Module 6 (Ch. 14 and 16) Flashcards
It is the coordination of ______, not muscles, that creates the movement patterns of the body.
motor units
What is the Henneman size principle?
Hierarchy of motor unit recruitment.
When a muscle needs a weak contraction, a smaller motor unit is recruited. When muscle needs a stronger contraction, a larger motor unit is recruited in addition to the smaller unit.
Generally, smaller motor units are innervated by [smaller/larger] motor neurons and contain [red/white] muscle fibers
Smaller motor neurons
Red slow-twitch fibers
Generally, larger motor units are innervated by [smaller/larger] motor neurons and contain [red/white] muscle fibers
Larger motor neurons
White fast-twitch fibers
Implication of recruiting a smaller motor unit first?
Smaller units generally contain red slow-twitch muscle fibers which are adapted toward creating joint stabilization. Therefore, they stabilize a joint before larger motor units are recruited.
What determines the degree of a partial contraction?
Number of motor units recruited
Number of muscle fibers in those motor units
Size of a muscle fiber (how many cross-bridges are made)
Orientation of the pull of the cross-bridges relative to the line of pull of the muscle.
What is intrinsic strength of a muscle?
Strength that muscle generates within itself - sliding filament mechanism (active tension) and elastic recoil property of tissues (passive tension).
What is extrinsic strength of a muscle?
Factors outside of the muscle: leverage of muscle on attachments, angle of pull relative to joint
What is the muscle fiber arrangement of longitudinal muscles?
Fibers run along the length of the muscle (most from attachment to attachment).
The force of the contraction of the fibers in longitudinal muscles is in what direction?
Same as the length of the muscle
What are the most common types of longitudinal muscles?
Fusiform (spindle) Strap Rectangular Rhomboidal Triangular (fan shaped)
What is a sphincter muscle?
Circular muscle (e.g., orbicularis oculi) that could be classified as longitudinal
What is a spiral muscle?
Muscle with a twist (e.g., latissimus dorsi) that could be classified as longitudinal
What is the muscle fiber arrangement of pennate muscles?
Arranged in a feather-like manner (central fibrous tendon runs length of muscle with fibers arranged obliquely to central tendon
Is the force of contraction of the fibers in pennate muscles in the same direction as the length of the muscle?
No
What are the 3 types of pennate muscles?
unipennate
bipennate
multipennate
What is a unipennate muscle?
Central tendon and fibers oriented diagonally off one side of the tendon (e.g., vastus lateralis)
What is a bipennate muscle?
Central tendon and fibers oriented diagonally off both sides of the tendon (e.g., rectus femoris)
What is a multipennate muscle?
More than 1 central tendon with fibers oriented diagonally either to one and/or both sides (combos of uni and bipennates) - e.g., deltoid
What is the difference in length between longitudinal and pennate muscle fibers?
Longitudinal = long Pennate = short
What is the difference in amount of muscle fibers between longitudinal and pennate muscle fibers?
Longitudinal = less Pennate = more
What is the difference in amount or sarcomeres/cross-bridges between longitudinal and pennate muscle fibers?
Same number in muscles of the same overall size
Based on fiber orientation, why are longitudinal muscles more suited to create large ranges of motion?
Longitudinal muscles can shorten more than pennate because the fibers are longer
What percentage of its resting length can a muscle fiber shorten?
50%
Why do pennate muscles exhibit greater strength over a shorter range of motion than longitudinal muscles?
Pennate muscles have the same number of sarcomeres generating strength but that is concentrated over a shorter range of motion
A longitudinal muscle is generally better suited for a ______ range of motion contraction but with _____ force.
greater; less
A pennate muscle is generally better suited for a ______ range of motion contraction but with _____ force.
shorter; greater
What are the 2 types of force a muscle can generate?
Active and passive
What is tension in relation to muscle?
pulling force a muscle generates (active or passive)
How is active tension generated?
By sliding filament mechanism (contraction) - muscle expends energy to generate a contraction
What causes passive tension?
Muscle’s natural elasticity creates a pulling force that would pull the muscle’s attachments toward the center of the muscle.
Why is there a backswing in sports like tennis, golf, and baseball?
It first stretches the muscle that will be performing the stroke and adds the passive elastic recoil force to the active contraction force of the muscle –> more powerful pulling force by muscle
What is active insufficiency?
When a muscle cannot generate sufficient strength actively via sliding filament mechanism (weak due to decreased cross-bridges)
What are the 2 types of active insufficiency?
shortened and lengthened
What is shortened active insufficiency?
Muscle is shorter than its resting length and weak because of decrease in cross-bridges (many are overlapping)
Ex: wrist fully flexed can’t make a tight fist (shortened wrist flexors)
What is lengthened active insufficiency?
Muscle is longer than its resting length and weak because of decrease in cross-bridges (actin filaments pulled too far from center and myosin heads can’t reach)
Ex: wrist fully extended can’t make a tight fist (lengthened wrist flexors)
What is the length-tension relationship?
Relationship between the length of a muscle and the active tension it can generate is related to the length of the sarcomeres and the tension that they can generate.
How much passive tension is there when a muscle is shortened? When it is lengthened beyond resting length?
Shortened = nonexistent
Lengthened past resting = increases
Overall tension [increases/decreases] from a shortened length to resting length? From what?
increases from active tension
Overall tension [increases/decreases] past resting length? From what?
Increases from passive tension
What can happen if you frequently work a muscle from an over-lengthened state?
Tearing/injury to muscle tissue
The length-tension relationship is technically for a [concentrically/eccentrically/isometrically] contracting muscle
isometrically
What curve expresses tension force better for when a muscle is moving?
Force-velocity relationship curve
What is the force-velocity relationship (concentric contractions)?
The tension force of a muscle is greatest when a muscle is contracting slowly. As contraction velocity increases, tension force decreases.
What explains the concentric contraction force-velocity relationship?
As speed of muscle contraction increases, there is less time for cross-bridges to form.
What is different about the eccentric contraction force-velocity relationship compared to concentric?
Less dependent on velocity of contraction and stays fairly constant/high; much of this results from addition of passive tension as myofascial tissue resists stretching.
What does the force-velocity curve mean to strengthening muscles?
More strengthening occurs if us through eccentrics or slow concentric contractions