Which concept is described as part of thixotropy?

• A. Gel-Sol Model
• B. Action potentials
• C. Calcium pumps
• D. Nerve conduction

Answer: (A)

Thixotropy involves a time-dependent change in viscosity driven by shear, due to reversible breakdown and rebuilding of a gel-like internal network. The gel-sol model captures this by depicting how applying shear disrupts the solid-like gel structure into a more fluid sol, lowering viscosity, and then, once the shear stops, the network gradually reforms back into a gel, increasing viscosity again. This gel-to-sol and back transition under varying shear is the hallmark of thixotropic behavior.

The other processes listed are electrical or active transport phenomena: action potentials are rapid electrical signals in nerves, calcium pumps move calcium ions across membranes, and nerve conduction is the propagation of electrical impulses along neurons. They do not describe time-dependent changes in a material’s viscosity or a shear-induced gel-sol transition, so they don’t describe thixotropy.