Kidneys: Filtration Flashcards
What three mechanisms regulate kidney filtration?
Renal auto regulation
Hormonal
Neural regulation
Where is renal autoregulation?
It’s intrinsic to the kidney itself
What two mechanisms control renal autoregulation?
Myogenic mechanism- Tendency of vascular smooth muscle to contract when stretched
Tubuloglomerular feedback mechanism- See Macula Densa cells
Which two hormones regulate filtration?
Angiotensin II
ADH
In general, what does angiotensin II do?
Raise BP
Specifically, how does angiotensin II raise BP (4 things)
By causing widespread arteriolar vasoconstriction
Activating thirst centers
Stimulate aldosterone release → makes kidney retain Na+
Stimulates ADH release
How does angiotensinogen become angiotensin II?
Angiotensinogen → (via renin) Angiotensin I → (via ACE in lungs) Angiotensin II
What is renin?
What does it do?
Renin is a proteolytic enzyme from the JG cells of the kidney
Eventually creates more angiotensin II, so ↑ BP
What 2 types of cells are in the juxtaglomerular apparatus?
Juxtaglomerular cells/JG cells/granular cells
Macula densa cells
Where is the juxtaglomerular apparatus?
Occurs where afferent arteriole comes in contact with distal convoluted tubule (DCT)
Where are juxtaglomerular cells?
Enlarged specialized smooth muscle cells wrapped around afferent arteriole
What do juxtaglomerular cells do?
Secrete renin when they detect a low BP
Where are macula densa cells?
Closely packed cells in the ascending loop of Henle
lie adjacent to JG cells
What do macula dense cells do?
Are chemoreceptors that respond to changes in NaCl of filtrate
Macula dense cells release a ________, to slow glomerular filtration rate (___). This slowdown allows more time for the _______ to filter blood.
vasoconstrictor
GFR
Glomerulus
What is a Tx for hypotension?
Tx for hypotension is ACE-inhibitors which blocks the formation of angiotensin II, so no vasoconstriction.
What is the RAAS system? And what does it do?
RAAS (Renin, Angiotensin, Aldosterone System) plays an important part in regulating blood volume and systemic vascular resistance, which together influence cardiac output and arterial pressure
Where does ADH come from?
Posterior pituitary
When is ADH released? What does it do?
Release in response to dehydration, ↑blood osmolarity (more particles in blood)
Results in ↑BP by ↑H2O resorption by collecting ducts
Without ADH what disease occurs?
Diabetes insipitus
What kind of neural regulation occurs: at rest; under moderate stress; under severe stress?
At rest- Sympathetic nervous system is minimal
Moderate stress- Both afferent and efferent arterioles constrict the same
Extreme stress- Vasoconstriction of the afferent predominates- blood to brain/heart
What two substances are produced by the kidneys, and what do they do? (Enzyme and hormone)
Renin- A proteolytic enzyme
Erythropoietin- A hormone that regulates the production of RBCs. Stimulated whenever the delivery of O2 is less than normal
What is GFR, how much does it amount to?
Glomerular filtration rate- The total amount of filtrate formed per minute by the kidneys
Normal amount is 120 mL/minute
Equivalent to 150 L/day
