MCAT practice questions

by goldstandard_mcat (Posted Sun Dec 14, 2014 7:07 am)The plasma proteins that bind thyroid hormones are albumin, a prealbumin called thyroxine-binding prealbumin (TBPA), and thyroxine-binding globulin (TBG). The free thyroid hormones in plasma are in equilibrium with the protein-bound thyroid hormones in the tissues. Free thyroid hormones are added to the circulating pool by the thyroid. It is the free thyroid hormones in plasma that are physiologically active (increasing the metabolic rate) and imbalances in these hormones result in thyroid disease. In thyroid storm, a form of hyperthyroidism, the normal body temperature of 37.5 C may rise to over 40 C.Parathormone and the thyroid hormone calcitonin work antagonistically to regulate the plasma calcium and phosphate levels. Which of the following is an example of positive feedback?A. A body temperature of 39 C causes a further increaseB. Elevated TSH results in elevated thyroxineC. Calcitonin and parathormone regulate calcium levelsD. Increased TBG leads to an increase in TSHAnswer AEndocrine glands are often linked to neural control centers by homeostatic feedback mechanisms. The two types of feedback mechanisms, which happen to be frequent visitors to the real MCAT, are negative feedback and positive feedback. Negative feedback decreases the deviation from the normal value, and is important in maintaining homeostasis and thus controls most endocrine glands.The classic example of negative feedback is the thermostat in you...
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