The Urinary System and Balance Part 2

Question 1

Describe how Aldosterone and ANP regulate plasma Na+ levels. Include an explanation of stimuli that release these hormones.

Answer 1

When MAP or osmolarity go down, Renin is released from the Juxtaglomerular cells. Renin then turns Angiotensinogen into Angiotensin 1, which gets turned into Angiotensin 2 by ACE on the capillary wall. Angiotensin 2 stimulates the release of Aldosterone from the Adrenal Gland. Aldosterone then binds to the cytosolic receptor and opens Na+ and K+ channels.
ANP is released from the atria when the baroreceptors detect stretch. ANP shuts the Na+ channels on the apical side of principal cells at the DCT and DC

Question 2

Describe the major mechanisms which water and sodium balance influence MAP

Answer 2

When osmolarity increases, MAP decreases

Question 3

What is Aldosterone’s role in Potassium balance?

Answer 3

Aldosterone regulates principal cells and K+ stimulates Aldosterone release.

Question 4

Name the three hormones that affect plasma calcium levels. Describe the effects of each.

Answer 4

PTH, released from the Parathyroid Gland, increases blood Ca++
1,25 -(OH2)D3, precursor to Vitamin D3, helps with absorption
Calcitonin, secreted from C cells of the Thyroid Gland, increases bone formation, decreases Ca++ reabsorption by kidneys

Question 5

How does an increase in Aldosterone secretion affect Na+ reabsorption?

Answer 5

It increases Na+ reabsorption in the DCT and CD

Question 6

Where are the cells located that secrete Renin and what are the three stimuli for Renin secretion?

Answer 6

Renin secretion happens in the granular cells of the Afferent Arteriole. The stimuli are decrease pressure in Afferent Arteriole, renal sympathetic nerve activity, and decreases in Na+ and Cl- in DCT filtrate.

Question 7

Which hormone regulates K+ secretion? What stimulates this?

Answer 7

Aldosterone regulates K+ secretion. Aldosterone’s released when K+ levels increase.

Question 8

99% of Ca++ is reabsorbed. How much is done at the PCT, Loop of Henle, and DCT?

Answer 8

PCT 70%
Loop of Henle 19-20%
DCT 9-10%

Question 9

True or False. Hormones have no affect at the PCT

Answer 9

True

Question 10

Which hormone is antagonistic to Aldosterone?

Answer 10

ANP

Question 11

What are the Starling Forces and how do they contribute to GFR?

Answer 11

Hydrostatic pressure of Glomerulus, Hydrostatic pressure of the Bowmans Capsule, Oncotic pressure of the Glomerulus, Oncotic pressure of the Bowmans Capsule. The driving force is the hydrostatic pressure of the Glomerulus. It changes the diameter of the Afferent Arteriole and Efferent Arteriole to contribute to GFR.