Question

1. the muscle that closes a joint is the *

extensor
fiber
flexor
smooth

1. muscle tone is *

the natural tension in the fibers of muscles
type of muscle that forms the wall of the heart.
an inherited disorder in which muscle fibers are destroyed.
the inflammation of a tendon.

1. which problem of the muscular system results when muscles are stretched or partially torn from overexertion?

bruise
strain
hernia
muscular dystrophy

Explanation:

1. Flexor muscles are responsible for closing joints by decreasing the angle between bones. Extensors do the opposite (increase the angle). Fibers are the basic units of muscle, and smooth refers to a type of muscle tissue not related to joint - closing action.
2. Muscle tone is the natural, continuous, and passive partial contraction of the muscle fibers, providing a state of readiness. The muscle that forms the heart wall is cardiac muscle. An inherited disorder with muscle - fiber destruction is muscular dystrophy. Tendon inflammation is tendonitis.
3. When muscles are stretched or partially torn due to overexertion, it is called a strain. A bruise is damage to blood vessels under the skin. A hernia is the protrusion of an organ through a weak spot. Muscular dystrophy is an inherited muscle - wasting disease.

Answer:

1. C. flexor
2. A. the natural tension in the fibers of muscles
3. B. strain