Human Anatomy and Physiology : Systems Physiology

Study concepts, example questions & explanations for Human Anatomy and Physiology

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Example Questions

Example Question #5 : Excretory Physiology

Which of the following is true regarding the nephron?

Possible Answers:

The macula densa cells are found within the lumen of the distal convoluted tubule

Water is reabsorbed in the descending limb of the loop of Henle

Water is reabsorbed in the distal convoluted tubule

All of these

Correct answer:

All of these

Explanation:

All of the answer choices are true. The macula densa cells are sensitive to changes in concentration of sodium chloride. A decrease in concentration of  is detected, which stimulates the macula densa cells to secrete paracrine factors that ultimately increase the pressure in the glomerulus, and thus the glomerular filtration rate, and stimulates the release of renin, which ultimately increases blood pressure, volume and cardiac output.

Example Question #6 : Excretory Physiology

The major reabsorption of water, ions, and other important molecules such as glucose occurs in what part of the nephron?

Possible Answers:

Vasa recta

Collecting duct

Proximal convoluted tubule

Glomerulus

Distal convoluted tubule

Correct answer:

Proximal convoluted tubule

Explanation:

After filtration of the blood through the glomerulus, approximately 70% of the water and salts is reabsorbed in the proximal convoluted tubule.  Additionally, 100% of the glucose is reabsorbed here in a healthy, functioning nephron.  The lumenal cells of the proximal convoluted tubule are lined with microvilli and are called brush border cells.  Histology of the proximal convoluted tubule is indicative of these structures and the proximal convoluted tubule's lumen can be seen as "crowded" with epithelial surface area, which is distinct from the lumen of the distal convoluted tubule.

Example Question #7 : Excretory Physiology

ADH (antidiuretic hormone, also known as vasopressin) has which of the following effects on nephron function?

Possible Answers:

Reabsorption of water increases as a result of more ATP-dependent water pumps in the distal convoluted tubule and collecting duct

Reabsorption of water increases as a result of additional aquaporins being placed in the distal convoluted tubules and collecting duct

Reabsorption of water increases as a result of additional aquaporins being placed in the proximal convoluted tubule

Reabsorption of water decreases as a result of less aquaporins being placed in the proximal convoluted tubule

Reabsorption of water decreases as a result of additional aquaporins being placed in the distal convoluted tubule and collecting duct

Correct answer:

Reabsorption of water increases as a result of additional aquaporins being placed in the distal convoluted tubules and collecting duct

Explanation:

ADH acts upon the collecting ducts and distal convoluted tubules of nephrons to increase water reabsorption.  It causes an increase in the number of aquaporins in order to allow for this.

Example Question #6 : Excretory And Digestive Physiology

Concentration and dilution of urine is a major responsibility of what part of the nephron?

Possible Answers:

Glomerulus

Proximal convoluted tubule

Loop of Henle

Collecting duct

Distal convoluted tubule

Correct answer:

Loop of Henle

Explanation:

As filtrate passes through the Loop of Henle, the level of concentration of the fluid that will become urine is determined by the length of the loop of Henle (how far into the medulla it dips) and, the osmolality of the medulla. Depending on the levels of circulating hormones, the distal convoluted tubule and collecting duct could be the part of the nephron that determines the concentration of the urine, but to a lesser extent than the length of the loop of Henle. 

Example Question #8 : Excretory Physiology

The descending limb of the loop of Henle is __________.

Possible Answers:

water permeable

water and solute impermeable

solute permeable

water permeable and solute impermeable

solute impermeable

Correct answer:

water permeable and solute impermeable

Explanation:

The descending limb of the loop of Henle is both water permeable and solute impermeable.  These properties of the limb allow the filtrate moving through the nephron to become either concentrated or diluted depending on the circumstance.

Example Question #9 : Excretory Physiology

The vessels surrounding the Loop of Henle are called __________.

Possible Answers:

peritubular capillaries

renal vein

efferent arterioles

afferent arterioles

vasa recta

Correct answer:

vasa recta

Explanation:

The afferent and efferent arterioles are located near the glomerulus and control the glomerular filtration rate by constriction and dilation.  The peritubular capillaries wind around the proximal convoluted tubule and the distal convoluted tubule to allow for reabsorption and secretion there.  The vasa recta on the other hand wind around the loop of Henle and maintain countercurrent multiplication.

Example Question #11 : Excretory Physiology

What is the main purpose of the vasa recta?

Possible Answers:

Secretes the majority of the  and  ions into the filtrate

Maintains countercurrent multiplication to prevent disregulation in the concentration gradients set up in the renal medulla

Provides the nephron with oxygen-rich blood

Maintains appropriate temperature in the renal medulla to allow for regular blood flow

Reabsorbs the majority of the solute from the filtrate

Correct answer:

Maintains countercurrent multiplication to prevent disregulation in the concentration gradients set up in the renal medulla

Explanation:

The vasa recta wind around the loop of Henle and maintain a countercurrent multiplication to prevent any disregulation or washout of the concentration gradient that has been set up in the renal medulla.  Without this gradient, the nephron would be unable to concentrate filtrate.  Since the vasa recta carry venous blood, it's oxygen concentration is low and thus needs to go through the pulmonary circuit to pick up more oxygen.

Example Question #12 : Excretory Physiology

Which of the following is the most concentrated part of the nephron?

Possible Answers:

Thick ascending loop of Henle

Thin descending loop of Henle

Distal convoluted tubule

Proximal convoluted tublue

Collecting duct

Correct answer:

Thin descending loop of Henle

Explanation:

Thin descending loop of Henle is the most concentrated part of the nephron. As you progress up and down the nephron, the closer the nephron is to the medulla, the more concentrated it is. This ability is due to the increases absorption of water and the inability to reabsorb solute at this level. 

The other mentioned parts of the nephron are permeable to solute and some water and thus are not as concentrated as the thin descending loop of Henle.

Example Question #13 : Excretory Physiology

If the efferent arteriole becomes constricted, what is likely to occur in the nephron? 

Possible Answers:

The increased osmotic pressure will elevate glomerular filtration rate

Fluid backup will cause the nephron to rupture

The increased hydrostatic pressure will elevate glomerular filtration rate

Glomerular filtration rate will decrease due to a loss in blood pressure

Glomerular filtration rate will remain the same

Correct answer:

The increased hydrostatic pressure will elevate glomerular filtration rate

Explanation:

The efferent arteriole carries blood away from the glomerulus, and so if it is constricted, the blood pressure behind it will increase.  The raise in blood pressure will result in an increase in hydrostatic pressure, pushing additional fluid through the glomerulus i.e elevated glomerular filtration rate. While high hydrostatic pressure does cause damage to the nephron, the nephron rupturing is too extreme of a statement and requires assumptions that are not necessarily valid.

Example Question #14 : Excretory Physiology

The release of renin ultimately results in the stimulation of which gland?

Possible Answers:

Anterior pituitary gland

Thyroid gland

Adrenal cortex

Adrenal medulla

Correct answer:

Adrenal cortex

Explanation:

Renin is a hormone released by granular cells in the juxtaglomerular apparatus, near the nephron glomerulus. These cells monitor the pressure of the filtrate in the distal convoluted tubule. The release of renin will stimulate a cascade of angiotensin I and II. Angiotensin II will ultimately stimulate the adrenal cortex to release aldosterone and increase sodium reabsorption and potassium excretion from the filtrate, leading to water retention.

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