Packet 27 Flashcards
Most abundant extracellular ion
Sodium
Average daily intake exceeds normal requirements
Hormonal controls
–aldosterone causes increased reabsorption Na+
–ADH release ceases if Na+ levels too low–dilute urine lost until Na+ levels rise
–ANP increases Na+ and water excretion if Na+ levels too high
Sodium
Sodium retention causes
water retention
abnormal accumulation of interstitial fluid
edema
Causes of sodium retention
renal failure
hyperaldosterone
Excessive loss of sodium causes ___
- due to inadequate secretion of aldosterone
- -too many diuretics
excessive loss of water
Most prevalent extracellular anion
chloride
- Moves easily between compartments due to Cl- leakage channels
- Helps balance anions in different compartments
- Regulation
- –passively follows Na+ so it is regulated indirectly by aldosterone levels
- –ADH helps regulate Cl- in body fluids because it controls water loss in urine
- Chloride shift & hydrochloric acid of gastric juice
Chloride
Most abundant cation in intracellular fluid
Potassium
- Helps establish resting membrane potential & repolarize nerve & muscle tissue
- Exchanged for H+ to help regulate pH in intracellular fluid
- Control is mainly by aldosterone which stimulates principal cells to increase K+ secretion into the urine
- –abnormal plasma K+ levels adversely affect cardiac and neuromuscular function
Potassium
Common extracellular anion
Major buffer in plasma
Bicarbonate
Concentration increases as blood flows through systemic capillaries due to CO2 released from metabolically active cells
Concentration decreases as blood flows through pulmonary capillaries and CO2 is exhaled
Kidneys are main regulator of plasma levels
- -intercalated cells form more if levels are too low
- -excrete excess in the urine
Bicarbonate
Most abundant mineral in body (skeleton & teeth)
Abundant extracellular cation in body fluids
Calcium
Important role in blood clotting, neurotransmitter release, muscle tone & nerve and muscle function
Regulated by parathyroid hormone
- –stimulates osteoclasts to release calcium from bone
- –increases production of calcitriol (Ca+2 absorption from GI tract and reabsorption from glomerular filtrate)
Calcium
important intracellular anion and acts as buffer of H+ in body fluids and in urine
Phosphate
Present as calcium phosphate in bones and teeth, and in phospholipids, ATP, DNA and RNA
Plasma levels are regulated by parathyroid hormone & calcitriol
- -resorption of bone releases phosphate
- -in the kidney, PTH increase phosphate excretion
- -calcitriol increases GI absorption of phosphate
Phosphate
Found in bone matrix and as ions in body fluids
intracellular cofactor for metabolic enzymes, heart, muscle & nerve function
Magnesium
Urinary excretion increased in hypercalcemia, hypermagnesemia, increased extracellular fluid volume, decreases in parathyroid hormone and acidosis
Magnesium
Micro Essay
3 major mechanisms to regulate pH
- Chemical Buffer System
- Respiratory system (exhalation of CO2)
- Kidney excretion of H+ (urinary system)
Homeostasis of H+ concentration is vital
- -proteins 3-D structure sensitive to pH changes
- -normal plasma pH must be maintained between 7.35 - 7.45
- -diet high in proteins tends to acidify the blood
Acid-Base Balance
Micro Essay
3 Principal buffer systems
- Protein
- Carbonic acid-bicarbonate
- Phosphate
- Prevent rapid, drastic changes in pH
- Change either strong acid or base into weaker one
- Work in fractions of a second
- Found in fluids of the body
actions of buffer systems
Abundant in intracellular fluids & in plasma
protein buffer system
main plasma protein buffer
albumin
very good at buffering H+ in RBCs
acts as a buffer in blood by picking up CO2 or H+
hemoglobin
contains at least one carboxyl group (-COOH) and at least one amino group (-NH2)
amino acid
acts like an acid & releases H+
carboxyl group
acts like a base & combines with H+
amino group
Acts as extracellular & intracellular buffer system
carbonic acid-bicarbonate buffer system
can act as a weak base
holds excess H+
bicarbonate ion
can act as weak acid
dissociates into H+ ions
carbonic acid
At a pH of 7.4, bicarbonate ion concentration is about 20 times that of carbonic acid
Can not protect against pH changes due to respiratory problems
carbonic acid-bicarbonate buffer system
Most important intracellularly, but also acts to buffer acids in the urine
Phosphate buffer system
acts as a weak acid that can buffer a strong base
dihydrogen phosphate
acts a weak base by buffering the H+ released by a strong acid
monohydrogen phosphate
