Summary Electrolyte Balance and Thermoregulation

Electrolyte Balance and
Thermoregulation
Electrolytes in Body Fluids  [Na+] in ECF normally stable
 Rate of sodium uptake across
 Electrolytes – critical to a
digestive tract directly
range of functions
proportional to dietary intake
 Help maintain acid-base
 Sodium losses
balance
 Urine
 Carry electrical current
 Perspiration
 Act as enzyme cofactors
 Changes in plasma sodium
 Transport nutrients
levels affect
(symports/antiport)
 Plasma volume, blood
 Support mental function
pressure
 Convertion of substrates into
 IFC, interstitial fluid
energy
volume
Fluid distribution in the  Large variations in sodium
body correct by homeostatic
mechanisms
 Intracellular fluid = 67%  If sodium levels too
(28L) low, antidiuretic
 Extracellular fluid (14L) hormone (ADH),
 Interstitial fluid = 26% aldosterone secreted
 Intravascular fluid (water retention)
(blood plasma) = 7%  If sodium levels too
 Cerebrospinal fluid = high, arterial
less than 1% natriuretic peptide
Sodium (ANP) secreted
(diuresis)
 Sodium ions (Na+)
 Main extracellular Sodium Reabsorption
cation  65% of sodium in filtrate is
 Contributes 125 reabsorbed in proximal
mOsm/L of total tubules
 Involved in action  25% reclaimed in loops of
potentials, muscle Henle
contraction  When aldosterone levels are
 Central position in fluid and high, all remaining Na+
electrolyte balance actively reabsorbed in distal
 Only cation to exert tubule
significant osmotic  If ADH has increase, water
pressure (low permeability in the collecting
membrane duct, the sodium will also be
permeability, unlike K+) increased and be retained in
 Sodium ions leak into cells the body
 Pumped out against
electrochemical
gradient

, Excess Dietary Salt
Sodium Imbalance  Brain
 Sensitized sympathetic
Hyponatremia
neurons
 Low sodium in the blood  Heart
 Causes  Increased left ventricle
 Burns hypertrophy
 Congestive heart  Kidney
failure  Decreased glomerular
 Diarrhea filtration rate
 Kidney diseases  Increased protein
 Sweating excretion
 Vomiting  Blood vessels
 Dilution  Impaired endothelial
 Hyperglycemia function
 Effects  Increased arterial
 Abnormal mental stiffness
status
Chloride and other anions
 Convulsions
 Fatigue  Calcium Salt (Cl-)
 Muscle cramps  Structural component
 Weakness of bones, teeth
 Important in
Hypernatremia
intracellular signaling
 Increased concentration of  About 50% of extracellular
sodium Ca2+ in bound to proteins
 Causes  The rest is ionized and
 Dehydration involved in
 Found in  Blood counting
 Babies  Neurotransmitter
 Impaired mental status release
elderly  Concentration of
 Aldosterone over muscle
secretion  Intracellular
 People that drink less signaling
water than they should  Very low intracellular levels
 Effects that is toxic at higher
 Lethargy concentration
 Weakness  For any Ca2+ that
 Irritability goes in one Ca2+ is
 Oedema pumped out for ATP
 Leading to seizures
 Coma




Hypocalcemia – low Ca2+
concentration