12. CPR Endocrinology

Question 1

Where are the cell bodies of the neurons that release ADH? Where do they synapse?

Answer 1

Supraoptic nuclei of the hypothalamus then synapse in posterior pituitary

Question 2

What are triggers for ADH secretion? What is it most sensitive to?

Answer 2

Low BP
Arterial stretch due to low blood volume
High osmolality (most sensitive)

Question 3

What are the main effects of ADH?

Answer 3

Raise blood pressure and blood volume via vasoconstriction in blood vessels (V1) and/or increased absorption of water in the kidneys (V2)

Question 4

What is ADH’s effect on the renal collecting ducts?

Answer 4

It binds to V2 receptors then is taken into principal cell. Leads to increased aquaporin-2 on apical surface.

Question 5

What is another word for hyperosmolarity?

Answer 5

Dehydration

Question 6

Describe central diabetes insipidus and its effects on ADH.

Answer 6

Lack of ADH (low plasma ADH). Could result from damage to pituitary and destruction of the hypothalamus. Can be treated with desmopressin (drug that prevents water excretion)

Question 7

Describe nephrogenic diabetes insipidus and its effects on ADH

Answer 7

Kidneys unable to respond to ADH (high plasma ADH). Could result from kidney diseases and drugs like lithium.

Question 8

What occurs during syndrome of inappropriate ADH secretion (SIADH)?

Answer 8

Excessive secretion of ADH. Excessive water retention. Hypoosmolality fails to inhibit ADH release.

Question 9

What are triggers for aldosterone secretion?

Answer 9

Decreased Na+ or increased K+ in blood

Decreased blood volume and/or blood pressure

Question 10

What is aldosterone’s effect on the renal collecting ducts?

Answer 10

It enters principal cells then binds to aldosterone receptor in cytosol. Leads to synthesis of new protein channels and pumps. Results in increased Na+ reabsorption and K+ secretion.

Question 11

What is the heart’s role in renal NaCl excretion?

Answer 11

The atria release ANP when the atria are distended. The ventricles similarly release BNP when distended. Both ANP and BNP are natriuretic peptides that decrease total peripheral resistance and enhance urinary excretion of NaCl and water.

Question 12

What is the natriuretic peptide released by the kidney? What does it do?

Answer 12

Urodilatin. It inhibits NaCl and water reabsorption across the medullary portion of the collecting duct.

Question 13

What are the main effects of natriuretic peptides related to the control of renal NaCl excretion?

Answer 13

Inhibition of renin/aldosterone secretion
Inhibition of ADH secretion
Inhibition of NaCl reabsorption by the collecting duct

Question 14

What is the role of sympathetics in renal NaCl excretion?

Answer 14

They stimulate the reabsorption of NaCl and water by the proximal tubule, thick ascending limb, distal tubule, and collecting duct.

Question 15

What is the effect of insulin on K+ levels.

Answer 15

Insulin stimulates K+ uptake into cells by increasing activity of Na+/K+ ATPase

Question 16

How does Ca2+ levels effect action potentials?

Answer 16

During hypocalcemia, the activation threshold is lower, resulting in increased membrane excitability. This leads to hyperreflexia. (positive Chvostek and Trousseau sign)

Question 17

How are the concentrations of phosphate and calcium related?

Answer 17

An increased in phosphate concentration will lead to a decrease in Ca2+ concentration and vice versa.

Question 18

How does acidemia effect Ca2+ concentration?

Answer 18

Free ionized Ca2+ goes up because less Ca2+ is bound to albumin

Question 19

How does alkalemia effect Ca2+ concentration?

Answer 19

Free ionized Ca2+ goes down because more Ca2+ is bound to albumin. Often accompanied by hypocalcemia.

Question 20

What stimulates PTH secretion?

Answer 20

Stimulated by low plasma Ca2+. Leads to increase in plasma Ca2+.

Question 21

What are the effects of PTH on the bones, kidneys, and intestines?

Answer 21

Bone: increased bone resorption

Kidney: increased Ca2+ reabsorption and urinary cAMP
decreased phosphate reabsorption

Intestine: increased Ca2+ absorption

Question 22

What is the main circulating (but low activity) form of vitamin D?

Answer 22

25-OH-cholecalciferol

Question 23

What is the active form of vitamin D? What enzyme activates it?

Answer 23

1,25-(OH)2-cholecalciferol

Activated by 1alpha-hydroxylase

Question 24

What occurs during familial hypocalciuric hypercalcemia (FHH)?

Answer 24

Autosomal dominant disorder. Mutation inactivates CaSR in parathyroid glands and parallel Ca2+ receptors in ascending limb of the kidney. This leads to less negative feedback on PTH, increasing blood Ca2+ levels and decreasing urine Ca2+ levels.