Kinesiology Chapter 6: Muscular System

A set of vocabulary flashcards on the muscular system covering key concepts, properties, structures, and functions of muscles.

Normal resting length

The length of a muscle when it is not shortened or lengthened.

Irritability

Ability of muscle to respond to a stimulus, such as nerve impulse.

Contractility

Ability of muscle to contract and generate force when stimulated.

Concentric contraction

Muscle shortening during contraction.

Eccentric contraction

Muscle lengthening during contraction.

Isometric contraction

Muscle contraction without a change in length.

Extensibility

Ability of muscle to lengthen when force is applied.

Elasticity

Ability of muscle to return to its normal resting length.

Fascicles

Bundles of muscle fibers bound together.

Myofibrils

Smaller bundles within a muscle fiber, divided into sarcomeres.

Sarcomere

The structural unit of a myofibril where length change occurs.

Actin

Thin filaments in a sarcomere.

Myosin

Thicker filaments in a sarcomere.

Cross-bridges

Binding of myosin heads to actin filaments during contraction.

Type I muscle fibers

Slow twitch fibers better for endurance and lower force production.

Type II muscle fibers

Fast twitch fibers that generate high force but fatigue quickly.

Motor Unit

A motor neuron and the muscle fibers it innervates.

Gradation of motor units

Recruitment of motor units based on force required.

Musculotendinous junction

The area where muscle joins tendon.

Tenoperiosteal junction

The area where tendon joins bone.

Origin

The proximal attachment of a muscle.

Insertion

The distal attachment of a muscle.

Angle of insertion

The angle at which muscle attaches to bone.

Line of pull

The directional path from origin to insertion of a muscle.

Angle of pennation

The angle at which oblique fibers attach to tendons.

Agonist

Muscle responsible for the desired motion.

Antagonist

Muscle that performs the opposite motion of the agonist.

Co-contraction

Simultaneous contraction of agonist and antagonist muscles.

Synergist

Muscles that work together to produce motion.

Isometric contraction

Force produced without change in muscle length.

Concentric contraction

Muscle attachments move toward each other.

Eccentric contraction

Muscle attachments move away from each other.

Active insufficiency

Inability to contract effectively across multiple joints simultaneously.

Passive insufficiency

Inability of a muscle to lengthen effectively across multiple joints.

Tenodesis

Closure of the fist through passive insufficiency.

Adaptive shortening

Loss of sarcomeres due to maintained shortened positions.

Adaptive lengthening

Addition of sarcomeres due to maintained lengthened positions.

Strain

Overstretching of a muscle.

Rupture

Complete tearing of a tendon.

Trigger points

Hyperirritable, painful points within a muscle.

Tendonitis

Inflammation of a tendon.