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Which tissue is least & most hydrated

Least-adipose 20%
Most-Skeletal muscle-75%

Consists of trillions of tiny individual compartments

Intracellular fluid compartments

the bodys internal environment, external environment of each cell

extracellular fld compartment

The 2 subcompartments of ECF

1. Plasma-fluid portion of the blood
2. Interstitial Fluid-fluid between tissue cells

Have bonds that prevent them from dissociating in solution


chemical compounds that do dissociate into ions in water


How does water move?

according to osmotic gradients-from lesser osmolarity to an area of greater osmolarity

The one difference between the two extracellular fluid components

Plasma has more protein than interstitial fld

What are the most abundant ECF electrolytes?

Sodium, Chloride, and bicarbonate ions

What substances does ICF contain

Protein Anions, potassium, phosphate, and magnesium

What regulates fluid exchange between compartments?

osmotic and hydrostatic pressures

Filtrate is forced out of capillaries by?
and pulled back in by?

Filtrate is forced out of capillaries by hydrostatic pressure and pulled back in by colloid osmotic pressure

How does water move between ECF and ICF

Freely by osmosis

How are solute movements restricted?

size, charge, and dependence of transport proteins

Water flows always follow changes in what?

ECF osmolarity

The hypothalamic thirst center is excited by what?

A increase 2-3% in plasma osmolarity

Three ways hypothalamic thirst center neurons are stimulated

osmoreceptors lose water by:
osmosis to the hypertonic ECF, activated by angiotensin II, by barorecptor inputs

What causes aquaporins to be inserted in the cell membranes of the collecting ducts?

Antidiuretic hormone

The amount of water reabsorbed in the renal collecting ducts is ________ to ADH release


Diluted urine and a reduced volume of body fluids


Fever, excessive sweating, diarrhea, vomiting what to ADH

Trigger it's release

Due to stress on the body, ADH also increases BP by?

constricting arterioles


Decreased urine output

Hypovolemic Shock

water loss from plasma results in inadequate blood volume, unable to maintain normal circulation

In dehydration, water is lost from where?

the ECF

Low ECF Na+


body fluids are excessively diluted, cells swollen...can result in cerebral edema

hypotonic hydration


abnormally low level of protein in the blood, results in tissue edema

disorder entailing deficient mineralocorticoid hormone production by the adrenal cortex, can result in severe cravings for salty foods

Addisons disease

Promotes sodium reabsorption and water conservation


When do the granular cells release Renin?

declining BP and falling filtrate osmolarity

Enhances systemic BP and aldosterone release

Angiotensin II (renin converted)

The cario baroreceptors sense changing arterial BP, prompting?

changes in sympathetic vasomotor activity

Rising Arterial pressure leads to?

vasodilation and enhanced sodium and water loss in urine

Falling arterial pressure leads to?

vasoconstriction, conserves sodium and water

What is the effect of Atrial Natriuretic Peptide?

released when BP is high, vasodilation, inhibits renin, aldosterone and ADH release. Enhances sodium and water excretion-reduces BV & BP

Increase Renal retention of sodium

Estrogens and glucocorticoids

Enhances sodium and water excretion in urine


About 90% of filtered potassium is reabsorbed by what structure?

proximal regions of the nephrons

Which cells secrete potassium?

Principle cells

What enhances K+ secretion by the principle cells?

Increased plasma K+ and aldosterone

During a K+ deficit which cells reabsorb small amounts of K+?

Type A cells of CD

Where does PTH regulated reabsorption occur?

Mainly in the DCT

PTH decreases renal absorption of what ion?


Declining plasma levels of calcium stimulate the parathyroid gland to release PTH, increases calcium by targeting which organs?

Bones, Small Intestine, and Kidneys

The major anion accompanying sodium in the ECF?


the pH of arterial blood rises above 7.45


Drop in arterial pH to below 7.35


In acidosis, which ion goes with sodium reabsorption?


Proton (H+) donors


Proton acceptors


3 ways acids are generated in the body

1. breakdown of phosphorus containing proteins
2. incomplete oxidation of fats or glucose
3. loading and transport of carbon dioxide in the blood

The only important ECF buffer

Bicarbonate Buffer system

Phosphate Buffer system is effective in buffering ? Ineffective?

Effective buffering urine in ICF (due to high phosphate concentrations)
Ineffective-blood plasma

Mose plentiful and powerful source of buffers

protein buffer system

Amphoteric molecules

protein can function as either an acid or base depending on the pH of its environment

What two things active the respiratory center?

Hypercapnia--- medullary chemoreceptors
rising plasma H+ concentrations

To counteract acidosis, either one of two mechanisms may be used

1. Secreted H+ in the urine
2. NH4+ excreted in urine

How is alkalosis counteracted?

Bicarbonate ion is secreted into the filtrate and H+ is absorbed

Results from CO2 retention

Respiratory Acidosis

Occurs when CO2 is eliminated faster than it's produced

Respiratory Alkalosis

Occurs when fixed acids accumulate in the blood or when bicarbonate is lost

Metabolic Acidosis

Occurs when bicarbonate levels are excessive

Metabolic Alkalosis

Involve changes in respiratory rate and depth

Respiratory compensations

modify blood levels of HCO3-

Renal compensations

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