Practice Questions

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#Question id: 12958

The Norway rat (Rattus Norvegicus), a widespread pest, was controlled for about a decade by the anticoagulant warfarin. This chemical substance, placed in food pellets, is absorbed by the intestinal tract and inhibits the clotting of blood. After a population decline for about 10 years, rat populations increased and stabilized. In one European population, as illustrated in the graph below, the percentage of rats resistant to warfarin has remained fairly stable over a number of years
Resistance to warfarin is governed by a dominant autosomal gene, R. More than 15 percent of the resistant animals are heterozygous at this locus (Rr). The table below indicates the response to warfarin and relative reproductive fitness of individuals that are homozygous or heterozygous for the dominant gene (R). The RR individuals have a 20-fold increase in vitamin K requirement over individuals.

Fitness is a measure of the reproductive success of a particular genotype. The highest fitness is 1.00.
The strong dependence of RR individuals on large quantities of vitamin K probably is responsible for

#Unit 10. Ecological Principles

Their lowered fitness
Their susceptibility to warfarin
Their superiority to heterozygotes (Rr)
Their increasing numbers in the population each generation

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TLS Online TPP Program

#Question id: 20274

#Unit 7. System Physiology – Animal

ADH has two actions, one on the kidney and the other on vascular smooth muscle, these actions are mediated by different receptors, different intracellular mechanisms, and different secondary messengers.

a. The major action of ADH is to increase the water permeability of principal cells in the late distal tubule and collecting duct.

b. The receptor for ADH on the principal cells is a V2 receptor, which is coupled to adenylyl cyclase via a Gs protein.

c. The second messenger is cAMP, via phosphorylation steps, directs the insertion of water channels, aquaporin 2 (AQP2), in luminal membranes.

d. The receptor for ADH on the principal cells is a V1 receptor, which is coupled to phospholipase C via Gq protein.

Which one of the following combination of above statements is correct?

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#Question id: 20273

#Unit 7. System Physiology – Animal

Primary site of action of thiazide diuretics in the nephron is;

TLS Online TPP Program

#Question id: 20272

#Unit 7. System Physiology – Animal

The factors that stimulate or inhibit the secretion of ADH by the posterior pituitary are:

a. Pain, nausea, hypoglycemia, and various drugs all inhibit the secretion of ADH.

b. Pain, nausea, hypoglycemia, and various drugs all stimulate the secretion of ADH.

c. Ethanol, α-adrenergic agonists, and atrial natriuretic peptide inhibit secretion of ADH.

d. Nicotine, opiates, antineoplastic agents stimulate the secretion of ADH.

Which one of the following combinations of above statements is correct?

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#Question id: 20271

#Unit 7. System Physiology – Animal

Nephrogenic diabetes insipidus is treated with thiazide diuretics. The usefulness of thiazide diuretics in treating nephrogenic diabetes insipidus is explained as follows:

a. Thiazide diuretics inhibit Na+ reabsorption in the early distal tubule. By preventing dilution of the urine at that site, the final, excreted urine is less dilute.

b. Thiazide diuretics decrease glomerular filtration rate; because less water is filtered, less water is excreted.

c. Thiazide diuretics, by increasing Na+ excretion, can cause a secondary ECF volume contraction.

Which one of the following combination of above statements is correct?

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#Question id: 20270

#Unit 7. System Physiology – Animal

Oxytocin is formed primarily in the paraventricular nuclei of the hypothalamus. Which of the following statement is FALSE regarding oxytocin?

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#Question id: 20269

#Unit 7. System Physiology – Animal

The antidiuretic hormone (ADH) originates primarily in the supraoptic nuclei of the hypothalamus, which of the following statement is FALSE regarding ADH?