Mairead - Fluid Balance Flashcards
What is fluid balance regulated in association with?
Electrolyte balance
Acid/base balance
What does it mean if you are in fluid balance?
Fluid in=fluid out
Where does fluid in come from
From ingested food and metabolic fluid
Where does fluid out come from
Urinary output
Evaporation
Sweat
Faecal output
What are the main differences between ICF and ECF
(4 characteristics of ICF)
High K+
High MG++
High PO4-
High protein
What are the main differences between ICF and ECF
(3 characteristics of ECF)
High Na+
High Cl-
High HCO3-
Write a note on ECF in fluid balance
All homeostatic mechanisms for fluid balance adjust composition of the body fluids response to changes in the ECF not the ICF
The ECF is constantly mixing -> change in one area affect all of the ECF
Where are the receptors for fluid balance
(6)
Aortic arch
Carotids
JGA
Medulla oblongata
Hypothalamus
Brainstem
What do receptors for fluid balance respond to?
(2)
Change - increase or decrease in blood pressure
Change in osmolarity of the blood and cerebro-spinal fluid
What sensory receptors are responsible for fluid balance
Baroreceptors
Chemoreceptors
Osmoreceptors
How is fluid balance altered
(3)
Fluid shifts (ECF <-> ICF)
Short term regulation of circulation (ANS and hormones)
Long term restoration of homeostasis (hormones)
Our cells cannot move water by active transport, how is water moved?
(2)
Water follows salt
Salts are moved by active transport: H2O follows by osmosis
Give three examples of where water follows salt
GIT absorption
Reabsorption in the renal tubule
Production of sweat
When will body H2O or electrolytes rise?
(2)
Intake > output
Output < intake
What hormones are involved in renal excretion and thirst (4)
Aldosterone (renin-angiotensin pathway)
Anti-diuretic hormone
Atrial and Brain Naturetic Peptide (ANP and BNP)
Adrenaline and noradrenaline also involved if blood pressure is lowered
What does ANP stand for
Atrial Naturetic Peptide
What does BNP stand for
Brain naturetic peptide
How are hormones involved in regulation
(4)
Enhance the short term (ANS) response
Direct the long term response.
A) Affect cardiac output and peripheral
resistance and in the longer term
B) Regulate blood volume and blood
composition
Write a note on how fluid shifts between ECF to ICF
(4)
If ECF osmotic concentration decreases; H2O shifts from ECF
to ICF.
This is a water gain and no change in the electrolytes.
The ICF acts as a reservoir (2/3 H2O in ICF).
At first little effect on ICF (larger vol) but may proceed to CVS shock
Give three situations for water loss
Following severe perspiration (ex in heat)
With inadequate H2O consumption (elderly),
Following repeated vomiting or diarrhoea
How does the body respond to water loss?
(2)
To prevent further fluid loss with ADH and Renin
To stimulate fluid intake
How does the body respond to water gain
(3)
Inhibiting ADH and Aldosterone,
Increasing renal output and
Avoidance of fluid intake
What does a shift of water into the cells do?
(4)
This is H2O intoxication and results in confusion, and leads to hallucinations, convulsions, coma and death
Distorts the cells
Changes the solute concentration around enzymes
Disturbs normal cell function.
What happens when ECF osmotic concentration increases?
(4)
H2O shifts from ICF to ECF.
This is a
water loss, with no change in electrolytes.
The ICF acts as a reservoir (2/3 H2O in
ICF).
If there is a large shift the cell solute
concentration may result in altered cell
function.
How is fluid intake regulated
(3)
Partially regulated by thirst.
If output > input dehydration initiates thirst
Thirst stimulates fluid intake and return to
homeostasis
What does dehydration do?
(3)
Dryness of the mouth
Wrinkling of skin
Increase osmotic pressure
What are electrolytes
(4)
Inorganic elements of body fluids with at
least one ionic bond.
Dissociate into cations (positive) and anions
(negative).
Can conduct electrical current in a solution.
Eg acids, bases and salts
What are the functions of electrolytes?
(4)
As essential minerals in the diet.
To control osmosis.
For excitability of nervous and muscle
tissue
To maintain acid/base balance
Describe the relationship between electrolytes and osmosis
(4)
Electrolytes dissociate
Electrolytes have a greater effect on
osmosis than a nonelectrolyte solute as it is
the number of particles that attract H2O.
Total electrolyte balance directly affects
water balance.
The concentration of individual electrolytes
can affect cell function
What are the two most common electrolytes
Na+
K+
What problems surround Na+
The most common problems with electrolyte
balance are caused by an imbalance between
gains and losses in Na+
What problems surround K+
Problems with K+ balance are less common but
significantly more dangerous than those
related to sodium balance
Write a note on sodium
Represents 90% of all extracellular cations.
◦ Regulated at 132 – 142mEq/L
◦ Important for nervous excitation.
◦ Creates most of the ECF Osmotic pressure.
◦ Dietary Intake (NaCl 18g)»_space; requirement (NaCl
6g)
◦ Xs excreted by the kidney, with small losses in
perspiration.
◦ Regulation by Aldosterone (increases absorption
in the distal tubule in exchange for K+ or H+
Write a note on hyponatremia
(5)
(low levels of sodium in the blood:
<130mEq/L) results from:
xs perspiration,
vomiting, diarrhoea and
burns
ingestion of hypotonic fluids
How is hyponatremia treated
Sodium imbalances do not alter sodium
concentration as water will follow salt.
Regulatory mechanisms change the ECF
volume but keep the sodium concentration
relatively constant.
When [sodium] in blood is reduced ADH is
inhibited and water is excreted.
When [sodium] in the blood is increased,
ADH is released to conserve water and
homeostasis is restored
List the symptoms of hyponatremia
muscular weakness, dizziness, headache
hypotension
mental confusion, stupor and coma.
Treatment includes diuretic use and
infusion of hypertonic salt.
What happens if you try to rehydrate without salts
Decreased Na+ in ECF
Decreased ECF osmotic pressure
Decreased interstitial osmotic pressure
Water moves from the plasma to interstitial fluid.
Plasma volume decreases and this may lead to :
Circulatory shock.
Water may also move to the ICF and cause
overhydration (intoxification) of cells
Write a note on hypernatremia
high blood sodium, >150mEq/L
results from dehydration.
Symptoms include:
◦ Thirst
◦ dryness of mouth
◦ reduced blood volume and pressure
◦ may proceed to circulatory collapse.
Treatment includes ingestion of water or
intravenous infusion of hypotonic solution
Write a note on chloride
major extracellular anion
moves between the ICF and ECF
easily
reabsorbed with Na+ by Active
Transport
What causes hyperchloremia
Dietary xs or
increased chloride retention
Symptoms include Acidosis (Cl- moves into
the RBC in exchange for HCO3-). (Metabolic
acidosis in late stage diabetes)
What causes hypochloremia
xs vomiting
dehydration
What are the symptoms of hypochloremia
muscle spasm
◦ alkalosis
◦ depresses respiration
◦ coma
What happens in hypokalemia?
Membrane hyperpolarisation occurs and
they become less responsive to stimulation.
Nodal cells become hyperpolarized, this
slows the heart rate, decreases cardiac
output and blood pressure falls.
In severe cases the heart may stop
What happens in hypoerkalemia
Muscle depolarises, repolarisation is
inhibited, cardiac contractions become
weak and irregular
Write a note on calcium
most abundant ion in the body
found with phosphorus in bone matrix
98% as bone/teeth
What are the functions of calcium
◦ bone structure
◦ blood clotting
◦ nervous system function – presynaptic release
of NT
◦ muscle contraction – NB cardiac muscle
How is Calcium regulated
Calcium is regulated by Parathyroid
hormone (PTH), Calcitonin and
Calcitriol
PTH and Calcitriol increase the release of
Ca++ from the bone and increase the
absorption of calcium from the GIT.
Calcitonin (from the thyroid C cells)
decreases blood Ca++ by increasing the
absorption of calcium by bone
Write a note on hyppercalcemia
(5)
Calcium elevated.
Cardiac muscle cells become extremely
excitable, in extreme cases the muscle
may enter an extended state of
contraction.
Contractions of skeletal muscle become
powerful and prolonged.
Calcification of the kidney and
connective tissue.
Caused by hyperparathyroidism, Vit D
toxicity, XS calcium supplements
Write a note on hypocalcemia
Calcium lowered
Contractions of the heart become weak
and may cease
Very rare condition
Symptoms include skeletal muscle spasm,
osteoporosis., intestinal cramps.
Causes include poor diet, lack of Vit D,
hypoparathyroidism, hypomagnesia
Write a note on phosphate
85% in bone as Ca10(PO4)6(OH)2
mainly intracellular.
Rest combines with:
Lipids
Protein
CHO
Nucleic acids
ATP/ADP
Buffer
Regulated by the PTH, Calcitriol and
Calcitonin in a similar manner to
Calcium.
Write a note on magnesium
50% in bone, 45% intracellular and 5% in
the ECF
Acts as a Co-enzyme
Important in nervous function.
Regulated by Aldosterone, increases Mg+
+ reabsorption.
