Bistability in a biological system can be accompanied by hysteresis. Consider switchlike cellular responses to a signal molecule, as shown in the following graphs. In each graph, the solid curve corresponds to the change in cellular response when the signal concentration is being increased over time, whereas the dashed curve corresponds to the change when the signal concentration is being decreased. Which graph do you think corresponds to a system with a greater degree of hysteresis? What mechanism is responsible for this behavior?
A) Graph A; negative feedback
B) Graph A; positive feedback
C) Graph B; negative feedback
D) Graph B; positive feedback

Question

Bistability in a biological system can be accompanied by hysteresis. Consider switchlike cellular responses to a signal molecule, as shown in the following graphs. In each graph, the solid curve corresponds to the change in cellular response when the signal concentration is being increased over time, whereas the dashed curve corresponds to the change when the signal concentration is being decreased. Which graph do you think corresponds to a system with a greater degree of hysteresis? What mechanism is responsible for this behavior? 
A) Graph A; negative feedback 
B) Graph A; positive feedback 
C) Graph B; negative feedback 
D) Graph B; positive feedback

Quizplus · Accepted Answer

In hysteresis, the current state of the system depends on the route it has taken in the past. In the presence of hysteresis in a bistable system, the transition points for switching on (solid curve) and switching off (dashed curve) are different.

Bistability in a Biological System Can Be Accompanied by Hysteresis