Chapter 11: Muscles Flashcards
What is the origin?
The attachment of a muscles tendon to the stationary bone (proximal)
What is the insertion?
The attachment of the muscles other tendon to the MOVEABLE bone. Pulls toward the origin (distal)
What’s the lever?
Rigid structure that can move around a fixed point called a fulcrum.
Acted on at two different points by two different forces: EFFORT AND LOAD
What’s the fulcrum?
The point on which lever rest or is supported and on which it pivots (ex:joint)
What is load?
Weight of an object (bone) opposes movement (resistance)
Diagram of effort, fulcrum, and load
Agonist
Prime mover, muscle that contracts to cause action
Antagonist
Stretches and yields to the effects of the prime mover (agonist). Relaxed
Synergist
Muscles that contract and stabilize the prime mover (agonist)
Fixator
Stabilizing the origin of the prime mover so that it can act more efficiently.
Steady the proximal end of a limb while movements occur at the distal end.
How do muscles get their names?
Direction
Size
Shape
Action
Number of origins
Location
Origin and insertion
Muscle direction
Muscle size
Muscle shape
Muscle action
Muscle number of origins/location/insertion
What is the action of occipitofrontalis? (Scalp muscle)
Frontal belly: draws scalp ANTERIOR, raises eyebrows, wrinkles skin of forehead horizontally (surprised look)
Occipital belly: draws scalp posteriorly
What is the action of the orbicularis oris? (Mouth muscle)
Closes and protrudes lips (kissing), compresses lips against teeth, and shapes lips during speech
What is the action of the zygomaticus major? (Mouth muscle) AKA cheek bone
Draws angle of mouth superiorly, and laterally (smiling)
What’s the action of the buccinator? (Mouth muscle) AKA cheek
Presses cheeks against teeth and lips, as in whistling, blowing, and sucking
Draws corner of mouth laterally and assists in chewing by keeping food between teeth (not between teeth and cheeks)
What is the action of the orbicularis oculi? (Orbit and eyebrow muscle)
Closes eye
Origin of a muscle is ___ and insertion is ___
Proximal
Distal
Mechanical advantage
Load is CLOSER to fulcrum, effort is FARTHER from fulcrum.
Small effort required to move large load over small distance
Mechanical disadvantage
Load is FARTHER from fulcrum, effort is CLOSER to fulcrum.
Large effort is required to move smaller load (at greater speed)
First class lever
Fulcrum between effort and load (ex: scissors and seasaw)
Produce both mechanical advantage and disadvantage
Second class lever
Load is between fulcrum and effort (ex: wheelbarrow)
ALWAYS produce mechanical advantage
Third class lever
Effort between fulcrum and load (ex: pair of forceps)
Produce mechanical disadvantage