Question

Arrector pili muscles in humans are:

• A. Voluntary
• B. Involuntary
• C. Voluntary as well as involuntary
• D. None of the above

Answer 1

The correct option is B Involuntary

• There are two types of muscles, voluntary and involuntary. Voluntary muscles are under our own control while involuntary muscles are not.
• The arrector pili muscles are small muscles attached to hair follicles in mammals. Contraction of these muscles causes the hairs to stand on end. Each arrector pili is composed of a bundle of smooth muscle fibres, which is attached to several follicles (a follicular unit) and is innervated by the sympathetic branch of the autonomic nervous system.
• The contraction of the muscle is, therefore, involuntary and stresses such as cold, fear etc., may stimulate the sympathetic nervous system and thus, cause contraction.
• Thus the correct option is B.