Question

An example of unstriated muscles which are entirely involuntary are located
A) In diaphragm
B) In eyelids
C) In pylorus
D) At the base of the external ear.

Answer 1

Hint: Unstriated muscles are the muscles which do not striations. They look smooth so they are known as smooth muscles. These are involuntary muscles and are controlled by autonomic nervous systems. These muscles are present in the eyes, reproductive system, digestive system.

Complete answer:
Smooth muscles are the non-striated muscles that are involuntary in nature. The function of non-striated muscle is it stimulates the contraction of the digestive, urinary, respiratory, reproductive systems and blood vessels.

Let us discuss the options given in the question.
A) Diaphragm- The diaphragm is made up of thin skeletal muscle which is located at the base of the abdomen. It contracts and expands during inhalation and exhalation.
B) Eyelids- Eyelids are thin folds of skin which protects the eyes. The muscle present in the eyelid is levator palpebrae superioris which helps in opening and closing of eyelids. The movement of this muscle can be both voluntary and involuntary.
C) Pylorus- The pylorus is the part of the stomach which connects to the duodenum. It consists of pyloric sphincter muscle which is present at the lower end of the stomach. It is involuntary in nature and is made up of unstriated muscles.
D) External ear- There are two muscles present in the external ear which serves as the function of protection of the middle and internal ear. These muscles are voluntary in nature.

Hence the correct answer is option ‘C’.

Note: Involuntary movements are the movement in our body which is not under our control. These movements are quick and like jerks, tremors and seizures. These movements can be felt in almost all the parts of our body. An example of involuntary movement is knee jerk, movement of eyelids etc.