Osmoregulation and Excretion

Concept: Osmoregulation and Nitrogenous Waste


Concept: Osmosis and Osmolarity


Concept: Active and Passive Transport


Concept: Kidney and Nephron


Concept: Filtration, Reabsorption, and Excretion


Concept: Glomerulus and Bowman's Capsule


Concept: Proximal Tubule


Concept: Loop of Henle


Concept: Distal Tubule and Collecting Duct


Concept: Renin-Angiotensin-Aldosterone-System


Osmoregulation and Excretion Additional Practice Problems

Blood passes from the capsular space through the _____ to the renal corpuscle.

A. capillary endothelium

B. capillary endothelium and the basement membrane

C. capillary endothelium, the basement membrane, and the podocytes

D. capillary endothelium, the basement membrane, and between the foot processes of the podocytes

Watch Solution

Sulfate (SO42-) transport occurs within kidney cells by ion transport. What is the Gibbs free energy associated with moving SO42- into the cell (in kcal/mol) if the sulfate concentration outside is 5mM and 25mM inside? 

(R = 1.987 cal/mol K; T=37ºC; ΔEm = +60mV; F = 23.06 kcal/V mol)

A. 3.76 kcal/mol

B. 1.78 kcal/mol

C. 1.56 kcal/mol

D. -1.78 kcal/mol

E. -3.76 kcal/mol

Watch Solution

Na+ and Cl- are reabsorbed from the ascending loop of Henle.

A. True

B. False

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CaCl2 is a strong electrolyte. When dissolved in water, it readily dissociates into calcium and chloride. A 0.3 M solution will be _______ osmoles/liter.

Assume that it completely dissolves.

A. 0.1

B. 0.3

C. 0.6

D. 0.9

E. 1.2

Watch Solution

Discuss the structure and the functions of the kidneys.

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Why would kidney function diminish if nephrons were straight in structure and did not include a loop?

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How does the nephron contribute to acid base balance?

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Hormonal regulation by ADH and aldosterone: You have probably noticed that urine is not always the same. The body is capable of adjusting the volume and the osmolarity of its urine output depending on a number of factors. The kidneys are regulated by hormones such as antidiuretic hormone (ADH) and aldosterone. These hormones are secreted in response to changes in the animal's internal water and salt balance. For example, sweating or blood loss can disrupt water and/or salt balance in the body, leading to a hormonal response that returns the system to homeostasis. Mechanisms for adjusting blood volume or osmolarity include increasing water and/or sodium reabsorption in the nephrons and collecting ducts. How do the following stimuli affect water and sodium (Na+) reabsorption in the kidneys? Drag each item to the appropriate bin.

Watch Solution

Which of the following is NOT a characteristic of the cortical nephrons?

a. Their nephron loop is closely wrapped with vasa recta.

b. Cortical nephrons form the majority of nephrons in the kidney.

c. The efferent arteriole of the cortical nephrons supplies the peritubular capillaries.

d. Cortical nephrons have a short nephron loop.

Watch Solution

Briefly describe how the actions that regulate blood volume interact with those that regulate blood osmolarity, and explain why you would be more dehydrated after consuming saltwater.

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Specifically describe the roles of aldosterone and atrial natriuretic hormone in regulating salt and water in the blood, and in producing hypertonic urine.

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Name the 4 hormones that act on the nephron to control reabsorption of various components in the filtrate?

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Which of the following animals generally has the lowest volume of urine production?

a. vampire bat

b. salmon in fresh water

c. marine bony fish

d. freshwater flatworm

Watch Solution

Which process in the nephron is least selective?

a. filtration

b. reabsorption

c. active transport

d. secretion

Watch Solution

After drinking alcoholic beverages, increased urine excretion is the result of ________.

a. increased aldosterone production

b. increased blood pressure

c. inhibited secretion of antidiuretic hormone (ADH)

d. increased reabsorption of water in the proximal tubule

Watch Solution

After blood flow is artificially reduced at one kidney, you would expect that kidney to secrete more of the hormone known as ________.

a. angiotensin

b. renin

c. antidiuretic hormone

d. atrial natriuretic peptide

Watch Solution

Increased antidiuretic hormone (ADH) secretion is likely after ________.

a. drinking lots of pure water

b. sweating-induced dehydration increases plasma osmolarity

c. eating a small sugary snack

d. blood pressure becomes abnormally high

Watch Solution

The loop of Henle dips into the renal medulla. This is an important feature of osmoregulation in terrestrial vertebrates because ________.

a. absorptive processes taking place in the loop of Henle are hormonally regulated

b. differential permeabilities of ascending and descending limbs of the loop of Henle are important in establishing an osmotic gradient

c. the loop of Henle plays an important role in detoxification

d. additional filtration takes place along the loop of Henle

Watch Solution

A primary reason that the kidneys have one of the highest metabolic rates of all body organs is that ________.

a. they have membranes of varying permeability to water

b. they operate an extensive set of active-transport ion pumps

c. they are the body's only means of shedding excess nutrients

d. they have an abundance of myogenic smooth muscle

Watch Solution

Within a normally functioning kidney, red blood cells can be found in ________.

a. the vasa recta

b. Bowman's capsule

c. the proximal tubule

d. the collecting duct

Watch Solution