Renal - Physiology (Hormones) Flashcards
Pg. 530-531 in First Aid 2014 Pg. 485-486 in First Aid 2013 Sections include: -Renin-angiotensin-aldosterone system -Juxtaglomerular apparatus -Kidney endocrine functions -Hormones acting on kidney
What are 3 stimuli that cause the release of renin? Which structures are responsible for detection of these stimuli?
Kidney; (1) Decreased BP (JG cells) (2) Decreased Na + delivery (macula densa cells) (3) Increased sympathetic tone (Beta 1-receptors)
What releases renin? What function does renin serve?
Kidney; Converts angiotensinogen to angiotensin I
What releases Angiotensinogen?
Liver
What releases ACE? What functions does it serve?
Lungs and kidney; (1) Converts angiotensin I to angiotensin II (2) Bradykinin breakdown
What 6 functions does angiotensin II have?
(1) Acts at AT I receptors on vascular smooth muscle –> Vasoconstriction –> Increase BP (2) Constricts efferent arteriole of glomerulus –> Increase FF to preserve renal function (GFR) in low-volume states (i.e., when RBF decrease) (3) Triggers release of Aldosterone (from adrenal gland) –> Increase Na+ channel and Na+/K+ pump insertion in principal cells, Enhances K+ and H+ excretion (upregulates principal cell K+ channels and intercalated cell H+ ATPases) –> Creates favorable Na+ gradient for Na+ and H2O reabsorption (4) Triggers release of ADH (from posterior pituitary) –> Increase H2O channel insertion in principal cells –> H2O reabsorption (5) Increase proximal tubule Na+/H+ activity –> Na+, HCO3-, and H2O reabsorption (can permit contraction alkalosis) (6) Simulates hypothalamus –> Thirst
What effect does angiotensin II have on vasculature, and how? What ultimate effect does this have?
Acts at AT I receptors on vascular smooth muscle –> Vasoconstriction –> Increase BP
What effect does angiotensin II have on the glomerulus? What consequence does this have?
Constricts efferent arteriole of glomerulus –> Increase FF to preserve renal function (GFR) in low-volume states (i.e., when RBF decreases)
What effect does angiotensin II have on the adrenal gland? What consequence does this have?
Aldosterone (adrenal gland) –> Increase Na+ channel and Na+/K+ pump insertion in principal cells; Enhances K+ and H+ excretion (upregulates principal cell K+ channels and intercalated cell H+ ATPases) –> Creates favorable Na+ gradient for Na+ and H2O reabsorption
What effect does angiotensin II have on the posterior pituitary? What consequence does this have?
ADH (posterior pituitary) –> Increase H2O channel insertion in principal cells –> H2O reabsorption
What effect does angiotensin II have on the proximal tubule? What consequence does this have?
Increase proximal tubule Na+/H+ activity –> Na+, HCO3-, and H2O reabsorption (can permit contraction alkalosis)
What part of the brain does angiotensin II affect? What consequence does this have?
Stimulates hypothalamus –> thirst
What is the main purpose of ATII, and how does it mainly accomplish this?
Affects baroreceptor function; limits reflex bradycardia, which would normally accompany its pressor effects. Helps maintain blood volume and blood pressure.
From where is ANP released, and in response to what?
Released from atria in response to increased volume
What impact can ANP have on the renin-angiotensin-aldosterone system?
May act as a “check” on renin-angiotensin-aldosterone system
What effect does ANP have on vasculature, and how? What consequences does this have?
Relaxes vascular smooth muscle via cGMP, causing increased GFR, decreased renin.
What is the primary function of ADH? To what does it respond?
Primarily regulates osmolarity; also responds to low blood volume states.
What is the primary function of Aldosterone? To what does it respond?
Primarily regulates ECF Na+ content and volume; Responds to low blood volume states.
What does “Juxta” mean? What is contained in the juxtaglomerular apparatus? Name and define these parts.
Juxta = close by; Consists of JG cells (modified smooth muscle of afferent arteriole) and the macula densa (NaCl sensor, part of the distal convoluted tubule)
What is the act of JG cells? In response to what 3 things does it act?
JG cells secrete renin in response to (1) decreased renal blood pressure, (2) decreased NaCl delivery to distal tubule, and (3) increased sympathetic tone (Beta 1).
What end goal does the JGA accomplish, and how?
JGA defends GFR via renin-angiotensin-aldosterone system.
How do Beta-blockers work in the kidney?
Beta-blockers can decrease BP by inhibiting Beta1-receptors of the JGA, causing decreased renin release
What releases erythropoietin? To what is it released in response?
Released by interstitial cells in the peritubular capillary bed in response to hypoxia.
What relation does vitamin D have to the kidney? Which part of the kidney is involved?
Proximal tubule cells convert 25-OH vitamin D (inactive form) to 1,25-(OH)2 vitamin D (active form)
What enzyme converts 25-OH vitamin D to 1,25-(OH)2 vitamin D, and where? What stimulates this enzyme?
1 alpha-hydroxylase; Proximal tubule cells; PTH
What secretes renin, and in response to what?
Secreted by JG cells in response to decreased renal arterial pressure and increased renal sympathetic discharge (Beta 1 effect).
How are prostaglandins secreted, and what effect do they have?
Paracrine secretion vasodilates the afferent arterioles to increase RBF
By what mechanism do NSAIDs work? What effects can they have?
NSAIDs block renal-protective prostaglandin synthesis –> constriction of afferent arteriole and decreased GFR; this may result in acute renal failure
Name 5 hormones acting on the kidney.
(1) Angiotensin II (AT II) (2) Atrial natriuretic peptide (ANP) (3) Parathyroid hormone (PTH) (4) Aldosterone (5) ADH (vasopressin)
In response to what is AT II synthesized?
Synthesized in response to decreased BP.
What direct effects does AT II have on the kidney? What is the net effect?
Causes efferent arteriole constriction –> increased GFR and increased FF but with compensatory Na+ reabsorption in proximal and distal nephron. Net effect: preservation of renal function in low-volume state (increased FF) with simultaneous Na+ reabsorption (both proximal and distal) to maintain circulating volume.
In response to what is ANP synthesized?
Secreted in response to increased atrial pressure.
What direct effects does ANP have on the kidney? What is the net effect?
Causes increased GFR and increased Na+ filtration with no compensatory Na+ reabsorption in distal nephron. Net effect: Na+ loss and volume loss.
In response to what is PTH secreted?
Secreted in response to decreased plasma [Ca2+], increased plasma [(PO4)3-], or decreased plasma [1,25-(OH)2 vitamin D].
What direct effects does PTH have?
Causes increased [Ca2+] reabsorption (DCT), decreased [(PO4)3-] reabsorption (PCT), and increased 1,25-(OH)2 vitamin D production (increased Ca2+ and (PO4)3- absorption from gut via vitamin D)
In response to what is Aldosterone secreted?
Secreted in response to decreased blood volume (via AT II) and increased plasma [K+]
What direct effects does Aldosterone cause?
Causes increased Na+ reabsorption, increased K+ secretion, and increased H+ secretion.
What is another name for ADH? In response to what is it secreted?
ADH (vasopressin); Secreted in response to increased plasma osmolarity and decreased blood volume.
What direct effects does ADH (vasopressin) cause, and how?
Binds to receptors on principal cells, causing increased number of water channels and increased H2O reabsorption.
Where in the kidney do each of the following hormones mainly act: (1) AT II (2) ANP (3) PTH (4) Aldosterone (5) ADH (vasopressin).
(1) Glomerulus (2) Glomerulus & DCT (3) PCT & DCT (4) Collecting tubule (5) Collecting tubule.
