Chapter Eleven: Fascicle Arrangements, Muscle Actions + Contractions

What are fascicles?

bundles of skeletal muscle fibers within the muscle

Within a fascicle muscle fibers are X to?

parallel to one another

The arrangement of fascicles is correlated to? 

power and range of motion 

A muscle fiber shortens to a length just slightly greater than half of its resting length. Therefore:

the longer the fibers (fascicles) in a muscle, the greater ROM it can produce, but less force

Muscle strength is determined by the number of fibers it contains. Therefore:

a short fiber can contract just as forcefully as a long one, but has a smaller ROM

What are the five patterns fascicles form?

parallel, fusiform, circular, triangular, or pennate

FA: parallel

Ex)

fascicles parallel to the longitudinal (long) axis of muscle, terminate at either end in flat tendons

sternohyoid muscle

Parallel consists of and it arrangements provides what?

consists of long fibers, providing the greatest ROM but not much power

FA: Fusiform

Ex)

fascicles are nearly parallel to the long axis of the muscle, and terminate in flat tendons 

digastric muscle

FA: Circular 

Ex)

fascicles in concentric circular arrangements form sphincter muscles that enclose an orifice 

orbicularis oculi 

FA: Triangular

Ex) 

fascicles spread over broad area, converge at thick central tendon, giving muscle a triangular appearance

pectoralis major muscle

Pennate

have short fascicles and tendons extends nearly the entire length of the muscle

Pennate consists of and it arrangements provides what?

consist of short fibers and provides good power but a small range of motion

What are the three types of pennate muscles?

unipennate, bipennate, multipennate

Unipennate

Ex)

fascicles are arranged on only one side of the tendon

extensor digitorium longus 

Bipennate

Ex) 

fascicles are arranged on both sides of centrally positioned tendons

rectus femoris muscle 

Multipennate

Ex)

fascicles attach obliquely from many directions to several tendons 

deltoid muscle

MA: isotonic contraction

enough muscle fibers are contracting to shorten the muscle against the load

MA: isometric contraction

number of fibers contracting and generating a force are equal to the opposite force of the load

the muscle does not change length 

MA: concentric contraction

the muscle shortens as it produces a constant tension and overcomes the load it is moving

MA: eccentric contraction

muscle produces a constant tension but lengthens as it gives in to the load it is moving

Movements are the result of? 

several skeletal muscles acting as a group 

How are most skeletal muscles arranged?

ex)

as opposing (antagonistic) pairs at joints 

flexion and extension 

CM: What is the prime mover?

(agonist), contracts to cause an action

CM: What is an antagonist?

stretches and yields to the effects of the prime mover

Provide an example of agonist and antagonistic

biceps brachii is the prime mover, and the triceps brachii is the antagonist

MC: What is the synergist?

aids in the movement of the prime mover by contracting and stabilizing the intermediate joints

MC: What are the fixators?

What end?

stabilize the origin of the prime mover so that it can act more efficiently 

steady the proximal end of a limb while movement occurs at the distal end