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Muscular Disorders

There are approx 640 named muscles in the human body - in addition to thousands of smaller (un-named) muscles. This page summarizes some of the most common muscular diseases and disorders. The following table lists them in alphabetical order.

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 show exaggerated 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

See also skeletal disorders and neck pain, shoulder pain and elbow pain.

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