Question

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

Answer 1

Hint: Two kinds of muscles exist- voluntary and unwilling. Voluntary muscles are regulated by us while unintentional muscles are not. The pili muscles of the arrector are present in mammals. The hair appears to be standing as these muscles contract and is usually called goosebumps.

Complete answer: The muscle of the arrector pili is fixed to the hair follicle base. At one end, it is attached to the hair follicle and at the other end to the dermis.
Choice A: It is under our power willingly. If we feel terror, anxiety and so on the hair will stand alone without us being aware of it. Thus, pili muscles directors are not voluntary. This is the wrong choice.
Choice B: It implies that it is not under our influence accidentally. It leads to hair standing at one end when these muscles contract. Such circumstances come when the individual is cold, nervous, fearful, etc. Without us, hair standing occurs. The pili muscles are also unintentional.
Choice C: These muscles are accidental as mentioned above. This is the right option. Thus, this is the wrong choice.
Choice D: Since one of the options is right, this is also the wrong option.
Hence, option B-Involuntary is the correct answer.

Note: In the event of feelings, such as fear, anxiety, cold signals are transmitted to the nervous system that transmits further signals to the arrector pili. Each pili reactor consists of a bundle of smooth muscle fibres, attached to various follicles (a follicular unit), that is intractable to the sympathetic branch of the autonomic nervous system. Therefore, the muscle contraction is unwitting and pressures such as cold, anxiety, etc can induce contraction and can activate the sympathetic nervous system.