Chapter 27 - Electrolyte Balance - Part 2 - Final

Essential Electrolytes

Sodium, chloride, potassium, calcium, magnesium, phosphate

Essential Electrolytes Functions

-Balance blood pH

-Facilitate waste excretion from cells

-Maintain fluid balance

-Promotes proper functioning of nerve, muscle, heart, and brain cells

-Transports nutrients into cells

Electrolytes

-Chemical compounds that dissociate into ions in water

-Due to the ions being charged particles they conduct electrical current -> electrolytes

Categories of Electrolyte

-Inorganic salts

-Inorganic/organic acids and bases

-Some proteins

Electrolyte - Increased Osmotic Pressure

-Due to dissociation into at least two ions -> NaCl or MgCl2

-Causes fluid shifts, influences movement of water from lesser osmolality to higher osmolality (osmosis)

Extracellular Ions

-Consumed in food/water we ingest

-Removed from the body by kidneys, liver, skin and lungs

Concentration of Electrolytes

Change when the individual is growing, or gaining/losing weight

Electrolyte Balance =

= Salt Balance

Electrolyte Roles

-Control fluid movements

-Provide minerals for excitability

-Secretory activity

-Membrane permeability

Sodium

Most abundant cation in the ECF

Sodium Role

Control ECF volume and water distribution in the body

-Exerts significant osmotic pressure

-Cellular plasma membranes = impermeable to sodium

What follows sodium?

Water follows sodium -> when change in plasma sodium, change in plasma, BP, ICF, and IF volumes

Content of Sodium

Total amount of sodium in the body determines ECF volume and BP

What increases sodium and ECF content?

Low BP activates renin-angiotensin-aldosterone -> increased sodium, and water volume in ECF

What decreases sodium and ECF content?

BP elevated -> increased sodium and water excretion -> ANF secretion -> inhibit sodium reabsorption and inhibit ADH effect of DCT/CD

ECF Sodium Content Increases

Rise in ECF osmolality -> ADH + thirst -> increased water retention and intake -> reduced sodium concentration and increased ECF volume

Hyponatremia

-Over dilution of blood due to excess water consumed post exercise -> mental confusion, seizures, coma

-Solute loss -> water retention, decreased BV and BP (circulatory shock)

Hypernatremia

-Due to excess aldosterone secretion -> pulmonary edema and muscle convulsion

-May be caused by dehydration -> leads to thirst, confusion, lethargy, coma

Chloride

-Predominant anions of the ECF

-Accompanies sodium in ECF

Chloride Regulation

-Predominant cation sodium -> most important factor in regulation

-Acidosis -> less chloride accompanies sodium due to HCO3 reabsorption -> restore blood pH to normal

Hypochloremia

-Due to excess sweat, diuresis, vomiting, diarrhea,

-Low salt intake/SIADH

Hyperchloremia

-Dehydration

-High blood sodium (Cushing syndrome)

-Kidney disease

Potassium

-Chief intracellular cation

-Tightly regulated -> determine RMP for electrically excitable cells

Potassium Regulation

Regulated by aldosterone secretion

Elevated potassium -> aldosterone secretion -> increases sodium reabsorption and potassium secretion (depolarization and hyperpolarization)

Hypokalemia

-Excess potassium secretion -> due to excess elevation of aldosterone and insulin administration (activates sodium potassium pump)

-Fatigue, muscle cramps, temporary paralysis

-Due to water pills/diuretics

Hyperkalemia

Due to renal disease -> less renal excretion -> intestinal cramping, diarrhea, temporary paralysis

Calcium

-Role in exocytosis (including NT), muscle contraction

-Regulates AP in cardiac muscle, blood clotting

Sites for ECF Calcium Regulation

Kidneys, GI tract, and bones (majority)

Calcium Regulation

Deposit into and reabsorption from bone

Long term -> maintain balance between absorption across intestine wall and excretion by kidneys

Calcium Regulation Hormones

PTH, vitamin D, calcitonin

-PTH increases blood calcium via osteoclasts, renal tubules resorption

-Vitamin D absorbed in SI

-Calcitonin decreases blood calcium, inhibits osteoclasts preventing bone breakdown

Hypocalcemia

Affects PM permeability to sodium causing nerve and muscle tissue to spontaneous AP -> muscle tetany

Hypercalcemia

Prevents depolarization of nerve and muscle cells -> deposit CaCO3 salts in soft tissues -> irritation and inflammation

Can lead to cardiac arrhythmias

Phosphate

85% in the body in the form of CaPO4 salts in bone and teeth, the rest is in cells

Phosphate Roles

-Binds to lipids, proteins and carbs

-Component of DNA, RNA, ATP

-Regulate enzyme activity

-Act as buffer

Hypophosphatemia

Due to vitamin D deficiency

Alcohol abuse -> decreased blood clotting and WBC function

Hyperphosphatemia

Due to acute and chronic renal failure, decreased filtrate by kidneys, chronic laxative use

Magnesium

Stored in bones or ICF

Hypomagnesium

Due to alcohol abuse -> muscle convulsions and weakness

Hypermagnesemia

Rare

Due to renal failure -> nausea, hypotension, and low RR

Also due to chronic laxative use, excess ingestion of antacids, or magnesium intake