Chapter 22, Problem 22.1CC

Ouabain is an African plant derivative that has been used historically to make poison-tipped hunting arrows. It disables the main Na⁺/K⁺ ATPase in neurons. How would the resting potential of neurons in an organism exposed to ouabain change relative to the normal situation? Explain your answer.

Summary Introduction

To explain: The way in which the resting potential of neurons in an organism exposed to Ouabain would change relative to the normal situation.

Introduction: Ouabain is a poisonous substance found in some African plants. It is a plant derivative in nature. It is generally used by Africans to make poison-tipped hunting arrows to hunt animals. This derivate is highly toxic. It has the capability to inhibit the normal Na⁺/K⁺ ATPase activity in the nerve cells.

Explanation of Solution

The role of the sodium-potassium pump is to maintain the sodium and potassium ion concentration in the nerve cells. The maintained potassium gradient provides resting membrane potential. The permeability of the membrane is high towards potassium during the resting phase. This is observed in the normal situation in which Na⁺/K⁺ ATPase activity is present in the nerve cells.

The organism exposed to Ouabain has severe effects on the resting potential. This is because Ouabain inhibits the normal Na⁺/K⁺ ATPase activity in the nerve cells. This results in an abnormal amount of sodium and potassium in the cells. The nervous system cannot maintain the ion gradient due to the inhibited sodium-potassium channels. This affects the normal functioning of the nervous system.

Therefore, an organism exposed to Ouabain has a very high positive value of resting potential as compared to the normal situation. This is because the membrane depicts a high permeability for potassium and thus, the concentration of potassium ions gets higher as compared to the rest of the ions due to inhibited Na⁺/K⁺ ATPase activity. A high potassium gradient results in positive resting potential.