Midterm Part 2 Muscle types, action, function, and mechanical levers Flashcards
Muscle types, action, function, and mechanical levers
How many skeletal muscles are there? how much our body weight?
over 600.
40-50%
Definition: muscles work in groups rather than independently to achieve a given joint motion
aggregate muscle action
diff shapes and fiber arrangements affect a muscle’s ability to exert…
force.
diff shapes and fiber arrangements affect the ____ through which a muscle can effectively exert _____ onto a bone.
diff shapes and fiber arrangements affect the range through which a muscle can effectively exert force onto a bone.
greater cross section diameter of muscle means…
greater force
longer muscles can shorter through a greater range and are more effective at what?
moving joints through large ranges of motion.
What are the five fiber arrangements?
parallel, fusiform, pennate, convergent, circular
Parallel muscles fiber arrangement?
arranged parallel to length of muscle (sartorius). - produce greater range of movement than similar sized muscle w pennate arrangement.
Fusiform muscles fiber arrangement?
spindle. parallel. w large cross section diameter.
produce greater range of movement than similar sized muscle w pennate arrangement.
ex. biceps brachii
Pennate muscles fiber arrangement?
feather-like. shorter fibers. obliquely to tendons like a feather. increases cross sectional area of muscle, increasing POWER (tension).
uni, bi, multi
Pennate Muscles: uni, bi, multi?
deltoid?
extensor digitorum?
rectus femoris?
deltoid - multi
ext - uni
rectus - bi
convergent fiber arrangement?
broad origin, pointed insertion. versatile w direction of pull.
ex. pec major
Circular muscles fiber arrangement?
derr
sphincter, orbicularis oris
Strength definition
max force a muscle can generate for a single max effort.
amt of tension muscle produces.
power definition
work done over a given period of time (work/time)
torque definition
muscle force causing rotary movement of a body around an axis
Contraction definition
tension developed in a muscle as a result of a stimulus
muscle contractions used to…
control or prevent joint movement: isometric or isotonic.
Isometric Contraction
same length.
static contractions. stabilizes joints.
tension in muscle = force applied to muscle
Isotonic Contraction
same tone. muscle contraction with change in muscle length. initiates or controls movement.
concentric - shortening contraction
eccentric - lengthening contraction
Concentric Contraction. definition?
when is it used?
isotonic.
“coming to center”
used to initiate movement against gravity or resistance.
Eccentric Contraction. definition? when is it used?
isotonic.
“away from center”
used to decelerate body segment movement.
Line of Pull
direction of movement produced by the contracting muscle — origin to insertion —
line of pull is a function of?
muscle’s attachment, plane of joint motion, muscle’s distance from the joint’s axis of rotation
Angle of Pull
angle between the line of pull of the muscle and the bone on which it inserts - changes w every degree of joint motion
When is the force 100% rotational?
when angle of pull is 90 degrees
rotational and stabilizing forces are equal when?
the angle of pull is 45 degrees.
Reverse-Action of Concentric Muscle Contractions
muscle w origin and insertion - (usually, one bone’s attachments is more stabilized than the other so the less stabilized bone moves to the more stabilized bone.)
USUALLY: biceps curl (open chain) - biceps brachii origin on scapula and insertion on radius
REVERSED: a chin up - closed chain - radius is relatively stable and scapula moves
ROM depends on?
muscle length of fibers. long fibers = large ROM
Power depends on?
of muscle fibers. the more, the more power.
Properties of muscle force production and movement:
- irritability or excitability
- contractility
- extensibility
- elasticity
definition: ability of a muscle to return to its original length following stretching
elasticity
definition: ability of a muscle to be passively stretched beyond its normal resting length
extensibility
definition: property of a muscle being sensitive or responsive to chemical electrical or mechanical stimuli
irritability/excitability
definition: ability of muscle to contract and develop tension (internal force) against resistance when stimulated
contractility
Agonist
muscle that assume major responsibility for producing a specific movement
Antagonist
oppose or reverse movement by prime mover (agonist)
also, helps regulate action of prime mover by partially contracting.
Synergist
helper - assists same joint motion as agonist
Stabilizer (fixator)
synergist. control motion of prime mover. immobilize origin or prime mover - usually isometric or eccentric pull.
Lever definition? What does it allow you to do?
rigid bar that moves on a fixed point. BONES.
a lever allows a muscle to move a heavier load or to move a load farther or faster than it otherwise could.
Fulcrum
a fixed point of leverage. JOINTS
Effort
force applied to move a resistance. TENSION (TORQUE)
Load
resistance to be moved. BONE, TISSUE MASS, OBJECTS TO BE MOVED
Function of Lever
convert force into torque. contracting muscle to force of rotating a bone. internal and external forces involved
Forces involved in musculoskeletal levers produced by:
muscle, gravity, external physical contacts
Mechanical Advantage
Power lever.
load close to fulcrum
effort applied far from fulcrum
> small effort applied over a relatively long distance can be used to move large load over small distance
Mechanical Disadvantage
Speed Lever.
load far from fulcrum.
effort applied near fulcrum.
force exerted must be greater than load moved.
load moves rapidly through larger ROM
a ____ difference in the site of a muscle’s insertion can translate into a ____ difference in the amt of force that must be generated to move a given load.
small difference in site of muscle’s insertion
=
large difference in amt of force you need to move load
First Class Lever
fulcrum between effort and load. think seesaw.
atlanto-occipital joint: weight of face (load)…. posterior cervical muscles contract (effort)
Second Class Lever
load between fulcrum and effort. think wheel-barrel (fulcrum at wheel)
mechanical advantage.
ex. plantar flexion of foot. toe bones are fulcrum. load is the weight of your body. effort in gastrocnemius. load in between fulcrum and effort.
Which lever class is rare in the body?
Second Class Lever
Most levers in the body are which class?
third class levers
Third Class Lever
effort applied at point between load and fulcrum. think bicep curl.
load is the weight in hand. fulcrum is at elbow joint. biceps is between as effort.
mechanical disadvantage
differences in positioning of the effort, load, and fulcrum modify muscle activity w respect to:
speed of contraction
ROM
weight of load
mechanical advantage or disadvantage?
ROM lost.
mech adv
mechanical advantage or disadvantage?
Effort farther than load from the fulcrum.
mech adv
