Page 1 of 8 Occupational Therapy Physiology, Summer 2002 Examination 1 August 9, 2002 Dr. Heckman's section is questions 1-6 and each question is worth 5 points for a total of 30 points. Dr. Driska's section is worth a total of 70 points. The number of points for each question is indicated. Make sure you have a complete examination and that your name is on each page. You may not consult your notes or books. You may use a calculator. You have 1 hour. The exam is worth 100 points Please show all your work. Turn in your complete examination at the end of the exam period. Good luck!
Page 2 of 8 100 Mean Bl oodpr essur e ( mm Hg) Mean Blood Pressure (mm Hg) 80 60 40 20 0 B A 60 20 = 40 mm Hg 0 1 2 3 4 5 Cardiac Output (Liters / minute) 1. If the cardiac output is 3 liters / minute, by how much does the mean blood pressure increase when the total peripheral resistance is increased from curve A to curve B? Increase in mean blood pressure = 40 mm Hg 2. If the set point for the control of mean blood pressure is 95 mm Hg and the current mean blood pressure is 150 mm Hg, what will be the response of the negative feedback control system (the baroreceptor reflex)? Decrease BP back toward 95 mm Hg by decreasing cardiac output and decreasing TPR 3. Explain why the velocity of blood flow in the region of the carotid artery, in which plaque has accumulated, will be higher than normal. Be sure to use the continuity equation, F = v A. v = F A 4. Explain by using the equation, Concentration = Amount / Volume, the effect of drinking pure water on the concentration of sodium chloride in the plasma. C = Amount Volume
Page 3 of 8 5. If an experiment is performed to determine the effect of increasing the P a CO 2 on ventilation (V A ), which variable will be the independent variable? P a CO 2 or V A (circle one) Variable B Vari abl e B Variable A 6. Draw a graph which represents a nonlinear, inverse relationship between variable A and variable B.
Page 4 of 8 7. Synaptic transmission (8 points) A number of events take place in the process of synaptic transmission. Place the following events in their cause-and-effect sequence by writing them in the list on the right. In other words, arrange them so that each event directly leads to the event below it. (Please write the event in the list; don t draw lines to their new location or renumber the list on the left.) a. binding of neurotransmitter to receptor sites on the post-synaptic cell b. fusion of synaptic vesicles with the membrane of the pre-synaptic cell c. diffusion of neurotransmitter across the synaptic cleft d. action potential in the pre-synaptic cell e. release of neurotransmitter into the synaptic cleft f. inactivation of the neurotransmitter g. action potential in the post-synaptic cell h. entry of Ca2+ into the pre-synaptic cell 1. action potential in the pre-synaptic cell 2. entry of Ca2+ into the pre-synaptic cell 3. fusion of synaptic vesicles with the membrane of the pre-synaptic cell 4. release of neurotransmitter into the synaptic cleft 5. diffusion of neurotransmitter across the synaptic cleft 6. binding of neurotransmitter to receptor sites on the post-synaptic cell 7. action potential in the post-synaptic cell 8. inactivation of the neurotransmitter About the grading of this question: The post-synaptic action potential normally occurs before inactivation of the neurotransmitter. However, interchanging items 7 and 8 was allowed because they are not truly cause-and-effect. Inactivation of neurotransmitter can take place without an action potential. This was a difficult question to grade, and I tried to give you the maximum points possible. When I graded your papers, I "moved" the incorrect item to its proper position in the sequence. For each item I moved, I deducted one point. If you can see another way of moving items that gives you a higher score, let me know.
Page 5 of 8 8. More synaptic transmission (7 points) a. Many drugs work by blocking the removal of a neurotransmitter from the synaptic cleft. For example, a drug called physostigmine blocks the action of the enzyme acetylcholinesterase in the synaptic cleft of the neuromuscular junction. If a patient is given physostigmine, will acetylcholine released from the motor axon have a greater effect or a lesser effect on the muscle cell? Circle your answer: In the presence of physostigmine, acetylcholine will have a greater effect lesser effect b. Explain your answer: Acetylcholine is normally inactivated by acetylcholinesterase in the synaptic cleft. Because physostigmine inhibits acetylcholinesterase, the acetylcholine is present for a longer time in the synaptic cleft, so it has a greater effect. 9. Membrane transport (10 points) a. What transport mechanism is used by glucose to enter muscle cells? Facilitated diffusion, a form of carrier-mediated transport b. Why does it use this mechanism? (Your answer should say what properties of the glucose molecule make this mechanism necessary.) Glucose is hydrophilic so it cannot dissolve in the phospholipid bilayer to diffuse across the membrane. Glucose is too big to fit through channels or pores, so the only way for it to enter a cell is by carrier-mediated transport. 10. (5 points) State the Law of Electroneutrality and briefly explain what this law says must happen when a positively charged ion like Na+ enters a cell. The Law of Electroneutrality says that a solution must have an equal amount of positive and negative charges. In other words, it must be neutral. Thus when a Na+ ion enters the cell, either a different positively charged ion has to leave the cell, or a negatively charged ion such as Cl- will have to enter with the Na+.
Page 6 of 8 11. Osmolarity and cell volume (10 points) a. What is the osmolarity of a 100 mm solution of NaCl? 200 mosm b. If a normal blood cell is placed into a large volume of the solution described in part a, will the cell shrink or swell? Circle your answer: Cell will shrink Cell will swell c. Explain your answer to part b. Water will enter the cell by osmosis because the initial osmolarity inside the normal cell, 290 mosm is greater than that in external solution, 200 mosm. When enough water has entered the cell that the new osmolarity inside is 200 mosm, osmotic flow of water stops. d. Calculate the new volume of the cell in part b., assuming that its original volume was 10 µ 3. Please show all your work and assumptions. i V i = V f = V i i f f V f ( )( 10) ( ) = 290 200 =14.5 3 14.5 µ 3
Page 7 of 8 12. (15 points) In a physiology experiment, a muscle cell is placed in a solution that has a [Na+] of 45 mm, instead of the normal 140 mm Na+ present in the extracellular fluid. 7. Use the Nernst equation (given below) to calculate the equilibrium potential for Na+ (E Na ) under these conditions. Assume the Na+ concentration inside the cell is 15 mm. Please show all your work. E = 61 z log C in C out E = 61mV (+1) log 15 45 E = ( 61mV) ( 0.477) E = +29.1mV E Na = 29 mv 8. If Na+ and K+ are the only permeable ions in this cell, what is the K+ transference (T K ) if the Na+ transference (T Na ) = 0.1? T K = 0.9 9. Write the transference equation and explain what each variable in the equation means. E m = T K E K + T Na E Na T is the transference of the ion, i.e. the ion's conductance expresse as a fraction of the cell's total conductance. g T Na = Na g and T g Na + g K = K K g Na + g K E is the Nernst equilibrium potential for each ion. 10. Use the transference equation to calculate what the resting membrane potential of this cell would be under these conditions. Assume E K = -90 mv and use the values of E Na and transference from your answer above. E m = T K E K + T Na E Na E m = (0.9)( 90mV ) + (0.1)(+29mV) E m = 81mV + 2.9mV = 78.1mV 11. When the cell immersed in the 45 mm Na+ solution fires an action potential, what is the maximum value of the overshoot, in mv? In other words, how high can the action potential go? 29 mv
Page 8 of 8 13. (10 points) Answer the following questions about the role of the voltagedependent Na + and K + channels in the nerve action potential. a. Describe the state of the Na+ channel at the resting potential by answering these questions. (Circle your choice.) i. The m gate (activation gate) is : open closed ii. The h gate (inactivation gate) is : open closed iii. The Na+ channel is : open closed b. Describe the state of the Na+ channel during the upstroke of the action potential by answering these questions. (Circle your choice.) i. The m gate (activation gate) is : open closed ii. The h gate (inactivation gate) is : open closed iii. The Na+ channel is : open closed c. Describe the state of the Na+ channel during the downstroke of the action potential by answering these questions. (Circle your choice.) i. The m gate (activation gate) is : open closed ii. The h gate (inactivation gate) is : open closed iii. The Na+ channel is : open closed d. At the undershoot of the action potential, most of the K + channels are open closed 14. (5 points) During an action potential, which ion flows into the cell, and which flows out? Circle your choice. Na + flows into the cell and K + flows out. OR K + flows into the cell and Na + flows out.