C. Arrangement of Fasciculi

C. Arrangement of Fasciculi

1. Skeletal muscle fibers(cells) are arranged with in the muscle in bundles called fasciculi

2. The muscle fibers are arranged in a parallel fashion within each bundle,

but with respect to the tendons can take one of four forms

a. Parallel- parallel with longitudinal axis of the

muscle and end with flat tendons

b. Fusiform- nearly parallel with a fat belly ending in flat tendons

c. Pennate- short fasciculi with tendons almost the entire length

1. Unipennate- only to one side of the tendon2. Bipennate- both sides of a central tendon3.. Multipennate- attach obliquely from many directions to several tendons

d. circular- arranged in a circular pattern and enclose an

orifice

e. This arrangement correlates with power and R.O.M.

D. Group Actions

1. Most movements are coordinated by several skeletal muscles acting in

groups a. Arranged in antagonistic pairs at the joints

2. A muscle that produces the desired action is the prime mover or agonist

a. The antagonist produces the opposite action

3. Most movements also involve muscles called synergists, which serve to steady a movement preventing unwanted movements and helping the prime mover

a. Some synergists also act as fixators to stabilize

4. Under different conditions and depending on the movement and

which point is fixed, many muscles act as all 4 of the above movers