PHYSIOLOGICAL PROPERTIES OF SKELETAL MUSCLE
Skeletal muscle possesses four essential properties:
Excitability: this refers to muscle tissue being able to react to nervous stimulation.
Extensibility: this refers to the ability of muscle tissue to lengthen when contracting and
provide the effort required to move the lever system (the bones and joints), producing
coordinated movement.
Elasticity: this refers to the ability of muscle tissue to return to its normal resting length
once it has been stretched. A useful analogy is that of an elastic band, that will always
resume its resting shape after it has been stretched. This property enables the muscle to
prepare for a series of repeated contractions, which is normally required when performing
exercise or sport.
Contractility: this refers to the capacity of a muscle to contract or shorten forcibly when
stimulated by nerves and hormones (excitability).
All these properties are essential for all body actions including movement and posture.
DISORDERS (DEFINITION)
Osteoporosis-
Disease of bones that leads to an increased risk of fracture. In osteoporosis, the bone mineral
density (BMD) is reduced, bone microarchitecture deteriorates, and the amount and variety of
proteins in bone is altered. The three main mechanisms by which osteoporosis develop are an
inadequate peak bone mass (the skeleton develops insufficient mass and strength during growth),
excessive bone resorption, and inadequate formation of new bone during remodeling.
Pagets Disease-
Pagets disease of bone is a chronic disorder that can result in enlarged and misshapen bones.
The excessive breakdown and formation of bone tissue causes affected bone to weaken, resulting
in pain, misshapen bones, fractures, and arthritis in the joints near the affected bones. Pagets
disease typically is localized, affecting just one or a few bones, as opposed to osteoporosis, for
example, which affects all the bones in the body.
Arthritis
Inflammation of a joint. When joints are inflamed they can develop stiffness, warmth, swelling,
redness and pain. There are over 100 types of arthritis.
Tetany
A condition that is due usually to low blood calcium (hypocalcemia) and is characterized by
spasms of the hands and feet, cramps, spasm of the voice box (larynx), and overactive
neurological reflexes. Tetany is generally considered to result from very low calcium levels in
the blood.
Muscular dystrophy
Muscular dystrophy is a group of diseases that cause progressive weakness and loss
of muscle mass. In muscular dystrophy, abnormal genes (mutations) interfere with the
production of proteins needed to form healthy muscle.