Cellular Neurobiology Problem Set 2: Electrical Potentials and Ionic Currents in Neurons, Assignments of Biology

Download Cellular Neurobiology Problem Set 2: Electrical Potentials and Ionic Currents in Neurons and more Assignments Biology in PDF only on Docsity! Cellular Neurobiology BIPN 140 Fall 2007 Problem Set 2 Lectures 3 & 4 1. You use current clamp methods to inject a constant current into a neuron: a) Draw a passive electrical response of the neuron’s membrane potential. What type of current causes this? b) Draw an active electrical response of the neuron’s membrane potential. What type of current causes this? c) If currents of two different amplitudes are injected into a neuron, both of which cause an active electrical response, and the currents are maintained for 100 ms, draw what happens. What is the significance of your observations? 2. How are electrical potentials generated across the membrane of neurons? Give specific examples. 3. What are Ri and Rm? Which one is greater and why is this important? 4. Discuss the permeability of the membrane during an AP. What causes this? Explain how this relates to conductance and resistance. 5. What ion is largely responsible for the resting membrane potential? Be specific and include an experiment that proves this. What type of relationship was discovered for this ion? What is it called? 6. A cell is voltage clamped at –10 mV in the presence of tetrodotoxin. Then tetraethylammonium ions are added. Draw what happens in each case. 7. Derive the equation for the current carried by an ion. What does each variable mean? Explain each assumption you make. 8. When talking about ionic conductance, it is common to talk about inward and outward current. What is meant by “inward” and “outward” current? 9. Hodgkin and Huxley were the first to test the idea that the potential-sensitive permeabilities of ions were involved in the generation action potentials. a) What recording technique did they use and why was it necessary to use this technique as opposed to earlier forms of electrical recordings? Explain how the technique works. b) What experiment did they do to show that ionic permeability of the channels that generate action potentials are voltage-sensitive? 10. Hodgkin and Huxley found that two ions were involved in the generation of an action potential. a) Which two ions did they find were involved? b) Describe the temporal relationship between the flux of these two ions during an action potential. b) Describe an experiment and the results that determine which ions flow during the early and late phases? 1