Exam 45: Hormones and the Endocrine System

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?

Which of the following is the most likely explanation for hypothyroidism in a patient whose iodine level is normal?

What would be a likely outcome of a person not consuming enough iodine in their diet?

Testosterone is an example of a chemical signal that affects the very cells that synthesize it, the neighboring cells in the testis, along with distant cells outside the gonads. Thus, testosterone is an example of ________. I.an autocrine signal II.a paracrine signal III.an endocrine signal

What do steroid and peptide hormones typically have in common?

Nitric oxide and epinephrine ________.

During mammalian labor and delivery, the contraction of uterine muscles is enhanced by oxytocin. This is an example of ________.

Prostaglandins are local regulators whose chemical structure is derived from ________.

DES is called an "endocrine disrupting chemical" because it interferes with the endocrine secretions of the ________.

Insect hormones and their receptors ________.

Correct and appropriate signal transduction processes are generally under strong selective pressure and are determined by the properties of the molecules involved, the concentrations of signal and receptor molecules, and the binding affinities between signal and receptor. Therefore, a hormone action is very specific in a species at any one point in time. However, there are examples of very diverse functions of a specific hormone between groups of organisms. For example, thyroxin, which is produced in all vertebrates and many invertebrates, can trigger growth, differentiation, metamorphosis, maturation, reproduction, behavior, temperature tolerance, osmoregulation, or seasonal adaptation depending on the organism in which it is produced. What is the most logical explanation for such different responses triggered by thyroxin in organisms?

The amino acid tyrosine is a starting substrate for the synthesis of ________.

The steroid hormone that coordinates molting in arthropods is ________.

A product of the anterior pituitary gland that causes color changes in its target cells is ________.

Which of the following has both endocrine and exocrine activity?

Which of the following are properties of steroid hormones? I.Steroid hormones are lipid soluble and easily cross the phospholipid bilayer. II.Steroid hormones usually exert their effects on target cells through membrane receptor proteins. III.Steroid hormones act on cells close to where they were produced. IV.Steroid hormones regulate gene transcription by binding to intracellular receptor proteins.

If a biochemist discovers a new molecule, which of the following pieces of data would allow her to draw the conclusion that the molecule is a steroid hormone? I.The molecule is lipid soluble. II.The molecule is derived from a series of steps beginning with cholesterol. III.The molecule acts at a target tissue some distance from where it is produced. IV.The molecule uses a transport protein when in an aqueous solution such as blood.

Hormones secreted by the posterior pituitary gland are made in the ________.

Portal blood vessels connect two capillary beds found in the ________.

The steroid hormone aldosterone affects only a small number of cells in the body because ________.