Muscle Biology

When a muscle contracts, it shortens. It returns to its original length when it relaxes, not when it contracts.

Muscles work by contracting and pulling on bones. Because they are attached to bones via tendons, this contraction creates movement at the joints.

The three main types of muscular tissue are skeletal, smooth, and cardiac. Cartilage is a type of connective tissue, not muscular tissue.

Regular exercise increases the body's ability to store glycogen in the muscles to support sustained energy demands.

The heart is a specialized cardiac muscle that functions continuously throughout a person's life without experiencing fatigue like skeletal muscles.

The internal anal sphincter is composed of smooth muscle and is under involuntary control. The external anal sphincter is composed of skeletal muscle and is under voluntary control.

Adipose tissue (fat) is hydrophobic and contains very little water compared to muscle, bone, or nervous tissue.

The diaphragm, located below the lungs, is the major muscle of respiration. It is a large, dome-shaped muscle that contracts rhythmically and continuously, and most of the time, involuntarily. Upon inhalation, the diaphragm contracts and flattens and the chest cavity enlarges. This contraction creates a vacuum, which pulls air into the lungs. Upon exhalation, the diaphragm relaxes and returns to its dome like shape, and air is forced out of the lungs. Thus, option B is correct. 

When the diaphragm muscles contract, the diaphragm flattens, which increases the vertical dimension of the thoracic cavity to facilitate air intake.

An intramuscular (IM) injection is administered directly into the muscle tissue. This allows for relatively rapid absorption compared to subcutaneous injections.

The calcium ions are responsible for muscle contraction by generating the action potential in the muscle cells. More influx of calcium ions may contract the heart muscle to a prolonged state of contraction, which will lead to abnormal increase in the heart rate.