Guyton Hall Flashcards Preview

Endo-Repro Questions > Guyton Hall > Flashcards

Flashcards in Guyton Hall Deck (152)
Loading flashcards...

1. Which receptor controls nitric oxide (NO) release to cause vasodilation during penile erection? A) Leptin receptor B) Angiotensin AT1 receptor C) Endothelin ETA receptor D) Muscarinic receptor

1. D) Parasympathetic postganglionic fibers release acetylcholine that activates muscarinic receptors on endothelium to produce NO and increases cyclic guanosine monophosphate, which activates protein kinase G, causing a reduction in intracellular calcium (also increasing NO by positive feedback) and causing vasodilation


2. Which statement about antidiuretic hormone (ADH) is true? A) It is synthesized in the posterior pituitary gland B) It increases salt and water reabsorption in the collecting tubules and ducts C) It stimulates thirst D) It has opposite effects on urine and plasma osmolality

2. D) ADH increases the permeability of the collecting tubules and ducts to water, but not to sodium, which in turn increases water reabsorption and decreases water excretion. As a result, urine concentration increases and the retained water dilutes the plasma. ADH is synthesized in the supraoptic and paraventricular nuclei of the hypothalamus and has no direct effect on the thirst center


3. After menopause, hormone replacement therapy with estrogen-like compounds is effective in preventing the progression of osteoporosis. What is the mechanism of their protective effect? A) They stimulate the activity of osteoblasts B) They increase absorption of calcium from the gastrointestinal tract C) They stimulate calcium reabsorption by the renal tubules D) They stimulate parathyroid hormone (PTH) secretion by the parathyroid gland

3. A) Estrogen compounds are believed to have an osteoblast-stimulating effect. When the amount of estrogen in the blood falls to very low levels after menopause, the balance between the bone-building activity of the osteoblasts and the bone-degrading activity of the osteoclasts is tipped toward bone degradation. When estrogen compounds are added as part of hormone replacement therapy, the bone-building activity of the osteoblasts is increased to balance the osteoclastic activity.


4. A patient has nephrogenic diabetes insipidus. Of the following options, which outcome would be expected or which intervention would be suggested? A) Expected outcome: decreased plasma sodium concentration B) Expected outcome: increased secretion of ADH from the supraoptic and paraventricular nuclei C) Expected outcome: high urine osmolality D) Suggested intervention: water restriction E) Suggested intervention: ADH antagonists (vaptans)

4. B) In nephrogenic diabetes insipidus, the kidneys cannot respond to ADH. Consequently, dilute urine and loss of water from the extracellular fluid occurs, resulting in hypernatremia. Hypernatremia stimulates thirst, which attenuates the severity of hypernatremia, whereas water restriction exacerbates hypernatremia. Hypernatremia also stimulates ADH secretion from the magnocellular neurons in the hypothalamus.


5. Within minutes after a normal delivery, flow through the foramen ovale decreases dramatically. What is the cause of this change? A) Increased formation of prostaglandin E2 (PGE2) in the endocardium B) Increased rate of flow through the pulmonary artery C) Increased left atrial pressure D) Increased right atrial pressure E) Increased partial pressure of oxygen (Po2)

5. C) After birth, systemic arterial resistance increases dramatically due to loss of the placental vasculature. Consequently, arterial pressure, left ventricular pressure, and left atrial pressure all increase. At the same time, pulmonary vascular resistance decreases due to expansion of the lungs, and pulmonary artery pressure, right ventricular pressure, and right atrial pressure all fall. Blood flow through the foramen is a function of the pressure gradient, which after birth favors flow from the left to the right atrium, but most of the flow is blocked by the septal flap on the septal wall of the left atrium.


6. Which hormones antagonize the effect of NO and cause the penis to become flaccid after orgasm? A) Endothelin and norepinephrine B) Estrogen and progesterone C) Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) D) Progesterone and LH

6. A) Norepinephrine is released from the nerve terminals and endothelin is released from endothelial cells in the vasculature, causing vasoconstriction of the vasculature.


7. Which lines most likely illustrate these relationships in a patient with type 2 diabetes? A) A and C B) A and D C) B and C D) B and D

7. C) Type 2 DM is characterized by diminished sensitivity of target tissues to the metabolic effects of insulin—that is, there is insulin resistance. As a result, hepatic uptake of glucose is impaired and glucose release is enhanced. In muscle, the uptake of glucose is impaired.


8. Which lines most likely illustrate these relationships in a patient with acromegaly? A) A and C B) A and D C) B and C D) B and D

8. C) In acromegaly, high plasma levels of GH cause insulin resistance. Consequently, glucose production by the liver is increased and glucose uptake by peripheral tissues is impaired.


9. Line D most likely illustrates the influence of which of the following? A) Exercise B) Obesity C) Growth hormone (GH) D) Cortisol E) Glucagon

9. A) During exercise, glucose utilization by muscle is increased, which is largely independent of insulin.


10. Thecal cells in the follicle are not able to produce what sex steroid? A) Estradiol B) Testosterone C) Progesterone D) Dihydrotestosterone

10. A) Thecal cells do not have the capacity to produce estradiol because they lack aromatase.


11. A baby is born with a penis, a scrotum with no testes, no vagina, and XX chromosomes. This condition is referred to as hermaphroditism. What could cause this abnormality? A) Abnormally high levels of human chorionic gonadotropin (HCG) production by the trophoblast cells B) The presence of a testosterone-secreting tumor in the mother’s right adrenal gland C) Abnormally high levels of LH in the maternal blood D) Abnormally low levels of testosterone in the maternal blood E) Abnormally low rates of estrogen production by the placenta

11. B) A very high concentration of testosterone in a female embryo will induce formation of male genitalia. An adrenal tumor in the mother that synthesizes testosterone at a high, uncontrolled rate could produce the masculinizing effect.


12. A young woman is given daily injections of a substance beginning on the sixteenth day of her normal menstrual cycle and continuing for 3 weeks. As long as the injections continue, she does not menstruate. The injected substance could be which of the following? A) Testosterone B) FSH C) An inhibitor of progesterone’s actions D) A PGE2 inhibitor E) HCG

12. E) HCG has the same stimulatory effect as LH on the corpus luteum. Administration of HCG would cause the corpus luteum to continue to secrete estrogen and progesterone, preventing degradation of the endometrium and the onset of menstruation.


13. Which of the following increases secretion of GH? A) Senescence B) Insulin-like growth factor-1 (IGF-1) C) Somatostatin D) Hypoglycemia E) Exogenous GH administration

13. D) Hypoglycemia is a potent stimulus for GH. GH decreases with aging and in response to the hypothalamic inhibitory hormone somatostatin. GH secretion would decrease in response to both exogenous GH administration and IGF-1 as a result of negative feedback inhibition.


14. Which of the following could inhibit the initiation of labor? A) Administration of an antagonist of the actions of progesterone B) Administration of LH C) Administration of an antagonist of PGE2 effects D) Mechanically dilating and stimulating the cervix E) Administration of oxytocin

14. C) Antagonism of progesterone’s effects, dilation of the cervix, and oxytocin all increase uterine smooth muscle excitability and facilitate contractions and the onset of labor. LH would have no effect. Prostaglandin E2 strongly stimulates uterine smooth muscle contraction and is formed at an increasing rate by the placenta late in gestation.


15. Exposure to ultraviolet light directly facilitates which of the following? A) Conversion of cholesterol to 25-hydroxycholicalciferol B) Conversion of 25-hydroxycholicalciferol to 1,25- dihydroxycholicalciferol C) Transport of calcium into the extracellular fluid D) Formation of calcium-binding protein E) Storage of vitamin D3 in the liver

15. A) Ultraviolet light absorbed by the skin directly facilitates conversion of cholesterol to 25-hydroxycholesterol.


16. Which of the following decreases the pressure in the pulmonary artery after birth? A) An increase in systemic arterial pressure B) Closure of ductus arteriosus C) An increase in left ventricular pressure D) A decrease in pulmonary vascular resistance

16. D) Pulmonary vascular resistance greatly decreases as a result of expansion of the lungs. In the unexpanded fetal lungs, the blood vessels are compressed because of the small volume of the lungs. Immediately upon expansion, these vessels are no longer compressed, and the resistance to blood flow decreases severalfold.


17. Which of the following is both synthesized and stored in the hypothalamus? A) ADH B) Thyroid-stimulating hormone (TSH) C) LH D) Somatostatin E) Somatomedin

17. D) The inhibitory hormone somatostatin is both synthesized and stored in the hypothalamus. Both TSH and LH are synthesized and stored in the anterior pituitary gland. ADH is synthesized in the hypothalamus but is stored in the posterior pituitary gland. Somatomedin (IGF-1) is synthesized in the liver.


18. If a radioimmunoassay is properly conducted and the amount of radioactive hormone bound to antibody is low, what would this result indicate? A) Plasma levels of endogenous hormone are high B) Plasma levels of endogenous hormone are low C) More antibody is needed D) Less radioactive hormone is needed

18. A) In a radioimmunoassay, there is too little antibody to completely bind the radioactively tagged hormone and the hormone in the fluid (plasma) to be assayed. Thus, there is competition between the labeled and endogenous hormone for binding sites on the antibody. Consequently, if the amount of radioactive hormone bound to antibody is low, this finding would indicate that plasma levels of endogenous hormone are high.


19. By which mechanism do LH and FSH return to baseline levels? A) LH surge B) Negative feedback on gonadotropin-releasing hormone (GnRH) by progesterone C) Negative feedback on GnRH by estradiol D) Negative feedback on GnRH from testosterone

19. C) Just before the LH surge, estradiol levels increase, which causes negative feedback on GnRH to stop producing LH and FSH, resulting in the decrease in their levels.


20. Spermatogenesis is regulated by a negative feedback control system in which FSH stimulates the steps in sperm cell formation. Which negative feedback signal associated with sperm cell production inhibits pituitary formation of FSH? A) Testosterone B) Inhibin C) Estrogen D) LH

20. B) The Sertoli cells of the seminiferous tubules secrete inhibin at a rate proportional to the rate of production of sperm cells. Inhibin has a direct inhibitory effect on anterior pituitary secretion of FSH. FSH binds to specific receptors on the Sertoli cells, causing the cells to grow and secrete substances that stimulate sperm cell production. The secretion of inhibin thereby provides the negative feedback control signal from the seminiferous tubules to the pituitary gland.


21. Which of the following is true during the 12-hour period preceding ovulation? A) A surge of LH is secreted from the pituitary B) The surge occurs immediately after the formation of the corpus luteum C) The surge is followed immediately by a fall in the plasma concentration of progesterone D) The number of developing follicles is increasing

21. B) Ovulation will not take place unless a surge of LH precedes it. Immediately prior to ovulation, the number of follicles is decreasing due to normal attrition of all but one follicle, and consequently estrogen synthesis by the ovary is decreasing. Progesterone synthesis is stimulated by the LH surge.


22. When do progesterone levels rise to their highest point during the female hormonal cycle? A) Between ovulation and the beginning of menstruation B) Immediately before ovulation C) When the blood concentration of LH is at its highest point D) When 12 primary follicles are developing to the antral stage

22. A) The corpus luteum is the only source of progesterone production, except for minute quantities secreted from the follicle before ovulation. The corpus luteum is functional between ovulation and the beginning of menstruation, during which time the concentration of LH is suppressed below the level achieved during the preovulatory LH surge.


23. What accompanies sloughing of the endometrium during the endometrial cycle in a normal woman? A) An increase in progesterone B) The LH “surge” C) A decrease in both progesterone and estrogen D) An increase in estradiol

23. C) At the end of the luteal phase, the corpus luteum is resorbed and fails to produce progesterone and estradiol, making levels fall precipitously and causing the endometrium to slough.


24. Some cells secrete chemicals into the extracellular fluid that act on cells in the same tissue. Which of the following refers to this type of regulation? A) Neural B) Endocrine C) Neuroendocrine D) Paracrine E) Autocrine

24. D) Paracrine communication refers to cell secretions that diffuse into the extracellular fluid to affect neighboring cells.


25. Which of the following pairs is an example of the type of regulation referred to in Question 24? A) Somatostatin—GH secretion B) Somatostatin—insulin secretion C) Dopamine—prolactin secretion D) Norepinephrine—corticotropin-releasing hormone (CRH) secretion E) CRH—adrenocorticotropic hormone (ACTH) secretion

25. B) The delta cells of the pancreas secrete somatostatin, which inhibits the secretion of insulin and glucagon from the pancreatic beta and alpha cells, respectively. Choice D is an example of neural communication, and the remaining choices are examples of neuroendocrine communication.


26. A professional athlete in her mid-20s has not had a menstrual cycle for 5 years, although a bone density scan revealed normal skeletal mineralization. Which fact may explain these observations? A) She consumes a high-carbohydrate diet B) Her grandmother sustained a hip fracture at age 79 years C) Her blood pressure is higher than normal D) Her plasma estrogen concentration is very low E) She has been taking anabolic steroid supplements for 5 years

26. E) Anabolic steroids bind to testosterone receptors in the hypothalamus, providing feedback inhibition of normal ovarian cycling and preventing menstrual cycling as well as stimulation of osteoblastic activity in the bones.


27. What is the nongenomic effect of testosterone on vascular smooth muscle? A) Vasodilation B) Vasoconstriction C) Increase in prostaglandins D) Increase in estrogen receptors

27. A) Testosterone causes vasodilation by inhibiting L-type calcium channels to inhibit calcium influx into the cells, thus causing vasodilation.


28. In the circulatory system of a fetus, which of the following is greater before birth than after birth? A) Arterial Po2 B) Right atrial pressure C) Aortic pressure D) Left ventricular pressure

28. B) Right atrial pressure falls dramatically after the onset of breathing because of a reduction in pulmonary vascular resistance, pulmonary arterial pressure, and right ventricular pressure.



29. E) Patients with Conn’s syndrome have tumors of the zona glomerulosa that secrete large amounts of aldosterone. Consequently, plasma levels of aldosterone are elevated, causing hypokalemia. The secretion of cortisol from the zona fasciculata is normal.



30. D) Aldosterone secretion is elevated when dietary sodium intake is low, but cortisol secretion is normal. Although aldosterone increases the rate of potassium secretion by the principal cells of the collecting tubules, this effect is offset by a low distal tubular flow rate. Consequently, there is little change in either potassium excretion or plasma potassium concentration.