The muscular system is the biological system of humans that produces movement. The muscular system, in vertebrates, is controlled through the nervous system, although some muscles, like cardiac muscle, can be completely autonomous. Muscle is contractile tissue and is derived from the mesodermal layer of embryonic germ cells (Campbell p. 3). Its function is to produce force and cause motion, either locomotion or movement within internal organs. Much of muscle contraction occurs without conscious thought and is necessary for survival, like the contraction of the heart or peristalsis, which pushes food through the digestive system. Voluntary muscle contraction is used to move the body and can be finely controlled, such as movements of the finger or gross movements that of the biceps and triceps (Campbell p. 3).
There are three types of muscle in the human body (Van De Graaff and Forx p. 10). The most abundant type is called skeletal muscle because virtually all these muscles are attached to the bones of the skeletal system (Van De Graaff and Forx p. 10). Skeletal muscle makes up the more than 600 muscles in the body, most of which are close to the surface of the body, between the integumentary system and the bones. Many muscles bulge when they contract; therefore, they are visible and can be felt as firm lumps under the skin. Cardiac muscle is found exclusively in the heart. Visceral muscle, or smooth muscle, is found within organs in many body systems (Van De Graaff and Forx p. 10).
The Human Muscular System
The muscle system performs three functions that help maintain homeostasis: movement, support, and heat production (Van De Graaff and Forx p. 10).
The movement produced by muscles allows a person to carry out the last step in negative feedback systems: making an adjustment to a change in conditions (Vellacott and Side p. 5). Movement is used to get away from impending danger (e.g., fire, falling objects), escape from unfavorable conditions (e.g., intense sunlight), and eliminate wastes and unwanted materials (e.g., carbon dioxide, splinters) (Vellacott and Side p. 5). Movement is also important in taking positive actions (Vellacott and Side p. 5). It allows a person to move toward, obtain, and use items and conditions that promote the welfare of the body and quality of life (Vellacott and Side p. 5).
The muscle system provides support when muscle contractions prevent the movement of a part of the body. Support maintains proper positional conditions of parts of the body so that they function well. For example, muscle contractions can maintain an upright posture. This activity includes holding the bones in place and preventing the protrusion of the organs in the lower trunk. With proper posture, circulation is improved because blood vessels are open rather than pinched shut, and respiration is assisted because the lungs have room to inflate easily. Holding the head up; positions the eyes for viewing the surrounding environment.
Heat production is essential for maintaining a proper and fairly stable body temperature because most people ...