CH11 Flashcards
what is the muscular system?
Usually refers to the voluntary muscles of the body that are composed of skeletal muscle tissue
what is the function of most skeletal muscles in terms of movement?
- produce movement of body parts
- some stabilize bones so that other skeletal muscles can execute a movement more effectively
how do skeletal muscles produce movement?
by exerting force on tendons, which in turn pull on bones or other structures (such as skin)
do both articulating bones move equally in response to a contraction of a skeletal muscle?
No, 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
what is the origin?
the attachment of a muscle tendon to a stationary bone or the end opposite the insertion
what is the insertion?
the attachment of a muscle tendon to a movable bone or the end opposite the origin
what is a useful rule of thumb regarding origins and insertions?
the origin is usually proximal and the insertion distal; the insertion is usually pulled toward the origin
what is the belly?
the fleshy portion of the muscle between the tendons
what is reverse muscle action?
during specific movements of the body, the actions are reversed
- therefore, the positions of the origin and insertion of a specific muscle are switched
what do bones act as when producing movement?
they act as levers
what do joints act as when producing movement?
act as fulcrums of the levers
what is a lever?
a rigid structure that can move around a fixed point called a fulcrum
what different forces act on a lever?
- load/resistance = opposes movement
- effort = causes movement
what is effort?
the force exerted by muscular contraction
what is load?
typically the weight of the body part that is moved or some resistance that the moving body part is trying to overcome
how does motion occur in terms of loads and effort?
when the effort applied to the bone at the insertion exceeds the load
E > L
what is mechanical advantage?
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
what is mechanical disadvantage?
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)
why is chewing used the back teeth easier than chewing with the front teeth?
It is much easier to crush the hard food item with the back teeth because they are closer to the fulcrum
what are the types of levers?
- first-class levers
- second-class levers
- third-class levers
what are first-class levers?
E > F > L
- fulcrum btwn effort and load
- ex. scissors and seesaws
- can produce mechanical advantage/disadvantage
what are second-class levers?
- F > L > E
- load is btwn fulcrum and effort
- ex. wheelbarrow
- always produce mechanical advantage b/c load is closer to fulcrum than effort
- favors force over speed and range of motion
- uncommon
what are third-class levers?
- F > E > L
- effort btwn fulcrum and load
- ex. forceps
- most common
- always produce mechanical disadvantage b/c effort is always closer to fulcrum than load
- favors speed and range of motion over force
what are muscle fascicles?
a small bundle/cluster of muscle fibers
what are the patters muscle fascicles can make with respect to tendons?
- parallel
- fusiform
- circular
- triangular
- pennate (unipennate, binpennate, multipennate)
Which type of lever produces the most force?
Second-class levers produce the most force
what is the relationship between the length of the muscle fibers and the range of motion they can produce?
The longer the fibers in a muscle, the greater the range of motion it can produce
what does the power of a muscle depend on?
the muscle’s total cross-sectional area
what is relationship between the amount of fibers per unit of cross-sectional area and the amount of power it can produce?
the more fibers per unit of cross-sectional area a muscle has, the more power it can produce
by how much does a muscle fiber shorten as it contracts?
As a muscle fiber contracts, it shortens to about 70% of its resting length
what is an intramuscular injection?
- An injection that penetrates the skin and subcutaneous tissue to enter a skeletal muscle
- Common sites are the deltoid, gluteus medius, and vastus lateralis muscles
- Muscles in these areas are fairly thick, and absorption is promoted by their extensive blood supply
- IM injections are given deep within the muscle, away from major nerves and blood vessels to avoid injury
- have a faster speed of delivery than oral medications but are slower than intravenous infusions
what is the prime mover/agonist?
The muscle directly responsible for producing a desired motion
- contracts to cause an action
what is the antagonist?
A muscle that has an action opposite that of the prime mover - stretches & yields to the movement of the prime mover
where are the agonist and antagonist usually located to each other?
on opposite sides of bone or joint they are moving
what happens when an agonist and antagonist contract at the same time with equal force?
there will be no movement
what are synergists?
A muscle that assists the prime mover by reducing undesired action or unnecessary movement
what are fixators?
A muscle that stabilizes the origin of the prime mover so that the prime mover can act more efficiently
