These steps of the renin-angiotensin mechanism are in the wrong order…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
These steps of the renin-angiotensin mechanism are in the wrong order. Aldosterone is released; renin is released by the JG cells; the glomerular blood flow falls; angiotensinogen is changed to angiotensin I; Na and water are reabsorbed; angiotensin I is changed to angiotensin II.
- Write the steps in the right order.
- Which step makes the vessels narrower?
- Which step raises the reabsorption of Na and water?
Need a reminder? The key ideaShow
ADH is made in the hypothalamus and released by the neurohypophysis. It helps the reabsorption of water and prevents diuresis. Renin from the JG cells changes angiotensinogen to angiotensin I and II. Angiotensin II narrows the vessels and makes the adrenal cortex release aldosterone. ANF from the atria widens the vessels and lowers the blood pressure. In a model, the urine volume is .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) 1. The glomerular blood flow falls. 2. The JG cells release renin. 3. Angiotensinogen is changed to angiotensin I. 4. Angiotensin I is changed to angiotensin II. 5. Aldosterone is released. 6. Na and water are reabsorbed.
Step 2. (b) Angiotensin II, a powerful vasoconstrictor, narrows the vessels.
Step 3. (c) The release of aldosterone, which acts on the distal parts of the tubule.
Answer: the order is flow falls, renin, angiotensin I, angiotensin II, aldosterone, Na and water back; angiotensin II narrows the vessels; aldosterone raises the reabsorption.
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