Exam 47: Chemical Signals in Animals

In the cAMP pathway,a signalling molecule binds to and activates the cell surface receptor but the adenylyl cyclase remains inactivated.What is the most likely reason for this?

A weightlifter decides to try taking steroids to improve his performance level.Following a month of use,he notes that the steroids have had no effect on his performance.Which of the following is the most likely reason for this?

A cluster of tumor cells that produces and secretes growth factors to induce surrounding cells to grow and divide are showing which type of cell-to-cell signalling?

Which of the following statements is not true of hormones?

What condition would exist in a patient whose thyroid gland cannot sequester iodine?

Why would most of the females in a college dormitory tend to have their menstrual cycles synchronized after living together for an extended period of time?

Signal transduction occurs when a chemical message at the cell surface elicits a response inside the cell.Which one of the following events is not associated with signal transduction?

Tadpoles must undergo a major metamorphosis to become frogs.This change includes reabsorption of the tail,growth of limbs,calcification of the skeleton,increase in rhodopsin in the eye,development of lungs,change in hemoglobin structure,and reformation of the gut from the long gut of an herbivore to the short gut of a carnivore.Amazingly,all of these changes are induced by thyroxine.What is the most likely explanation for such a wide array of effects of thyroxine?

If a portion of the pancreas is surgically removed from a rat and the rat subsequently loses its appetite,one explanation is that the removed portion contains cells that secrete a chemical signal that somehow stimulates appetite.Given this scenario,what type of chemical signalling is occurring?

The posterior pituitary is anatomically and developmentally an extension of the hypothalamus.Which of the following is a true statement about the posterior pituitary?

You have three strains of mice: A,B,and C.You experimentally manipulate each strain and find that all three show increased secretion of molecule X.Now you perform a parabiosis experiment with the three combinations of these mice: AB,AC,and BC.You perform the same experimental manipulation as above on one mouse of each pair without directly affecting the other mouse and look for effects on the other mouse.You find no detectable effect on the unmanipulated partner in any of the combinations.What is the logical conclusion based on these results?

Which of these glands lies closest to the throat region?

Which of the following statements correctly describes the relationship between the hypothalamus (H)and the anterior (AP)and posterior (PP)lobes of the pituitary?

When partially digested food enters the small intestine from the stomach,several events must occur to protect the intestine and allow for the continued digestion of the food.One hormone in particular performs two of these functions.What intestinal hormone is responsible for causing the pancreas to release digestive enzymes and the gall bladder to release bile salts into the intestine?

How can the body prevent a hormone with different effects on different tissues from acting on inappropriate cells at inappropriate times?

Osteoporosis is a condition in which the density of bones is decreased so much that the individual is at a higher risk of fractures.The more calcium in the bones,the better the bone density.Which of the following would have the greatest effect on calcium levels in the bones?

In experiments where researchers suspect that a hormone may be responsible for a certain physiological effect,they may cut the neurons leading to the organ where the effect being studied occurs.What is the purpose of cutting these neurons?

Removing which of the following glands would have the most wide-reaching effect on bodily functions of an adult human?