Question

State two functions of skeletal muscles. (p. 80)

Short answer

Answer: The two main functions of skeletal muscles are 1) generating movement and 2) maintaining posture and supporting the body.

Step-by-step solution

Identify Function 1

Skeletal muscles are responsible for generating movement in the body by contracting and pulling on bones. This ability to move is one of the main functions of skeletal muscles.

Identify Function 2

Another crucial function of skeletal muscles is to maintain posture and support the body. Skeletal muscles contract to stabilize and hold the body upright. So, the two main functions of skeletal muscles are: 1. Generating movement 2. Maintaining posture and supporting the body.

Key concepts

Muscle-Generated Movement

The marvel of muscle-generated movement lies in the intricate and coordinated actions of skeletal muscles. These muscles are like the ropes of a marionette, pulling on the bones to create motion. When you decide to walk, jump, or wave your hand, it is the skeletal muscles at work. They contract, which means they shorten, pulling the bones closer together and resulting in movement.

The beauty of this system is that muscles work in pairs. While one muscle contracts, its partner relaxes, creating a smooth and controlled motion. This is known as the agonist-antagonist relationship. For instance, when you bend your elbow, your bicep contracts and your tricep relaxes. Reverse the action, and you straighten your arm.

Posture Maintenance

Posture maintenance is another key function of skeletal muscles that is often overlooked. It's not just about standing upright; maintaining posture is a dynamic process that requires constant muscle adjustment and balance. Even when you're sitting still, muscles are actively working to keep your body aligned.

Muscles responsible for maintaining posture are mostly found in the back, abdomen, and legs. These postural muscles are constantly making small contractions to counteract the forces of gravity that try to pull us forward or sideways. Good posture is vital for minimizing strain on muscles and ligaments, which could lead to pain and injury over time.

Body Support

Body support is fundamentally linked to skeletal muscles. Without these muscles, our bodies would lack the structure needed to stand or move effectively. While the skeleton provides a frame, it's the muscles that flesh out this framework, giving it strength and the ability to withstand stresses.

Think of the body as a building, and the muscles as the beams that support it. Core muscles, like those in the abdomen and back, are especially important for this. They ensure the body's stability and balance, allowing us to perform tasks like carrying groceries or lifting weights with confidence.

Muscle Contraction

Muscle contraction is a physiological process that underpins all muscle functions. It is the mechanism by which a muscle fiber shortens, generating force. This process is powered by a complex interaction of proteins within the muscle cells—actin and myosin.

When a muscle contracts, myosin filaments form cross-bridges with actin filaments, pulling them inward. This action, powered by ATP (adenosine triphosphate), results in the sliding filament theory. As myosin and actin slide past each other, the muscle fiber shortens, causing the muscle to contract and produce movement. This is the process behind the contraction and relaxation of muscles during various activities, from typing on a keyboard to sprinting on a track.