The arrector pilli muscle causes:

The arrector pilli muscle causes:

• A. The Hair to Shed
• B. The Hair to Shine
• C. The Hair to Stand on End
• D. The Hair to Grow Faster

Answer: (C)

The arrector pili muscle causes hair to stand on end. This tiny smooth muscle sits at the base of each hair follicle; when it contracts, it pulls the follicle upright, making the hair shaft rise. This autonomic response produces goosebumps. In humans it’s a vestigial reflex, but in other species it helps with insulation or making the animal look larger when threatened. The other options miss the mechanism: shedding relates to the hair growth cycle, shine comes from surface oils and cuticle smoothness, and growth rate is driven by the activity of the hair follicle rather than muscle contraction.

The arrector pili muscle causes hair to stand on end. This tiny smooth muscle sits at the base of each hair follicle; when it contracts, it pulls the follicle upright, making the hair shaft rise. This autonomic response produces goosebumps. In humans it’s a vestigial reflex, but in other species it helps with insulation or making the animal look larger when threatened. The other options miss the mechanism: shedding relates to the hair growth cycle, shine comes from surface oils and cuticle smoothness, and growth rate is driven by the activity of the hair follicle rather than muscle contraction.