Quick Hits - Kidney Flashcards
What 4 things does the kidney produce?
Renin
Erythropoietin (Secreted in response to hypoxia)
Calcitriol (converts inactive Vitamin D to active)
Prostaglandins - vasodilate renal arteries, Thromboxane A2 constricts the renal arteries
What is the function of aldosterone?
Controls extracellular volume
(Na and water are reabsorbed together)
What is antidiuretic hormone?
Produced in the hypothalamus and stored in the posterior pituitary
Water is reabsorbed but Na is not
How is long, intermediate, and short term BP controlled?
Long - thirst and sodium/water excretion
Intermediate - Renin, aldosterone, angiotensin system
Short- Baroreceptor reflex
Which two organs maintain pH balance?
Kidneys - titrating non volatile acids (Hydrogen)
Lungs- volatile acids (CO2)
How can the kidneys regulate glucose homeostasis?
The kidneys can synthesize glucose from amino acids
How much of the Cardiac output do the kidneys receive ?
25% or 1250 mL
What are the parameters of autoregulation?
MAP 50-180
Sys - 80-180
Which area of the kidney is more sensitive to hypotension?
Medulla because it only receives 10% of the renal blood flow why the cortex receives 90%
Blood pathway through the kidneys?
- Renal artery
- Renal segmental artery
- Interlobar artery
- Arcuate Artery
- Interlobar artery
- Afferent arterioles
- Glomeular bed
- Efferent arterioles
- Peritubular bed
- Venules
- Interlobar vein
- Arcuate vein
- Interlobar vein
- Renal segmental vein
How does the kidney respond if they perfusion is too low? Too high?
Too low -increases flow by reducing renal vascular resistance
Too high - decreases flow by increasing renal vascular resistance
Is urine autoregulated?
NO, it’s lineraly related to MAP
What are the most important mechanisms to renal autoregulation?
Myogenic Mechanism - Constriction or dilation of afferent arteriole
Tubuloglomerular feedback- juxtaglomerular negative feedback of chloride and sodium
What renal structures receive sympathetic innervation? Which levels?
Afferent and efferent arterioles
T8 - L1
How does ischemia, sepsis, and surgical stress affect the kidneys?
Vasoconstricts and retains sodium
How does vasoconstrtion and sodium retention affect renal blood flow, GFR, Urine output, and sodium excretion?
Decreases all of them
How does prostaglandins, ANP, and Kinins affect the kidneys?
Causes vasodilation and sodium excretion
How does vasodilation and sodium excretion affect the RBF, GFR, Urine output, and sodium excretion?
Increases them
Which three things increase renin release?
1, Decreased renal perfusion
2. Beta 1 stimulation (SNS activation)
3. Decreased Na and Cl delivery to the distal tubule (Tubuloglomerular feedback)
Where is aldosterone synthesized?
Zona Glomerulosa of the adrenal gland
How does ADH affect the aquaporin-2 channels?
It upregulates them
Which two mechanisms control the release of ADH?
- Increased osmolarity
- Decreased blood volume
How does ADH restore blood pressure?
- Stimulates V1 receptor which causes vasoconstriction (IP3, DAG, CA)
- Stimulates V2 receptor in the collecting ducts (Increased cAMP) which upregulates aquaporin 2 channels
Which three pathways promote renal vasodilation?
- Prostaglandins
- Natriuretic peptides
- Dopamine receptors
How can NSAIDS affect the kidneys?
Harm them through inhibition of COX. (this prevents renal arteries from vasodilating)
What is the response from the kidneys with increased ANP?
Inhibit renin release
Promote Na and water excretion
What is fenoldopam?
Selective DA1 receptor agonist that increases renal blood flow
What is a normal GFR? What substances are freely filtered?
125mL/min
Water, electrolytes, and glucose are filtered
Plasma protein are not
What is the most important determinant of GFR?
Glomerular hydrostatic pressure which determined by arterial BP, afferent arteriole resistance, and efferent arteriole resistance
nephron photo
photo
**What is reabsorption?
Substance is transferred from the tubule to the peritubular capillaries
**What is secretion?
Substance is transferred from the peritubular capillaries to the tubule
What is excretion?
Substance is removed from the body to urine
What is an example of maximum transport?
Glucose - only so much can be transported so the excess is eliminated through the urine
Where does the bulk of reabsorption of solutes and water occur?
Proximal convoluted tubule
What occurs in the descending loop of Henle?
Forms concentrated urine
Permeable to water and solutes
What occurs in the ascending loop of Henle?
Not permeable to water
Reabsorbs 20% of sodium
What occurs in the distal convoluted tubule?
Fine Tunes solute concentration
What occurs in the collecting duct?
regulation of final concentration of water
Where does aldosterone and ADH act on the nephron?
Collecting ducts
Distal tubule