Question

Arrector pili muscles are
A. Voluntary
B. Involuntary
C. Voluntary as well as involuntary
D. None of the above

Answer 1

Arrector pili muscles are present at the base of the hair follicle and also another end of it is attached to the dermal tissue. In cold conditions, to generate heat the arrector pili muscles contracts that cause hairs on the skin to stand straight.

Complete answer: The muscular system of the human body allows movement and is made up of different types of muscles. The cells present in muscles are referred to as muscle fibres. Movements in human muscles can be classified as voluntary or involuntary. Voluntary actions are under our control while involuntary actions are unconscious and are not under our control. The human body comprises three types of muscle tissues: smooth muscles, cardiac muscles, and skeletal muscles. Smooth muscles are involuntary muscles and non-striated in appearance. They are associated with organs and systems like the digestive system, respiratory system, etc. Cardiac muscles are striated (having a repeating functional unit called sarcomeres) in appearance and are involuntary. These are found in cardiac tissues that help them for synchronic contraction. Skeletal muscles are voluntary muscles and striated with sarcomeres. Sarcomeres of skeletal muscles shorten when an object is moved. Arrector pili muscles are tiny muscles attached to follicles of hair in mammals. Contraction of these muscles causes hairs to stand on end also known as goosebumps. Each arrector pili muscle is composed of a bundle of smooth muscle fibers that attach to several follicles. The contraction of these muscles is controlled by the autonomic nervous system (ANS). ANS is involved in the regulation of physiological processes hence is involuntary in nature.
Hence, the correct answer is option B.

Note: Arrector pili muscles in mammals help in causing inflammation and maintaining the body heat. Contraction of these muscles helps animals to up stand hairs while scaring predators. The effectiveness of this muscle in humans is however less as the human body has less hair on the skin.