BIO Learning Objective #11

5. How do peptide (water-soluble) & steroid (lipid-soluble) hormones differ in action on target cells?

A water soluble hormone binds to a receptor protein on the surface of a target cell. A lipid soluble protein binds to a receptor protein either in the cytoplasm or in the nucleus. Water Soluble: binding triggers events at the plasma membrane that result in a cellular response, or alter transcription of specific genes (gene regulation) which then affects the cytoplasmic response. Lipid soluble: the activation of a receptor directly triggers the cell's response, which is often a change in gene expression.

2. Tell what happens in positive feedback. Does it relate to homeostasis? Make up an example.

Positive feedback is a control mechanism that amplifies rather than reduces the stimulus. Positive feedback loops in animals do not play a major role in homeostasis but instead help drive the processes to completion. During childbirth the pressure of the baby's head against the receptors near the opening of the mother's uterus stimulates the uterus to contract. These contractions result in greater pressure against the opening of the uterus, heightening the contractions and there by causing even greater pressure, until the baby is born.

13. Name two endocrine systems that are regulated by the hypothalamus and two hormone systems that are regulated with no input from the hypothalamus.

Regulated by hypothalamus: adrenal cortex, thyroid No input from hypothalamus: adrenal medulla, pancreas/insulin and glucagon

When neurons in the brain's hypothalamus detect an increase in blood solute concentration, the pituitary secretes anti-diuretic hormone (ADH). (ADH in blood circulation cause the transport epithelium in the kidney excretory tubules to be more permeable to water; as a result more water is reabsorbed back into the blood and the urine produced is more concentrated.) Explain how ADH thus helps maintain homeostasis of solute-water in the blood. Alcohol inhibits ADH secretion--What results?

ADH increases water retention in the kidneys, thus decreasing urine volume. The net result is to help maintain blood osmolality within a normal range. Alcohol reduces the calcium-dependent secretion of ADH by blocking voltage-gated calcium channels in neurohypophyseal nerve terminals.

11. Compare and contrast the adrenal medulla and the adrenal cortex (how each gland is stimulated, their hormone products, relative speed and duration of response) in the body's stress response.

Adrenal Medulla: the central portion; secretory cells derive from neural tissue during embryonic development. The adrenal medulla secretes epinephrine and norepinephrine in response to stress- whether extreme pleasure or life threatening. Increases the amount of chemical available for immediate use. Increase blood glucose, blood pressure, breathing rate, metabolic rate, and change in blood flow patterns. Adrenal Cortex: the outer portion; consists of true endocrine cells. Responds to endocrine signals. Secretes mineralocorticoids and glucocorticoids. Retention of sodium ions and water by kidneys, increase blood pressure and blood volume, proteins and fats are broken down and converted to glucose, and partial suppression of immune system.

10. Why can a hyperactive thyroid (high thyroxine) lead to a slightly elevated body temperature? (application problem) Patient A is found to have a deficiency of dietary iodine. Explain how this dietary deficiency could lead to goiter (enlarged thyroid gland).

As thyroid hormone accumulates, it increases the metabolic rate, resulting in the release of thermal energy, which raises body temperature. Without sufficient iodine, the thyroid gland cannot synthesize adequate amounts of T3 and T4 and the resulting low blood levels of T3 and T4 cannot exert the usual negative feedback on the hypothalamus and anterior pituitary. As a consequence the pituitary continues to secrete TSH. Elevated TSH levels cause an enlargement of the thyroid gland resulting in goiter, a characteristic swelling of the neck.

4. Define: hormone, endocrine gland, neurosecretory cell, tropic hormone ( = "tropin").

Hormone: In multi-celluar organisms, one of many types of secreted chemicals that are formed in specialized cells, travel in body fluids, and act on specific target cells in other parts of the body, changing the target cells' functioning. Hormones are thus important in long-distance signaling. Endocrine gland: a ductless glans that secretes hormones directly into the interstitial fluid, from which they diffuse into the bloodstream Neurosecretory cell: Specialized neurons that secrete molecule that diffuse form nerve cell ending into the bloodstream. Occurs in neuroendocrine signaling Tropic Hormone: regulates the function of other endocrine cells or glands

3. Draw a flow chart or diagram, and use the following terms to describe homeostatic mechanisms to keep body temperature from getting too warm or too cool, and point out the negative feedback: set point, monitor (or sensor), effector.

Image 40.8

12. How can the same hormone - e.g., epinephrine - affect different target organs in different ways.

The effect of a hormone is determined not by the hormone itself but by the receptor in the target cell. So the same hormone can have different effects in different target cells. A receptor that relates with a different signal transduction pathway

8. One cause of juvenile-onset diabetes is an autoimmune attack of the beta cells of pancreas. Which type of diabetes would result?

Type 1 diabetes

7. Explain how type I and type II diabetes mellitus differ in cause and how each can be controlled.

Type 1 diabetes: insulin-dependent diabetes, an autoimmune disorder in which the immune system destroys the beta cells of the pancreas, Usually appears during childhood, destroys the person ability to produce insulin. Treatment consists of insulin, typically injected several times daily. Type 2 diabetes: non-insulin dependent diabetes, is characterized by a failure of target cels to take up glucose from the blood, and blood glucose levels remain elevated. Although heredity can play a role in type 2 diabetes, excess body weight and lack of exercise significantly increase the risk. Many can control their blood glucose levels with regular exercise and a healthy diet, some require medications.

1. What is homeostasis? How does negative feedback help maintain homeostasis?

homeostasis is the steady state physiological condition of the body, Negative feedback is a control mechanism that reduces or "damps" the stimulus.

9. Draw a homeostatic feedback diagram involving thyroxine, TSH (thyroid-stimulating hormone) and TRH (a TSH-releasing hormone). Indicate what stimulates what. Also, indicate two possible negative feedback loops.

picture drawn in lecture