Unit 3: Fluids and Electrolytes

Infant Total Body Water (TBW) %

70%

Male Total Body Water (TBW) %

60%

Female Total Body Water (TBW) %

50%

T/F: Older adults and obese persons have higher proportion of water.

False

ICF

Intracellular fluid (within cells) 2/3 of TBW

ECF

Extracellular fluid (outside cell) 1/3 of TBW

Electrolytes

inorganic salts, acids & bases, and some proteins that conduct electricity in solution

non-electrolytes

covalent bonds that don't dissociate in water, don't conduct electricity, and can cause fluid shifts

E.g. Electrolytes

Sodium, potassium, chloride, magnesium, bicarbonate, phosphate, sulfate, and calcium

E.g. Non-electrolytes

Lipids, glucose, creatinine, and urea

intravascular (IVF) and interstitial (ISF) are part of the...

extracellular fluid

Thirst Mechanism

Osmoreceptors in the hypothalamus promote intake when needed

Antidiuretic hormone (ADH)

Promotes normal reabsorption of water into the blood from the kidneys

Atrial Natriaretic peptide - ANP

Regulates fluid, sodium, and potassium levels to reduce workload of heart by lowering blood pressure

Renin Angiotensin Aldosterone System (RAAS)

Renin- kidney releases to blood. Angiotensinogen- liver secretes to blood. Renin breaks down AGT to inactivate AGT 1. Angiotensin Converting Enzyme (ACE)- lung secretes to blood. Inactive AGT 1 and ACE meet in blood. AGT 1 --> AGT 2. AGT 2 acts on cells of the adrenal cortex to cause the secretion of Aldosterone.

Salts

Responsible for regulation of fluid movement, maintenance of cell excitability, membrane permeability, and secretory activity.

Sodium

Most abundant in ECF. Important in the control of fluid volume and water distribution in the body.

Sodium Balance

RAAS, ANP, estrogen (increase cause fluid retention), Progesterone, and Glucocorticoids.

Progesterone

Blocks Aldosterone effects

Aldosterone

secreted by the adrenal cortex; increases salt reabsorption; ECF increase. causes NA-K pump action

Potassium Balance

Most abundant cation in ICF, necessary for electrical conductivity in muscles and nerves

Calcium Balance

Important in blood coagulation, membrane permeability, cellular secretion, muscle contraction. Is regulated by the Parathyroid Hormone (PTH) & calcitonin

Phosphate & Anion Balance

most phosphate ions are reabsorbed in Proximal Convoluted Tubule (PCT) --> Important in pH regulation. Cl- is major anion in ECF --> reabsorbed in PCT

Greater in H+ ion concentration

more acidic/low pH 1-6

Lower in H+ ion concentration

more basic/high pH 8-14

Blood pH: 6-7 & 7.8-9

results in death

Blood pH: 7-7.35

results in acidosis

Blood pH: 7.35-7.45

normal blood pH level

Blood pH: 7.45-7.8

results in alkalosis

Optimal pH

Lungs, kidneys, and major organs involved in regulation acid-base balance

Buffer Systems

help maintain constancy of pH, changes stronger acids/bases to substances that don't greatly affect pH

H2CO3 / HCO3- system

one of the most important plasma buffer systems

carbonic acid-bicarbonate buffer system

major extracellular buffer, WB - bicarbonate, WA - carbonic acid

phospate buffer system

important in ICF, WB - monohydrogen phosphate, WA - dihydrogen phosphate

protein buffer system

most important buffer in body cells and blood, WB - the amine group (e.g. -NH2) , WA - the carboxyl group (e.g. -COOH)

Decompensation

Occurs when
-causative problem becomes more severe
-additional problems occur
-compensation mechanisms are exceeded or fail
(requires intervention to maintain homeostasis
life threatening)

Edema

Accumulation of fluid in the interstitial spaces, swelling

Dehydration

sodium levels rise, increased osmolaty

Hyponatremia

low sodium in the blood

Hypernatremia

high sodium in the blood

hypokalemia

low potassium in the blood

Hyperkalemia

high potassium in the blood

Hyperchloremia

an excess of chloride in the blood plasma

Hypochloremia

deficiency of chloride in the blood plasma

Sodium importance outside the cell

helps w/ nerve and muscle cell interaction (recommended daily does 1.5 g)

Chloride importance outside the cell

helps maintain osmotic pressure

Calcium importance outside the cell

stabilize the cell membrane and reduce its permeability to sodium, transmit nerve impulses, contract muscles

Potassium importance inside the cell

role in regulation of cell excitability, nerve impulse conduction, muscle contraction, myocardial membrane responsiveness

Phosphate importance inside the cell

essentially for energy metabolism. key role in mineralization of bones and teeth

Magnesium importance inside the cell

Acts as a catalyst for enzyme reactions. regulates neuromuscular contraction.