Patho week 4

juxtaglomerular apparatus role in regulation of water

Sense low sodium volume Release renin Converts angiotension I to Angiotension II Stimulates release of aldosterone (RAAS)

hearts role in water regulation

Senses increase volume: stretch receptors in the right atrium. Secretes ANP, BNP. Inhibits ADH, stops RAAS, increases sodium excretion through urine. stops reabsorption of sodium. dilates blood vessels. Decreases serum osmolarity

Extracellular fluid

fluid outside the cell

Intravascular fluid

fluid within blood vessels, plasma

Intracellular fluid

fluid within cells

Osmotic

pressure that must be applied to prevent osmotic movement across a selectively permeable membrane

Osmolarity

total concentration of all solute particles in a solution

Extracellular fluid (ECF)

(⅓ of the body's water) is found outside the cells and accounts for about one third of total body fluid. ECF is further subdivided into compartments. The two main compartments of ECF are intravascular and interstitial. Intravascular fluid, or plasma, accounts for approximately 20% of ECF and is found within the vascular system. Contains many proteins. Interstitial fluid, accounting for approximately 75% of ECF, surrounds the cells. The other compartments of ECF include the lymph and transcellular fluids. (transcellular and interstitial contain less proteins). Examples of transcellular fluid include cerebrospinal, pericardial, pancreatic, pleural, intraocular, biliary, peritoneal, and synovial fluids. In contrast to intracellular, the extracellular fluid in the vascular and interstitial compartments is relatively rich in sodium, chloride, and bicarbonate ions and relatively low in potassium, magnesium, and phosphate ions. Although ECF is in the smaller of the two compartments, it is the transport system that carries oxygen and nutrients to, and waste products from, body cells. For example, plasma carries oxygen from the lungs and glucose from the gastrointestinal tract to the capillaries of the vascular system. From there, the oxygen and glucose move across the capillary membranes into the interstitial spaces and then across the cellular membranes into the cells. The opposite route is taken for waste products, such as carbon dioxide going from the cells to the lungs, and metabolic waste going to the kidneys. Interstitial fluid transports wastes from cells by way of the lymph system, as well as directly into the blood plasma through capillaries.

Intracellular fluid (ICF)

(⅔ of the body's water) is found within the cells of the body. It constitutes approximately two thirds of the total body fluid in adults. Intracellular fluid is vital to normal cell functioning. It contains solutes such as oxygen, electrolytes, and glucose, and it provides a medium in which metabolic processes of the cell take place. It is relatively rich in potassium and magnesium ions, inorganic and organic phosphates, and proteins. It is relatively low in sodium and chloride ions.

Homeostasis

A tendency to maintain a balanced or constant internal state; the regulation of any aspect of body chemistry, such as blood glucose, around a particular level

Edema

Abnormal accumulation of fluid in interstitial spaces of tissues. caused by: -increased capillary hydrostatic pressure. -by increased interstitial fluid osmotic pressure from increased capillary permeability. -by blocked lymphatic drainage. -by decreased capillary osmotic pressure from hypoalbuminemia. (An increase in the forces that tend to move fluid from the capillaries into the interstitial compartment or a decrease in forces that tend to move fluid from the interstitial compartment into the capillaries will cause edema by altering normal fluid distribution between the vascular and interstitial compartments.)

Aldosterone effect on urine volume

Aldosterone is synthesized and secreted by cells in the adrenal cortex. The major stimuli for its release are angiotensin II (from the renin-angiotensin system, which is activated by decreased circulating blood volume) and an increased concentration of potassium ions in the plasma. Aldosterone causes the renal tubules to reabsorb sodium and water (saline), which expands the extracellular fluid volume. This renal action decreases fluid excretion, although by a different mechanism than ADH. When more aldosterone is secreted, the urine volume is smaller; decreased secretion of aldosterone causes a larger urine volume. A comparison of ADH and aldosterone is useful to remember their actions. ADH is the tap water hormone. It causes the kidneys to reabsorb water. Renal reabsorption of water caused by ADH makes a smaller volume of more concentrated urine and dilutes body fluids. Aldosterone is the salt water hormone. It causes the kidneys to reabsorb sodium and water. Renal reabsorption of sodium and water caused by aldosterone makes a smaller volume of urine and expands extracellular fluid volume.

Dehydration

An abnormally low amount of water in the body. Clinical dehydration is a combination of two fluid disorders: ECV deicit and hypernatremia. A person who has clinical dehydration has too small a volume of fluid in the extracellular compartment (vascular an interstitial), and the body fluids are too concentrated (problem with volume and concentration)

Osmosis

Diffusion of water through a selectively permeable membrane

Electrolytes in the compartments

Extracellular and intracellular fluids contain oxygen from the lungs, dissolved nutrients from the gastrointestinal tract, excretory products of metabolism such as carbon dioxide, and charged particles called ions. Many salts dissociate in water; that is, they break up into electrically charged ions. The salt called sodium chloride breaks up into one ion of sodium (Na) and one ion of chloride (Cl). These charged particles are called electrolytes because they are capable of conducting electricity. The number of ions that carry a positive charge, called cations, and ions that carry a negative charge, called anions, should be equal. Examples of cations are sodium (Na), potassium (K), calcium (Ca2), and magnesium (Mg2). Examples of anions include chloride (Cl), bicarbonate HCO3 , phosphate HPO4 2-, and sulfate SO4 2-. The composition of fluids varies from one body compartment to another. In ECF, the principal electrolytes are sodium, chloride, and bicarbonate. Other electrolytes such as potassium, calcium, and magnesium are present, but in much smaller quantities. Plasma and interstitial fluid, the two primary components of ECF, contain essentially the same electrolytes and solutes, with the exception of protein. Plasma is a protein-rich fluid, containing large amounts of albumin, but interstitial fluid contains little or no protein. The composition of ICF differs significantly from that of ECF. Potassium and magnesium are the primary cations present in ICF, and phosphate and sulfate are the major anions. As in ECF, other electrolytes are present within the cell, but in much smaller concentrations. (look at fig 52-2)

Filtration

Fluid distribution between the vascular and interstitial compartments is the net result of filtration across permeable capillaries.

Plasma

Fluid portion of blood

Hypotonic

Having a lower concentration of solute than another solution

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

Recognize differences in total body water (TBW) for infants, adults, older adults, men, women and obese individuals

Newborn infants 75% more sensitive to temperature changes and fluid loss. Higher metabolisim, HR and RR leaves newborns more vulnerable to fluid loss. Adult woman 50% Higher fat content, takes the space of water. Obese people will also have less water content due to the fat ratio. Adult male 60% And older male 50%

Recognize the normal serum osmolality range and utilize the concept to predict consequences of abnormal states.

Normal range is 280-300. High or hyper osmolality would indicate high level of solute in blood, this could trigger ADH to assist the body in holding onto water. The thirst mechanisim may be triggered. The body will have to work harder to move the hyper osmotic blood around raising BP. Hypo or low osmolality could result in muscle weakness as low solute is connected to low concentration of electrolytes which are responsible for muscle excitation.

Explain the role of the renin-angiotensin-aldosterone(RAAS) system in fluid and electrolyte balance

Renin is release from Juxtaglomerular cells into the bloodstream, then it interact with angiotensinogen to form angiotensin I. Angiotensin Converting Enzyme converts angiotensin I to angiotensin II. Below are the function of angiotensin II: Constrict blood vessels to increase arterial pressure. Stimulate sodium reabsorption to increase sodium and water retention in the body. Act on the adrenal cortex to release aldosterone, which also increase sodium and water retention. Stimulate the release of ADH from posterior pituitary gland to increase water retention by the kidneys. Stimulate thirst center in the brain.

Describe the various fluid compartments in terms of distribution and composition of water, electrolytes and other osmotically active solutes

The fluids in the various body compartments have different compositions, although their total particle concentration is equal. The body's fluid is divided into two major compartments, intracellular and extracellular.

Insensible loss

Water lost thru the skin (individual is unaware of losing that water) Water lost thru the lungs (lost through expired air that is saturated with water vapor)

Hypervolemia

abnormal increase in the volume of blood plasma in the body

Explain the role of ADH and how it contributes to the regulation of body water

amount of fluid excreted in urine is controlled by ADH, aldosterone and natriuretic peptides. ADH is released by the posterior pituitary. ADH is released when there is an increase in osmolality (concentrate) of extracellular fluid, decreased fluid volume, pain, nausea or stressors . It increases the reabsorption of water from the urine and conserves water in the kidneys returning it back to normal circulation. Causes decreases urine volume and decreased plasma osmolarity.

two forces tend to move fluid from the capillaries into the interstitial compartment:

capillary hydrostatic pressure (the outward push of vascular fluid against the capillary walls) and interstitial fluid osmotic pressure (the inward-pulling force of particles in the interstitial fluid). (these happen in filtration)

two forces tend to move fluid from the interstitial compartment into the capillaries:

capillary osmotic pressure (the inward-pulling force of particles in vascular fluid) and interstitial fluid hydrostatic pressure (the outward push of interstitial fluid against the outside of the capillary walls). (these happen in filtration)

osmosis

contrast, the distribution of fluid between the interstitial and intra cellular compartments occurs by osmosis, Osmosis occurs until the intracellular osmotic pressure and the interstitial fluid osmotic pressure become equal,

Hypovolemia

decreased blood volume

Polydipsia

excessive thirst

Polyuria

excessive/frequent urination

Interstitial fluid

fluid in the spaces between cells

Describe the four forces that control the movement of water between the capillary and interstitial spaces

from the capillaries to interstitial compartment; capillary hydrostatic pressure -the outward push against the vascular wall. Interstitial fluid osmotic pressure - the inward pull into the interstitial space. Forces which more fluid from interstitial compartments into capillaries are; capillary osmotic pressure - inward pulling of particles in vascular fluid. Interstitial fluid hydrostatic pressure- outward push of interstitial fluid against the walls of the capillary

Differentiate dehydration and hypovolemia.

hypovolemia (FVD): Isotonic fluid volume deficit (FVD) occurs when the body loses both water and electrolytes from the ECF in similar proportions. Thus, the decreased volume of fluid remains isotonic. In FVD, fluid is initially lost from the intravascular compartment... occurs as a result of (a) abnormal losses through the skin, gastrointestinal tract, or kidney; (b) decreased intake of fluid; (c) bleeding; or (d) movement of fluid into a third space. See the section on third space syndrome that follows Dehydration: , or a hyperosmolar fluid imbalance, occurs when water is lost from the body, leaving the client with excess sodium. Because water is lost while electrolytes, particularly sodium, are retained, serum osmolality and serum sodium levels increase. Water is drawn into the vascular compartment from the interstitial space and cells, resulting in cellular dehydration. Older adults are at particular risk for dehydration because of decreased thirst sensation. Dehydration can also affect clients who are hyperventilating, have a prolonged fever, are in diabetic ketoacidosis, or are receiving enteral feedings with insufficient water intake.

Factors that increase/decrease release of ADH into the blood include:

include increased osmolality (concentratedness) of the extracellular fluid, decreased circulating fluid volume, pain, nausea, and physiologic and psychological stressors. The hormone circulates to the distal tubules and collecting ducts in the kidneys where, consistent with its name, ADH causes reabsorption of water that dilutes the blood and other body fluids. Reabsorption of water decreases the urine volume and makes the urine concentrated, thus decreasing fluid excretion. Factors that decrease ADH release (such as decreased osmolality of the extracellular luid and ethanol intake) allow a large, dilute urine volume.

Physiologic triggers of thirst

increased osmolality (concentratedness) of extracellular fluid (osmoreceptor-mediated thirst); decreased circulating blood volume (baroreceptor-mediated and angiotensin II-mediated thirst); and dryness of the mucous membranes of the mouth and possibly other visceral signals (In older adults, cerebral osmoreceptor-mediated thirst diminishes; thus, older adults who do not have a habit of drinking fluids throughout the day may not have sufficient fluid intake to meet their needs.)

Describe the signs and symptoms as well as factors that contribute to fluid volume excess and deficit and factors that contribute to them

individuals have too much or too little extracellular fluid. These disorders are called extracellular fluid volume (ECV) imbalances because they involve a change in the amount (volume) of the extracellular fluid. In the case of volume deficit, it is caused by the removal of sodium containing fluid from the body {saline deficit}. increased insensible water loss, diabetes insipidus, hemorrhage, GI losses, inadequate fluid intake, "third space" - outside of the extracellular compartment.... ascites(fluid in peritoneal cavity), intestinal obstruction or burns can lead to ECV deficit. It can cause: sudden weight loss, postural decrease in BP with concurrent increased heart rate, lightheadedness, dizziness, syncope, Oliguria(production of abnormal small output of urine), drowsiness, lethargy severe ECV deficit can cause HYPOVOLEMIC SHOCK Whereas in volume excess, excessive amount of fluid is present. It is caused by saline retention, excessive Aldosterone secretion (Hyperaldosteronism), and also chronic heart failure(think about NP's). Excess weight gain, edema, crackles in the dependent portion of the lungs, dyspnea, orthopnea.

Recognize the basic cellular function, normal serum levels, signs and symptoms of imbalance, and factors that contribute to hypo and hyper states of the following electrolytes: Sodium(Na), potassium(K), magnesium(Mg), and calcium(Ca)

look at homework

Colloidal

pertaining to a gluelike substance

hypothalamus role in water regulation

senses high serum osmolarity or high sodium. Stimulates thirst. Triggers release of ADH (from pituitary) which is a vasopression. Retains water in the blood, concentrates urine, mild constriction of blood vessels, decreases serum osmolarity

adrenal cortex role in water regulation

senses low serum osmolarity or low sodium ...releases sodium, increases potassium excretion into the urine. Increases serum osmolarity. Excretes sodium in the urine but it also releases aldosterone which decreases serum osmolarity??

Serum vs plasma

serum lacks clotting proteins bc is clear fluid leftover after solid clot forms

Tonicity

the ability of a surrounding solution to cause a cell to gain or lose water

Osmolality

the concentration of a solution expressed as the total number of solute particles per kilogram.

osmolality

the concentration of a solution expressed as the total number of solute particles per kilogram. If the particle concentration (osmolality) of the interstitial fluid becomes higher than the particle concentration inside cells, water will move by osmosis from the cells to the interstitial fluid to equalize the osmolality in the two compartments.

The amount of fluid excreted in the urine is controlled primarily by

the hormones antidiuretic hormone (ADH), aldosterone, and natriuretic peptides (e.g., A-type natriuretic peptide [ANP]), and to a lesser degree by minor hormones such as renal prostaglandins and by the renal sympathetic nerves.

Hypertonic

when comparing two solutions, the solution with the greater concentration of solutes (of a solution) having a higher osmotic pressure than a comparison solution

Isotonic

when the concentration of two solutions is the same