Average Daily Intake and Output in an Adult Intake Output Oral Liquids 1,300 mL Urine 1,500 mL Water in Food 1,000 mL Stool 200 mL Water Poroduce by Metabolism 300 mL Insensible Lungs 300 mL skin 600 mL Total Gain 2,600 mL Total Loss 2,600 mL
Falling Systemic Blood Pressure/ Volume Reduces Filtrate Volume or Solute content in Renal Tubules JG Cells of Kidney Renin Angiotensin II Formed in Blood Baroreceptors in Blood Vessels Sympathetic Nervous System Systemic Arterioles Vasoconstriction Peripheral Resistance Hypothalamic Osmoreceptors Posterior Pituitary ADH (antidiuretic hormone Collecting Ducts of Kidneys Water Reabsorption
Regulation of Body Fluid Compartments When two different solutions are separated by a membrane that is impermeable to the dissolved substances, fluid shifts through te membrane from region of low concentration to the region of high solute concentration until the solutions are of equal concentration; this diffusion of water caused by a fluid concentration gradient is known as OSMOSIS
Regulation of Body Fluid Compartments Diffusion- is the normal tendency of a substance to move from an area of higher concentration to one of lower concentration . It occurs through the random movement of ions and molecules. Example of diffusion are the exchange of oxygen and carbon dioxide between the pulmonary capillaries and alveoli and the tendency of sodium to move from the ECF compartment, where the sodium concentration is high, to the ICF where its concentration is low.
Blood Urea Notrogen (BUN) - is made up of urea, an end product of metabolism of protein by the liver. Amino acid breakdown produces large amounts of amonia molecules, which are absorbed into the bloodstream. Amonia molecules are converted to urea and excreted in the urine.
KIDNEYS the usual daily urine in the adult is 1 to 2 L. A general rule is that the output is approximately 1 mL of urine per kilogram of body weight per hour in all age groups.
Routes of Gains and Losses LUNGS lungs normally eliminate water vapor (insensible loss) at rate of approximately 400mL everyday. . SKIN Sensible perspiration refers to visible water and electrolyte loss through the skin (sweating). Continuous water loss by evaporation occurs through the skin as insensible perspiration, a nonvisible form of water loss.
Routes of Gains and Losses GI TRACT the usual loss through the GIT is only 100 to 200 mL daily, even through approximately 8 L of fluid circulates through the GI system every 24 hours. Because the bulk of fluid is reabsorbed in the small intestine, diarrhea and fistulas cause larger losses. In healthy people, the daily average intake and output of water are approximately equal.
the hypothalamus manufactures ADH, which is stored in the posterior pituitary gland and released as needed. ADH sometimes called the water-conserving hormone because it causes the body to retain water.
functions of ADH include maintaining the osmotic pressure of the cells by controlling the retention or excretion of water by the kidneys and by regulating blood volume.
Aldosterone, a mineralococticoid secreted by the zona glomerulosa (outer zone) of the adrenal cortex, has profound effect on fluid balance.
increased secretion of aldosterone causes sodium retention (and thus water retention) and potassium loss.
conversely, decreased secretion of aldosterone causes sodium and water loss and potassium retention.
Cortisol, another adrenocortical hormone, has only a fraction of the mineralocorticoid potency of aldosterone. When secreted in large quantities, however, it can also produce sodium retention and fluid retention and potassium deficit.
important roles in maintaining sodium concentration and oral intake of fluids.
Oral intake is controlled by the thirst center located in the hypothalamus.
as serum concentration or osmolality increases or blood volume decreases, neuron in the hypothalamus are stimulated by intracellular dehydration; thirst then occurs, and the person increases oral intake of fluids.
water excretion is controlled by ADH, aldosterone, and basoreceptors
Absence or presence of ADH is the most significant factor in determining whether the urine that is excreted is concentrated or dilute.
Located on the surfaceof the hypothalamus, osmoreceptors sense changes in sodium concentration.
as osmotic pressure increases,the neurons become dehydrated and quickly release impulses to the posterior pituitary, which increases the release of ADH. ADH travels in the blood to the kidneys, where it alters permeability to water, causing increased reabsorption of water and decreased urine output.
The retained water dilutes the ECF and returns its concentration to normal. Restoration of normal osmotic pressure provides feedback to the osmoreceptors to inhibit further ADH release.
FVD occurs when loss of extracellular fluid volume exceeds the intake of fluid. It occurs when water and electrolytes are lost in the same proportion as they exist in normal body fluids, so that the ratio of serum electrolytes to water remains the same.
Abnormally low volume of body fluid in intravascular and/or interstitial compartments
Gain of Na in excess of water or loss of water in excess of Na
Deprivation of water; hypertonic tube feedings without water supplements, watery diarrhea, greatly increased insensible water loss, renal failure, inadequate blood circulation to kidneys, use of large doses of adrenal corticoids, excess sodium intake
Vital in maintaining normal cardiac and neuromuscular function, influences nerve impulse conduction, important in CHO metabolism, helps maintain acid-base balance, control fluid movement in and out of cells by osmosis