Renal Physio (Nephron/function) Flashcards
What are the functions of the nephron
1) filtration
- filter the blood
2) reabsorption
- molecules in the tubules being sent back to the blood
3) Secretion
- molecules from the blood being sent to the tubules
Anatomy of glomerulus and loop on henle
Where does filtration happen in the nephron?
- only occurs in the glomerulus
- fluid/molecules move from glomerulus into PCT -proteins don’t cross;too big
What is the glomerular filtration rate?
125 ml/min
What causes filtration in the nephron?
-hydrostatic pressure (blood pressure)
What determines the GFR?
- Filtration pressure
- filtration coefficient
What is autoregulation?
Maintenance of constant GFR within a wide range of blood pressure.
What is the myogenic response when MAP is high (autoregulation)?
-Causes GFR to temporarily increase > Vasoconstriction of afferent arteriole (to decrease blood flow to glomerulus) -increases resistance -decrease renal blood flow
What is the myogenic response when MAP is low (autoregulation)?
-GFR is temporarily low > -increase resistance of efferent arteriole -decreases renal blood flow -increases PH and GFR
How does the tubuloglomerular feedback help GFR autoregulation?
What is the function of macula dense cells?
-sense distal tubule ‘flow’ and release paracrine signals that affect afferent and efferent arteriole diameter
What happens during reabsorption in the nephron?
-returns 99% of filtrate back to peritubular capillaries
What are the 2 ways reabsorption can occur?
1) epithelial transport
2) transcellular pathway
How is Na+ reabsorbed?
How is Glucose reabsorbed?
-in the PCT
-
What happens during saturation?
-‘transport rate of substance is proportional to the plasma concentration of the substance, up to the point at which transporters become saturated’
- once saturation occurs, transport rate reaches maximum - the plasma concentration of substrate at which the transport maximum occurs is called renal threshold
What happens during secretion?
Molecules move from peritubular capillaries into kidney tubule
What happens during excretion?
-eliminate waste from body
Amount excreted= amount filtered - amount reabsorbed +amount secreted
What is the clearance of excretion?
-rate a solute is cleared from plasma
