Fluid And Electrolytes

Front 1

Extracellular fluid consists

Back 1

of both interstitial fluid and the plasma in the blood stream.

Front 2

Intracellular fluid

Back 2

interstitial fluid > plasma

Front 3

Intracellular fluid: High concentrations of

Back 3

K+ Mg++ Phosphate Sulfate Protein

Front 4

Extracellular fluid: High concentrations of

Back 4

Na+ Bicarbonate Cl-

Front 5

we can only alter EXTRACELLULAR fluid directly

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by adding substances into the plasma (via IV fluids, etc

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Water Balance primarily controlled by the hypothalamus:

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1. makes us feel thirsty
2. secretes ADH (causes the kidney to retain water)

Front 7

Water balance problems OVERHYDRATION (hypotonic hydration

Back 7

If too much water is allowed into the plasma, water will flow into the interstitial fluid by osmosis

Front 8

Water balance problems DEHYDRATION (due to water loss).

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If water in the plasma is lost (hemorrhage, vomiting, burns), then blood volume will decrease.

Front 9

Water balance problems EDEMA (due to increased water in interstitial fluid

Back 9

This is due to high venous pressure in the capillaries, increased capillary permeability (during bacterial infection), poor lymph drainage, or lack of albumin in the blood. Remember that protein (albumin) in the blood is higher than interstitial fluid. If the protein is lost to the interstitial fluid, edema will result.

Front 10

Hyponatremia:

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loss of sodium (goes hand in hand with overhydration) Can lead to influx of water into brain cells à the brain swells.

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Hypernatremia:

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excess of sodium (goes hand in hand with dehydration) Will lead to outflow of water out of the brain à brain dehydrates.

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so what controls the Na+ balance?

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1. hypothalamus (ADH secretion when blood is too “salty“) Note that this does not directly affect sodium, but the reabsorption of water will dilute the sodium in the bloodstream when Na levels are too high. 2. aldosterone (secretion when Na+ levels are low). This leads to an increase in Na+ in the blood stream. 3. ANP (atrial natriuretic peptide secretion when Na+ levels are high). This leads to an increase of Na+ loss in the urine. This hormone is made by the atrium of the heart. 4. renin (indirectly) since renin à angiotensin II à aldosterone 5. other hormones: Estrogen promotes Na+ reabsorption (Women in the class will relate to this “bloating” monthly effect of estrogen). Cortisol also promotes Na+ reabsorption.

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Potassium BalanceThe major hormone that controls K+ balance

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aldesterone

Front 14

Aldosterone:

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Secreted by the adrenal gland when K+ in ECF is high. This will cause the distal tubule and collecting duct to secrete K+ into the urine.

Front 15

High levels of potassium cause

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secretion of aldosterone and renin. They in turn cause secretion of K+ by the kidney.

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Hypokalemia:

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low K+ in ECF will cause more K+ to leave the cell (to balance the K+). This will cause hyperpolarization (make the cell even more negative inside), and make it more difficult to send action potentials = paralysis.

Front 17

Hyperkalemia

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excess K+ in ECF will make repolarization of the action potential difficult and will lead to cardiac arrest.

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Hyperkalemia

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Acidosis

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Hypokalemia

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Alkalosis

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Acidosis leads to

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hyperkalemia and vice versa

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Alkalosis leads to

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hypokalemia and vice versa

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calcium is important for such things as:

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blood clotting 2. muscle contraction (especially plateau phase of heart) 3. nerve conduction (release of neurotransmitter

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Hypocalcemia:
Hypercalcemia:

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tetany and muscle spasms (increase in excitability)
depresses nerve conduction and muscle activity

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A pH > 7.45 =

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alkalosis

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pH < 7.35 =

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acidosis

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Respiratory Acidosis

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pH < 7.35, pCO2 is high = alveolar hypoventilation Due to hypoventilation CO2 in the blood increases. H+ will also increase.

Front 27

Respiratory Alkalosis

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pH > 7.45, pCO2 is low = hyperventilation Due to hyperventilation CO2 in the blood decreases. H+ will decrease.

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Metabolic Acidosis

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pH < 7.35, bicarbonate is low (carbon dioxide is normal) acidosis due to some other reason than the way we are breathing

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Metabolic Alkalosis

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pH > 7.45, bicarbonate is high (carbon dioxide is normal) alkalosis due to some other reason than the way we are breathing Ex: stomach vomiting (bulemics), constipation, antacid abuse

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If I am in respiratory alkalosis (hyperventilation

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the kidney will try and retain H+ ions by reducing the secretion of H+. It will get rid of more bicarbonate in the urine.