The Muscular System

Muscles allow you to…

move

hold your head up

Digest and control waste removal

breathe

Pump blood (cardiac m.t.)

Control blood flow (smooth m.t.)

Hold bones together

thermoregulate

Freeze-fractured muscle fiber…showing the “broken” myofibrils

Graded Muscle Responses

a. Muscle contractions vary in strength due to….

1. Frequency of stimulus

2. Strength of stimulus

a. The application of the first stimulus did not activate any motor units.

b. All motor units are active when the “level 6” stimulus was applied.

c. The application of a “level 10” stimulus would result in a stronger contraction than the “level 7 stimulus.”

d. Indicate which of the following would be best for lifting heavy objects and which would be best for performing surgery.

_________________ size of motor unit averages 1000 muscle cells

_________________ size of motor unit averages 14 muscle cells

Ponder this point……..

Types of Muscle Fibers

Slow twitch muscle fibers (Type I)

Fast twitch (Type II)

Type II A

Type II B

These studies and journal articles offer more insight on muscle fiber research:High-Intensity Training and Changes in Muscle Fiber Nature vs. Nurture: Can Exercise Really Alter Fiber Type Composition?Effects of Endurance Training on Muscle Fiber