Where is the concentration of Na, Cl and K greatest?
Na + Cl = outside the cell
K = inside the cell
What is a hypertonic solution and its effect on cells?
Hypertonic = increased conc of solutes
Causes cell to shrink
What is a hypotonic solution and its effect on cells?
Hypotonic = decreased conc of solutes (more water)
Causes cell to swell
What is the function of Na, Cl and K in the body?
Na + Cl = controls movement of water (water follows salt)
K = generates resting membrane potential
What cells produce renin and where are they found?
Granular cells in the walls of the efferent arteriole
What is the route of blood flow from the afferent arteriole?
Afferent arteriole - glomerular capillary - efferent arteriole - peritubular capillaries - venule - renal vein
What are the 3 layers of the glomerular capillary walls and what is their function?
Endothelium (large pores for solutes to pass through - too small for RBCs) Basement membrane (-ve charge to prevent plasma proteins crossing) Epithelium (podocytes - filtration barrier)
What is the main force involved in filtration through the capillary wall into the tubules?
Hydrostatic pressure (passive) from capillary BP
How is a constant blood pressure along the afferent arteriole maintained?
The efferent arteriole is narrower than the afferent
Why must the GFR be maintained?
To prevent shifts in salt and fluid balance
How is the GFR extrinsically maintained?
Control of BP:
Vasoconstriction = decreased blood flow = decreased GFR
Vasodilation = increased blood flow = increased GFR
How is the GFR intrinsically controlled?
Myogenic: smooth muscle contracts in response to stretch (controls blood flow = controls GFR)
Tubuloglomerular feedback: macula densa cells (salt sensitive) release chemicals to constrict smooth muscle of afferent arteriole (decreases blood flow = decreased GFR) - effective if salt increases
What cells are salt sensitive and where are they found?
Macula densa cells in distal tubule
How are the kidneys involved in acid base balance?
H ions are recreated into tubular fluid for excretion from peritubular capillaries
What is used to calculate plasma clearance?
Creatinine
What is the function of renin?
Converts angiotensinogen to angiotensin I
What is the outcome of RAAS?
Eventually causes Na reabsorption and thus water retention (via aldosterone) so increases BP
