- 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

regulator of plasma levels - intercalated cells form more if levels are too low - excrete excess in the urine

Lecture 27 Flashcards by Katie Hostetter

Sodium most abundant

extracellular ion

-accounts for 1/2 of osmolarity of ECF

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Sodium Average daily intake

exceeds normal requirements

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Sodium Hormonal controls: aldosterone causes

increased reabsorption Na+

- -acts on Principle cells

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Sodium Hormonal controls: ADH release ceases if

Na+ levels too low–dilute urine lost until Na+ levels rise

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Sodium Hormonal controls: ANP increases

Na+ and water excretion if Na+ levels too high

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Sodium retention causes

-water retention

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edema is

abnormal accumulation of interstitial fluid

water swelling

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Causes of sodium retention

renal failure

hyperaldosterone

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Excessive loss of sodium causes

excessive loss of water (low blood volume)
-due to inadequate secretion of aldosterone
-too many diuretics

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Chloride is the most

prevalent extracellular anion

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Chloride Moves

easily between compartments due to Cl- leakage channels

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Chloride Helps

balance anions in different compartments

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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

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Chloride shifts and

hydrochloric acid of gastric juice

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Potassium the most

abundant cation in intracellular fluid

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Potassium helps

establish resting membrane potential & repolarize nerve & muscle tissue

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Potassium is Exchanged for

H+ to help regulate pH in intracellular fluid

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Potassium Control is mainly by

aldosterone which stimulates principal cells to increase K+ secretion into the urine

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abnormal plasma K+ levels do what?

adversely affect cardiac and neuromuscular function

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Bicarbonate Common for

extracellular anion

Major buffer in plasma

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Bicarbonate Concentration increases as blood flows through

systemic capillaries due to CO2 released from metabolically active cells

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Bicarbonate Concentration decreases as blood flows through

pulmonary capillaries and CO2 is exhaled

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Kidneys are main

regulator of plasma levels

intercalated cells form more if levels are too low
excrete excess in the urine

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Calcium Most abundant

mineral in body (skeleton & teeth)

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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:

1. buffer system 2. exhalation of CO2 3. 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

1. protein buffer system 2. carbonic acid-bicarbonate buffer system 3. phosphate buffer system

Protein Buffer System:

1. Abundant in intracellular fluids & in plasma 2. Amino acids contains at least one carboxyl group (-COOH) and at least one amino group (-NH2) 3. Hemoglobin acts as a buffer in blood by picking up CO2 or H+

1. PBS: hemoglobin very good at

buffering H+ in RBCs

1. PBS: albumin is main

plasma protein buffer

2. PBs: carboxyl group acts like

an acid & releases H+

2. PBS: amino group acts like a

base & combines with H+

Carbonic Acid-Bicarbonate Buffer System:

1. Acts as extracellular & intracellular buffer system 2. At a pH of 7.4, bicarbonate ion concentration is about 20 times that of carbonic acid 3. 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