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
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