Muscles

There are three types of muscles: cardiac, smooth, and skeletal. Each type of muscle has its own characteristics and function in the body.

Cardiac muscle, as the name suggests, is found only in the heart. It is an involuntary muscle meaning that there is no conscious control over the action of the muscle, it is completely controlled by autonomic functions. This muscle is striated meaning that when viewed under a microscope, a banding pattern can be seen across the muscle fibers. Cardiac muscle also has intercalated disks, which are unique to it. Cardiac muscle functions to maintain an regular and even rhythm of contraction and relaxation to pump blood throughout the circulatory system. Because the heart must beat constantly and often react quickly, cardiac muscles are some of the hardest working muscles in the body.

Smooth muscles are found in many different locations throughout the body, such as the iris of the eye, the walls of arteries, surrounding the small intestine and stomach. Generally, smooth muscles are also involuntary. An exception to this is the diaphragm, a smooth muscle that regulates breathing, which can be consciously controlled, but generally functions without the individual’s notice. Smooth muscles are not striated. The functions of smooth muscles are as varied as their locations. These muscles regulate blood flow, move food through the digestive system, and even change the angle of hair follicles to maintain body temperature.

Skeletal muscles, which are the focus of this exercise, are the most apparent of all the types. As their name suggests, these muscles are associated with producing movement in the skeleton. These are voluntary muscles meaning that they generally do not function without some conscious stimulus from the individual. These muscles are often quite strong because they must produce the movements necessary for walking, running, lifting, swimming, and in some cases, flying.

The muscles of two animals can appear quite different even if they have the same name, because each animal has its own body plan and different movements are of varying importance to different animals. Because of this the muscles of the human can appear rather different on something like a rat.