Renal Physiology Flashcards
What pump performs primary active transport in the renal tubules?
Na/K ATPase
On which membrane of the tubule epithelial membrane is the Na/K ATPase pump?
Where does it transport Na from?
Located on basolateral membrane
Transports Na from inside tubular cell across BL membrane into the interstitial fluid (against concentration gradient)
Whats the difference between trancellular and paracellular movement of substances at the tubular epithelial cell?
Transcellular - through the tubular epithelial cells themselves
Paracellular - between the tublar epithelial cells
What is the net movement of Na and K with the Na/K ATPase pump on the tubular epithelial cell?
2 K IN to the tubular epithelial cell
3 Na OUT to the interstitial fluid
How does primary active transport via the Na/K/ATPase facilitate secondary active transport?
Na ions pumped out of the tubular cell into interstitial fluid
Creates electrical and concentration gradient allowing Na ions to move from luminal fluid into tubular cell and can co-transport or counter-transport other molecules ‘Secondary active transport’
What is the difference between simple and facilitated diffusion?
Simple diffusion - movement of ions/molecules through a membrane or space without interaction with other membrane proteins
Facilitates - movement with interaction of a carrier protein which ‘shuttles’ the substance across
Where goes gluconeogenesis take place?
Liver and kidneys
How does paracellular transport occur?
Diffusion only
Driven by osmotic, concentration and electrical gradients
What is Fick’s Law?
The rate of diffusion across a membrane is proportional to the concentration gradient
What is Graham’s Law?
The rate of diffusion across a membrane is inversely proportional to the square root of the molecular weight of the substance
Do uncharged weak acids or bases diffuse less or more readily?
Uncharged weak acids or bases diffuse MORE readily
Hydroxylation of vitamin D3 occurs in the kidneys and produces which molecule?
Calcitriol
What is the function of calcitriol? (2)
1) Promotes calcium reabsorption from the intestine and kidneys
2) Bone mineralisation
How much Na is reabsorbed throughout each section of the nephron?
65% in the PCT
25% in the ascending loop of Henle
8% in the DCT
2% in collecting tubules
What is the primary mechanism for driving all transport in the PCT?
Primary active transport
Where in the loop of Henle does most Na reabsorption take place?
Some in thin ascending limb
Most in thick ascending limb
Describe the thin ascending limb permeability to Na and H2O? How is Na reabsorbed?
Permeable to Na
Impermeable to H2O
Na transport via simple diffusion down concentration gradient
Describe the thick ascending limb permeability to Na and H2O? How is Na reabsorbed?
Impermeable to Na and H2O
Na reabsorbed via pumps (Secondary active transport)
Describe the movement of K, Cl H using secondary active transport driven by Na in the thick ascending limb of the loop of Henle?
K+ and Cl- : Co-transport from lumen into tubular cell
H+ : counter-transport from tubular cell into lumen
In the distal convoluted tubule how is Na absorbed?
Na channels
AND
Co-transport proteins
Secondary active transport
Describe the movement of Cl- using secondary active transport driven by Na in the DCT?
Co-transport of Cl- from the lumen into the epithelial cell alongside Na
What hormone influences Na reabsorption in the collecting tubules?
Aldosterone
How much of the filtered water is reabsorbed in the PCT? (%)
70%
How does water reabsorption occur in the PCT?
Through osmosis down osmotic gradient
(Follows Na)
