Superficial Back Flashcards
To produce an action at a joint a muscle must ___
Cross the joint
How do m uncle contractions produce movement
Pulling the movable attachment (insertion) toward the fixed attachment (origin)
The force a muscle exerts is proportional to _____
It’s physiological cross-section area
The muscle’s range of contraction is proportional to ____
The resting length of its fiber
How are muscle contractions classified?
Their effect on muscle fiber length and role in producing particular actions
Concentric contraction
. Active muscle’s fibers decrease in length
. Typical of agonist
Agonist
Muscle that functions to produce a desired action
Eccentric contraction
. Active muscle’s fibers increase in length
. Typical of antagonist
.Allow smooth, controlled movement and provide a brake during rapid or forceful movements
Antagonist
Muscle that produces the movement opposite to the agonist
Isometric contraction
. Active muscle’s fibers maintain length
. Typical of a fixator
Fixator
. Muscle that stabilizes or supports an element (usually fixed attachment) against the pull of the agonist
Synergistic contraction
. Muscle contraction tends to produce motion around all possible axes
. Neutralizers contraction prevents an undesired action
. Synergists contract in coordination to produce desired motions while neutralizing undesired motions
Nerve lesion
. Injury that innervates some, but not all of the muscles that produce a particular action that action is weakened
. If lesion enervates all muscles that produce action that action is lost
Neutral position
. Point of balance from which all motions characteristic of a joint may occur
. Involves minimal ligamentous tension and requires the least muscular effort to maintain
What contractions balance forces acting around a joint to maintain it in the desired neutral position?
Isometric (tonic) contractions of antagonistic muscle groups
Muscle imbalance
Some, but not all, muscles acting across a joint are weakened or paralyzed
Unopposed contraction of normal muscles produces _______
Stereotypical limb postures associated w/ different neuromuscular syndromes
Muscle contracture
Permanent deformity that happens when Unopposed muscles shorten
Pectoral girdle
Functional unit formed by the clavicle and scapula
What does the pectoral girdle articulate with?
. Axial skeleton at sternoclavicular (SC) joint
. only bony articulation between upper extremity and the axial skeleton
Elevation of pectoral girdle
. Moving pectoral girdle superiority (shrugging shoulders)
Elevation/depression plane and axis of movement in pectoral girdle
Coronal plane around the AP axis of the SC joint
Depression in pectoral girdle
Returning to neutral position (unshrugging)
Protraction/retraction plane and axis in pectoral girdle
Transverse plane around the vertical axis of SC joint