Question

If blood pressure drops over a long period of time, fluid in the distal convoluted tubule would become Select one:

a. Concentrated b. Dilute

Answer 1

If blood pressure drops over a long period of time, renin-angiotensin-adlosteron system play their role for the maintenance of the normal blood pressure in the body.

Low blood pressure or when the sodium level in the blood falls, then this renin angiotensin system is activated and stimulate zona glomerulosa cell of adrenal cortex to secrete aldosteron. This aldosteron hormone acts on the distal convoluted tubule and increases the sodium ion reabsorption to the blood capillaries. This high sodium ion level in blood, increases blood pressure to the normal and increases the extracellular fluid volume. This sodium reabsorption in the distal tubule is followed by water reabsorption. Aldosteron increases the ENaC channel (epithelium sodium channel) in the distal tubule for the reabsorption of sodium ion to the blood. The sodium then reabsorbed by Na+-K+ channel in the basolateral membrane. This reabsorption creates a concentration gradient which drive water molecules to transport to the blood capillaries from the distal tubule. This water reabsorption makes the tubular fluid more concentrated.

So, aldosteron enhance the sodium and water reabsorption in the distal tubule and makes the tubular fluid more concentrated. When blood pressure falls for a long time it will stimulate renin angiotensin aldosteron system to enhance the blood pressure by renal adjustment , and makeing the distal convoluted tubular fluid more concentrated.