What type of tissues does the muscle system include?
Contractile: skeletal, cardiac, smooth muscle
What does the efficiency of muscles depend on?
How their fibers are arranged and how they attach to bones
What are the three defining characteristics of skeletal muscle?
Cylindrical-shaped muscle fibers, 3-5 nuclei per muscle fiber, and striations
What are muscle striations?
The organization of actin (thin) and myosin (thick) filaments gives skeletal muscle tissue its striated appearance
What is the sarcomere?
The most basic unit of contraction in skeletal muscle
What is a z disc?
Forms the boundary of each sarcomere and anchors the thin filaments
What is an I band?
Contains only thin filaments (actin), the light striations under the microscope
What is the H zone?
Contains only thick filaments (myosin)
What is the A band?
Spans the length of the thick filament, including areas where thick and thin filaments overlap, the dark striations under the microscope
What is the zone of overlap?
The region where thick and thin filaments interact (overlap) to produce contraction, two zones of overlap in each A band
What is the M line?
A central structure that helps stabilize the thick filaments
What is the origin of the muscle?
The fixed or less moveable attachment, proximal to the point of attachment
What is the insertion of the muscle?
The more moveable attachment of the muscle, distal to the point of attachment
When a muscle contracts, the insertion is typically pulled toward the _____.
Origin
What is an agonist?
A prime mover, the muscle primarily responsible for producing a specific movement at a joint
What is a synergist?
Assists the agonist in performing its action by contributing additional pull or stabilizing the origin of the muscle
What is a fixator?
Joint stabilizer that prevents unwanted movement and enables the agonist to function more efficiently
What is an antagonist?
A muscle that opposes the action of an agonist
What is flexion?
Movement in the anterior-posterior plane that decreases the angle between two bones
What is hyperextension?
Occurs when a joint is extended beyond its normal range (past 180 degrees)
What is extension?
The opposite of flexion, straightening movement that increases the angle between two bones
What is lateral flexion?
When the trunk of the body moves in a frontal plane laterally away from the body
What is abduction?
A lateral movement of a body part away from the body midline
What is adduction?
The medial movement of a body part toward the body midline
