentration through a cell’s partially permeable membrane.
What is diffusion?
Tendency of solutes to move freely from areas of high to low concentration (down hill)
What is active transport?
Requires energy to move ions or molecules across cell membrane into a region of higher concentration
What is filtration?
Passage of fluid through a permeable membrane. Movement is from high to low pressure
What stimulates the desire to drink fluids? What is the effect?
-Thirst center in hypothalamus
-Effect: water is gained if thirst is quenced
What is the mechanism of ADH in its role? What is the effect?
Antidiuretic hormone binds to receptors on cells in the collecting ducts of the kidney and promotes reabsorption of water back into the circulation by stimulating insertion of “water channels” or aquaporins into the membranes of kidney tubules.
-Reduces water loss in urine
What is the mechanism of aldosterone? What are its effects?
-It promotes urinary reabsorption of Na, increases water reabsorption via osmosis
-Reduces loss of water in urine
What is the mechanism of atrial natriuretic peptide? What are the effects?
Promotes natriuresis, elevated urinary excretion of Na, accompanied by water
-Increases loss of water in urine
What is dilutional hyponatremia? What can it cause?
It is water intoxication, a potentially life-threatening condition which occurs when a person consumes too much water without an adequate intake of electrolytes.
-It can cause cells to swell dangerously
Name the disorder based on the symptoms
A woman drinks up to 2 gallons of water every day, causing dilution and water intoxication. Her serum sodium (sNa) dropped below normal - which is 135-145 milliequivalents per liter (mEq/L). Patients may develop significant symptoms and even coma, when sNa drops below 125 mEq/L.
Psychogenic polydipsia
What is the difference between pitting edema and nonpitting edema?
Pitting edema: fluid accumulates is GREATER than fluid absorption
Nonpitting edema: fluid accumulation rate is EQUAL to rate of absorption in interstitial fluid
What are the indentation criteria for pitting edema levels?
What is lymphedema? What are some causes of obstruction?
Edema (swelling) due to impaired lymph flow
-Causes: malignant involvement of lymph structures, removal of lymph node, infection of lymph nodes (lymphangitis)
What forms when electrolytes dissolve and dissociate?
ions
What are the 4 general functions of electrolytes?
- Controls osmosis of water between body fluid compartments
- Help maintain the acid-base balance
- Carry electrical current [GP/AP] and controls secretion of some
*Hormones and neurotransmitters - Serve as cofactors, needed for optimal activity of enzymes
What cations and anions are ECF and ICF abundant in?
ECF: most abundant cation is Na+, anion is Cl-
ICF: most abundant cation is K+, anion are proteins and phosphates (HPO4 2-)
What do Na/K pumps play a major role in? It keeps what inside/outside cell?
Keeps K+ high inside cells
Na+ high outside cell
What is mEq? What is mEq / liter?
Milliequivalent: used to measure the number of electrical charges (electrolytes) in blood serum and other solutions
mEq/liter: Gives the concentration of anions/cations in a given volume of solution
Discuss what hyponatremia is and the following criteria
Causes, mEq/L level, signs/symptoms
-Decreased sodium intake; increased sodium loss through vomiting, diarrhea, aldosterone deficiency, or taking certain diuretics; and
excessive water intake
-mEq/L: <136
-Symptoms: Muscular weakness; dizziness, headache, and hypotension; tachycardia;
mental confusion, and coma.
Discuss what hypernatremia is and the following criteria
Causes, mEq/L level, signs/symptoms
-Dehydration, excessive sodium in diet or intravenous fluids;
causes hypertonicity of ECF, which pulls water out of body cells into ECF —> cellular dehydration.
-(>145 mEq/L)
-Symptoms: Intense thirst, hypertension,
edema, agitation, convulsions.
Discuss what hypochloremia is and the following criteria
Causes, mEq/L, and symptoms
-Caused by low level of chloride in blood; excessive vomiting, overhydration,
aldosterone deficiency, congestive heart failure, and therapy with certain diuretics such as furosemide (Lasix®).
-mEq/L: <95
-Symptoms: Muscle spasms, metabolic alkalosis, shallow respirations, hypotension, and tetany.
Discuss what hyperchloremia is and the following criteria
Causes, mEq/L, and symptoms
-Dehydration due to excessive chloride intake; severe renal failure, hyper aldosteronism, certain types of acidosis
mEq/L: >107
Symptoms: Lethargy, weakness, metabolic acidosis, and rapid, deep breathing.
Discuss what hypokalemia is and the following criteria
Causes, mEq/L, and symptoms
-Caused by excessive fluid loss due to
vomiting or diarrhea, decreased potassium intake, hyperaldosteronism, kidney disease, and therapy with some diuretics.
-mEq/L: <3.0
-Symptoms: Muscle fatigue, flaccid paralysis,
mental confusion, increased urine output, shallow respirations, changes in ECG, including
flattening of T wave
Discuss what hyperkalemia is and the following criteria
Causes, mEq/L, and symptoms
Caused by excessive potassium intake,
renal failure, aldosterone deficiency, transfusion of hemolyzed blood.
mEq/L: >5
Symptoms: Irritability, nausea, vomiting, diarrhea, muscular weakness; can cause death by inducing ventricular fibrillation.
Discuss what hypocalcemia is and the following criteria
Causes and symptoms
mEq/L: 4.5-5.5
Caused by increased calcium loss,
reduced calcium intake, or hypoparathyroidism.
Symptoms: Numbness and tingling of
fingers; hyperactive reflexes, muscle cramps, tetany, and convulsions; bone fractures; spasms of laryngeal muscles that can cause death by asphyxiation
Discuss what hypercalcemia is and the following criteria
Causes and symptoms
mEq/L: 4.5-5.5
Caused by hyperparathyroidism, excessive intake of vitamin D
Symptoms: Lethargy, weakness, nausea, vomiting, polyuria, bone pain, depression,confusion, coma.
Discuss what hypophosphatemia is and the following criteria
Causes and symptoms
mEq/L: 1.7-2.6
Caused by increased urinary losses,
decreased intestinal absorption, increased utilization.
Symptoms: Confusion, seizures, coma,
chest and muscle pain, numbness and tingling of fingers, decreased coordination, memory loss, and lethargy
Discuss what hyperphosphatemia is and the following criteria
Causes and symptoms
mEq/L: 1.7-2.6
Caused by kidney’s failure to excrete excess phosphate (renal failure) increased intake of phosphates destruction of body cells, which
releases phosphates into blood.
Symptoms: Anorexia, nausea, vomiting,
muscular weakness, hyperactive reflexes,
tetany, and tachycardia.
Discuss what hypomagnesemia is and the following criteria
Causes and symptoms
mEq/L: 1.3 - 2.1
Caused by inadequate intake or excessive loss in urine or feces; alcoholism, malnutrition,
diabetes mellitus, and diuretic therapy.
Symptoms: Weakness, irritability, tetany,
delirium, convulsions, confusion, vomiting,
Cardiac arrhythmias.
Discuss what hypermagnesemia is and the following criteria
Causes and symptoms
mEq/L: 1.3 - 2.1
Caused by renal failure or due to increased
intake of Mg2+, such as Mg2+- containing antacids; aldosterone deficiency and hypothyroidism.
Symptoms: Hypotension, muscular weakness or paralysis, nausea, vomiting, and altered mental functioning.
What is acid base balance?
when H+ production = H+ loss and pH of body fluids are within normal limits
What do buffer systems do?
Buffer systems temporarily store H+ and provide short-term pH stability (7.35 and 7.45)
pH value higher than 7.8 or lower than 6.8 can lead to death.
Why is the phosphate buffer system important?
Because the concentration of phosphates is highest in intracellular fluid, the phosphate buffer system is an important regulator of pH in the cytosol.
What is the protein buffer system? What is it abundant in and what 2 proteins are important?
It maintains acidity in and around the cells. The most abundant in intracellular fluid and blood plasma. When pH rises, the COOH group dissociates to act like an acid.
What do amino acids contain?
What is respiratory acidosis and the symptoms/diseases associated with it?
Respiratory acidosis is the most common cause of acid-base imbalance (high levels of CO2 in blood)
◦ A person breathes shallowly, or gas exchange is hampered by diseases (pneumonia, cystic fibrosis, or emphysema); brain tumor
What is respiratory alkalosis?
Respiratory alkalosis (low level of CO2 in blood) is a common result of hyperventilation (anxiety, fever, hypoxia congestive heart failure)
newborn’s total body mass is about….
an adult’s total body mass is about…
A newborn’s total body mass is about 75% water (and can be as high as 90% in a premature infant);
An adult’s total body mass is about 55–60% water
Given that the rate of fluid intake and output is about… times higher in infants than in adults, the slightest
changes in …. can result in severe abnormalities.
Given that the rate of fluid intake and output is about seven times higher in infants than in adults, the slightest changes in fluid balance can result in severe abnormalities.
Compare the metabolic rate of infants to adults and its significance in production of metabolic waste.
Metabolic rate of infants is about double that of adults. This results in the production of more metabolic wastes and acids, which can lead to the development of acidosis in infants.
Compare infant kidneys to adult kidneys and its significance in concentrating urine. How does functional development play a role?
Infant kidneys are only about half as efficient in concentrating urine as those of adults. (Functional development is not complete until close to the end of the first month after birth.) As a result, the kidneys of newborns can neither concentrate urine nor rid the body of excess acids as effectively as those of adults
Compare the ratio of body surface area of infants to adults and how that affects water loss
The ratio of body surface area to body volume of infants is about 3X greater than that of adults. Water loss through the skin is significantly higher in infants than in adults.
Compare the breathing rate of infants to adults and its significance in respiratory alkalosis
The higher breathing rate of infants (about 30 to 80 times a minute) causes greater water loss from the lungs.
Respiratory alkalosis may occur because greater ventilation eliminates more CO2
