Chapter 25 Fluid and Electrolytes Objectives

List the factors that influence the percentage of body fluid

Age- Infants have about 75% body fluid and elderly have 45% body fluid, while middle-aged and young people are somewhere in between. Body fluid decreases with age. Amount of adipose connective tissue to skeletal tissue- % of body fluid depends on the ratio of connective tissue to skeletal tissue because of the difference in water content in both. Adipose tissue is 20% H2O where skeletal muscle is 75% H2O. A lean female has about 55% and lean male has 60% with difference reflecting how much of each muscle they have.

List the various sources of fixed acid

Examples of fixed acids include lactic acid from glycolysis, phosphoric acid from nucleic acid metabolism, and ketoacids from metabolism of fat

Define respiratory acidosis, and identify some of the causes of this type of acid-base disturbance

Respiratory acidosis occurs due to impaired elimination of CO2 by the respiratory system, causing arterial blood levels of P(CO2) to become elevated. Injury to the respiratory center maybe by trauma, disorders of the nerves or muscles involved with breathing, airway obstruction, or a decreased gas exchanged due to reduced respiratory surface area.

Define respiratory alkalosis, and identify some of the causes of this type of acid-base disturbance.

Respiratory alkalosis occurs due to an increase in respiration. This can be due to hyperventilating from serve anxiety and condition that someone isn't getting enough oxygen or an aspirin overdose.

Describe how the kidney counteract excess blood H+

To maintain acid-balance, excess H+ is eliminated by kidney tubules through the making and absorption of HCO3- and the excretion of H+ into the filtrate.

Describe the three actions of ADH

ADH stimulates the thirst center and, upon fluid intake, cause blood volume and pressure to increase and blood osmolarity to decrease. ADH increase water reabsorption in the kidneys in response to the osmotic gradient of the ISF, thus decreasing fluid loss through urine and decreasing blood osmolarity. High concentrations of ADH cause vasoconstriction of systemic blood vessels and therefore causes an increase in blood pressure.

Explain the ways in which the effects of ANP differ from the effects of ADH, aldosterone, and angiotensin II

ANP increases urine output, therefore, blood volume and systemic blood pressure decreases. ANP inhibits the release of renin, the action of angiotensin II, and the release of ADH and aldosterone, thus preventing the actions of these hormones

Describe the stimulus for the release of atrial natriutretic peptide (ANP) and its three actions

ANP is a hormone released from the atrial cells into the blood in response to stretching of heart chambers. ANP decreases blood volume and pressure by vasodilating the afferent arterioles in the kidney which control GFR, and through the inhibition of Na+ and water and reabsorption and release of renin.

Describe the changes that occurs in response to binding of aldosterone by kidney cells

Aldosterone binds to receptors on principal cells of the kidney. This binding causes cells to increase reabsorption and retention of Na+ and water. This hormone increases the number of Na+/K+ and Na+ channels so that more Na+ is reabsorbed from the filtrate. Water will follow the Na+. K+ excretion is normally increased except when there is low pH. As Na+ and K+ are reabsorbed H+ is excreted out of the blood, thus levels go up. low blood pressure and changes in Na+ and K+ blood plasma levels cause aldosterone release.

Explain the relationship between breathing rate and blood pH

An abnormal increase of the respiratory rate causes more CO2 to be expired, resulting in less CO2 in the blood. A decrease in CO2 blood levels causes the chemical reaction to shift left. Blood [H+] decreases, and blood pH increases (become more alkaline) An abnormal decrease of the respiratory rate results in an increase in the amount of CO2 retained, thus elevating blood CO2. These increased levels of blood CO2 push the equation to the right. Blood [H+] increases and blood pH decreases (becomes more acidic)

Name the four hormones that are involved in regulating fluid output

Angiotensin II, ADH, and aldosterone help decrease urine output therefore help to maintain blood volume and pressure. But atrial natriuretic peptide (ANP) increases urine out to decrease blood volume and pressure. These hormones will also regulate electrolytes.

Explain the means by which angiotensin II formation can be triggered

Angiotensinogen is constantly inactive made enzyme that is made by the liver. Its activation is initiated by renin. This is released in response to low blood pressure, or stimulation by the sympathetic division.

Explain why infants are more susceptible to respiratory acidosis.

Because they have smaller lungs and lower residual volume that does not eliminate CO2 as effectively. CO2 accumulates in the blood, with an increase in carbonic acid

Explain the significance of percentage of body fluid relative to fluid balance

Body's water content influences how susceptible you are to fluid imbalance. People who have lower body fluid content are more likely to have a fluid imbalance.

Identify the main location, functions, and the means of regulation for each electrolyte,

Cl- is associated with Na+ and abundant in ECF. Cl- is found in the stomach and hydrochloric acid, and help with the chloride shift of RBCs for transport of CO2 in the form of HCO3-. Chloride levels are directly related with Na+ levels. CA2+ is the most abundant electrolyte in bone and teeth. It is stored on the outside of these cells to harden them and Ca2+ pumps help so that they don't become calcified. It is also needed to start a muscle contraction. Is obtained by milk, soy, cheese and leafy veggies. Phosphate PO4- is the most abundant anion in ICF. And most phosphate is stored in bone and teeth as calcium phosphate. Serves as a buffer in ICF against pH changes and common urine buffer and can be obtained from many soft drinks and uses the same mechanisms as Ca2+ Magnesium Mg2+ is located within bone or in cells is in the ICF and participates in enzymatic reactions, assists in Na+ and K+ movement across membranes and muscle relaxation. Can be obtained from beans and peas and can be eliminated by sweat and urine.

Name the two buffering systems that regulate each category

Fixed acid is regulated by the kidney through the reabsorption and elimination of HCO3- and H+ Volatile acid is regulated by the respiratory system through the regulation of the respiratory rate

Distinguish between the two categories of acids in the body

Fixed acid is the metabolic acids produced from metabolic wastes, include lactic acid, ketoacids. Volatile acid is a carbonic acid produced from the combination of CO2 and water in the presence of carbonic anhydrase.

Define fluid balance

Fluid balance is when fluid intake equals fluid output and normal distribution of water and solutes is present in ICF and ECF.

Name the different causes of fluid imbalance

Fluid imbalance occurs when imput does not equal output or water is being distributed abnormally. The five categories include, volume depletion, volume excess, dehydration, hypotonic hydration, and fluid sequestration.

Describe the stimuli that increase fluid intake

Fluid intake increases blood volume (additional volume of blood) Blood pressure will increase and if water gain is higher than solute gain than blood osmolarity decreases. Fluid intake decreases blood volume (less volume of blood) Blood pressure will decrease and if water loss is greater than solute loss than osmolarity increases.

Explain the conditions and stimuli that decrease fluid intake

Fluid intake is controlled by activation and inhibition of the thirst center at hypothamalus. To turn on center: Decreased salivary secretions, as saliva production decreases the mucous membranes are not moist and less fluid is available. Sensory input is relayed to membranes of mouth and thirst center. Increased blood osmolarity occurs from not enough water intake, this will stimulate receptors in the thirst center at hypo for pituitary gland to release ADH also stimulates thirst center. A decrease in blood pressure will accompany decrease in fluid input, therefore renin is released> angiotensinogen>angiotensin I> angiotensin II which will stimulate the thirst center. If stimulated than H2O is absorbed from GI tract to blood. To turn off center: When body fluid is high there will be an increase in salivary secretions and everything will be most so sensory input to thirst center decreases. A stretched wall of the stomach will inhibit the thirst center. A decrease in blood osmolarity will make a decrease the release of ADH and an increase in blood pressure will inhibit kidney from releasing renin which will inhibit the stimulation of angiotensin II.

Describe the two major body fluid compartment and compare their composition

Intracellular fluid is the fluid inside the cells. This being the majority (2/3) of fluid within cells. The plasma membrane is the barrier and selects some but not all substances to flow through it. ICF contains K+, Mg2+, PO3-, and more of other negatively charged proteins than ECF. Ex. Na+/K+ pumps transport K+ into cell and Na+ out of a cell. Extracellular fluid is the fluid outside of cells. This is composed of interstitial fluid (80% surrounds cells) and blood plasma (20% inside vessel) The barrier separating ISF and blood plasma is capillary vessels, and both fluids are more chemically similar to each other than to ECF. The two fluid compartments of ECF are similar to each and both contain Na+, Ca2+, Cl-, HCO3-. One difference between ISF and blood plasma is plasma contains proteins. So during exchange, since proteins are too big to be filtered only blood plasma and all dissolved substances are filtered into ISF.

Explain how release of ADH occurs from the posterior pituitary

Is released in response to nerve signals from the hypothalamus. Is stimulated by angiotensin II binding to receptors on the hypothalamus which was due to low blood pressure. Sensory baroreceptors in the atria of the heart and carotid blood vessels stimulate hypothalamus and a decrease in this can be caused by low blood volume. This is only under critical conditions of blood loss. Hypothalamus chemoreceptors detect an increase in blood osmolarity, and is the primary stimulus for ADH release.

Explain what is meant by fluid sequestration

Means that they total body fluid may be normal but it is being distributed abnormally. Fluids pile up in one area and is not available for use anywhere else. Edema is one example because fluid builds up in ISF around cells and can be described as puffiness or swelling.

Define both metabolic acidosis and metabolic alkalosis, and identify some of the causes of each type of acid-base disturbance

Metabolic acidosis occurs when blood levels of HCO3- decrease, may be caused by increased production of metabolic acids, decreased the elimination of acid due to renal dysfunction, and increase elimination of HCO3- due to diarrhea. Metabolic alkalosis occurs when HCO3- blood levels increase. This may be caused by vomiting, increased acid loss due to overdose of diuretics, increased alkaline input.

Explain how metabolic acid-base disturbances differ from respiratory acid-base disturbances

Metabolic disturbances are reflected by blood plasma HCO3- concentration that is outside of normal range, while respiratory disturbances occur when changes in respiratory function result in an increase or decrease blood CO2 pressure.

Describe the difference between a nonelectrolyte and a electrolyte

Molecules that do not come apart in solution are called nonelectrolytes like glucose, urea, creatinine. AN electrolyte is any substance that will come apart to form a cation or anion, and include salts, acids, bases, and negatively charged proteins.

Explain how fluid moves between the major body fluid compartments

Movement happens continuously due to changes in osmolarity concentration. If one compartment becomes hypertonic or hypotonic H20 will follow solutes until all are equal again, because plasma membranes and capillary walls are permeable to water. Hypotonic to hypertonic. If you drink water your blood plasma becomes hypotonic to ICF, therefore water will move out of vessels to ISF and then will move into cells due to higher solute concentration in there. Vice versa for not drinking water.

List the 5 major electrolytes in body fluids other than H+ and HCO3-

Na+, K+, Cl-,Ca2+, PO4-, Mg2+

Distinguish between the categories of water loss

Normal fluid output can be from breathing, sweating, defecation, urination and amount loss depends on physical activity and internal conditions and environment. Sensible water loss is measurable and includes water lost through pooping and peeing, while insensible water loss is not measurable and happens through sweat and breathing. Obligatory water loss is loss that also occurs regardless of hydration state. Includes water lost in sweating, breathing, pooping, and some urine, while facultative water loss is controlled loss through regulation of the amount of pee leaving the body. Facultative is dependent on hydration state and hormonally controlled.

Describe the variable that influence K+ distribution

Potassium is the main cation on the ICF and exerts intracellular pressure. The gradient is maintained by the Na+/K+ pump and leaky K+ channel. Normal level of K+ is 3.5-5.0 mEq/L. Small changes can lead to a K+ imbalance which is the most lethal of electrolyte imbalances and can lead to neuromuscular changes, which leads to cardiac arrest and respiratory arrest. Input and output. Total body potassium is regulated by K+ intake and output. Dietary requirement of K+ is 40mEq/L and most K+ loss is through urine, Low blood pH, increased aldosterone secretion, and high blood K+ levels elevate potassium loss levels. Blood plasma K+ increases as a result in movent from ECF into ICF. The ICF acts as a K+ reservoir for excess blood plasma K+ levels. Increase in blood [H+] (pH decreases) causes excess K+ to move from ECF to ICF to reestablish acid-base balance. Insulin increases transport of K+ from ICF to ECF from Na+/K+ pumps to decrease blood plasma levels. Elevated K+ levels are called hyperkalemia

List the sources of fluid intake

Preformed water includes the water you get from food (700mL) or drinks (1600mL) from GI tract. 2300mL per day Metabolic water includes water produced from aerobic cellular respiration 200 mL per day. to increase blood volume in the body is to increase fluid intake from food or drink we eat.

List the three conditions that lead to aldosterone release

Release of angiotensin II, decreased blood plasma levels of Na+, or an increased blood plasma levels of K+

Describe renal and respiratory compensation

Renal compensation in response to elevated H+ concentration results in increased excretion of H+, increased production and reabsorption of HCO3- and lower than normal urine pH. Respiratory compensation is in response to metabolic acidosis results in increased expiration of CO2, showed by a lower than normal blood P(CO2) value. Respiratory compensation is in repsonse to metabolic alkalosis results in decreased expiration of CO2, showed by a high than normal blood P(CO2) value.

Explain why Na+ is a critical electrolyte in the body

Sodium is the main cation in the ECF and is present as sodium bicarbonate or sodium chloride and is maintained by Na+/K+ pumps and exerts the greatest amount of osmotic pressure. blood plasma Na+ concentration is 135-145mEq/L and required dietary intake is 1.5 to 2.3g/day, typical person has 3-7g/day. Na+ loss occurs in sweat and urine output and is regulated by aldosterone, ADH and ANP. Most important electrolyte in assessing blood osmolarity and controlling fluid balance. ECF becomes hypertonic w/ excess Na+ and decrease in water, and vice versa. H2O and Na+ retention increase blood pressure and volume, and vice versa. Hypernatremia refers to high levels of Na+ and hyponatremia refers to low levels of Na+ and major changes in Na+ or water input and output may cause changes in Na+ plasma concentration.

Discuss how the bicarbonate buffering system maintains acid-base balance in the ECF

The bicarbonate buffering system found within the ECF consists of bicarbonate (weak base) and carbonic acid (weak acid) and serves as a buffering system for the pH changes in the blood. HCO3- (weak base) + H+ (strong acid)+H2CO3---> H2CO3 (weak acid) + OH- (strong base)= HCO3- + H2O

Explain the reactions of the phosphate buffering system

The buffering system is found within the ICF is composed of hydrogen phosphate (weak base) and dihydrogen phosphate (weak acid) and serves as a buffering system for pH changes within cells. Like protein buffering either a strong acid buffered to produce a weak acid or a strong base buffered to produce a weak base.

Explain the general role of electrolytes in fluid balance

The term electrolyte refers to these substances ability to make an electrical current. NaCl can become two ions therefore has a greater osmotic pressure from a nonelectrolyte. To express the difference between these charges we use milliequivalents which is the amount of electrical charges in 1 L of solution.

Describe the components of the protein buffering system

This buffering system is composed of proteins within cells and in the blood plasma. The amine group (-NH2) of amino acids acts as weak base to buffer acid. Carboxylic acid of amino acids acts as a weak acid to buffer base. Intracellular proteins, plasma proteins, and hemoglobin all perform as pH buffers. weak base+strong acid= weak acid/weak acid+strong base= weak base

List four primary effects of angiotensin II

This can stimulate vasoconstriction of systemic blood vessels to increase resistance, which increases blood pressure. It also stimulates a decrease in urine output from the kidneys a result of lower filtration rate, by stimulating vasoconstriction of afferent arteriole. this helps maintain systemic blood volume and blood pressure. Stimulates the thirst center in the hypothalamus, which increases blood volume and blood pressure. Stimulates both the hypothalamus to activate posterior pituitary to release Adh and adrenal cortex to release aldosterone.

Compare and contrast the different types of fluid imbalances

Volume depletion occurs when isotonic fluid loss is greater than isotonic fluid gain. This can include hemorrhage, chronic vomiting or hyposecretion of aldosterone. Volume excess occurs when isotonic fluid gain is greater than isotonic fluid loss. Typically is when intake stays the same but fluid through kidneys decreases from like renal failure or hypersecretion of aldosterone. Dehyrdation can come from excessive sweating, alcohol, diabetes mellitus, or hyposecretion of ADH (stimulates H20 reabsorption), lack of water intake. This causes blood plasma to become hypertonic drawing water out of the cells. Hypotonic hydration or water intoxication. This can result from a hypersecretion of ADH, but is normally caused by drinking too much water. Too much water in blood plasma so water goes into cells making them swollen. Extreme case of hypotonic hydration would be cerebral edema, brain cells become impaired due to too much water in them and person can experience headaches, coma, or death.

Describe how the kidneys function with decreasing blood H+

When alkaline conditions are present the renal tubules will no longer reabsorb the HCO3-. It will secrete HCO3- from the blood into the filtrate while reabsorbing H+ in exchange through type B intercalated cells.

Explain acid-base disturbance, compensation, and acid-base imbalance

When the buffering capacity of the chemical buffering systems is exceeded and the physiologic buffering systems are required to intervene due to a change in blood pH, an acid-base disturbance is occurring. Compensation occurs when the body's buffering system returns the blood pH to normal. When the body's buffering systems are unable to return the blood pH to normal, the pH disturbance is called uncompensated and, should the pH change be continuous and persistent, it is called acid-base imbalance.