Chapter 14 | The Endocrine System

  1. Figure 14.5 Heat shock proteins (HSP) are so named because they help refold mis-folded proteins. In response to increased temperature (a “heat shock”), heat shock proteins are activated by release from the NR/HSP complex. At the same time, transcription of HSP genes is activated. Why do you think the cell responds to a heat shock by increasing the activity of proteins that help refold misfolded proteins?
    Illustration shows a hormone crossing the cellular membrane and attaching to the N R slash H S P complex. The complex dissociates, releasing the heat shock protein and a N R slash hormone complex. The complex dimerizes, enters the nucleus, and attaches to an H R E element on D N A, triggering transcription of certain genes.
    Figure 14.5 An intracellular nuclear receptor (NR) is located in the cytoplasm bound to a heat shock protein (HSP). Upon hormone binding, the receptor dissociates from the heat shock protein and translocates to the nucleus. In the nucleus, the hormone-receptor complex binds to a DNA sequence called a hormone response element (HRE), which triggers gene transcription and translation. The corresponding protein product can then mediate changes in cell function.
  2. Figure 14.11 Pancreatic tumors may cause excess secretion of glucagon. Type I diabetes results from the failure of the pancreas to produce insulin. Which of the following statement about these two conditions is true?
    1. A pancreatic tumor and type I diabetes will have the opposite effects on blood sugar levels.
    2. A pancreatic tumor and type I diabetes will both cause hyperglycemia.
    3. A pancreatic tumor and type I diabetes will both cause hypoglycemia.
    4. Both pancreatic tumors and type I diabetes result in the inability of cells to take up glucose.
      When blood glucose levels fall, the pancreas secretes the hormone glucagon. Glucagon causes the liver to break down glycogen, releasing glucose into the blood. As a result, blood glucose levels rise. In response to high glucose levels, the pancreas releases insulin. In response to insulin, target cells take up glucose, and the liver converts glucose to glycogen. As a result, blood glucose levels fall.
      Figure 14.11 Insulin and glucagon regulate blood glucose levels.
  3. Figure 14.14 Hyperthyroidism is a condition in which the thyroid gland is overactive. Hypothyroidism is a condition in which the thyroid gland is underactive. Which of the conditions are the following two patients most likely to have?

Patient A has symptoms including weight gain, cold sensitivity, low heart rate and fatigue.

Patient B has symptoms including weight loss, profuse sweating, increased heart rate and difficulty sleeping.

The hypothalamus secretes thyrotropin-releasing hormone, which causes the anterior pituitary gland to secrete thyroid-stimulating hormone, or T S H. Thyroid-stimulating hormone causes the thyroid gland to secrete the thyroid hormones T 3 and T 4, which increase metabolism, resulting in growth and development. In a negative feedback loop, T 3 and T 4 inhibit hormone secretion by the hypothalamus and pituitary, terminating the signal.
Figure 14.14 The anterior pituitary stimulates the thyroid gland to release thyroid hormones T3 and T4. Increasing levels of these hormones in the blood results in feedback to the hypothalamus and anterior pituitary to inhibit further signaling to the thyroid gland. (credit: modification of work by Mikael Häggström)

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