Biology: Organ Systems

Question 1

As glomerular filtrate moves through the ascending loop of Henle, the filtrate becomes more dilute: why?

Answer 1

The ascending loop of Henle is permeable to ions but impermeable to water

Question 2

Which of the following choices correctly traces the route of glomerular filtrate on its path to the collecting duct of a nephron?

Answer 2

Bowman’s capsule, proximal tubule, descending loop of Henle, ascending loop of Henle, distal tubule

Question 3

Which of the following has a rate of urinary excretion (units of solute per unit time) that is almost always identical to its rate of glomerular filtration in a healthy adult?

Answer 3

creatinine

Question 4

aldosterone vs adh

Answer 4

BOTH INCREASE BP

aldosterone: from adrenals
- distal convoluted tubule
- changes blood volume, NOT osmolarity
- increases activity of the Na+-K+ pump

ADH (from pituitary)
- changes blood volume and osmolarity by creating aquaporins, mostly at the collecting duct

Question 5

renin-angiotensin-aldosterone system

Answer 5

renin-angiotensin-aldosterone axis activated in response to low blood pressure.

renin released from JG cells in kidney > cleaves angiotensinogen to angiotensin I > angiotensin I released by liver, cleaved by ACE in endothelial cells to product angiotensin II > …

(1) Increases Na+ reabsorption in the
(2) Causes pituitary gland to secrete antidiuretic hormone
(3) aldosterone released from adrenal cortex > kidney to increase BP by increasing blood volume (Na K pump) [more details see diagram]
(4) Vasoconstriction — causes smooth muscle cells of blood vessels to constrict and increase resistance

• Recall, blood pressure can be measured with ∆P = Q x R ———> PA - PV = (SV x HR) x R,

Question 6

Juxta glomerular cells are part of which structure in the nephron?

Answer 6

afferent arterioles

Question 7

triggers for adh release from the posterior pituitary gland

Answer 7

high blood osmolarity
low blood pressure
Angiotensin 2 plasma levels
decrease in bp

Question 8

Mice subjected to a very high sodium diet were found to have a significant increase (p<0.05) in plasma renin concentration; in order to test the hypothesis that this increase is due to the sensing of increased sodium by macula densa cells, an assay designed to detect which of the following signalling molecules should be performed?

Answer 8

prostaglandins

Question 9

Renin

Answer 9

enzyme released from JG cells: It catalyzes the conversion of angiotensinogen to angiotensin 1.

Question 10

ACE inhibitors lower blood pressure: how?

Answer 10

Inhibit angiotensin converting enzyme, which disrupts the production angiotensin 2 from angiotensin 1

Question 11

Macula densa cells sense concentrations of which of the following?

Answer 11

sodium ions

Question 12

Macula densa cells are in what part of the nephron?

Answer 12

Macula densa cells line the distal convoluted tubule.

Macula densa cells detect low blood pressure by sensing sodium concentration in the glomerular filtrate, not in the blood plasma.

Question 13

Which of the following accurately describes a function of angiotensin 2?

Answer 13

Angiotensin 2 is part of the renin-angiotensin-aldosterone axis, which is activated in response to low blood pressure.

Question 14

Renin released in response to:

Answer 14

Renin is released in response to signals that represent low mean arterial pressure. (from juxtaglomerular cells)

• Macula densa cells detect low blood pressure by sensing sodium concentration in the glomerular filtrate, not in the blood plasma.
• baroreceptor cells sense low blood pressure
• innervation by sympathetic NS cells

Question 15

blood pressure equation

Answer 15

∆P = Q x R ———> PA - PV = (SV x HR) x R,

SV = stroke volume = mL of blood pumped out of the heart with each beat