CH 25: Fluids and Electrolytes
Explain the conditions and stimuli that decrease fluid intake
-Increased blood volume and blood pressure -Decreased blood osmolarity -Increased salivary secretions -Distension of stomach
Compare and contrast the different types of fluid imbalances
1) Fluid balances with constant osmolarity occur when isotonic fluid is lost or gained - Volume depletion: isotonic fluid loss is greater than isotonic fluid gain (ex: severe burns, vomiting, diarrhea, or hyposecretion of aldosterone (hormone that stimulates Na+ and water reabsorption in kidney) - Volume excess: occurs when isotonic fluid gain is greater than isotonic fluid loss. Typically results when fluid intake is normal, but there is decreased fluid loss through kidneys 2) Fluid imbalance with changes in osmolarity: - Dehydration: water loss that is greater than solute loss (Ex: profuse sweating, diabetes, alcohol intake, hyposecretion of ADH). Water moves between fluid compartments with a net movement of water from cells into the iF and then into blood plasma - Hypotonic hydration: Water intoxication, water gain greater than solute gain. (ex: ADH hyper secretion, too much plain water) . Brain cells can become impaired.
Describe the two major body fluid compartments and compare their chemical compositions
1) ICF (Intracellular fluid): ~2/3rds of our fluid, enclosed by the plasma membrane. > Contains more potassium, magnesium, phosphate, and negatively charged proteins than ECF. Reflect cell processes and substance transport due to protein synthesis. 2) ECF (Extracellular fluid): includes both IF (2/3) and blood plasma (1/3). Both more chemically similar to each other than they are to ICF. > Both have high concentrations of sodium and chloride as well as bicarbonate. But protein is present in blood plasma while little is in IF. Reflects relative permeability of capillary wall as proteins are too large to enter IF.
State the percentage of body fluids, and explain the significance of an individual's percentage relative to fluid balance
45-75% fluid by weight. Those with lower percentages are more likely to experience an imbalance.
Distinguish between the categories of water loss
> Breathing > Sweating > Cutaneous transpiration > Defecation > Urination Depends on physical activity, environment, and internal conditions Average: 60% is lost in urine and 40% lost in expired air, sweat, cutaneous transpiration, and in feces 1) Sensible/Insensible water loss: Sensible is measurable (feces and urine) 2) Obligatory/Facultative water loss: Obligatory always occurs regardless of state of body (breathing, insensible, feces, and some urine (500mL) whereas facultative is controlled through regulation of urine expelled from body depending on hydration
If you have an increase in muscle mass as a result of weight training, will your percentage of body fluid increase, decrease or stay the same? Explain
An increase in muscle mass will lead to an increase in percentage of body fluid
What is the major distinction in the chemical composition of blood plasma and the interstitial fluid?
Blood plasma has protein while the IF does not
Explain how fluid moves between the major body fluid compartments
Continuous in response to changes in relative osmolarity (concentration). Water always moves from hypotonic solution to the hypertonic solution.
Describe the stimuli that increase fluid intake
Fluid balance regulated indirectly via blood volume, pressure, and plasma osmolarity monitoring. -Decreased blood volume and pressure: decreased intake causes a decrease in volume and pressure. Renin released. Important when extreme volume depletion occurs -Increased blood osmolarity: most commonly from insufficient water intake and dehydration. Directly stimulates sensory receptors in the thirst center within the hypothalamus and stimulate hypothalamus to release ADH to increase thirst -Decreased salivary secretions: not related to blood conditions. Dry mucous membranes signal sensory receptors to signal thirst center
Name the different causes of fluid imbalance
Fluid output =/= fluid intake or distributed abnormally 1) volume depletion 2) volume excess 3) dehydration 4) hypotonic hydration 5) fluid sequestration
Which ions are more prevalent in the intracellular fluid? Which are more prevalent in the extracellular fluid?
ICF: potassium, magnesium, phosphate, and negatively charged proteins ECF: sodium and chloride as well as bicarbonate
What are the two major sources of fluid intake? What are two ways that fluid output is categorized and which one is based on the hydrated state of the body?
Ingested and metabolic. Obligatory and facultative.
List the sources of fluid intake
Ingested/preformed water: water from food and drink in the GI tracts (2300 mL avg daily) Metabolic water: produced daily from aerobic cellular respiration and dehydration synthesis (200 mL a day)
List the factors that influence the percentage of body fluid
The specific percentage depends on age (the younger, the higher) and relative amounts of adipose tissue to skeletal tissue (skeletal contains more water).
Explain what is meant by fluid sequestration
Total body fluid may be normal, but it is distributed abnormally. Ex: Edema) Fluid accumulates in IF and causes swelling. Caused by abnormal cardio changes, blood composition, or lymph vessel changes. Alter net filtration pressure at systemic capillaries, causing additional fluid to either leave the capillaries or remain in the IF.
When you are dehydrated, is the net movement of fluid from the blood plasma into the cells or from the cells into the blood plasma?
When dehydrated, net movement of fluid is from cells into the blood plasma
Define fluid balance
When fluid intake is equal to fluid output, and a normal distribution of water and solutes is present in the two major fluid compartments
Name the two buffering systems that regulate each category
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Define how metabolic acidosis and metabolic alkalosis, identify some of the causes of each type of acid base disturbance, and explain how each occurs
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Define respiratory acidosis, identify some of the causes of this type of acid-base disturbance, and explain how it occurs
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Define respiratory alkalosis, identify some of the causes of this type of acid-base disturbance, and explain how it occurs
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Describe how the kidneys counteract increase blood H+
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Describe renal and respiratory compensation
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Describe the change (increase, decrease, or same) for each of the follow variables if an individual hyperventilates: a) blood CO2, b) blood H+ concentration, and c) blood pH
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Describe the changes that occur in response to binding of aldosterone by kidney cells
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Describe the components of the protein buffering system and where and how they help prevent pH changes
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Describe the difference between a nonelectrolyte and an electrolyte
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Describe the stimulus for the release of atrial natriuretic peptide (ANP) and its three actions
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Describe the three actions of antidiuretic hormone
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Describe the variables that influence K+ distribution
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Discuss how the bicarbonate buffering system maintains acid-base balance in the ECF
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Distinguish between the two categories of acids in the body
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Explain acid-base disturbance, compensation, and acid-base imbalance
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Explain how release of antidiuretic hormone occurs from the posterior pituitary
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Explain how the kidneys function in response to decrease blood H+
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Explain the general role of electrolytes in fluid balance
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Explain the means by which angiotensin II formation can be triggered
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Explain the normal relationship between breathing rate and acid-base balance
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Explain the reactions of the phosphate buffering system within the ICF
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Explain the ways in which the effects of atrial natriuretic peptide differ from the effects of angiotensin II, ADH, and aldosterone
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Explain why Na+ is a critical electrolyte in the body
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Explain why infants are more susceptible to respiratory acidosis
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Explain why respiration does not normally influence acid-base balance
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How are fixed acids distinguished from volatile acids?
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How do the kidneys regulate fixed acids to help maintain blood pH In response to increased blood H+ concentration
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How does ANP influence fluid output, blood volume, and systemic blood pressure
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How does a compensated acid-base disturbance differ from an uncompensated acid base imbalance
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How does aldosterone influence the contents and volume of fluid output
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How does angiotensin II alter fluid output and potentially alter fluid intake
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How does the homeostatic system involving ADH function? Include how it is released and its actions
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Identify the four hormones that are involved in regulating fluid output
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Identify the main location, functions, and means of regulation for each of the common electrolytes
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List the four primary effects of angiotensin II
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List the six major electrolytes found in body fluids, other than H+ and HCO3-
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List the various sources of fixed acid
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List three conditions that lead to aldosterone release
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What are the three chemical buffering systems, and where do they function?
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What is meant by acid base balance?
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What is the general amount of time required to maintain pH by a) the chemical buffering systems, b) the respiratory system, and c) the kidneys?
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What is the net direction of K+ movement in response to a decrease in pH? Explain
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What is the primary cause of metabolic alkalosis
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What stimuli activate the thirst center?
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Which of these four hormones-- angiotensin II, antidiuretic hormone, aldosterone, and atrial natriuretic peptide-- increases urine output?
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Why do electrolytes exert a greater osmotic pressure than non electrolytes?
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