Muscular system

The muscular system is a system of tissues - called muscles - throughout the body which allow you to move. Most of the muscles in the body are under conscious control and are moved by commands sent to the muscles from the brain via the nervous system. However, some muscles (such as the cardiac muscles) are involuntary - that is, they move regularly without any conscious control. Except for the involuntary muscles, muscle fibers are connected to the skeletal system by tendons and other tissues; the muscles exert force by converting chemical energy into tension and contraction. Muscles are made up of millions of tiny protein filaments which work together to produce motion in the body. They move and make us capable of a variety of actions by simply contracting and becoming shorter or by relaxing and becoming longer. Muscles pull, but they cannot push.

Each person has over six hundred muscles; these are served by nerves which link each individual muscle to the brain and spinal cord. Our bodily needs demand that muscles accomplish different chores, so we are equipped with three types of muscles. Cardiac muscles, found only in the heart, power the action that pumps blood throughout the body. Smooth muscles surround - or are part of - the internal organs. Both cardiac and smooth muscles are called involuntary muscles, because they cannot be consciously controlled. The skeletal muscles are the third muscle type. These carry out voluntary movements and are what ache after strenuous exercise. Skeletal muscles are the body's most abundant tissue, comprising about 23% of a woman's body weight and around 40% of a man's body weight.

Functions of Muscular System:

Muscular system has the following important functions in human body;

1. MOVEMENTS OF BODY PARTS: Skeletal muscles are responsible for all voluntary movements of human body parts. They provide the force by contracting actively at the expense of energy. In other words, muscles are motors of body where chemical energy of food is converted into mechanical work.
2. STABILITY AND POSTURE: Skeletal muscles stabilize human skeleton and give a proper posture to human beings. Some joints of human body are weak and they require the support of muscular system to achieve stability. Skeletal muscles are very important for such joints.
3. HEAT PRODUCTION: A large share of body’s energy is used by muscular system. As a result of high metabolic rate, muscles produce great amount of heat in the body. Heat produced by muscles is very important in cold climates.
4. CIRCULATION: Cardiac muscles provide the main force for circulation of blood throughout human body. The regular pumping of heat keeps the blood in motion and nutrients are readily available to every tissue of human body.
5. HELP IN DIGESTION: Smooth muscles of organs like stomach and intestine help the digestive system in the process of digestion of food.

Muscular Disorders

Term	Definition	Cause	Effect
Atony	A state in which muscles are floppy, lacking their normal elasticity.	Many possible causes.	Muscles are floppy, lacking their normal elasticity.
Atrophy	Generally, the wasting away of a normally developed organ or tissue due to degeneration of cells. In the case of muscle tissue, the individual muscle fibers decrease in size due to a progressive loss of myofibrils.	Generally, possible causes include undernourishment, disuse or ageing. (a) Disuse Atrophy : muscles atrophy because they are not used. Bedridden individuals and people with casts that immobilize large muscle groups may experience disuse atrophy because the flow of nerve impulses to the inactive muscle is greatly reduced. (b) Denervation atrophy : occurs when a muscle's nerve impulses cease in it's motor neurons.	(a) Need physiotherapy to gradually re-build the muscle. (b) In 6-24 months the denervated muscle will be one quarter of it's original size and the muscle fibers will be replaced by fibrous connective tissue. The transition to fibrous connective tissue, when complete, cannot be reversed.
Cramp	Prolonged painful involuntary contraction of skeletal muscle.	It is sometimes caused by an imbalance of the salts in the body, but is more often a result of fatigue, imperfect posture, or stress.	Pain. Possibly inability to perform specific tasks (e.g. of 'occupational cramp' is 'writer's cramp')
Fibrositis	Inflammation of fibrous connective tissues in muscles. It often affects the muscles of the trunk and back.	It may be a symptom of another disease, such as Sciatica, but in most cases the cause is unknown.	Pain and stiffness.
Muscle Fatigue	Tiredness following prolonged or intense activity.	May be due to de-hydration (loss of water and NaCl, that is "sodium chloride", or "common salt"), and the waste products of metabolism accumulating in the muscles faster than they can be removed by the venous blood.	Tired/aching muscles.

Myositis	Inflammation of muscle fibers / Any of a group of muscle diseases in which inflammation and degenerative changes occur.	(A minority are caused by bacterial or parasitic infections.)
Spasm	A sustained involuntary muscular contraction (which may occur either as part of a generalized disorder such as spastic paralysis, or as a local response to an otherwise unconnected painful condition.)	May occur either as part of a generalized disorder such as spastic paralysis, or as a local response to an otherwise unconnected painful condition.	Painful. Lack of use of body parts normally moved by the muscle in spasm.
Spasticity	= Muscular Hypertonicity (i.e. an increase in the state of readiness of muscle fibers to contract; an increase in partial contraction) with an increased resistance to stretch. Moderate cases show movement requiring great effort and a lack of normal coordination, while slight cases show exaggerated movements that are coordinated. = Resistance to the passive movement of a limb that is maximal at the beginning of the movement and gives way as more pressure is applied.	This is a symptom of damage to the cortiscospinal tracts in the brain or spinal cord. It is usually accompanied by weakness in the affected limb.	Increase in the state of readiness of muscle fibers to contract with an increased resistance to stretch. Moderate cases show movement requiring great effort and a lack of normal coordination, while slight cases showexaggerated movements that are coordinated.
Sprain	Injury to a ligament, caused by overstretching.	Overstretching of ligament.	As the ligament is not severed it gradually heals, but this may take several months.
Strain	Excessive stretching or working of a muscle, resulting in pain and swelling of the muscle.	Damage to muscle caused by overstretching.	Pain

Skeletal and Smooth Muscle Tumors

Rhabdomyomas are rare benign tumors of skeletal muscle usually found in the area of the head and neck.

Rhabdomyosarcomas are malignant tumors of skeletal muscle. These tumors are typically found on the arms and legs. Over 85% of rhabdomyosarcomas occur in infants, children, and teenagers.

Leiomyomas are benign tumors of smooth muscle. These tumors are uncommon.

Leiomyosarcomas are malignant tumors of smooth muscle tissue. These are rare tumors in the USA.

Swollen Arm