AnP Chapter 20 (LO3) Flashcards
Intracellular fluid (ICF)
Most of the bodies water about 65% resides in the cells
Extracellular fluid (ECF)
the remaining 35% of the bodies water resides outside cells
Includes interstitial fluid as well as the fluid within vessels as blood plasma and lymph
Interstitial fluid
the fluid between the cells inside tissues
Transcellular fluid
various other extra cellular fluid such as cerebral spinal fluid, synovial fluid in the joints, vitreous and aqueous humor of the eye and digestive secretions
Fluid deficiency
Occurs when output exceeds intake over a period of time
Two types of flu deficiency volume depletion (hypovolemia) and dehydration
Volume depletion
results from blood loss or when both sodium and water or loss such as from diarrhea
Dehydration
results when the body eliminates more water than sodium and results from consuming an adequate amount of water to cover the amount of water loss
Hypovolemic shock
circulatory collapse as a result of loss of blood volume
Fluid Excess
The kidneys usually compensate for excessive fluid intake by producing more year consequently fluid excess occurs less commonly than fluid deficit
causes of fluid excess
One cause of fluid excess is renal failure
Another type of fluid excess is called water intoxication which can occur if someone consumes an excessive amount of water or if someone replaces heavy losses of water and sodium with just water
–When this occurs the amount of sodium drops water moves into the cells causing them to swell
Fluid Accumulation
type of water imbalance involves the accumulation of fluid within a body compartment example: edema
Typically affects the lungs, brain and dependent areas such as legs
Electrolytes
are substances that break up into electrically charged particles called ions when dissolved in water
Electrolyte Balance
A balance of electrolytes is crucial for the body to function properly because electrolytes drive chemical reactions, affect distribution of the body’s water content and determine a cells electrical potential
The major cations of the body are
sodium, potassium, calcium and hydrogen
The major anions are
chloride, bicarbonate, and phosphates
Sodium
The main electrolyte in the extra cellular fluid accounting for 90% of its osmolarity
Determines the volume of total body water and influences how body water is distributed between fluid compartments
Plays a role in depolarization making it crucial for proper nerve and muscle function
Sodium levels are primarily regulated by aldosterone and ADH
Aldosterone adjust the excretion of sodium where a DH adjust the excretion of water
sodium osmolarity How it works (water excess)
Decreased serum Na+ (water excess)
Serum osmolarity decreases
Aldosterone prompts renal tubules to reabsorb sodium
ADH release is suppressed causing the kidneys to secrete more water
Reabsorption of sodium combined with secretion of water causes serum sodium levels to rise
Serum osmolarity normalizes
sodium osmolarity How it works (water deficit)
Increase serum sodium (water deficit)
Serum osmolarity increases
ADH stimulates the kidneys to reabsorb water
ADH stimulates thirst to promote water consumption
Increased renal absorption of water combined with
increased water intake causes serum sodium levels to fall
Serum osmolarity normalizes
Sodium imbalances
Sodium is the chief cat ion in extra cellular fluid
And balances and sodium affects total body water, the distribution of water between compartments and nerve and muscle function
Hypernatremia
Hyponatremia refers to a plasma sodium concentration greater than 145 mEq/l
It usually indicates a water deficit
Other possible causes including excessive loss of body water such as from diarrhea or the use of certain types of diuretics
Hypernatremia usually self corrects because even a small rise in sodium triggers thirst
If uncorrected hypernatremia can cause edema, lethargy and weakness
Hyponatremia
Hyponatremia: Refers to a plasma sodium concentration of less than 135 mEq/l
It usually results from an excess of body water such as when someone drinks on the water to replace heavy losses of sodium and water through perspiration
Hyponatremia is usually corrected by excretion of excess water
Uncorrected can result in pulmonary or cerebral oedema as fluid moves into cells
Potassium
Potassium is the chief cat ion of intracellular fluid and works hand-in-hand with sodium
It is crucial for proper nerve and muscle function
Aldosterone regulate serum levels of potassium just as it does sodium
Rising potassium levels stimulate the adrenal cortex to secrete aldosterone
–Aldosterone causes the kidneys to excrete potassium as they reabsorb sodium
Potassium imbalances
Imbalances in potassium can develop suddenly or over a long period but either way can cause life-threatening arrhythmias
Hyperkalemia
Hyperkalemia: refers to a plasma concentration of potassium greater than 5.3
mEq/l
Levels greater than 6.2 are considered critical and require immediate intervention
It may develop suddenly after a crush injury or severe burn
It may also develop gradually from the use of potassium sparing diuretics or renal insufficiency
Hyperkalemia makes nerve and muscle cells irritable leading to potentially fatal cardiac arrhythmias
Hypokalemia
Hypokalemia: refers to a plasma concentration of potassium less than 3.6 mEq/l
Levels less than 2.5 are considered critical and requires immediate intervention
Often results from prolonged do use of potassium wasting diuretics
May also result from chronic vomiting or diarrhea
Hypokalemia causes potassium to move out of the cell into plasma making cells less excitable
Hypokalemia results in muscle weakness, depressed reflexes and cardiac arrythmias
Calcium
plays a key role in muscle contraction, nerve transmission, and blood clotting
Plasma calcium levels are regulated by parathyroid hormone which affects intestinal absorption of calcium and enhances the release of calcium from bones
Calcium imbalances
Calcium is a cation that exist mostly outside the cell
Hypercalcemia
Hypercalcemia: refers to a plasma concentration greater than 10.2 mg/dl
It may result from hyperparathyroidism, hypothyroidism, or alkalosis
Hypercalcemia inhibits depolarization of nerve and muscle cells leading to muscle weakness, depressed reflexes and cardiac arrhythmia
Hypocalcemia
Hypocalcemia: refers to a plasma concentration less than 8.2 mg/dl
It may result from hypothyroidism, hyperthyroidism, acidosis or diarrhea
Hyper calcium increases excitation of nerves and muscles leading to muscle spasms and tetany
Chloride
Chloride the most abundant extracellular anion
strongly linked to sodium; as sodium is retained or excreted so is chloride; Chloride balance occurs along with sodium balance
Chloride contribute to the formation of stomach acid and helps regulate fluid balance and pH
Phosphate
participates in carbohydrate metabolism, bone formation and acid base balancen
Acid Base Balance
Most important factors influencing homeostasis is the body’s balance between acid and bases even slight deviations in pH can have a fatal consequence
Most enzymes used in the bodies metabolic reactions are very sensitive to pH
Electrolyte activity to can be profoundly affected by changes in pH
Buffers
A Buffer is any mechanism that resist changes in pH by converting a strong acid or base into a week one
There are two categories of buffers: Chemical buffers and physiological buffers
Chemical buffers
Chemical buffers use a chemical to bind hydrogen and remove it from solution when levels rise to high end to release hydrogen when levels fall
Three main chemical buffer systems are the bicarbonate buffer system, the phosphate buffer system and the protein buffer system
Bicarbonate buffer system
Main buffering system of extracellular fluid
Uses bicarbonate and carbonic acid
Reaction is reversible it proceeds to the right when the body needs to lower pH and proceeds to the left when pH needs to be raised
Bicarbonate buffer system how it works
CO2+H20->H2CO3->H+HCO3
When carbon dioxide combines with water it forms carbonic acid—> carbonic acid disassociate into hydrogen ions and bicarbonate lowering pH
H + HCO3–>H2CO3–>CO2+H20
It’s more hydrogen ions are added to the system some of the added hydrogen ions will react with the bicarbonate ions to produce carbonic acid finding with bicarbonate removes the hydrogen ions from the solution and raisins PH–>the carbonic acid disassociate into carbon dioxide and water
CO2 + H20–>H2CO3–>H+HCO3
When more hydrogen ions are removed from the system more carbon dioxide will combine with water to produce more carbonic acid–> the carbonic acid will then disassociate producing more hydrogen and bicarbonate ions ‘
Physiological buffers
Physiological buffers use the respiratory and urinary systems to alter the output of acids, bases or CO2 to stabilize pH
Respiratory control of pH
- Central chemoreceptors in the brain stem detect a fall in pH resulting from an accumulation of CO2
- The central chemo receptor signal respire Tori centres to increase the rate and depth of breathing resulting in expulsion of CO2
- Because less CO2 is available to combine with water to form carbonic acid, the concentration of hydrogen ions falls and pH rises
Death occurs when PH falls to less than – or rises to more than –
Death occurs when PH falls to less than 6.8 or rises to more than 8.0
Renal control of pH
The renal system is the most powerful of all buffer systems
- Carbon dioxide leaves the blood enters into cells along the distal kidney tubules
- In the cell CO2 combines with water to form carbonic acid
- The carbonic acid immediately disassociate to yield hydrogen ions and bicarbonate ions
- –The hydrogen ions diffuse out of the cell and into the tubular fluid where they displace sodium
- –The displaced sodium diffuses into the tubular cell where it combines with the bicarbonate to form sodium bicarbonate - Sodium bicarbonate is then reabsorbed into the blood
- The end result is that hydrogen ions are excreted into the year in while sodium bicarbonate is reabsorbed into the blood both actions help raise plasma PH
Respiratory imbalances
result from either an excess or deficiency of carbon dioxide
Metabolic imbalances
results from an excess or deficiency of bicarbonate
respiratory
Causes of acid gain (acidosis)
Causes of acid loss (alkalosis)
Causes of acid gain (acidosis)
-Retention of CO2 (hypoventilation)
Causes of acid loss (alkalosis)
-loss of carbon dioxide (hyperventilation)
Metabolic
Causes of acid gain (acidosis)
Causes of acid loss (alkalosis)
Causes of acid gain (acidosis)
- Increase production of acids
- Consumption of acidic drugs
- Inability of the kidneys to excrete hydrogen ions
- Loss of bicarbonate
Causes of acid loss (alkalosis)
- Loss of gastric juices
- Excessive ingestion of bicarbonates
Compensation for Acid Base Imbalances
The body uses the respiratory system to compensate for metabolic pH imbalance is in the kidneys to compensate for respiratory pH imbalances
Respiratory compensation
Changing the rate of ventilation alerts the concentration of CO2 in the plasma and therefore alters pH
For imbalances with a metabolic caused the respiratory system is the quickest means of raising or lowering pH
If the pH is too low as in metabolic acidosis the respiratory center increases the rate of respirations which blows off CO2 and raises ph
In metabolic alkalosis the pH is too high breathing slow allows CO2 to accumulate and drops pH
Renal compensation
Although the kidneys are the most effective regulators of pH they take hours or days to respond to an acid base in balance
The kidneys alter pH by adjusting the rate of hydrogen ion excretion
In response to acidosis the kidneys eliminate hydrogen and re-absorb more bicarbonate
In response to alkalosis the kidneys conserve hydrogen and excrete more bicarbonate
