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BELLE MCAT Biology > Excretory System > Flashcards

Excretory System Flashcards

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1
Q

True or False: The excretoy system maintains fluid balance

A

True:
The excretory system maintains blood volume, pressure, and osmolarity through secretion and reabsorption of solutes and water in the nephron. Several key hormones act on the nephron to promote these processes.

D

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2
Q

True or False: The excretory system monitors plasma pH

A

True:
Multiple body systems help regulate the acid-base balance within the bloodstream and the excretory system is one of them. When the blood becomes too acidic, protons are secreted into the filtrate within the nephron to raise blood pH. When the blood becomes too alkaline, protons are reabsorbed from the filtrate and returned to circulation.

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3
Q

True or False: the excretory system helps regulate metabolism

A

False

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4
Q

What is filtered through the renal corpuscle?

A

waste products, glucose, amino acids, vitamins (other metabolites)

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5
Q

These convey blood to the renal corpuscle

A

Afferent Arterioles

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6
Q

Vassopressin

A

ALSO CALLED ADH!
Secreted by: ?
Acts on: collecting duct
Action:

PROMOTES WATER REABSORBTION by the insertion of water channels, called aquaporins, into the membranes of collecting duct cells. This allows water to flow passively back into circulation along its osmotic gradient, increasing blood volume and pressure. Since the blood becomes more dilute, its osmolarity decreases.

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7
Q

True or false: Atrial natriuretic peptide (ANP) decreases blood volume and pressure.

A

This statement is true. ANP is secreted from the heart in response to atrial stretching, which is a sign of high blood pressure. It decreases sodium reabsorption in the nephron, which promotes the loss of both sodium and water in the urine. This causes blood pressure to decrease.

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8
Q

Where in the loop of henle is water reabsorped?

A

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

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9
Q

True or False: Filtrate exiting the descending loop of henle has a lower volume but effectively the same osmolarity, since it has lost both water and solutes.

A

They said true but technically it has only lost water really by the time it reaches the base of the descending loop

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10
Q

Descending Loop of Henle

A

Permeable to water but NOT ions

More water flows out of the filtrate

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11
Q

Ascending Loop of Henle

A

Contains a thin and thick part. This whole limb is impermeable to water, but it is permeable to Na and K. The thin limb relies on passive transport of Na and K whereas the thick uper limb relies on active (which is why it is bigger)

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12
Q

Proximal Convoluted Tubules

A

A large amount of water is reabsorbed in the PCT, many solutes are reabsorbed as well. These solutes include: glucose, amino acids, vitamins, and a multiplicity of ions like sodium. As a result, the PCT does not increase filtrate osmolarity.

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13
Q

True or false: The direction of blood flow through the arterioles of the vasa recta is opposite the direction of filtrate movement through the loop of Henle.

A

This statement is true. Filtrate moving through the loop of Henle flows in the opposite direction of blood moving through the vasa recta surrounding the loop. This mechanism is known as a countercurrent multiplier system. It prevents the concentrations of fluids in the two compartments from equalizing, which facilitates the exchange of water and solutes between them.

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14
Q

Collecting Duct

A

The collecting duct plays a major role in water reabsorption, due to the action of antidiuretic hormone (ADH). ADH stimulates free water uptake from cells of the collecting duct to increase blood volume and pressure. Therefore, the collecting duct typically plays the largest role in concentrating filtrate. MAJOR SITE OF CONCENTRATION!

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15
Q

True or false: Filtrate passing through the nephron is not considered urine until it drains through the collecting duct.

A

This statement is true. Filtrate consists of water and solutes, some of which are reabsorbed in the nephron and some of which are ultimately excreted. The collecting duct is the distal portion of the nephron. When filtrate passes through the collecting duct, it is considered urine.

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16
Q

True or False: proteins are filtered into the bowmans capsule

A

no, they tend to be too large

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17
Q

True or False: RBC’s can filter into the bowman’s capsule

A

false, they are too large

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18
Q

What are the components of the renal tubule?

A

proximal convoluted tubule, loop of henle, distal convoluted tubule

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19
Q

What are the two major parts of the nephron?

A

Renal corpuscle and renal tubule

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20
Q

True or False: Filtration is a specific process that excludes valuable metabolites so they arent taken out of circulation

A

False- valuable metabolites and compounds like glucose, vitamins, and amino acids become part of the initial filtrate because filtration is NONSPECIFIC

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21
Q

True or False: peritubular capillaries are in close proximity to the proximal convoluted tubule

A

True, this is what allows the reabsorption of valuable metbolites and ions

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22
Q

True or False: glucose is normally expelled from the body and is not reabsorbed

A

FALSE- virtually all glucose is reabsorbed in large quantities by the PCT and none should be lost to urine

23
Q

What is reabsorption?

A

The reuptake of substances back into circulation

24
Q

What is secretion?

A

Opposite of reabsorption

25
Q

True or False: The loop of henle serves to drastically change the osmolarity of the urine produced

A

False, it changes the volume without drastically changing the osmolarity

26
Q

True or False: the adrenal medulla is hypertonic compared to the adrenal cortex

A

True

27
Q

True or False: water is reabsorbed mostly through the ascending loop of henle and reenters circulation via the peritubular vessels

A

False: water is reabsorbed mostly through the descending loop of henle and reenters circulation via the vasa recta

28
Q

True or False: the ascending loop is not permeable to water

A

True- its permeable to sodium and potassium

29
Q

How does the concentration of the filtrate compare from the top of the descending to the bottom of the desceding loop of henle?

A

It is more concentrated at the bottom because the filtrate has essentially been dehydrated

30
Q

How does the transport of ions in the thin and thick ascending loop of henle differ?

A

Passive diffusion of K and Na is used in the thin limb but active is needed in the thick upper portion because the filtrate has become more dilute. It is thicker because of the need for mitochonidria i believe.

31
Q

True or False: the main site of urine concentration is in the collecting duct

A

true

32
Q

Aldosterone

A

Secreted by:
Act on: DCT and Collecting duct

Action:
Stimulates sodium reabsobtion and where salt goes water follows

33
Q

PTH

A

Promotes Ca reabsorption in the DCT

34
Q

What hormones can act on the kidney?

A

ADH (Vasopressin), Aldosterone, PTH

35
Q

Aldosterone

A

Secreted by: ADRENAL CORTEX
Act on: DCT and Collecting duct

Action:
Stimulates sodium reabsobtion and where salt goes water follows

36
Q 
In just a few words, describe the importance of each of the following: 
Renal Corpuscle
PCT
Descending Loop of Henle
Ascending Loop of Henle
DCT
Collecting Duct
A

Renal Corpuscle: filtration
PCT: reabsorption of metabolites
Descending Loop of Henle: reabsorption of water
Ascending Loop of Henle: reabsorption of K and Na
DCT: acted on by hormones, plays a role in concentration and PH
Collecting Duct: also under hormonal mod, concentration

37
Q

True or False: the descending loop of henle concentrates the filtrate

A

True- but when it exits the ascending loop the reabsorption of ions makes it so that the concentration is not greatly changed

38
Q

How is the osmotic gradient in the renal medulla established?

A

The ascending limb of the loop of Henle facilitates the reabsorption of ions into the renal medulla. This creates an osmotic gradient within the medulla that allows water to flow passively out of the descending limb.

39
Q

True or false: Filtrate exiting the loop of Henle is more concentrated than filtrate entering the loop of Henle.

A

This statement is false. Although water is lost in the descending limb of the loop of Henle, solutes are lost in the ascending limb. Thus, filtrate emerging from the loop of Henle is not more concentrated then the filtrate that entered, even though it has a lower volume.

40
Q

Acts on DCT, Collecting Duct, or both:

Vasopressin

A

Collecting Duct

41
Q

Acts on DCT, Collecting Duct, or both:

Aldosterone

A

BOTH

42
Q

Acts on DCT, Collecting Duct, or both:

PTH

A

DCT

43
Q

If aldosterone promotes the reuptake of salt, how does it impact blood volume?

A

Where salt goes, water follows

44
Q

How would an ACE inhibitor impact blood pressure?

A

An ACE inhibitor acts to hault the renin-angiotensin-aldosterone system by inhibiting ACE from converting Angiotensin I to Angiotensin II. This keeps Angiotensin II from doing vasoconstriction and also ultimately blocks aldosterone from being released which would have raised blood pressure. ACE inhibitors decrease BP.

45
Q

True or False: Angiotensin I acts to vasoconstrict

A

false- Angiotnesin II

46
Q

Increases aquaporins in the collecting duct

A

ADH

47
Q

How does ADH reduce the osmolarity of the blood?

A

It promotes the reabsorbtion of water but not solutes therefore diluting the blood

48
Q

ANP

A

Atrial Natriuretic Peptide
Secreted by: atria
Action: decrease BP such as in cases of over hydration. It promotes sodium retention in the urine

49
Q

True or false: Regulation of blood pH within the nephron occurs primarily in the collecting duct.

A

This statement is false. The distal convoluted tubules, rather than the collecting duct, is the major site of blood pH regulation within the nephron. In the DCT, protons can be secreted into the filtrate or reabsorbed into circulation depending on blood pH.

50
Q

Suppose that a patient is found to carry a genetic mutation that results in overexpression of renin. Which of the following physiological findings are likely?

A

High blood pressure and high plasma sodium

51
Q

True or false: Anti-diuretic hormone (ADH) acts on cells of the distal convoluted tubule and collecting duct of the nephron to increase blood volume and pressure.

A

This statement is false. ADH does work to increase blood volume and pressure, but it does not act on cells of the distal convoluted tubule. ADH promotes the insertion of water channels called aquaporins into the membranes of collecting duct cells, which allows water to flow out of the nephron back into the bloodstream.

52
Q 
The juxtaglomerular cells in the kidney are responsible for the synthesis, storage and secretion of the enzyme renin. These cells are of the same type found in:
The hippocampus
The quadriceps
The small intestine
The nephron
A

The small intestine. Juxtoglomerular cells are found within the afferent (and a little in the efferent) arterioles. They are composed of smooth muscle tissue just as the small intestine is.
This is one you got wrong. It is a BRUTAL level question. It is under STRUCTURE AND FUNCTION OF ORGAN SYSTEMS*

53
Q

Which organ is involved in regulation of all of the following: acid-base balance, blood pressure, water balance, and removal of nitrogen wastes?

A

Kidney:
Within the nephron, the reabsorption of protons and bicarbonate from the filtrate contributes to acid-base balance within the body; secretion of renin from the juxtaglomerular cells helps regulate the secretion of aldosterone from the adrenal cortex (which plays a role in regulating blood pressure, through its effects on Na+ reabsorption in the nephron); Na+ and urea reabsorption in the nephron creates osmotic pressure within the medullary interstitium of the kidney and draws water from the filtrate into surrounding tissues; and excretion of nitrogenous wastes takes place due to the urea transporter, which removes urea from the interstitium and transports it back into the ascending loop of Henle.

BELLE MCAT Biology (20 decks)

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