6th Grade Science

Muscular System

I. General

A. Numbers = 600 musclesB. Terminology

1. Muscle means “little mouse”C. Amount

1. 50% of body weightD. Groups

1. Involuntary = Not controlled2. Voluntary = You have to think about

E. Types

E. Types

1. Cardiac Muscle (Heart)i. Moves blood

2. Smooth Musclei. Move fluids inside bodyii. Slow actingiii. Long lasting

3. Skeletal Muscle

i. Voluntaryii. Get tirediii. React quicklyiv. Pull on bones (tendon)

a. Must work in pairsv. Maintain posturevi. Stabilize jointsvii. Generate heat

II. Injuries

A. Pulled muscle1. Overworked or overstretched2. Tendons can also be partially torn

B. Cramps1. Muscle stays contracted

III. Diseases

A. Muscular Dystrophy – Convert muscle to fat

IV. Structure

A. Muscle Bundles

B. Skeletal Muscle Cell

C. Myofibril

D. Skeletal Muscle Fibers

1. Actin2. Myosin

V. Mechanism of Contraction

VI. Skeletal Muscle Motor Units

Figure 10.1a