Electrolytes

Electrolytes

1. Sodium, Na+

   • Main cation in ECF Promotes water retention Maintains blood pressure Resting membrane potential Maintains blood volume
   • RDI = 1500 mg/day • Many people > 3000mg/day
     • Adults need about 0.5 g of sodium each day, many people get over 7g
   • Homeostasis
     • Aldosterone
       • When BP is to low - kindeys to retain sodium
     • • Anti-Diuretic Hormone (ADH)
       • When BP is to low and blood osmolarity is high - targets kindeys to retain water
     • Atrial Natriuretic Peptide (ANP)
       • When BP is to HIGH -hormone is excreted by HEART - Tells kindeys to dump sodium and to urine - H20
   • In balances
     • Hypernatremia
       • Dehydration, H2O deprivation - Normally caused by to much NA+ in diet
         • Symptoms - Thristy, hypertension, oedema, agitation and convulsions
     • Hyponatremia
       • Cause: ↓ diet Na+ , ↑ ↑ H2O, vomiting
         • Symptoms: Muscular weakness, dizziness, hypotension

2. Total body water content – thirst • Distribution within body compartments • Fluid shifts between ECF and ICF • Intracellular dehydration and oedema • Osmosis • Nerve impulse conduction and muscle contraction • Action potentials https://www.youtube.com/watch?v=u6njr0nZcCU

3. Potassium, K+

   • Main cation in ICF Small amounts in ECF Maintain normal ICF volume Neuromuscular function • Resting membrane potential
   • RDI = 3500 mg/day
   • Homeostasis
     • • Aldosterone
     • • Closely linked to sodium homeostasis • Excess excreted in urine
   • In balances
     • Hyperkalemia
       • Causes: Renal failure, Crush injury
         • Symptoms: Irritability, nausea, vomiting, diarrhoea, cardiac irregularities → arrest
     • Hypokalemia
       • Causes: rolonged vomiting/diarrhoea, kidney disease, diuretics
         • Sympotoms: Muscle fatigue, confusion, Cardiac irregularities → arrest

4. Chloride, Cl

   • Functions • Stomach Acid • Main Anion in ECF • Regulating pH
   • Homestastis
     • Linked to sodium… • Strong attraction
   • Imbalances • Disturbed Acid-Base Balance • Hyperchloremia • Dietary excess? • IV saline solution • Hypochloremia • Side effect of hyponatremia • Hyperkalemia? Acidosis?

5. Calcium, Ca2+

   • Functions • Skeletal strength • Muscle contractions • Neurotransmitter • Blood clotting
   • Homeostasis
     • Hormonal Control • Parathyroid Hormone • Calcitrol/Calcitonin
   • Imbalances • Hypercalcemia • Reduced membrane Na+ permeability • Depressed reflexes, muscular weakness, cardiac arrhythmias • Hypocalcemia • Abnormal nervous & muscular excitement • Weak bones

6. Phosphates

   • Functions • Energy • Components of phospholipids and nucleic acids • Activating enzymes & metabolic pathways • Regulating pH - Main anion in ICF
   • Homeostasis
     • Renal control • Parathyroid Hormone
   • Imbalances • Not as critical – we can tolerate broad variations