BIOD152 Essential Human Anatomy and
Physiology II w-Lab Complete. Graded
A+.
1. Electrolyte Balance
What are the salts which are of greatest physiological importance?
How are these gained by the body and how are they lost? - ANSNa+, K+, Ca+2 and
Mg+2
These salts are obtained from ingested foods and fluids and are lost by way of
defecation, sweating and urination.
What is the predominant positively-charged ion in extracellular fluid? - ANSNa+ is the
predominant positive ion of the plasma and interstitial fluid (extracellular) compartments
What does the statement "water follows salt" mean? - ANSWhen salt is absorbed, water
must also be absorbed to maintain osmotic pressure
What are the 3 main ways in which sodium balance (and water) is maintained? - ANS3
main ways in which sodium balance and water is maintained: (1) the effect of the
hormone aldosterone, (2) the cardiovascular baroceptors and (3) the antidiuretic
hormone (ADH).
Explain, in detail, how the cardiovascular baroceptors work to maintain blood pressure. -
ANSThe cardiovascular baroceptors monitor and regulate blood volume (which is
influenced directly by Na+ ion concentration) to maintain blood pressure. If blood
volume (and consequently blood pressure) rises, the baroceptors signal the kidney
causing a dramatic increase in the filtration rate, increasing the output of water and Na+
which reduces blood volume to quickly normalize the pressure.
Explain, in detail, how Antidiuretic hormone (ADH) maintains Na+ concentration (and
water volume) in the extracellular fluid compartment. - ANSAntidiuretic hormone (ADH)
is released by the posterior pituitary in response to triggers by the hypothalamus
osmoreceptors which have sensed higher Na+ concentration (likely due to a lower water
volume) in the extracellular fluid compartment. ADH binds to receptors cells of the
collecting ducts of the kidney and promotes reabsorption of water into the blood system.
In the absence of ADH (likely due to higher water volume in the extracellular
compartment, low Na+ concentration), the collecting ducts allow all water to be freely
excreted as very dilute urine.
, List and give the names for sodium deficiency and excess. Give a cause of each. -
ANSSodium ion excess is called hypernatremia and is usually caused by dehydration.
Sodium ion deficiency is called hyponatremia and can be caused by solute loss and/or
water retention due to renal disease, diarrhea, skin burns, excessive sweating, vomiting
or Addison's disease (aldosterone deficiency)
What are the 2 main ways in which potassium balance is maintained? - ANSThe 2 main
ways in which potassium balance is maintained are the role of the cortical collecting
ducts of the renal medulla and the effect of the hormone aldosterone.
Explain, in detail, how the renal cortical collecting ducts act to maintain potassium
balance. - ANSWhen K+ is high in blood plasma because of high K+ in the diet, the
renal cortical collecting ducts reabsorb 90% of the ion, allowing the remainder to be
excreted in the urine. When K+ is low in blood plasma because of low K+ in the diet, the
intercalated cells of the renal cortical collecting ducts reabsorb greater than 90% of the
ion, allowing a smaller amount to be excreted in the urine.
Explain in detail, how aldosterone acts to maintain potassium balance. - ANSThe
adrenal cortex cells which secrete aldosterone are triggered by higher K+ levels to
increase the excretion of K+ to maintain potassium balance
List and give the names for potassium deficiency and excess. Give a cause of each. -
ANSPotassium ion excess, called hyperkalemia, can be due to renal or adrenal gland
disease or potassium leaking out of cells into the blood circulation due to severe tissue
damage. Potassium ion deficiency, called hypokalemia, can be due to diarrhea,
vomiting or hyperaldosteronism (over-secretion of aldosterone).
What are the 2 main ways in which calcium balance is maintained? - ANSCalcium
balance is maintained by the action of calcitonin and parathyroid hormones which cause
the reabsorption of 98% of calcium by the kidney, small intestines and bones.
Explain, in detail, how calcitonin and parathyroid hormones act to maintain calcium
balance. - ANSIf plasma calcium levels decrease, the parathyroid glands secrete
parathyroid hormone (PTH) which causes a subsequent increase in calcium levels by:
(1) activating bone-digesting osteoclasts which release Ca+2 from the bones into the
blood, (2) stimulating the small intestine to absorb Ca+2 and (3) increasing the
reabsorption of Ca+2 by the renal tubules. In response to increasing plasma calcium
levels, calcitonin is released by the thyroid, inhibiting the bone reabsorption action of
osteoclasts.
List and give the names for calcium deficiency and excess. Give a cause of each. -
ANSCalcium ion excess, called hypercalcemia, can be due to hyperparathyroidism or
renal disease. Calcium ion deficiency, called hypocalcemia, can be due to diarrhea,
burns, Vitamin D deficiency and alkalosis
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