PHYS 560 Cellular Physiology MCQs - Answers 2023/24

Homeostasis 1. Which one of the following is an example of a homeostatically controlled variable? (A)Heart rate (B) Body temperature (C) Hypothalamus (D)Thermoreceptors (E) Autonomic nervous system Answer: B. Only choice A and B are variable, and the body doesn’t maintain heart rate homeostatically. Feedback System 2. Which of the following is an example of negative feedback? (A)Increasing blood glucose level in hyperglycemia (B) Decreasing blood glucose level in hypoglycemia (C) Release of insulin as a response to high blood sugar level (D)Release of insulin as a response to high blood pressure (E) Release of oxytocin as a response to uterine contraction during child birth (F) A and E (G)B and C (H)All of the above (I) None of the above Answer: C. Negative feedback tries to suppress the margin of errors. Choice A and B increase the error further more. Choice C, there is no known direct relationship to control blood pressure by insulin. And choice E is a typical example of “Positive Feedback.” 3. David is suffering from hypocalcemia. In response to the low levels of free calcium in his blood his parathyroid gland secretes greater amounts of parathyroid hormone. Elevated levels of parathyroid hormone increase the levels of calcium in his blood. This is an example of… (A)Negative feedback (B) Feed forward control (C) Hierarchy of importance of control mechanisms (D)Set point deviation (E) Positive feedback Answer: A. Negative feedback minimizes the set point deviation (hypocalcemia). Positive feedback will further decrease serum calcium level. 4. In your endocrinology lectures you will find out that a decrease in plasma free calcium levels leads to an increase in the secretion of parathyroid hormone from the parathyroid gland which in turn causes plasma free calcium levels to rise. This is an example of… (A)A negative feedback mechanism (B) A positive feedback mechanism (C) Feed-forward regulation (D)A homeostatic imbalance (E) Saturation kinetics Answer: A. Negative feedback minimizes the error, (hypocalcemia). Positive feedback would further decrease serum [Ca2+] in this scenario. 5. Rebecca is running a 10-mile cross-country race on a warm sunny day. Three miles into the race the sympathetic outflow to her cutaneous vessels is decreased by the temperature regulation center of her hypothalamus. This can best be described by which term; (A)Hierarchy of response (B) Mechanism redundancy (C) Feed forward regulation (D)Negative feedback (E) Positive feedback Answer: A. Maintain blood pressure required for her activity has more priority than maintain her body temperature at this moment. Body Fluid/Compartment 6. Identify the fluid compartment that contains approximately two-thirds of the total body water. (A)Transcellular (B) Plasma (C) Interstitial (D)Intracellular (E) Extracellular Answer: D. Body water is approximately distributed as 2/3 intracellular fluid and 1/3 extracellular fluid. 7. Which of the following statements concerning intracellular fluid that is true: (A)It contains more than 50% of the body water (B) It has a higher osmotic pressure than extracellular fluid (C) It has a higher concentration of organic anions than extracellular fluid (D)Both A and B (E) Both A and C (F) All of A, B and C Answer: E. Intracellular fluid contains 2/3 of body water. Under steady-state conditions the intracellular osmolarity and extracellular osmolarity are equal. If there was a difference, water would diffuse until they were equal. The intracellular compartment does have a higher concentration of organic anions, mainly proteins, than the extracellular fluid. Membrane Transport Use below diagram for next 4 questions 8. Which curves could represent simple diffusion? If the surface area for diffusion increased, what would happen to the slope of the diffusion curve? Answer: A. It is a straight-line relationship: the greater the concentration gradient, the greater the rate of diffusion. If the surface area for diffusion increased, the slope would increase. This means that at a given concentration gradient the rate of diffusion would be greater. 9. Which curves could represent protein-mediated transport? Could you separate active transport versus facilitated transport curves? Answers: B, C, D. These three curves demonstrate saturation kinetics (plateau), which is a characteristic of all protein-mediated transport. You cannot determine which curves would represent facilitated transport versus active transport. Facilitated transport is always down a concentration gradient, whereas active transport can be against a concentration gradient. This information is not presented in the graph. 10. Which curves demonstrate a TM? Which curve has the lowest TM, and which curve has the greatest TM? Answers: B, C, D. Again, this is a characteristic of all protein-mediated transport. TM is the rate of transport of the plateau (measured on the y axis). D has the lowest TM and B the greatest. 11. If “C” represents the movement of glucose into skeletal muscle under control conditions, which curve would represent glucose transport after adding additional insulin? What does insulin do to the number of functioning transporters in the system? Answer: B. Insulin simply places more transporters in the membrane system, which would increase TM. 12. All of the following transport processes display saturation (Michaelis-Menten) kinetics EXCEPT… (A) Na+ -coupled active transport (B) Primary active transport (C) Facilitated diffusion (D) Simple diffusion (E) Na+ -Ca2+ exchanger Answer: D. Saturation occurs in all carrier-mediated transport processes when all of the carrier proteins are occupied. There is a limit to the number of particles that can pass through membrane channels by simple diffusion, so, theoretically, saturation CAN also be achieved via this process. (not under physiological conditions) . . . . . ..