Fluid and Electrolyte Imbalances

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Fluid and electrolytes in the body Fluid volume changes due to pressure Hormonal regulation of fluid balance Electrolyte imbalance

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2/3 (65%) of TBW is intracellular (ICF)

1/3 extracellular water 75 % interstitial fluid (ISF) 25% in blood

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Fluid and electrolyte homeostasis is maintained in the body

Neutral balance: input = output Positive balance(excess): input > output Negative balance(deficit): input <

output

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Electrolytes – Cations

Na+, K+ , Ca++, H+

Anions Cl-, HCO3

- , PO43-

Proteins, urea, glucose, O2, CO2

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Tonicity

Isotonic

Hypertonic

Hypotonic

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Cell in a hypertonic solution

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Cell in a hypotonic solution

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Movement of body fluids

Diffusion – movement of particles down a concentration gradient.

Osmosis – diffusion of water across a selectively permeable membrane

Active transport – movement of particles up a concentration gradient ; requires energy

ADH - antidiuretic hormone thirst

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Decreased amount of water in body Increased amount of Na+ in the body Increased blood osmolality Decreased circulating blood volume

Stimulate osmoreceptors in hypothalamus

ADH released from posterior pituitaryIncreased thirst

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Result:increased water consumptionincreased water conservation

Increased water in body, increased volume and decreased Na+ concentration

Water content of the blood normal

Water content of the blood HIGH

Water content of the blood LOW

Too much water drunk

Too much salt or sweating

Brain producesMore ADH

Urine output LOW

Brain produces Less ADH

Urine output HIGH

High volume of waterreabsorbed by kidney

Low volume of waterreabsorbed by kidney

(small volume of Concentrated urine)

(large volume of dilute urine)

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1. Decrease in blood pressure causes decrease in amount of extracellular fluid.

2. Decrease in extracellular pressure near distal convoluted tubule causes juxtaglomerular cells to release the hormone RENIN.

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3. RENIN in blood stream converts the liver enzyme ANGIOTENSINOGEN into ANGIOTENSIN I.

4. ANGIOTENSIN CONVERTING ENZYME (in the lung) converts Angiotensin I into ANGIOTENSIN II.

5. Angiotensin II causes ADRENAL GLAND to secrete/release ALDOSTERONE.

6. Aldosterone is a vasoconstrictor (increasing blood pressure) and INCREASES COLLECTING DUCT PERMIABILITY.

•7.Urine volume decreased•Fluid retained•Blood volume increases•Blood pressure up.

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