A Muscular System is the system of our body which provides us the power of movement. There are nearly 700 muscles attached to the bones and it makes up to 40% of the total body weight. The system consists of muscle tissue, blood vessels, tendons (fibrous connective tissue that binds the muscle to the bones), nerves and ligaments (fibrous tissue that binds bones and directs the movements). Every organ of our body has muscle tissues in them that help them to transport substances from one organ to another and also to make some external physical movement.
There are three types of muscles. They are:
Visceral muscle: It is the weakest of all the three types and is also known as an involuntary muscle because its movement is controlled by the unconscious part of the brain. Also known as the “smooth muscle”, it is found inside stomach, intestines and blood vessels. It makes the organs to contract and move the substances through.
Cardiac muscle: It is a stronger muscle than the visceral muscle and is found only in the heart. It is also an involuntary muscle and its responsibility is to pump blood throughout the body. It is a self-stimulated muscle in terms of its contraction but the hormones and the signals from the brain controls its rate of contraction. Its cells are tightly joined forming an interlocked junction known as intercalated disks which helps in preventing high blood pressure.
Skeletal muscle: It is the only voluntary muscle of human body and is also very strong muscle. It is required for all the actions that we do consciously, such as talking, writing, walking etc. The skeletal muscle contracts the body parts closer to the bone on which the muscle is attached to.
The Muscular System has different roles to play in our body and all of their functions are based on its contraction. The most important function is movement. With the help of its ability to contract, the Muscular System helps each and every part of our body to move. Another function is to maintain the body posture and position. These muscles holding up the body position and posture are strong. The Muscular System, by contracting, allows the movement of substances inside our body, such as food, blood etc. As a result of its contraction, the muscles also generate body heat which maintains our body temperature. At the time of extra work out, there is an increased rate of muscle contraction leading to rise in body temperature which eventually produces sweat from our body.
There are two factors that control the contraction of muscle. They are the amount of stimulus transmitted from the nervous system and the number of motor units involved in the contraction. The motor unit is a group of muscle cells whose functions are controlled by a nerve cell known as motor neuron which transmits signals from the nervous system to the muscle.
There are two types of muscle contraction. The ones that produce movements are known as isotonic while the muscle contraction which does not produce movement is known as isometric. Isometric contractions are mainly due to the stress which increases tension in the muscle, but does not exert any force to move any body part.
There are also two more types of contractions known as twitch contraction and temporal contraction. In twitch contraction, a motor unit is slightly contracted before relaxing after receiving an impulse from a single motor neuron. In case, if the motor neuron is providing several signals, then it is known as temporal contraction and its strength and duration also increases.
For different situations, our body muscle has different energy sources. When our body calls for a low to moderate level of force, the muscle gets its energy through aerobic respiration which receives oxygen and uses the glucose to keep the muscle contracting. While, on the other hand, when a high level of force is required, energy is produced through anaerobic respiration which does not require oxygen. It is so because in this situation the muscle becomes very tight for the oxygen carrying blood vessels to enter. Thus energy is created through anaerobic respiration using lactic acid fermentation in the body.
More energy is produced during aerobic respiration than in anaerobic respiration. Another source is the energy molecules in the muscle fibres such as myoglobin, which is a red pigment containing iron and oxygen which is used for aerobic respiration in the absence of oxygen. The muscles also get their energy from a chemical known as creatine phosphate which donates its phosphate to produce energy. The last source of energy for the muscles is the macromolecule, glycogen, which is made up of glucoses. The glycogen in the muscle fibres breaks it down into glucoses to provide the muscles with the required energy.
Any dysfunction in the Muscular System will affect our body mechanism, from the simplest to the most critical aspect. The Muscular System disorders are:
Muscular dystrophy: It is a genetic disease where the muscle fibres get damaged. The person suffering from this disease will have symptoms, such as weakness, loss of mobility and lack of coordination.
Cerebral palsy: It is the loss of muscle tone which is a continuous or passive partial contraction of muscles that helps in maintaining our body posture while resting. Its major cause is the brain damage before or during the birth of a child.
Myasthenia gravis: It is an autoimmune disorder where its antibodies attack the muscle itself and either destroy or block receptor cells. It thus results in lack of communication leading to lesser contraction and finally becomes weaker and fatigued. The disorder has symptoms such as difficulty in breathing, walking, vision and swallowing.
Amyotrophic lateral sclerosis (ALS): It is a genetic disease and is widely known as “Lou Gehrig’s disease”. It is caused due to the loss of control over the voluntary muscles leading to difficulties in swallowing, breathing and speaking which might ultimately cause paralysis and then death.
Fibromyalgia: It is a chronic disease affecting widely all over the body. Its symptoms are muscle pain, joint stiffness, sleep disturbance, fatigue etc.