Microgravity and the Musculoskeletal System
What is the Muscular and Skeletal System?
The skeletal and muscular system is strongly interconnected. The human body’s skeletal structure gives protection to our internal organs and gives our body’s shape. In conjunction with the framework the skeletal system offers the muscular system moves that framework. In a mechanical analogy the human skeletal structure are the levers that exert force muscles create. The skeletal system is made of joints that lend to its mobility. There are six types of these joints in the human skeletal system. Ball-and-socket joints are found in the hip and shoulder, which give a rotational range of motion. Gliding joints are found in the wrist and ankle, which offer a back and forth range of motion. There are pivotal joints, that combine the motions of gliding and ball-and-socket joints, saddle joints, hinge joints, and ellipsoid joints, which move along two-axis, or in three dimensions (jaw, toes, fingers). Therefore, the skeletal system is like a door. The structure is in place for the door to move but it is contingent on an outside force to cause that movement.
Muscles offer the energy needed to move the skeletal system. There are three types of muscles. Cardiac and smooth muscles are involuntary muscles that function without conscious thought. Cardiac muscles pump blood through the body while smooth muscles allow the eyes and stomach to function. The structure of the muscle is dense and fleshy. It is made of fibers made of smaller parts called myofibrils. These fibers are made of proteins called myosin (thick filaments) and actin (thin filaments). All human muscle fibers exert the same force but the strength differences between individuals depend on the compactness and volume of fibers. There are two types of fibers Type I and Type II. Type I muscle fibers are slow twitch. These muscle fibers are slow but have high stamina. Type II are fast twitch muscles having fast movements but low endurance.
To move the skeletal system muscles contract of come together as a complimentary one relaxes or expands. The energy to cause muscle contractions comes from two different metabolic processes- aerobic and anaerobic systems. The aerobic process uses oxygen to create adenosine tri-phosphate (ATP) a form of energy and is used for endurance exertions and requires a steady supply of oxygen. The anaerobic process depends on a steady supply of glucose and does not rely on oxygen but the process cannot continue indefinitely because the build up of lactic acid causes fatigue.
-- Muscular atrophy occurs during space travel due to the lack of muscular exercises by astronauts.
Effects on Both Systems by Microgravity
The most apparent effect of microgravity on the musculoskeletal system is atrophy or the degeneration of cells not in use. The human body constantly adjusts to its environment. In fact, our muscle is literally rebuilt every month. When the body constantly uses up nutrients and discards to remake muscles the body it “rebuilds” according to the use or what is necessary. For example, if someone does not work his or her muscles the body will cease the production of that muscle or change the type of the muscle. A sedentary lifestyle parallels a life in space very closely because the muscles in space than on Earth exert less work since gravity puts a stress on muscles. In space astronauts exercise habitually to counter the effects of microgravity but they still come to Earth weaker because the stress gravity exerts makes us stronger. Without gravity muscles get weaker.
The skeletal system is very similar to the muscular system in its discard and utilizes adapting. Astronauts lose bone density when in microgravity and it takes a while for them to adapt and heal when they get back to Earth. The vertebrae get expanded in space, which increases the height of astronauts and the gravity bearing bones (femur, spine) loose strength. So that when astronauts get back to Earth they are more susceptible to osteoporosis and injury.
Written By: Alexander