Lecture: Muscles and Muscle Tissue 4

female skeletal muscle makes up 36% of body mass

male skeletal muscle makes up 42% of body mass

muscle strength per unit is the same in both sexes

With age, connective tissue increases and muscle fiber decreases

By age 30, loss of muscle mass (sarcopenia) begins

regular exercise reverses sarcopenia

Atheroscerosis may block distal arteries, leading to intermittent claudication and sever pain in leg muscles

Group of inherited muscle-destroying diseases

Muscles enlarge due to fat and connective tissue deposits

Muscle fibers astrophy

Most common and sever type

Inherited, sex linked, carried by femailed and expressed in males (1/3500) as lack of dystrophin

Victims become clumsy and fall frequently; usually die of respiratory failure in their 20s

no cure, but Viral gene therapy or infusion of stem cells with correct dystrophin genes show promise

Cardiac and Skeletal cells become amitotic, but can lengthen and thickn

Myoblast like skeletal muscle cells have limited regenerative ability

Injured heart muscle is mostly replaced by connective tissue

-Smooth muscle regenerates throughout life

All muscle tissue develop from embryonic myoblasts

Multinucleated skeletal muscle cells form by fusion

Growth factor agrin stimulates clusting of ACh receptors at neuromuscular junctions

Cardiac and smooth muscle myoblasts develop gap junctions

muscular development reflects neuromuscular coordination

Development occurs head to toe, and promixmal to distal

peak natural neural control occurs by mid-adolescence

Athletics and training can improve neuromuscular control