Renal Physiology Notes
Renal Physiology Pathway of urine: - Starts from minor calyxes --> major calyxes --> renal pelvis --> leaves the kidney and onto the ureter --> urinary bladder->urethra
Nephron—functional unit of the kidney Pathway of Blood filtration - Blood goes to afferent arteriole then to the capillary beds --> Bowman’s Capsule -->blood then goes to efferent arteriole --> peritubular capillary --> goes to Loop of Henle (which are called vasa recta cells)
Function of Kidney
Factors for Constant GFR (renal physiology) - Increase in Blood pressure causes podocytes to reduce capillary permeability.
- Capillary is single squamous endothelium
- Special cells in the Bowman’s capsules (podocytes) wrap around the entire capillary bed in the Bowman’s capsule.
- Sympathetic stimulation of afferent arterioles. Vasoconstriction of afferent arterioles occur.
- Less blood flows into the capillary because the arterioles are closed off.
- Parasympathetic stimulation of efferent arterioles
- Blood pressure starts to drop and not as much blood in the capillary and filtration is not enough
- Vasoconstriction of efferent arterioles forces the blood to stay in the capillary beds causing filtration to increase
- If Blood pressure decreases in the Juxtaglomerular apparatus, then Renin concentration is increased.
Cotransport: You take advantage of one ion going with its gradient to move an ion that is going against its concentration. Countercurrent Exchange system - Gradient flows in one way
- Transfer is almost 100% efficient
- Warmer blood warms the colder blood
- Loop of Henle
- Ascending Limb
- Cl and Na are actively transported out to the interstitial fluid
- The interstitial fluid is hypertonic
- Water cannot leave the filtrate in the Ascending limb
- The ascending limb is not permeable to water
- The filtrate becomes less concentrated because particles exit while water stays.
- Descending Limb
- Permeable to water, therefore, the water can leave the filtrate out onto the interstitial fluid
- Water leaves because there is more particles in the interstitial fluid
- The filtrate becomes very concentrated because water leaves
- The Descending limb is impermeable to ions. Ions cannot leave the filtrate
- This is opposite of Ascending limb (example of countercurrent exchange)
Urea is placed around the Loop of Henle, so that water comes back into the interstitial fluid. Regulation of Blood Volume (renal physiology)
For the blood plasma to stay constant, there are mechanoreceptors in hypothalamus Increase plasma osmolality (blood has less volume) --> Osmoreceptors in hypothalamus activate posterior pituitary --> Increase ADH --> increase water reabsorption in kidneys --->Less water excreted in lung Decrease plasma osmolality --> osmoreceptors in hypothalamus --> activates posterior pituitary --> Decrease ADH Regulation of Na+ (renal physiology)
Increase Na+ reabsorption - Aldosterone
- from the adrenal cortex of adrenal glands
- The hormone is a steroid (hydrophobic)
- Stimulates reabsorption in the collecting duct
- Brings in more Na+ into the cell by increasing the activity of sodium potassium pump.
- Causes small intestinal cells to take out sodium from the food we digest
- Causes sweat glands to produces less sweat
- Renin
- Released by cells
- Produced when the pressure in afferent arteriole reduces (because of less pressure, the arterioles shrink
- Renin converts angiotension into angiotension II
- Angiotension II causes vasodilation of the afferent arteriole.
- Causes vasoconstriction of the efferent arteriole
- This increases glomerular filtration rate
- Increased Renin stimulates aldosterone
Decrease Na+ Reabsorption - ANP
- The is a peptide (protein) hormone
- Travels through the bloodstream when the atria is stretched
- Decreases sodium reabsorption by stopping the sodium/potassium pump
- Renal Hypertension
- Increase in sodium reabsorption
- Blocks renal arteries?
- Increase in blood volume and increase in blood pressure
Regulation of K+ (renal physiology) - If K+ levels are too high, then potassium is dumped into the urine
- Increased Sodium reabsorption
- In exchange, you lose more Potassium that goes to the urine
- Potassium is secreted into the urine
Thirst Response (renal physiology) - Osmoreceptors in hypothalamus --> hypothalamus signals the GI tract to ask for more water
- Water Toxicity->Drinking way too much water --> too much water in the blood, leads to decreased blood osmolarity
Sodium intake increases blood osmolarity Drugs regulating Blood Pressure - Beta Blockers
- Calcium channel blockers
- Diuretics
- Furosamide
- Act on ascending limb of Loop Henle
- Also prescribed potassium pills so that potassium wouldn’t be urinated
- Aldosterone Blockers
Regulation of Blood Volume (renal physiology) Blood volume affects arteriole pressure (increased blood volume increases pressure - Increased arteriole pressure -> increases GFR in kidney -> Kidney releases renin in response --> increase renin --> increase angiotension --> decreased GFR
- Also, Increased renin --> increase aldosterone --> increase Na reabsorption
- Also, Increased arteriole pressure --> increase ANP --> goes to kidney and decrease Na+ reabsorption
- Also, increased arteriole pressure --> activates baroreceptors (in carotid arteries and aortic arch)
- Also, increased arteriole pressure --> activates osmoreceptors->tells hypothalamus to signal posterior pituitary --> posterior pituitary releases ADH
- Also, hypothalamus tell us that we are thirsty --> we drink in responses
Regulation of pH - Increase in H ion, H ion will be actively from the distal convoluted tubule and collecting duct.
- To get H ion out of the blood, you have to pee it out.
- Potassium cannot be secreted into the urine.
Bicarbonate buffering - Bicarbonate going into the glomerulus and gets filtered and gets reabsorbed
- Increase H can bind to phosphate and make hydrogen phosphate and this gets excreted
- Increase H can bind to ammonia and make ammonium and this gets excreted
Control of Urination (micturition) - Detrusor smooth muscle
- As urine fills the urinary bladder, the bladder stretches. A spinal reflex occurs, the parasympathetic ns activates the detrusor which squeezes the urinary bladder.
- Also by voluntary control—external urinary sphincter is a skeletal muscle
End of Renal Physiology Notes
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