Purdue BME 330 Practice Exam - Answers PDF

Name:_________________________ PUID:____________________ PURDUE BME 330 Practice EXAM - Answers COURSENAME/SECTIONNUM BER EXAM TITLE NAME...

Name:_________________________ PUID:____________________ PURDUE BME 330 Practice EXAM - Answers COURSENAME/SECTIONNUM BER EXAM TITLE NAME PUID ____________________________________ ________________________________________ Tips for making sure GradeScope can read your exam: 1. Make sure your name and PUID are clearly written at the top of every page, including any additional blank pages you use. 2. Write only on the front of the exam pages. 3. Add any additional pages used to the back of the exam before turning it in. 4. Ensure that all pages are facing the same direction. 5. Answer all questions in the area designated for that answer. Do not run over into the next question space. 1  Name:_________________________ PUID:____________________ Q1. The extracellular medium has the following ionic composition: [Na+]e = 120mM, [K+]e = 4mM, [Cl-]e = 110mM. The cytoplasmic (intracellular) ionic concentrations are: [Na+]i = 15mM, [K+]i = 120mM, [Cl-]i = 20mM, (assume charge balance is maintained by fixed negative charges associated with large molecules in the cytoplasm). Assume PNa = 0.02. PK = 1 and PCl=0.5. a. What are the reversal potentials for Na+, K+ and Cl- ? (5 pts) b. What is the resting membrane voltage? (10 pts) c. The reversal potential for an excitatory channel is 0 mV while the reversal potential for an inhibitory channel is -45mV. Draw out the resultant voltage dynamics when an inhibitory input (duration 5 ms) arrives at i) rest ii) during a 30mV depolarization from rest that lasts 50ms. Assume the input arrives 10ms after the onset of depolarization (15 pts) 2  Name:_________________________ PUID:____________________ Q2. Plot the membrane current for the following voltage step applied to a squid giant axon using a whole-cell patch pipette (20 pts) 3  Name:_________________________ PUID:____________________ Q3. Plot the conductance curves for Sodium and Potassium as a function of the action-potential shown. (5 pts) 4  Name:_________________________ PUID:____________________ Q4. If you were to inject a negative current into an electrically small cell to hyperpolarize it to -100 mV, what will be the membrane voltage recorded at a distance of 10 cm from the injection point? Assume a resting membrane potential of -65mV, an external resistance of 10Ω/cm, an internal resistance of 500Ω/cm, and a membrane conductivity of 10e-4 S/m. (20 pts) a) -80.5mV b) -82.1mV c) -67.1mV d) -69.8mV e) -75.7mV 5  Name:_________________________ PUID:____________________ Q5. Use the opamp rules and assume all sources are ideal and solve for Vo in terms of resistors R1 to R6, Vs and Iin. (25 pts) 6  Name:_________________________ PUID:____________________ Q6. Bonus question (40 Pts) Let’s consider the patch clamp experiment outlined in the figure above. A pipette is brought in contact with a neuron but the seal is not open, i.e. the experimenter has formed Giga seal but not opened the membrane (membrane still closed as he forgets to pop the membrane open). The giga seal is represented by the blue resistor and this resistance is extremely high (several GΩ). Pipette resistance (Re) is 5 MΩ and can be neglected. a. What type of circuit configuration is the opamp in? (10 pts) Current Clamp/Voltage Buffer/Voltage Follower b. If the cell has the following intracellular dynamic (shown on next page), what would the resultant voltage recording look like at the patch amplifier output Vo? Draw out the waveform and write down the reasons and calculations that brought you to the solution. Assume 100 % capacitance neutralization so there is no filtering across the glass wall. The membrane inside the patch-pipette has a resistance of 1 GΩ and a total membrane capacitance of 0.2 pF. (30 pts) (HINT: Membrane is not open, so what does a membrane represent) 7 Name:_________________________ PUID:____________________ 8