Exam 2 Part two Flashcards
Prime movers are
Also called agonist. A muscle that contracts to produce a particular movement, such as extending the forearm. The triceps brachii of the posterior arm is an agonist that causes forearm extension
Antagonists are
A muscle whose actions oppose those of the agonist. The contraction of the agonist stretches the antagonist, & vise versa
Synergists are
A muscle that assists the agonist in performing its action. The contraction of a synergist usually either contributes to tension exerted close to the insertion of the muscle or stabilized the point of origin
How are the biceps brachia & triceps brachia act as agonist & antagonist?
When the triceps brachia acts as an agonist to extend the forearm, the biceps brachia on the anterior side of the humerus acts as an antagonist to stabilized the movement & produce the opposing action, which is flexion of the forearm
When are synergists most useful?
At the start of a movement when the agonist is stretched & cannot exert more power
What are some examples of synergist muscles?
The biceps brachii & brachialis muscles of the arm. Both muscles work synergistically “together” to flex the elbow joint
Synergists may also assist an agonist by?
Preventing movement at a joint & thereby stabilizing the origin of the agonist
How many levers are found in the human body?
Three classes of levers; first-class, second-class, and third-class
First-class levers
Has a fulcrum in the middle, between the effort & the resistance
An example of first-class levers are?
A pair of scissors. The effort is applied to the handle of the scissors while the resistance is at the cutting end of the scissors. The fulcrum (pivot for movement) is along the middle of the scissors, between the handle & the cutting ends
What is an example of a first-class lever in the body?
The atlanto-occipital joint of the neck, where the muscles on the posterior side of the neck pull inferiorly on the nuchal lines of the skull & oppose the tendency of the head to tip anteriorly
The resistance in a second-class lever is between the
Fulcrum & the applied effort
A common example of second class lever is
Lifting the handles of a wheelbarrow, allowing it to pivot on its wheel at the opposite end & lift a load in the middle.
An example of second-class lever in the body is?
They are rare, but occurs when the foot is depressed so that a person can stand on tiptoe. The contraction of the calf muscles causes a pull superiorly by the calcaneal tendon attached to the heel (calcaneus)
Third class levers are
An effort is applied between the resistance & the fulcrum, as when picking up a small object with a pair of forceps. These are the most common levers in the body
An example of third class levers found in the body is?
Found at the elbow, where the fulcrum is the joint between the humerus & ulna. The effort is applied by the biceps brachii muscle, & the resistance is provided by any weight in the hand, or by the weight of the forearm itself
How does the mandible act as a third class lever?
When you bite w/ your incisors on a piece of food. The temporomandibular joint is the fulcrum, & the temporal is muscle exerts the effort, while the resistance is the item of food being bitten
What are the 3 types of pennate muscles?
Unipennate muscle, bipennate, & multipennate
Unipennate muscle is
All of the muscle fibers are on the same side of the tendon. The extensor digitorum, a long muscle that extends the fingers, is a unipennate
Bipennate muscle is
The most common type, has muscle fibers on both sides of the tendon. The palmar & dorsal interosseous muscles that attach to the metacarpals are composed of bipennate muscle that helps adduct and abduct the digits
Multipennate muscle
Has branches of the tendon w/in the muscle. The triangular deltoid that covers the shoulder joint is a multipennate muscle
Convergent muscle
Has widespread muscle fibers that converge on a common attachment site. This attachment site may be a single tendon, a tendinous sheet, or a slender band of collagen fibers (raphe). These muscle fibers are often triangular in shape, resembling a broad fans/a tendon at the tip
How is convergent muscle versatile?
The direction of its pull can be modified merely by activating a single group of muscle fibers at one time
An example of a convergent muscle is?
The pectoralis major of the chest