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Calcium-Sensing Receptors and Their Role in Regulating Calcium Levels, Exams of Physiology

National Institute of Industrial EngineeringPhysiology

The function of calcium-sensing receptors (casrs) in regulating calcium levels in the body through negative feedback control systems. It also covers the effects of a new drug, antag-casr, on parathyroid hormone (pth) and calcium levels. Multiple choice questions related to calcium levels, receptors, and feedback systems.

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2012/2013

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STEIN IN-TERM EXAM -- BIOLOGY 3058 -- FEBRUARY 14, 2013 -- PAGE 1 of 8
STEIN IN-TERM EXAM -- BIOLOGY 3058 -- FEBRUARY 14, 2013 -- PAGE 1 of 8
There are 25 questions in this Biology 3058 exam.
All questions are "A, B, C, D, E, F, G, H" questions worth one point each.
There is a total of 25 points in this exam. Fill in your answers on the separate answer sheet.
The format for this exam is:
Fill in A if A is the only correct answer.
Fill in B if B is the only correct answer.
Fill in C if C is the only correct answer.
Fill in D if both A and B are correct (and C is NOT correct).
Fill in E if both A and C are correct (and B is NOT correct).
Fill in F if both B and C are correct (and A is NOT correct).
Fill in G if A and B and C are all correct.
Fill in H if none of the above is correct (A is NOT correct, B is NOT correct, and C is NOT
correct).
ONLY MARK ONE LETTER PER QUESTION.
You may keep the question sheets.
Use a dark (black or blue) pencil or dark (black or blue) pen to fill in the answers.
DO NOT USE A RED PEN; DO NOT USE A RED PENCIL.
1. Which of the following is true?
A. CaSRs (Calcium-Sensing Receptors) are GPCRs (G-Protein Coupled Receptors)
that are spanning proteins located in the plasma membranes of Parathyroid
Gland cells.
B. Calcium ions are agonists of the binding site of CaSRs.
C. CaSRs serve as effectors in a negative feedback control system that regulates
the blood plasma levels of Calcium.
D. A and B.
E. A and C.
F. B and C.
G. A, B, and C.
H. None of the above.
2. In a properly functioning negative feedback system, the
A. value of the controlled variable will always be very close to the threshold value
when the system is in steady state.
B. sensor measures the current value of the actuating signal.
C. the current value of the actuating signal will always be very close to the value of
the set point when the system is in steady state.
D. A and B.
E. A and C.
F. B and C.
G. A, B, and C.
H. None of the above.
3. Which of the following serves as an effector, or part of an effector, that functions in a
negative feedback system?
A. Vitamin D Receptors (VDRs) located in the nucleus of cells in the intestine.
B. Oxytocin Receptors (OXRs, also called OxyRs) located in the plasma
membranes of cells in the walls of the uterus of a pregnant female.
C. CaSRs (Calcium-Sensing Receptors) in the plasma membranes of cells in the
Parathryroid Gland.
D. A and B.
E. A and C.
F. B and C.
G. A, B, and C.
H. None of the above.
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There are 25 questions in this Biology 3058 exam. All questions are "A, B, C, D, E, F, G, H" questions worth one point each. There is a total of 25 points in this exam. Fill in your answers on the separate answer sheet. The format for this exam is: Fill in A if A is the only correct answer. Fill in B if B is the only correct answer. Fill in C if C is the only correct answer. Fill in D if both A and B are correct (and C is NOT correct). Fill in E if both A and C are correct (and B is NOT correct). Fill in F if both B and C are correct (and A is NOT correct). Fill in G if A and B and C are all correct. Fill in H if none of the above is correct (A is NOT correct, B is NOT correct, and C is NOT correct). ONLY MARK ONE LETTER PER QUESTION. You may keep the question sheets. Use a dark (black or blue) pencil or dark (black or blue) pen to fill in the answers.

DO NOT USE A RED PEN; DO NOT USE A RED PENCIL.

  1. Which of the following is true? A. CaSRs (Calcium-Sensing Receptors) are GPCRs (G-Protein Coupled Receptors) that are spanning proteins located in the plasma membranes of Parathyroid Gland cells. B. Calcium ions are agonists of the binding site of CaSRs. C. CaSRs serve as effectors in a negative feedback control system that regulates the blood plasma levels of Calcium. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  2. In a properly functioning negative feedback system, the A. value of the controlled variable will always be very close to the threshold value when the system is in steady state. B. sensor measures the current value of the actuating signal. C. the current value of the actuating signal will always be very close to the value of the set point when the system is in steady state. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  3. Which of the following serves as an effector, or part of an effector, that functions in a negative feedback system? A. Vitamin D Receptors (VDRs) located in the nucleus of cells in the intestine. B. Oxytocin Receptors (OXRs, also called OxyRs) located in the plasma membranes of cells in the walls of the uterus of a pregnant female. C. CaSRs (Calcium-Sensing Receptors) in the plasma membranes of cells in the Parathryroid Gland. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  1. Which of the following serves as an actuating signal, or as part of an actuating signal, in a negative feedback system? A. Blood plasma levels of Parathryroid Hormone Receptors (PTHRs). B. Blood plasma levels of Oxytocin. C. Blood plasma levels of Calcium. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  2. A new drug named ANTAG-CaSR has been developed that is an antagonist at calcium-binding sites of CaSRs (Calcium-Sensing Receptors) in the plasma membranes of parathyroid gland cells. Healthy Person P receives regular doses of ANTAG-CaSR as part of a clinical trial. When ANTAG-CaSR levels in the interstitial spaces surrounding parathyroid gland cells increase in Healthy Person P, this leads to A. a decrease in the levels of parathyroid hormone (PTH) in the blood plasma. B. an increase in the amount of PTH binding to PTH Receptors in bone. C. an increase in the levels of calcium in the blood plasma. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  3. Consider a properly functioning positive feedback system whose output variable is not equal to plateau at 1:00AM. At 1:00AM, A. a change in the value of the actuating signal will lead to a change in the output of the effector. B. when the value of threshold is greater than the value of the output variable, then the value of the output variable always increases to the value of the plateau. C. the sensor measures the current value of the output variable. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  4. Patient X has blood plasma levels of Parathyroid Hormone (PTH) that are always very high due to a tumor consisting of Parathyroid Gland cells that continuously secrete high levels of PTH into the blood plasma. Which of the following drugs will help relieve some of the problems for Patient X? A. Drug A that is an agonist of the Parathyroid Hormone Receptor (PTHR). B. Drug B that is an antagonist of the calcium-binding site of the Calcium-Sensing Receptor (CaSR). C. Drug C is a lipid-soluble molecule that is an agonist of the Vitamin D Receptor (VDR). D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  1. At 1 AM, an impermeable membrane separates a 1 liter solution of 1M NaCl in the left compartment from a 1 liter solution containing both 1M NaCl and 1M KCl in the right compartment. At 2 AM, the membrane became permeable to chloride ions. At 4 AM, the membrane once again became impermeable to chloride ions. At 6 AM, the membrane became permeable to sodium ions and, in addition, maintained chloride ion impermeability. At 8 AM, the membrane once again became impermeable to sodium ions. At 10 AM the membrane once again became permeable to chloride ions and, in addition, maintained sodium ion impermeability. The membrane maintained impermeability to potassium ions during the entire period. A. The amount of sodium ions in the left compartment at 7 AM will be less than the amount of sodium ions in the right compartment at 7 AM. B. The amount of chloride ions in the left compartment at 11 AM will be greater than the amount of chloride ions in the left compartment at 5 AM. C. The amount of chloride ions in the left compartment at 11 AM will be less than the amount of chloride ions in the right compartment at 11 AM. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  2. Which of the following is an agonist that binds to the receptor site that is part of a ligand- gated ionotropic ion channel? A. Insulin. B. Erythropoietin (EPO). C. Acetylcholine (ACh). D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  3. Which of the following is true for Vasopressin2 Receptors (V2Rs) in collecting duct epithelial cells? A. When agonists bind to V2Rs in the plasma membrane of the cells, this leads to an increase in the intracellular amount of cAMP. B. When agonists bind to V2Rs in the plasma membrane of the cells, this leads to an increase in the amount of AQP2 in the luminal plasma membranes of the cells. C. When agonists bind to V2Rs in the plasma membrane of the cells, this leads to an increase in the amount of ATP that is bound to alpha subunits of the G-proteins associated with the V2Rs. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  1. Which of the following substances serve as ligands that bind to G-Protein Coupled Receptors (GPCRs)? A. Cyclic AMP (cAMP). B. 1,25 dihydroxyvitamin D. C. Insulin. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  2. Which of the following is an effect of the following drugs? A. Drug A is an agonist of the Vasopressin2 Receptor (V2R). High levels of Drug A in the extracellular spaces surrounding epithelial cells of the kidney collecting ducts will lead to high levels of exocytosis of vesicles containing AQP2 in their vesicular membranes. B. Drug B is an agonist of the Insulin Receptor. High levels of Drug B in the extracellular spaces surrounding fat cells will lead to high levels of exocytosis of vesicles containing GLUT4 in their vesicular membranes. C. Drug C is an antagonist of the Insulin Receptor. High levels of Drug C in the extracellular spaces surrounding skeletal muscle cells will lead to high levels of exocytosis of vesicles containing GLUT4 in their vesicular membranes. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  3. The value of the Nernst equilibrium potential for sodium at 20 o C will be A. zero volts if extracellular sodium ion concentration is equal to intracellular sodium ion concentration. B. - 58 millivolts if extracellular sodium concentration is ten times that of intracellular sodium ion concentration. C. greater than zero volts if extracellular sodium ion concentration is less than intracellular sodium ion concentration. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  4. Which of the following is true for a G-protein? A. After the GTP-ase of the alpha subunit of a G-protein converts the GTP bound to the alpha subunit to GDP and inorganic phosphate (Pi), the alpha subunit of the G-protein dissociates from the beta and gamma subunits of the G-protein. B. When an agonist binds to the binding site of a G-protein-coupled receptor (GPCR), this leads to GTP displacing a GDP bound to the alpha subunit of the G-protein. C. When ADP binds to an alpha subunit of the G-protein, this leads to the alpha subunit of the G-protein associating with the beta and gamma subunits of the G-protein. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  1. Consider an axon of a neuron. At time=t 1 , its voltage is at threshold for an action potential; at time=t 2 , its voltage is at 0 millivolts prior to the peak of that action potential. In the time period between t 1 and t 2 of that single action potential, A. the amount of intracellular sodium increases. B. sodium conductance of the voltage-gated sodium channels decreases as membrane voltage increases. C. sodium conductance of the voltage-gated sodium channels changes with a slower time course than potassium conductance of the voltage-gated potassium channels. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  2. Which of the following is true for a toe motor neuron that excites a toe muscle that moves the big toe in the left foot? A. Some of the axon of the toe motor neuron is located in a peripheral nerve in the right leg. B. All of the axon terminals of the toe motor neuron are located in the left half of the spinal cord. C. The cell body of the toe motor neuron is located in the left half of the spinal cord. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  3. In a neuron at rest, A. the membrane voltage will be less than zero. B. the sodium conductance is less than the potassium conductance. C. the membrane voltage is less than the action potential threshold voltage. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  4. Which of the following is true for a primary motor cortex (M1) toe corticospinal interneuron N that produces action potentials during voluntary movements of the big toe of the right foot? A. A portion of the axon of interneuron N is located in a nerve in the right leg. B. The axon terminals of interneuron N are located in the right half of the spinal cord. C. The cell body of interneuron N is located in the right half of the spinal cord. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  1. In the axon of a nerve cell, A. there is a net flux of potassium ions out of the cell just after the maximum membrane voltage of the action potential. B. inactivation of the voltage-gated sodium channel only occurs when the potassium conductance of the cell is zero. C. the voltage-dependent conductance of the voltage-gated potassium channels increases as membrane voltage increases. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.
  2. A complete motor neuron is removed from a frog and placed in normal physiological saline at 1 AM. The neuron is healthy. At 2 AM, the physiological saline bathing the neuron is removed and replaced with a modified physiological saline. The composition of the modified physiological saline is as follows: its potassium concentration is the same as normal physiological saline; its sodium concentration is the same as the intracellular sodium concentration of the motor neuron; its total concentration of solutes (osmolarity) is the same as normal physiological saline. The modified physiological saline also contains molecules that block the flux of ions via the sodium-potassium primary active transport pump. At 2:05 AM, the resting membrane voltage of the neuron is
    • 70 millivolts. At 2:06 AM, A. the value of the Nernst equilibrium potential for sodium ions for the neuron is greater than +10 millivolts. B. an increase in sodium conductance will lead to no change in the amount of intracellular sodium. C. an increase in membrane voltage will lead to an increase in sodium conductance. D. A and B. E. A and C. F. B and C. G. A, B, and C. H. None of the above.