| Course | PA 522 Comprehensive Clinical Module Endocrinology |
|---|---|
| Week | 2 |
| Paper type | Feedback axis explainer |
| Length | About 670 words, 5 pages |
| Format | APA 7 student paper |
| School | Chamberlain University |
| Program | Master of Physician Assistant Studies (MPAS) |
| Updated | October 2026 |
Free sample paper for PA 522 Week 2
Feedback Axis Explainer: The Renin, Angiotensin and Aldosterone Loop in Four Stations and Five Arrows, With the Fifth Arrow Silencing Renin and Three Predictions When One Station Breaks
Student Name
Chamberlain University
PA 522: Comprehensive Clinical Module Endocrinology
Instructor Name
Month Day, Year
Feedback Axis Explainer: The Renin, Angiotensin and Aldosterone Loop in Four Stations and Five Arrows, With the Fifth Arrow Silencing Renin and Three Predictions When One Station Breaks
The Figure
Figure 1
Four Stations of the Loop in Table Form
| Station | What it releases or does | What tells it to release | What tells it to stop |
|---|---|---|---|
| 1. Juxtaglomerular cells of the kidney | Renin into the blood | Low pressure in the afferent arteriole, low sodium reaching the macula densa, sympathetic signals | Restored pressure and sodium delivery, angiotensin II |
| 2. Circulation (liver, lungs) | Angiotensin I from angiotensinogen, then angiotensin II through converting enzyme | Renin acting on angiotensinogen | Less renin |
| 3. Zona glomerulosa of the adrenal cortex | Aldosterone | Angiotensin II and a rising potassium | Falling angiotensin II and falling potassium |
| 4. Distal nephron and collecting duct | Sodium kept, potassium and hydrogen lost, so volume expands | Aldosterone | Less aldosterone |
Note. Note. Arrows 1 to 4 run downward from station 1 to station 4. Arrow 5 runs from station 4 back to station 1: expanded volume and higher pressure silence renin release.
Station 1: The Kidney Asks
The cells of the afferent arteriole sense stretch. When pressure in the arteriole falls, or when less sodium chloride reaches the macula densa in the nearby tubule, they release renin. Sympathetic nerve signals add to the release. Renin is the first request in the chain.
Station 2: The Blood Builds the Signal
Renin cuts angiotensinogen, a protein made by the liver, into angiotensin I. Converting enzyme, much of it on lung capillaries, turns angiotensin I into angiotensin II, which narrows arterioles and carries the request on to the adrenal gland.
Station 3: The Adrenal Answers
In the outer zone of the adrenal cortex, angiotensin II and potassium are the two main signals for aldosterone. Corticotropin from the pituitary plays a smaller, short-lived part, which is why aldosterone follows a mild morning peak.
Station 4: The Nephron Acts
In the distal nephron and collecting duct, aldosterone opens sodium channels and increases the pumps that exchange sodium for potassium. Sodium and water are kept, potassium is lost in the urine and volume expands.
The Fifth Arrow
As volume and arteriolar pressure rise, the first station stops asking: renin release falls. That arrow running back up is what keeps the loop in balance, and it is the one that shows when a station has stopped listening.
From Description to Prediction
If station 3 makes aldosterone on its own, as an aldosterone-producing adenoma does, aldosterone stays up, volume expands, potassium falls and the fifth arrow silences renin: high aldosterone, low renin. That is M.T.'s pattern (Funder et al., 2016).
If station 1 is driven, for example by a narrowed renal artery that makes the kidney sense low pressure, renin rises and aldosterone follows it: both high.
If the loop is pushed from outside, as with a diuretic that wastes sodium, renin and aldosterone both rise as the loop tries to defend volume.
A blocking drug at station 2, such as lisinopril, should lower angiotensin II and remove the brake on renin, so renin rises. A renin that stays low despite lisinopril means the fifth arrow is still pressing down, which points back to station 3.
Consistent Naming
Throughout, renin means plasma renin activity measured in ng/mL/h, the form M.T.'s laboratory reports, and aldosterone means plasma aldosterone in ng/dL. Renin concentration, which some laboratories report instead, uses different units and different cutoffs (Young, 2019).
Where the Explainer Stops
This document explains how the loop works and how a broken station shows up in the numbers. It does not say which station is broken in M.T. with certainty, and it says nothing about treatment. Those belong to the testing and decision documents later in the course.
References
Funder, J. W., Carey, R. M., Mantero, F., Murad, M. H., Reincke, M., Shibata, H., Stowasser, M., & Young, W. F., Jr. (2016). The management of primary aldosteronism: Case detection, diagnosis, and treatment: An Endocrine Society clinical practice guideline. The Journal of Clinical Endocrinology and Metabolism, 101(5), 1889-1916. https://doi.org/10.1210/jc.2015-4061
Young, W. F., Jr. (2019). Diagnosis and treatment of primary aldosteronism: Practical clinical perspectives. Journal of Internal Medicine, 285(2), 126-148. https://doi.org/10.1111/joim.12831
PA 522 Week 2 instructions, in plain terms
For week two you write an explainer of one hormonal feedback axis with a labeled figure. Show each station, what it releases, what tells it to release and what tells it to stop, and draw the downward arrows plus the arrow running back up, labeled with the station it silences. In the prose, give one paragraph to each station in order. Use the same names for each hormone and measurement throughout. Partway through, move from describing the axis to predicting it: if a particular station fails or acts on its own, what happens to the measurable values? Give at least two or three predictions. Keep treatment out of the explainer entirely. End by stating what the explainer does not do. Cite a source for the physiology and for any prediction tied to a disease.
How the PA 522 Week 2 example is put together
A table serves as Figure 1, listing the juxtaglomerular cells, the circulation where angiotensin II is built, the zona glomerulosa and the distal nephron, with release signals and stop signals for each and a note describing the five arrows. Four short paragraphs walk the stations, from pressure sensing in the afferent arteriole to sodium channels in the collecting duct. A separate section treats the feedback arrow, expanded volume silencing renin. The prediction section works four cases: an adenoma giving high aldosterone and low renin, a narrowed renal artery giving both high, a diuretic raising both and lisinopril raising renin unless the adrenal is autonomous, citing the Endocrine Society guideline. A naming section fixes renin activity and aldosterone units, and a closing section limits the explainer to physiology.
Where the points sit in the PA 522 Week 2 rubric
Faculty reward the figure and the feedback arrow first. An explainer that draws only the downward chain, or leaves the returning arrow unlabeled, loses the largest share, since the week tests understanding of feedback. Next comes the turn to prediction: a document that only describes, without saying what values a broken station would produce, misses a major section of the rubric. Credit goes to one clear paragraph per station and to consistent naming of hormones and units. Treatment slipped into the explainer is a deduction, as is a figure that conflicts with the prose. Predictions are graded for accuracy, so stating that renal artery narrowing lowers renin, for example, would cost heavily. A cited physiology source is expected, along with an explicit statement of where the explainer stops.
Common PA 522 Week 2 mistakes, and how to avoid them
A common shortfall on this explainer is a well-drawn chain with no predictions, or predictions that wander into treatment. Tell us which axis your section assigned, and the explainer drafted for you would build the labeled figure with the feedback arrow named, then walk each station in its own paragraph. The prediction section works through the failures your course covers, showing what happens to each measurable value. Hormone names and units are kept consistent, which matters if your laboratory reports renin as concentration rather than activity. Treatment stays out. If your instructor wants a drawn figure rather than a table, the layout can follow that. Check every arrow and prediction against your course text before relying on the model.
Get a PA-522 Week 2 example written to your instructions
Send the instructions and any diagram template your classroom supplies, and a custom PA-522 Week 2 explainer is built on the axis your section assigned and returned inside 24 to 48 hours, with the first one free. If the assignment names a particular figure format, say which, and the sample is drawn to it.
More PA 522 papers and MPAS samples
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- PA 522 Week 7: Incidental Nodule Workup
- PA 522 Week 8: Monitoring Interval Rationale
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PA 522 Week 2 questions, answered
Which axis should the explainer use if my section does not name one?
Where the choice is open, a sample defaults to an axis with a clean three-station structure and a well documented return arm, because those show the mechanism most legibly. If your classroom lists options, send the list and the sample takes one from it. If a classmate has claimed one and your section discourages duplicates, name what is already taken and a different axis is used.
Does the figure have to be original, or can I cite one?
Sections differ on this and the assignment text usually settles it. Where an original figure is expected, the sample includes a description precise enough to draw from, with every box and arrow labeled. Where a published figure may be reproduced, the sample cites it properly and spends its own words on what the figure does not show, which is generally the timing.
How much physiology is too much for an explainer?
The test is whether a paragraph changes how a number would be read. Receptor subtypes and second messenger detail rarely do, so they stay out unless the assignment asks for them. Pulse frequency, the rhythm of secretion and the strength of the inhibitory arm all do change a reading, so those stay in and get the space.
Where can I find a free PA 522 Week 2 sample paper?
The full PA 522 Week 2 explainer is on this page, the renin, angiotensin and aldosterone loop in four stations and five arrows, with predictions for broken stations.
What does the fifth arrow do in the PA 522 Week 2 sample?
It runs from the nephron back to the kidney's renin cells, showing that expanded volume and higher pressure switch off renin release.