Explain the results of renal nerve innervations & hormones on the kidney..
Sympathetic - Vasocontriction
Parasympathetic - Vasodilation
Adrenaline.vasporesin & angiogensin II - Vasoconstriction
Dopamine - vasodilation
Why is the kidney considered autoregulatory?
Blood flow to glomerulus unaffected by changes in blood pressure. Cab respond to levels of Na+ by Constricting or dialating afferent/efferent arterioles accordingly via the RAAS system or the release of nitric oxide
What are the components of the glomerulus that affect ultrafiltration?
- Endothelial cells - single layer, restrict passage of blood cells
- Basement membrane - Main filtration barrier
- Podocytes - Phagocytose macromolecules & restrict passage of medium sized proteins
Describe what occurs in Proximal convoluted tubule..
- Microvili to increase surface area/absorption
- resorbs 2/3 of filtered water,Na+,K+ & Cl- back into blood.
- Na pumps provide driving force to absorb amino acids and lactate, but metabolicly expensive
- Obligatory movement of water. Uptake of na and subsequently cl causes water movement by osmosis. Not independantly controlled.
Describe what occurs in the loop of henle..
Descending limb: Walls are impermeable to electrolytes but permeable to water. Therefore lumen is concentrated, water moves out by osmosis. Concentration increases down the loop, peaking at the bottom.
Ascedning limb: Walls impermeable to water but na and cl actively pumped into the medullary tissue and capillaries. Ca and Mg passively move into lumen creatic and osmotic pressure. Water is then drawn from the descending limb, setting up the countercurrent multiplier.
Describe what occurs in the distal convoluted tubule..
- Na resorbed, only 4%
- cl moves out with Na, as well as water (dependant on aldosterone release)
- K and H+ actively secreted. amount depedant on PH of the blood.
Describe ADH release…
Fluid balance
- Osmolarity increases (Not enough Water) and is detected by osmoreceptors in the hypothalamus
- ADH released from posterior pituitary
- Insertion of aquaporins in the collecting ducts
- more water resorption = lowers osmolarity
Describe the Renin-Angiotensin-Aldosterone system (RAAS)
NA Balance
- Low na levels detected by macula densa cells. Leads to granular cells of afferent arteriole to secrete Renin
- Renin converts Blood angiotensinogen into angiotensin I. (ACE from the lungs causes conversion into Angiotensin II)
- Angiotensin II acts on glormerulosa cells of the adrenal cortex, stimulating release of aldosterone.
- Aldosterone stimulates synthesis and insertion of Na channels. Na absorbed
