11.1 Flashcards
What muscle type produces movement by exerting force on tendons, which in turn pull on bones and other structures such as skin?
Skeletal muscles
True or false.
The involuntary muscles of your body compose the muscular system.
False.
Voluntary controlled muscles of your body compose muscular system
When a skeletal muscle contracts, it moves one of the articulating bones. The two articulating bones usually do not move equally in response to contraction. Explain what happens with the two articulating bones during contraction? Differentiate the attachment sites.
One bone remains stationary or near its original position, either because other muscles stabilize that bone by contracting and pulling it in the opposite direction or because its structure makes it less movable. The attachment of a muscle’s tendon to the stationary bone is called the ORIGIN; the attachment of the muscle’s other tendon to the movable bone is called the INSERTION
What is the fleshy portion of the muscle between tendons?
The belly of the muscle
What is the rule of thumb for differentiation of origin and insertion?
origin is usually proximal and the insertion distal; the insertion is usually pulled toward the origin.
The _______ of a muscle are the main movements that occur when the muscle contracts.
Actions
Certain muscles are also capable of reverse muscle action (RMA). What does this mean?
This means that during specific movements of the body the actions are reversed; therefore, the positions of the origin and insertion of a specific muscle are switched
True or false.
Muscles that move a body part often do not cover the moving part but always cross the joint that they move.
True
Example: biceps brachii belly lies on the humerus but insertions over the elbow joint, producing forearm movement.
In producing movement, bones act as levers, and joints function as the fulcrums of these levers. Explain how levers and fulcrums work together what define what the are.
A LEVER is a rigid structure that can move around a fixed point called a FULCRUM.
A lever is acted on at two different points by two different forces: the EFFORT (E), which causes movement, and the load or resistance, which opposes movement.
True or false?
The relative distance between the fulcrum and load and the point at which the effort is applied determine whether a given lever operates at a mechanical advantage or a mechanical disadvantage.
True
What are the differences between mechanical advantage and mechanical disadvantage?
Mechanical advantage = if the load is closer to the fulcrum and the effort farther from the fulcrum, then only a relatively small effort is required to move a large load over a small distance.
mechanical disadvantage= If, instead, the load is farther from the fulcrum and the effort is applied closer to the fulcrum, then a relatively large effort is required to move a small load (but at greater speed).
True or false?
Levers are categorized into three types according to the positions of the fulcrum, the effort, and the load. First class levers, second class levers and third class levers.
True
Define first-class lever. Do they produce MA or MDA?Give an example and explain why it is a first-class lever.
Definition: fulcrum is on between the effort and the load. It can produce both MA and MDA.
A first-class lever can produce MA or MDA depending on whether the effort or the load is closer to the fulcrum.if the effort (child) is farther from the fulcrum than the load (adult), a heavy load can be moved, but not very far or fast.
Ex: head resting on vertebral column
When the head is raised, the contraction of the posterior neck muscles provides the effort (E), the joint between the atlas and the occipital bone (atlanto-occipital joint) forms the fulcrum , and the weight of the anterior portion of the skull is the load
Define second-class lever. Do they produce MA or MDA?Give example of body movement that classified as a second class lever.
The load is between the fulcrum and the effort in second-class levers. They always produce a mechanical advantage because the load is always closer to the fulcrum than the effort.
Ex: standing up on your toes. The fulcrum is the ball of the foot. The load is the weight of the body. The effort (E) is the contraction of the muscles of the calf, which raise the heel off the ground.
Define third-class levers. Do they produce MA or MDA?Give example of body movement that classified as a third-class lever.
The effort is between the fulcrum and the load in third-class levers.Third-class levers always produce a mechanical disadvantage because the effort is always closer to the fulcrum than the load.
Ex: The elbow joint, the biceps brachii muscle, the bones of the arm and forearm. in flexing the forearm at the elbow, the elbow joint is the fulcrum , the contraction of the biceps brachii muscle provides the effort (E) and the weight of the hand and forearm is the load.
