Block 6 Renal Physio Prt 1

Based on the given values, the plasma HCO3 concentration is low (14 meq/L), indicating a decrease in bicarbonate levels. Additionally, the blood pH is below the normal range (7.3), indicating acidemia. These findings suggest a metabolic acidosis, which is characterized by a decrease in bicarbonate levels and an increase in acidity.

An increase in the plasma ADH concentration will lead to an increase in the water permeability of the apical membrane in the distal tubule and collecting ducts. This is because ADH, or antidiuretic hormone, acts on the cells of the distal tubule and collecting ducts to insert aquaporin channels into the apical membrane. These aquaporin channels allow water to pass through the membrane and be reabsorbed back into the bloodstream, resulting in a decrease in urine output and an increase in water reabsorption.

An increase in plasma aldosterone concentration will increase the apical-membrane potassium permeability in principal cells of the collecting ducts. Aldosterone acts on the principal cells of the collecting ducts to increase the reabsorption of sodium ions and the secretion of potassium ions. This leads to an increase in potassium permeability in the apical membrane of these cells, allowing more potassium ions to be secreted into the urine. This helps to maintain electrolyte balance in the body.

The correct answer is "None of the above (since all can influence renin secretion)". This means that all of the options listed in the question will influence renal renin secretion. A change in renal sympathetic nervous system activity can stimulate renin secretion, as can a rise in the plasma angiotensin II concentration. Additionally, a change in the flow rate of tubular fluid past the macula densa segment can also affect renin secretion. Therefore, none of the options provided will not influence renal renin secretion.

The correct answer is "All of the above." This means that all three statements mentioned in the options are true. Hydrogen-ion secretion by renal tubular cells will indeed rise in response to a fall in the plasma bicarbonate concentration. It will also result in the release of bicarbonate into plasma. Additionally, hydrogen-ion secretion will be reduced by the inhibition of cytosolic carbonic anhydrase.

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The limited ability of patients with renal insufficiency to excrete K+ is most likely due to the reduced amount of tubular fluid that enters the distal tubules. Since K+ secretion is a passive process, the total amount of tubular fluid entering the distal tubules determines the ability to secrete K+. In patients with low GFR, the filtered load of potassium is reduced, leading to a limited ability to excrete K+.

This is because bilateral renal-artery stenosis leads to reduced renal blood flow, which triggers the release of renin and production of angiotensin II. Angiotensin II causes vasoconstriction, leading to increased mean arterial blood pressure. Additionally, high levels of angiotensin II stimulate aldosterone secretion, which increases sodium and water reabsorption, leading to an increase in extracellular fluid volume. Therefore, all of the given options contribute to the rise in mean arterial blood pressure in cases of bilateral renal-artery stenosis.

Vitamin D, when converted into its activated form called calcitriol in the kidney, stimulates the absorption of calcium and phosphate in the gastrointestinal tract. This means that when vitamin D is activated, it helps the body absorb more calcium and phosphate from the food we eat. This is important for maintaining healthy levels of these minerals in the body, which are essential for bone health and other physiological processes.

A decrease in dietary sodium intake will result in the net loss of some water from the body. When sodium intake is reduced, the body tries to maintain a balance by excreting sodium through urine. This process requires water, leading to an increased loss of water from the body. Therefore, a decrease in dietary sodium intake will result in the net loss of some water from the body.

The process of countercurrent multiplication in the renal medulla refers to the exchange of solutes and water in the loop of Henle and vasa recta. This process is responsible for creating a concentration gradient in the medulla, which allows for the reabsorption of water and the excretion of concentrated urine when ADH levels are high. However, when ADH levels are low, countercurrent multiplication will result in the excretion of hypotonic urine, as less water is reabsorbed and more solutes are excreted. This is because the concentration gradient in the medulla is not maintained without the presence of ADH.

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ANP is a hormone secreted by the cardiac atria in response to increased stretch. It acts as a vasodilator and increases the glomerular filtration rate (GFR) by dilating the afferent arteriole. ANP also inhibits the secretion of renin, which is responsible for regulating blood pressure and fluid balance. Therefore, the statement that ANP will not affect the secretion of renin is false.

Based on the given information, the plasma bicarbonate (HCO3) concentration is 45 meq/L and the partial pressure of carbon dioxide (PCO2) is 50 mmHg. These values suggest a respiratory acidosis, which is characterized by an increase in PCO2 and a decrease in pH. Since the pH is inversely related to the PCO2, a higher PCO2 value would result in a lower pH. Therefore, the closest value to the plasma pH would be 7.1.

The statement that is FALSE is "In principle cells in the distal tubule, sodium uptake involves secondary active transport." The correct statement is that sodium uptake in the distal tubule does not involve secondary active transport.