Anatomy Lecture 4: Muscle Function and Superficial Back Flashcards
In which plane and axis does flexion/extension occur?
In the Sagittal plane around a transverse (horizontal) axis.
In which plane and axis does rotation occur?
In a horizontal plane around a vertical axis
In which plane and axis does abduction/adduction occur?
In a coronal plane around an anteroposterior axis.
What are the principles of muscle function?
- Muscle must cross a joint in order to produce an action at the joint
- With a muscle that crosses multiple joints, its action and ROM at one joint may be affected by positions of other joints
- Muscle contractions produce movement by pulling the movable attachment (usually the insertion) toward the fixed attachment (usually the origin)
- Force a muscle exerts is proportional to its cross-sectioned area
- Muscle’s range of contraction is proportional to its fibers’ resting length
What is proportional to the force a muscle exerts?
The muscle’s cross-sectional area
What is proportional to a muscle’s range of contraction?
The resting length of the muscle’s fibers.
What are the types of muscle contraction?
- Concentric contraction: active muscle decreases in length (agonist)
- Eccentric contraction: active muscle increases in length (antagonist)
- Isometric contraction: active muscle maintains length (fixator)
- Synergistic contraction: muscles contract in coordination, produces desired motions/limits undesired motions (synergists)
What is a nerve lesion and what are two types?
An injury to a nerve, can be weakened (partial loss of innervation) or lost (total loss of innervation)
What are the roles tonic contractions of antagonistic muscles?
Constantly balance forces acting around a joint to maintain it in a desired position.
What is neutral muscle position?
Position requiring the least muscular effort to maintain.
Define muscle imbalances
Occur when some, but not all, of the muscles acting across a joint are weakened or paralyzed.
What are muscle contractures and why are they an issue?
They are when unopposed muscles shorten resulting in permanent deformities.
What is the pectoral girdle and with what does it articulate?
Functional unit formed by the clavicle and scapula. Articulates with the axial skeleton at the sternoclaviclar joint. Articulates with the arm at the glenohumeral joint.
What are the movements of the pectoral girdle?
- Elevation/depression: in coronal plane around A/P axis of SC joint
- Protraction/retraction: transverse plane around vertical axis of SC joint
- Superior/inferior rotation: gliding movements of AC joint allows scapula to rotate in coronal plane
What type of joint is the glenohumeral joint and what movements occur?
A highly mobile, multiaxial synovial joint
- Abduction/adduction
- Flexion/extension
- Medial/lateral rotation
What is scapulohumeral rhythm?
Term for coordinated movement of the pectoral girdle and the glenohumeral joint required for full range of motion at the shoulder.
What are specific movements associated with scapulohumeral rhythm?
- Flexion/Extension of arm requires Protraction/Retraction of scapula
- Abduction/Adduction of arm is about 180 degrees, last 60 degrees of abduction requires rotation and fixation of scapula