OTA125_Ch. 6: Muscular System [Lippert]

50 vocabulary flashcards covering terms and concepts from Chapter 6 Muscular System of Kinesiology.

Normal resting length

The length of a muscle when it is not shortened or lengthened by active contraction or the application of external force.

Irritability

The ability of a muscle to respond to a stimulus, such as an impulse from a nerve or external stretch, resulting in a contraction.

Contractility

The ability of a muscle to contract and generate force when an adequate stimulus is applied.

Extensibility

The ability of a muscle to lengthen when a force is applied.

Elasticity

The ability of a muscle to return to normal resting length when force is removed.

Fascicles

Bundles of muscle fibers bound together inside a muscle.

Myofibrils

Smaller bundles that compose each muscle fiber, which are divided into sarcomeres.

Sarcomeres

Divisions of myofibrils where length change occurs in a muscle.

Actin

Thin muscle filaments attached to Z-lines within a sarcomere.

Myosin

Thicker muscle filaments attached to Z-lines within a sarcomere.

Myosin heads

Projections from myosin filaments that contract and temporarily bind with actin filaments when a muscle is activated.

Cross-bridges

The binding structures formed when myosin heads attach to actin filaments.

Type I muscle fibers

Slow twitch or slow oxidative fibers that are smaller in diameter, red, rich in blood supply, use oxygen as an energy source, and are better for endurance.

Type II muscle fibers

Fast twitch or fast glycolytic fibers that are larger in diameter, pale, use glycogen as an energy source, and are effective for short bursts of contraction.

Motor unit

Muscle fibers innervated by the same motor neuron.

Musculotendinous junction

The place where a muscle joins a tendon.

Tenoperiosteal junction

The place where a tendon joins a bone.

Origin

The proximal muscle attachment point.

Insertion

The distal muscle attachment point.

Parallel muscle fibers

Muscle fibers that extend the entire length of the muscle.

Oblique muscle fibers

Shorter muscle fibers that attach obliquely to a tendon, allowing for more cross-sectional area.

Angle of insertion

The angle at which a muscle attaches to a bone or other structure, which changes through the range of motion.

Line of pull

A line drawn from origin to insertion of a muscle accounting for twists and turns along its path.

Angle of pennation

The angle at which oblique fibers within a pennate or multipennate muscle attach to muscle tendons.

Agonist

The muscle responsible for producing the desired joint motion.

Antagonist

The muscle that performs the opposite motion of the agonist.

Co-contraction

The simultaneous contraction of an agonist and an antagonist muscle.

Synergist

Two or more muscles contracting together to produce a motion that neither can perform individually.

Isometric contraction

A muscle contraction where force is produced without a change in overall muscle length.

Concentric contraction

A shortening muscle contraction where attachments move toward each other, generally overcoming gravity.

Eccentric contraction

A lengthening muscle contraction where attachments move away from each other, generally slowing down gravity.

Open kinetic chain (Concentric)

A concentric movement configuration where the insertion attachment moves toward the origin.

Closed kinetic chain (Concentric)

A concentric movement configuration where the origin attachment moves toward the insertion.

Active insufficiency

The inability of a multi-joint muscle to actively shorten simultaneously through its full range of motion at all joints spanned.

Passive insufficiency

The inability of a multi-joint muscle to lengthen simultaneously through its full range of motion at all joints spanned.

Tenodesis

The closing of the fist through passive insufficiency, allowing grasp and release for individuals unable to actively grasp and release.

Adaptive shortening

The loss of sarcomeres that occurs when a muscle is maintained in a shortened position for prolonged periods.

Adaptive lengthening

The addition of sarcomeres that occurs when a muscle is maintained in a lengthened position for prolonged periods.

Strain

Overstretching of a muscle or tendon.

Rupture

The complete tearing of a tendon.

Trigger points

Hyperirritable, painful points located within a muscle.

Tendonitis

Inflammation of a tendon.

Anterior tibialis

An example of a muscle named according to its anatomical location.

Quadratus lumborum

An example of a muscle named according to its shape.

Flexor digitorum

An example of a muscle named according to its action.

Biceps brachii

An example of a muscle named according to its number of heads or divisions.

Sternocleidomastoid

An example of a muscle named according to its anatomical attachments.

External oblique

An example of a muscle named according to its fiber orientation.

Extensor radialis longus

An example of a muscle named according to its size.

Z-lines

Structures in a sarcomere to which thin actin and thicker myosin filaments attach.