Discussion 2 - Biology 365R Handout for Discussion Sessions...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Biology 365R Handout for Discussion Sessions Week of Sept 5 Objectives : To understand the Nernst equation and how it can be used. To know what the value given by the Nernst equation signifies. To understand the consequences of a membrane permeable to more than one ion. To understand how the Bernstein hypothesis can be modeled by a simple electrical circuit and what the elements in that circuit represent both physically in the nerve cell and electronically. To understand Ohm's law and how it can be used to determine in a simple resistive circuit any one of voltage, current, resistance provided you know the other two of these values. To understand the necessary role of the Na-K pump. To know the Nernst and Goldman-Hodgkin-Katz equations and how to use them. To know and understand some experiments showing the origin of the resting membrane potential. To understand the voltage clamp, how it works and how it shows us the conductances that underlie the action potential. To understand the concept of threshold and how it relates to ionic movements. To understand the phenomena of anode break excitation, the undershoot of the action potential, and the refractory period. Discussion questions: 1. List the factors that contribute to the resting membrane potential. How can this potential be measured? Explain the existence of the injury current observed by DuBois-Reymond. Predict the direction of the current observed (note you will have define whether you’re talking about the movement of + or – charge; by convention, physiologists define current as the movement of + ions, even though the movement might be of – ions in the opposite direction). 2. What is the experimental evidence supporting the idea that it is the movement of K that primarily accounts for the generation of the resting membrane potential? Describe how you would conduct such an experiment. Say you wanted to raise the extracellular K concentration by 50 mM. How would you do this? Describe experiments you could conduct that would suggest that other ions contribute less to the resting membrane potential. 3. What would be the expected consequence for the resting membrane potential of reversing the ions and their concentration inside and outside a nerve? Such an experiment is possible with the squid giant axon. 4. If a cell were permeable only to calcium and the calcium concentration ratio outside to inside were 100, what membrane potential would be present when Ca were distributed at equilibrium? What if the cell were permeable only to chloride and the concentration ratio outside to inside were 10; what would be the potential once equilibrium is reached? What if
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 3

Discussion 2 - Biology 365R Handout for Discussion Sessions...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online