Question

1. True or false: Urea is reabsorbed passively by diffusion along its concentration gradient as water is reabsorbed.

Select one:

True

False

2.

Anti-diuretic hormone (=vasopressin) acts on collecting duct cells with a vasopressin receptor by the following mechanism:

Select one:

a. activation of adrenergic receptors

b. increase in Na+/K+ pumps in the basal membrane

c. increase in Na+/K+ pumps in the apical membrane

d. exocytosis of vesicles that contain aquaporins

e. decrease in cell membrane cholesterol

3.

A decrease in blood volume, such as from hemorrhage, will cause each of the following except:

Select one:

a. increased thirst

b. increased angiotensin II production

c. increased norepinephrine secretion

d. increased sodium excretion

e. decreased ANP secretion

4.

An increase in aldosterone will cause ...

Select one:

a. an increase in sodium reabsorption

b. an increase in blood pressure

c. an increase in angiotensin II

d. an increase in calcium reabsorption

e. an increase in water excretion

5.

An individual who is chromosomally XY, but does not have the SRY gene, will have the following phenotype (morphology):

Select one:

a. no gonads and female-like external genitalia

b. no Mullerian duct differentiation

c. ovaries and female-like internal and external genitalia

d. ovaries and male-like internal and external genitalia

e. testes and male-like internal and external genitalia

Answer 1

1. Urea passively crosses biological membranes, but its permeability is low because of its low solubility in the lipid bilayer. Some cells speed up this process through urea transporters, which move urea by facilitated diffusion. Urea is passively reabsorbed in the proximal tubule, but its route of transport is not clear. They then diffuse in to the capillaries, so it can pass through membranes by lipid diffusion. Since this is a passive process, urea diffuses down its concentration gradient until the concentrations of urea in the filtrate and blood are equal.

Therefore the above statement is true.

2. The most important action of vasopressin is its antidiuretic action on the collecting ducts of the kidneys. Vasopressin binds to V2 receptors on the cell surface of tubular cells, initiating an intracellular cascade which results in the generation of the water channel, aqua prion - 2. Preformed aqua prion - 2 also migrates and inserts in to the luminal membrane of the tubule cells, where it acts a conduit for water to be reabsorbed from the urine, through the cell , and back in to the circulation

Therefore the correct answer is exocytosis of vesicles that contain aqua prion

3. The decrease in blood volume has mainly two mechanisms

• Endocrine mechanism - ADH, angiotensin II, aldosterone, EPO released that results in increased blood volume
• Neural mechanism -

1. Baroreceptors, chemoreceptors are stimulated
2. cardiovascular centers stimulated
3. general sympathetic activation, release norepinephrine and epinephrine

These collectively results in Increased cardiac output, peripheral vasoconstriction, increased blood pressure, decreased venous reserve.

ANP normally acts by increasing the sodium and water excretion thereby lowering the blood pressure. Therefore, its level is reduced

But during decrease in blood volume, the sodium will be retained in the body inorder to maintain the water level in the body.

Therefore the answer is increased sodium excretion

4. High levels of aldosterone results in

• high blood pressure
• low blood levels of potassium
• abnormal increase in blood volume
• excess sodium level

therefore increase in blood pressure is the correct answer

5.XY gonadal dysgenesis is also known as Swyer syndrome. It is a type of hypogonadism in a person whose karyotype is 46,XY. They typically have normal female external genitalia, identify as a female and are raised as girls. The person is externally female with streak gonads, and if left untreated will not experience puberty.

Therefore the correct answer is no gonads and female like external genitalia