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Unformatted text preview: c b f e d a x y T ime (ms) Membrane potential (mV) EXAM 1 Biol 350: 9-28-2010 Name: ANSWER KEY _______ ID: ______________________ 1. In negative feedback control systems a. The value of the controlled variable increases steadily b. The value of the controlled variable fluctuates across a nar row range of the set-point value c. The value of the controlled variable does not change at all d. The set point value assumes the value of the controlled variable e. The set point value fluctuates around the value of the controlled variable 2. Describe, in two short sentences, why negative feedback regulation is a key mechanism in homeostasis Homeostasis is maintained by negative feedback mechanisms because any change from the normal range is resisted. The change in the controlled value initiates responses that bring the value back within the normal range. 3. Give an example for negative feedback regulation at the cellular level When the external temperature drops, the body's homeostatic mechanisms make adjustments that result in the generation of body heat, thereby maintaining the internal temperature at constant levels. 4. The following are three hypothetical hormones named HA, HB, and HC are produced by their respective glands A, B, and C and constitute a negative feedback loop as follows: Hormone A is secreted by gland A Hormone A stimulates gland B to produce hormone B Hormone B stimulates gland C to produce hormone C Hormone C feeds back on gland A to inhibit secretion of hormone A What will happen if gland B becomes insensitive to hormone A, for example because it lost the receptors for hormone A? (choose one of the following answers) a. The secretion rates of Hormones A and B will increase; the secretion rate of hormone C will decrease b. The secretion rates of Hormones A and B will increase; the secretion rate of hormone C remains unchanged c. The secretion rates of Hormones A, B, and C will increase d. The secretion rate of Hormones A will increase; the secretion rates of Hormones B and C will decrease e. None of the hormones will be secreted anymore What will happen if gland A becomes insensitive to Hormone C? (choose one of the following answers) f. The secretion rates of Hormones A, B, and C will increase...
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