Renal Hemodynamics and RAAS Flashcards
The Juxtaglomerular Apparatus is a complex feedback mechanism used by the kidney to ____
Autoregulate the GFR
The thick segment of the ascending limb of the Loop of Henle becomes the ____ as it passes between the Afferent and Efferent Arterioles
Distal Tubule
The JG Apparatus consists primarily of two types of specialized cells:
Juxtaglomerular Cells
Macula Densa
Juxtaglomerular cells, sometimes called Granular cells, are ______ cells found in the wall of the Afferent and Efferent Arterioles adjacent to Bowman’s Capsule
specialized smooth muscle
Juxtaglomerular cells contain granules full of the hormone ____
Renin
The_____ is a region of specialized epithelium within the wall of the Distal Tubule immediately adjacent to the Afferent and Efferent Arterioles.
Macula Densa
Macula Densa cells are a type of____ and are especially sensitive to the concentration of Sodium (technically NaCl) within the lumen of the tubule
Chemoreceptor
Macula Densa cells are especially sensitive to the concentration of _____ within the lumen of the tubule.
Sodium (technically NaCl)
Where do sympathetic nerve endings synapse in the Juxtaglomerular Apparatus?
on Afferent and Efferent Arteriole smooth muscle fibers.
What do Mesangial cells do?
act primarily as support cells in the region where all these structures (of JA) come together.
There are three main mechanisms that trigger Renin release from the Juxtaglomerular Cells
Physical
Electrical
Chemical
Physical trigger for release of renin
Juxtaglomerular Cells in the walls of the Afferent Arterioles act as baroreceptors and respond to a drop in systemic blood pressure by releasing Renin directly into the blood
Electrical trigger for the release of renin
Stimulation of the Sympathetic Nerve Fibers during a “fight or flight” situation causes Afferent and Efferent Arterioles to vasoconstrict (thereby briefly and acutely dropping GFR), as well as stimulating release of Renin by the Juxtaglomerular Cells.
T/F Renin release is one mechanism by which BP increases
T
Chemical trigger for renin release
- When Macula Densa cells sense a drop in Na and Cl concentration in the tubule, this is interpreted as a decrease in GFR, and the Macula Densa cells respond by secreting Prostaglandins.
- Renal prostaglandins act as a paracrine messenger by triggering Afferent Arteriole vasodilation (increasing glomerular pressure, GFR), and by triggering Juxtaglomerular cells to release Renin.
The JAS is is also the beginning point of the _____
Renin-Angiotensin-Aldosterone System (RAAS)
The RAAS ultimately results in ____ and ____ in the tubules of the kidneys
peripheral vascular constriction; fluid/electrolyte retention
The end-goal and purpose of the RAAS is to _____
increase systemic blood pressure when blood pressure and/or GFR are low
When the peptide hormone Renin is released from the Juxtaglomerular Cells in the kidney, it enters ____
systemic circulation (meaning it goes everywhere)
Angiotensinogen is an ____ peptide hormone that is secreted continuously by Hepatocytes in the liver
inactive
While in circulation, Angiotensin I comes in contact with ____, which is largely found in pulmonary capillaries as well as other endovascular cells
Angiotensin Converting Enzyme (ACE)
ACE enzymatically slices Angiotensin I, converting it to the very active and potent _____.
Angiotensin II
When Renin comes in contact with Angiotensinogen, it enzymatically slices ____, converting it to mildly active Angiotensin I
Angiotensinogen
How does Angiotensin II work to increase arterial blood pressure?
One mechanism is by acting as a potent vasoconstrictor, causing contractions of peripheral vascular smooth muscle, which increases peripheral resistance, thereby increasing blood pressure.
Angiotensin II can also act directly on the ____ system of the kidney to increase Sodium reabsorption
tubular
Angiotensin II also causes ___ of the Efferent Arterioles
vasoconstriction
Angiotensin II also stimulates secretion of ____
Antidiuretic Hormone (also known as Arginine Vasopressin or AVP)
Angiotensin II also stimulates secretion of ____ from the Adrenal glands
Aldosterone
Aldosterone works primarily at the distal convoluted tubule and collecting tubules of the kidney to increase ___ secretion and ___ reabsorption.
K+; Na+ (& water)
Renal Artery Stenosis is a _____ of the renal arteries that supply blood flow to the kidneys.
narrowing
Two common classes of medications that work by influencing the RAAS are
Angiotensin Converting Enzyme Inhibitors (ACE-Is)
Angiotensin Receptor Blockers (ARBs)
