Muscle Biology

Collagen is the most abundant protein in the extracellular matrix of connective tissues, providing strength, structure, and support. While elastin and reticulin are also found in connective tissues, collagen is by far the most dominant and widespread fiber type. Actin is primarily a contractile protein found inside muscle cells.

While we know that higher protein intake helps preserve lean body mass during weight loss, the precise optimal protein requirement to maximize muscle maintenance in individual obese dogs and cats remains undetermined. Current veterinary guidelines recommend elevated protein levels, but individual metabolic variations make a single universal value difficult to define.

Muscles contract and relax to create movement in our body. They work with bones to help us walk, run, and perform physical activities. Breathing involves the diaphragm muscle and lungs, while digestion is handled by the digestive system organs.

During vigorous exercise, muscle cells may lack sufficient oxygen, leading to anaerobic respiration which produces lactic acid as a byproduct, causing muscle fatigue and cramps.

Effectors are parts of the body, such as muscles and glands, that produce a response to a stimulus.

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.