Renal physiology and blood pressure Flashcards
What is the primary function of the nephron?
The primary functions of the nephron are filtration, reabsorption, and secretion.
What is the role of the Bowman’s capsule in the nephron?
The Bowman’s capsule helps filter waste products from the bloodstream flowing through the capillaries.
What happens in the proximal convoluted tubule (PCT) of the nephron?
In the PCT, sodium ions are actively reabsorbed, which causes excess water to leave. This is the site for reabsorbing glucose, amino acids, and ions. It is also the largest site for water reabsorption, where 60-70% of water is reabsorbed by osmosis.
What role does the sodium-glucose transporter (SGLT2) play in the proximal convoluted tubule?
The sodium-glucose transporter (SGLT2) in the PCT actively reabsorbs glucose. Drugs like gliflozins, which block this transporter, are used in the treatment of type 2 diabetes.
What is the countercurrent mechanism in the loop of Henle?
The countercurrent mechanism occurs in the loop of Henle, where the descending limb is permeable to water, and the ascending limb is permeable to solutes but impermeable to water. This creates a concentration gradient for the active removal of sodium and chloride ions.
What is the action of loop diuretics in the loop of Henle?
Loop diuretics act on the NKCC transporter in the loop of Henle, which removes Na+, K+, and Cl- ions from the filtrate, reducing sodium reabsorption and increasing urine output.
How does the distal convoluted tubule (DCT) contribute to the nephron’s function?
In the DCT, sodium chloride (NaCl) is actively reabsorbed through the Na/Cl transporter (NCC), and it is the site of action for thiazide diuretics.
What is the role of aldosterone in the collecting duct?
Aldosterone acts on the collecting duct by stimulating the epithelial sodium channels (ENaC) to reabsorb sodium. It also increases the expression of aquaporins to enhance water reabsorption.
What happens in the collecting duct when there is a signal from osmoreceptors indicating low water levels in the body?
When osmoreceptors detect low water levels, aquaporins are inserted into the collecting duct and distal convoluted tubule, allowing more water to be reabsorbed, thus conserving water in the body.
How does the Renin-Angiotensin-Aldosterone System (RAAS) affect kidney function and blood pressure?
The RAAS responds to decreased perfusion pressure, leading to the secretion of renin, which activates angiotensin II. Angiotensin II stimulates sodium reabsorption, increasing blood volume, stroke volume, and blood pressure. It also triggers aldosterone and vasopressin (ADH) release to further promote water retention and vasoconstriction.
What is the effect of natriuretic peptides on kidney function?
Natriuretic peptides inhibit sodium reabsorption in the kidneys by blocking the activity of epithelial sodium channels (ENaC). This promotes diuresis (urine production) and natriuresis (excretion of sodium), helping to reduce extracellular fluid volume and lower blood pressure.
What triggers the release of natriuretic peptides in the body?
Natriuretic peptides are released from cardiomyocytes in response to stretch detected by baroreceptors, which are activated by high extracellular fluid volume and blood pressure.
How does the sympathetic nervous system influence the renin-angiotensin-aldosterone system (RAAS)?
The sympathetic nervous system stimulates the RAAS by inhibiting baroreceptors. This leads to the secretion of renin, which activates angiotensin II, increasing sodium reabsorption, blood volume, and blood pressure.
What is the role of vasopressin (ADH) in regulating water balance?
Vasopressin (ADH) increases the expression of aquaporins in the collecting duct, promoting water reabsorption. It also constricts blood vessels and triggers the sensation of thirst to help restore water balance.
How does blood volume affect glomerular filtration rate (GFR) and kidney function?
An increase in blood volume, which occurs with higher blood pressure, leads to an increase in cardiac output, glomerular filtration rate (GFR), and kidney perfusion, enhancing kidney function. Conversely, a decrease in blood volume can lower GFR and kidney function.
What happens to the filtrate as it moves through the descending limb of the loop of Henle?
The descending limb of the loop of Henle is permeable to water but impermeable to solutes. As the filtrate moves through, water is reabsorbed, making the filtrate more concentrated.
How do loop diuretics affect sodium reabsorption in the kidney?
Loop diuretics inhibit the NKCC transporter in the loop of Henle, which prevents the reabsorption of sodium (Na+), potassium (K+), and chloride (Cl-) ions, leading to increased urine production and decreased sodium retention.
What is the role of the Na/K ATPase in the nephron?
The Na/K ATPase pump plays a crucial role in maintaining sodium and potassium gradients by actively pumping sodium out of the cell and potassium into the cell, which is essential for sodium reabsorption in the loop of Henle and other parts of the nephron.
How do thiazide diuretics affect the distal convoluted tubule?
Thiazide diuretics inhibit the Na/Cl transporter (NCC) in the distal convoluted tubule, reducing sodium and chloride reabsorption, which increases urine output and decreases blood volume.
What effect does angiotensin II have on the blood vessels and kidneys?
Angiotensin II causes vasoconstriction, which increases total peripheral resistance and blood pressure. In the kidneys, it stimulates sodium reabsorption and aldosterone release, contributing to water retention and further increasing blood pressure.
