fluid electrolyte pengampuan sy 1213

Body CompartmentsRegulation of Fluid & Electrolyte

Balance Volume Osmolarity Disturbance Potassium Balance

Acid-Base Balance

OUTLINE

Body Compartments

Body Compartments

Fluid compartments are separated by membranes that are freely permeable to water

Movement of fluids due to: hydrostatic pressure osmotic pressure Starling forces

Fluid Movement

Starling Forces

Swelling of tissues due to excess interstitial fluidCauses:

Increased venous pressure (e.g. heart failure) Increased capillary permeability leak of plasma

proteins to interstitial fluid (e.g. anaphylactic shock)

Decreased plasma proteins (e.g. liver disease, malnutrition)

Inadequate lymph drainage (e.g. filariasis)

Edema

Body Compartments

All homeostatic mechanisms that monitor and adjust composition of body fluids respond to changes in ECF, not ICF

No receptors directly monitor fluid or electrolyte balance plasma volume & osmotic concentration

Cells cannot move water by active transport “water follows salt”

Regulation of Fluid & Electrolyte Balance

Osmolarity Tonicity Through water balance

Volume Blood Pressure Through salt balance

Regulation of ECF

Tonicity

Water Balance

Water Output

Regulation of Fluid Intake – Thirst

Regulation of Fluid Output – Urine

Kidneys conserve water by regulating urine concentration/osmolarity: 50-1200 mOsM

Countercurrent mechanism producing vertical osmotic gradient

Vasopressin/Antidiuretic Hormone (ADH) controls water reabsorption

Obligatory urine volume: 500 mL

Regulation of Fluid Output – Urine

Countercurrent Mechanism

Countercurrent Mechanism

Vasopressin/ADH

Vasopressin/ADH

Vasopressin/ADH

Short-term: Baroreceptor reflex cardiac output and

total peripheral resistance Fluid shifts due to Starling forces

Long-term: ECF volume salt balance

Regulation of Blood Pressure

Sodium account for >90% of ECF’s osmotic activity conservation of salt = conservation of water (“water follows salt”) primary determinant of ECF volume

Salt Balance

Intake: Poorly regulated; usually >>

Output: Obligatory loss in sweat and feces (0.5

g/day) Urine: controlled, very precise

Filtration: GFR Reabsorption: Renin-Angiotensin-Aldosterone

(RAA) system; Atrial Natriuretic Peptide (ANP)

Salt Balance

Salt Balance

RAA System

RAA System - Aldosterone

RAA System - Aldosterone

ANP

Integration of Fluid & Electrolyte Balance

Integration of Fluid & Electrolyte Balance

Disturbances of Fluid and Electrolyte Balance

98% in ICF

Intake: DietaryOutput: Urine

Disturbances in Potassium balance are less common than sodium balance, but significantly more dangerous

Potassium Balance

Factors affecting rate of K+ tubular secretion: K+ concentration in ECF (from dietary

intake) Aldosterone levels (promotes secretion) pH of ECF (acidosis: decreases secretion,

vice versa)

Potassium Balance

Potassium Balance

Acid-Base Balance

Buffer System

Buffer SystemLungs

Buffer System - Renal

Buffer System - Renal

Buffer System - Renal

Buffer System - Renal

Acid-Base Balance

Disturbances of Acid-Base Balance

SUMMARY

Guyton AC, Hall JE. Textbook of medical physiology.11th ed. Philadelphia. Elsevier, Inc. 2006.

Martini FH, Nath JL, Bartholomew EF. Fundamentals of anatomy & physiology. 9th ed. Boston. Benjamin Cummings. 2012

Sherwood L. Human Physiology from cells to system, 7th ed. Australia. Brooks/Cole Cengange Learning. 2011.

Silverthorn DU. Human physiology: an integrated approach. 5th ed. San Francisco. Pearson Education, Inc. 2010.

Tortora GJ, Derrickson B. Principles of anatomy and physiology. 12th ed. USA. John Wiley & Sons, Inc. 2009.

REFERENCES

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