Lecture 27 Flashcards
Sodium most abundant
extracellular ion
-accounts for 1/2 of osmolarity of ECF
Sodium Average daily intake
exceeds normal requirements
Sodium Hormonal controls: aldosterone causes
- increased reabsorption Na+
- -acts on Principle cells
Sodium Hormonal controls: ADH release ceases if
Na+ levels too low–dilute urine lost until Na+ levels rise
Sodium Hormonal controls: ANP increases
Na+ and water excretion if Na+ levels too high
Sodium retention causes
-water retention
edema is
abnormal accumulation of interstitial fluid
water swelling
Causes of sodium retention
renal failure
hyperaldosterone
Excessive loss of sodium causes
- excessive loss of water (low blood volume)
- -due to inadequate secretion of aldosterone
- -too many diuretics
Chloride is the most
prevalent extracellular anion
Chloride Moves
easily between compartments due to Cl- leakage channels
Chloride Helps
balance anions in different compartments
Chloride 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 shifts and
hydrochloric acid of gastric juice
Potassium the most
abundant cation in intracellular fluid
Potassium helps
establish resting membrane potential & repolarize nerve & muscle tissue
Potassium is Exchanged for
H+ to help regulate pH in intracellular fluid
Potassium Control is mainly by
aldosterone which stimulates principal cells to increase K+ secretion into the urine
abnormal plasma K+ levels do what?
adversely affect cardiac and neuromuscular function
Bicarbonate Common for
extracellular anion
Major buffer in plasma
Bicarbonate Concentration increases as blood flows through
systemic capillaries due to CO2 released from metabolically active cells
Bicarbonate 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
Calcium Most abundant
mineral in body (skeleton & teeth)
Calcium has what cation?
Abundant extracellular cation in body fluids
Important role in calcium
blood clotting, neurotransmitter release, muscle tone & nerve and muscle function
Calcium Regulated by
parathyroid hormone
Calcium in parathyroid hormone stimulates
osteoclasts to release calcium from bone
Calcium in parathyroid hormone increases
production of calcitriol
-cannot absorb calcium from food
Phosphate Present as
calcium phosphate in bones and teeth, and in phospholipids, ATP, DNA and RNA
HPO4 -2 is important
intracellular anion and acts as buffer of H+ in body fluids and in urine
What act as buffers in the blood
mono and dihydrogen phosphate
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
Magnesium Found in
bone matrix and as ions in body fluids
***Magnesium has the
intracellular cofactor for metabolic enzymes, heart, muscle & nerve function
Magnesium is first thing that is dumped due to these problems:
Urinary excretion increased in hypercalcemia, hypermagnesemia, increased extracellular fluid volume, decreases in parathyroid hormone and acidosis
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
***3 major MECHANISMS to regulate pH:
- buffer system
- exhalation of CO2
- kidney excretion of H+
Actions of Buffer Systems Prevent
rapid, drastic changes in pH
Actions of Buffer Systems work in how much time?
fractions of a second
Buffers Found in
fluids of the body
Buffers do what to strong acid or base?
change either into weak ones
***3 principal BUFFER systems
- protein buffer system
- carbonic acid-bicarbonate buffer system
- phosphate buffer system
Protein Buffer System:
- Abundant in intracellular fluids & in plasma
- Amino acids contains at least one carboxyl group (-COOH) and at least one amino group (-NH2)
- Hemoglobin acts as a buffer in blood by picking up CO2 or H+
- PBS: hemoglobin very good at
buffering H+ in RBCs
- PBS: albumin is main
plasma protein buffer
- PBs: carboxyl group acts like
an acid & releases H+
- PBS: amino group acts like a
base & combines with H+
Carbonic Acid-Bicarbonate Buffer System:
- Acts as extracellular & intracellular buffer system
- 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
CAB: 1. bicarbonate ion (HCO3-) can act as
a weak base
-holds excess H+
CAB: 1.
carbonic acid (H2CO3) can act as weak acid -dissociates into H+ ions
Phosphate Buffer System: Most important
intracellularly, but also acts to buffer acids in the urine
Phosphate Buffer System: Dihydrogen phosphate ion acts as a
weak acid that can buffer a strong base
Phosphate Buffer System: Monohydrogen phosphate acts a
weak base by buffering the H+ released by a strong acid
