Block 4 Objectives and Study Guide

Question 1

Understand the regulation of plasma osmolality

Answer 1

Plasma osmolality is regulated by renal reabsorption/excretion of solute (sodium) and water. The proximal tubule reabsorbs most (60%) and is not regulated

Question 2

Know the role of osmoreceptors in antidiuretic hormone (ADH) release

Answer 2

As an increase in plasma osmolality occurs, osmoreceptors are stimulated. As osmoreceptors are stimulated, ADH is released. ADH regulates aquaporin expression in the collecting duct

Question 3

Understand the mechanism of action of ADH, as well as physiological effects

Answer 3

ADH binds to receptors on collecting duct cells. An increase in ADH secretion decreased urine blood volume, decreases blood osmolality, and increases water retention. This increases blood volume as well.

Question 4

Understand the renal mechanisms (transporters) involved in plasma Na+ homeostasis, including the role of aldosterone

Answer 4

Na+/K+ ATPase plays a huge role as it makes a concentration gradient for reabsorption of sodium, as well as cotransport (reabsorption) of a number of solutes. Aldosterone increases sodium reabsoprtion via ENaC (epithelial sodium channels) at the plasma membrane principal cells in the collecting duct cells.

Question 5

Know the mechanism of water and chloride reabsorption

Answer 5

Water and chloride reabsorption can be paracellular in the proximal tubule and transporter-mediated. Aquaporin expression is regulated in the collecting duct by ADH.

Question 6

Define the regulation and effect of atrial natriuretic peptide

Answer 6

Released by the atria when the walls stretch as increases in plasma volume occur, which increases sodium water/excretion

Question 7

Understand the mechanisms involved in plasma K+ homeostasis – ICF-ECF shifts

Answer 7

ICF-ECF shifts are important to regulate potassium while the kidney regulates plasma potassium.

Question 8

Understand the mechanisms involved in plasma K+ homeostasis – Renal handling of K+ regulated by aldosterone

Answer 8

Potassium reabsorption is nearly complete by the Loop of Henle and not independently regulated, with a paracellular route. An increase in K+ plasma directly stimulates secretion of aldosterone which stimulates K+ secretion

Question 9

Understand the regulation of calcium

Answer 9

Most of the calcium is in the bone with the free fraction of calcium in the plasma being very small. It is regulated by the kidney. Calcium and phosphate are reciprocally regulated.

Question 10

Define the role of parathyroid hormone in calcium regulation

Answer 10

PTH stimulated by low calcium directly increases calcium by:
1). Stimulating release from the bone
2). Increasing renal reabsorption
3). Increasing renal tubular loss of PO4-
4). Indirectly increases calcium via vitamin D by increasing intestinal absorption

Question 11

Define the role of vitamin D in calcium regulation

Answer 11

Vitamin D increases intestinal absorption and stimulated by low plasma calcium

Question 12

Define the role of calcitonin in calcium regulation

Answer 12

Calcitonin is stimulated by high calcium, decreasing calcium by promoting bone formation

Question 13

Delineate the systems important in regulating pH – Intracellular buffers

Question 14

Delineate the systems important in regulating pH – Extracellular buffers (Carbon dioxide-Bicarbonate)