1. Mannitol is sugar (small) that cannot enter cells but can be filtered into the renal
tubules. What would happen to urine volume if mannitol were injected into the
bloodstream and why?
2. The kidney can regulate the glomerular filtration rate by altering
constriction/dilation of the afferent and/or efferent arterioles. Each arteriole can
be altered independently. If overall blood pressure in the body decreased, how
might the kidney adjust the diameters of the afferent and efferent arterioles to
maintain normal glomerular filtration and why?
10 Points for correct answer. Thanks.
tubules. What would happen to urine volume if mannitol were injected into the
bloodstream and why?
2. The kidney can regulate the glomerular filtration rate by altering
constriction/dilation of the afferent and/or efferent arterioles. Each arteriole can
be altered independently. If overall blood pressure in the body decreased, how
might the kidney adjust the diameters of the afferent and efferent arterioles to
maintain normal glomerular filtration and why?
10 Points for correct answer. Thanks.
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1 The volume would increase because of the osmotic properties of mannitol which makes it so there is a higher concentration of particles inside the renal tubules which brings water from the cells into the tubule and keeps the water from the tubule into the tubule itself until excretion.
2 The kidney should increase the diameter of afferent arterioles and slightly decrease the ones of efferent arterioles to have a local increase of the blood pressure to compensate the decrease of the blood pressure in the body. By increasing the diameter of afferent arterioles the blood will find less resistance and will pass in a greater amount. By decreasing the efferent arterioles, the blood would find a higher resistance and this will increase the pressure. To regulate arterioles, the nervous system innervates the precapillary sphincters and that regulates the amount of blood that gets into the capillary and out from the capillary.
In order to have a correct glomerular filtration the pressure of blood must be maintained constant at about 50 mmHg. This pressure is contrasted by 10 mmHg of pressure coming from Bowman's capsule and by 30 mmHg coming from the blood's oncotic pressure in the capillary, that would then to make water enter the blood stream. The difference between these strengths results in a 10 mmHg of pressure for the filtration of plasma. That is how 180 L of liquids are filtered every day in the kidney. Although there is immediately after that a reabsorption of liquids in the renal tubule of about 70% in the first trait, 15% in the second and a final reabsorption in the last part of the tubule, which makes it so that just a small quantity of urine is excreted.
2 The kidney should increase the diameter of afferent arterioles and slightly decrease the ones of efferent arterioles to have a local increase of the blood pressure to compensate the decrease of the blood pressure in the body. By increasing the diameter of afferent arterioles the blood will find less resistance and will pass in a greater amount. By decreasing the efferent arterioles, the blood would find a higher resistance and this will increase the pressure. To regulate arterioles, the nervous system innervates the precapillary sphincters and that regulates the amount of blood that gets into the capillary and out from the capillary.
In order to have a correct glomerular filtration the pressure of blood must be maintained constant at about 50 mmHg. This pressure is contrasted by 10 mmHg of pressure coming from Bowman's capsule and by 30 mmHg coming from the blood's oncotic pressure in the capillary, that would then to make water enter the blood stream. The difference between these strengths results in a 10 mmHg of pressure for the filtration of plasma. That is how 180 L of liquids are filtered every day in the kidney. Although there is immediately after that a reabsorption of liquids in the renal tubule of about 70% in the first trait, 15% in the second and a final reabsorption in the last part of the tubule, which makes it so that just a small quantity of urine is excreted.