Biomechanics - lecture 2 Flashcards
Three characteristics of skeletal muscle?
Always attached to bone, responsible for movement of body and joints, aids fluid and blood movement
What is the force that muscle contractions produced to move joints called?
Torque
How many skeletal muscles?
over 600
What % of body weight is muscle?
40-50%
What does muscle provide for body?
protection, posture, and support
how many pairs of skeletal muscles?
215 that work in cooperation
what do pair of skeletal muscles do?
perform opposite actions at joints at which they cross
What is an aggregate muscle action?
muscles work in groups rather than independently to achieve motion
what does the fiber arrangment and muscle shape do?
affect muscles ability to exert force and affect range it can effectively exhert force
what does cross section diameter affect?
Greater cross section yields greater force exhertion
what muscles can shorten the most?
the longes ones,?sartorius
what muscles are more effective in moving joints throught large ranges of motion?
longer muscles
what are the 5 fiber arrangments of skeletal muscles?
parallel, fusiform, pennate, convergent, circular
Example of a parallel muscle?
sartarious
Example of a fusiform muscle?
biceps brachii, it has two heads
Example of a pennate muscle?
extensor digitorium longus ,
What are the types of pennate muscle?
unipenate or bipennate like the rectus femorus
Convergent muscle example?
pectoralis major
Circular muscle example?
orbicularis oris
If compairing a parallel muscle to a pennate muscle, what whould produce a greater range of movement?
The parallel muscle has greater range of movement for a similar size muscle.
What is the shape of a fusiform muscle?
Spindle shaped, parallel fibers with a large cross section diameter.
Similar sized pennate VS fusiform, what produces greater range of movement?
Fusiform will have greater range of movement over similarly sized pennate
Why do pennate seem to not have the larges range of motion?
they have shorter fibers
How are pennate muscles arranged?
Short fibers arranged obliquely to their tendons, like a feather.
What does the pennate muscle gain by their oblique arrangment to their tendon?
Increased power or tension.
What are the three types of pennate?
unipennate, bipennate, multipennate
Multipennate example?
deltioid
Bipennate example?
rectus femoris - middle head of quad
Unipennate example?
extensor digitorium longus ,
Expample of a convergent muscle?
pectoralis major
Describe a convergent muscle?
broad orgin, pointed orgin
Advantage of convergent muscles?
versatile direction of pull.
What are circular muscles used for?
concentric fibers are used to adjust openings
what is the strength?
Max force a muscle can generate for a single max effort,
what is the amount of tension a muscle can produce at one time?
strength
What is power?
work done over a time, or muscle that?s contracting in a very brief amount of time
What is torque?
muscle force causign rotary movment of a body around an axis, turning or twisting
what is muscle contracting in a very brief amount of time?
power
what is developed in a muscle as a result of a stimulus?
contraction or tension
what can cause, control or prevent joint movement?
muscle contraction
Muscle contractions must be one of what two things?
isometric or isotonic
what can initiate or accelerate movement?
contraction of muscle
what can slow down movement?
contraction of muscle
what can prevent body movement?
contaction of muscle
Wht type of contraction os isometric?
where there is tension but no movement, kid making muscle, static contractions
What are the two types of isotonic contractions?
concentric and eccentric
When does isometric conctaction occur?
when tension in muscle is the same as force appled to that muscle.
What is isometric contaction used for?
to stabilize joints.
Explain isotonic contaction.
muscle contraction that maintains tension under constant load.
What is dynamic contraction?
Tension is developed within muscle for either initiating movement or controlling movement.
Concentric contraction is what?
shortening
Eccentric contraction is what?
legnthing contaction - negative
When is concentric contraction used?
to initiate movement against gravity or resistance.
When is eccentric contraction used?
used to decelerate body segment movement, results in controlled joint motion.
what is a “line of Pull”?
The direction of movement produced by the contracting muscle, from orgin to incertion
can a line of pull change during joint motion?
Line of pull may change during joint motion.
what three things are line of pull a function of?
muscle attachment, plane of joint motion, muscle distance from joints axis.
What can lead to muscle/joint injury?
if line of pull is altered from its optimal position due to weakenss or poor posture.
Why can altered pull lead to injury?
because makes muscle inefficient so it works harder and has more strain leading to injury
Expain line of pull change sinario?
Pectoralis is a flexor if arm is hanging but can be and abductor if arm is out. The line of pull is up in one and horizontal in the other.
What is the “angle of pull”?
angle between the line of pull of the muscle and the bone that it incerts
what changes the angle of pull?
THe angle of pull changes with every degree of joint movement.
What is the force when the angle of pull is 90 degrees?
the force is 100% rotational
What is always perpendicular to the lever (attachment) of muscle?
the vertical component, it causes rotational movement at joint axis
what is always parallel to the lever?
the horizontal component, it causes non rotational movement at joint axis.
what happens when angle of pull is 45 degrees?
rotational and stabilizing forces are equal.
what “?of pull” affects the force applied to that joint?
angle of pull, the constantly changing angle
what 6 things is muscle action dependent on?
number of motor units, type of motor units. Size, muscle length, angle of pull, speed of contraction.
which direction does a muscle contract in?
pulls both ends to center.
What direction does a bone ususally move?
the less stabalized , or open chain end bone ususally moves tword more stable bone.
Range of motion depends on what?
length of muscle fibers
Muscle power depends on what?
total number of muscle fibers, more fiber means greater power.
what are the muscles shapes that have more power?
convergent, and pennate
what are the 4 properties of muscle force production?
irritability, contactility, extensibility, elasticity
Irritability means what?
Muscle that is sensitive to chemical, electrical, or mechanical stimul
What is contractility?
ability of muscle to contract/develop tension agains resistance when stimulated.
What is extensibility?
ability of muscle to be passively stretched beyond its normal resting length
What is muscle elasticity?
ability of muscle to return to its original length following stretch.
How do all muscles always work?
in groups, they never work in isolation.
How are muscles innervatied?
Innervated by one or more nerve, and one nerve may innervate more than one muscles.
What is interdigitation?
one nerve innervation of more than one muscle and vice versa.
What muscles share a tendon?
grastrocnemius and soleus muscles., or triceps brachii
what are the 4 roles of muscles?
prime mover, antagonist, synergist, stabilizer
Prime mover
mucle that move muscle primarily
Antagonist
muscles that oppose or revers movement of prime mover.
what happens to antagonist when prime mover is moving?
its relaxed allowing joint movement.
What would slow or stop an action of a prime mover?
its antagonist, it can help control momentium
Synergist
assists in same joint motion as agonis
Stabilizers
act to control motion of prime mover
How does a stabilizer help control muscle of prime mover?
Can immobilize orgin , ie shoulder blade, so prime mover the deltoid, can work more effectively.
what is the general type of pull of the stabilizer?
isometric or isotonic, continuous low level activity
Agaonis and antagonis of pronation?
Pronator teres and supinator
Agonist and antagonis of supination
Supinator and pronator teres
Elbow flexion agonist and antagonist?
biceps brachii and triceps brachii
Flexion of shoullder, agonist and antagonist?
Ant delt, post delt.
Inernal rotation of shoulder agonist and antagonist
subscap/teres maj and infraspinatus/teres minor
external rotation os shoulder angonis and antagonist
infraspinatus/teres min, and subscapularis/teres maj
Internal rotation of hip agonist and anatagonis
glut med/min and glut max/piriformis
hip adduction agonis and antagonist
adductor group and glut med/mid
Lever
rigid bar that moves on a fixed point, bones
Fulcrum
fixed point of leverage, joints
Effort
force applied to move resistance, torque tension
load
resistance to be moved, bone, tissue, object
what is the function of a lever?
to convert force to torque, rotaton of bone
what forces can produce torque throughout the body?
internal andexternal forces
What are the 3 forces that are involved with ms levers produced by?
muscle, gravity, external physcal contacts
Where is the load in a power lever with mechanical advantage?
Load is really close to fulcrum (joint)
where is effort applied in mechanical advantage power lever?
effert is far away, little effort over long distance.
What lever has load far from the fulcrum?
mechanical disadvantage lever, speed lever
what is advantage of speed lever?
move lever rapidly through large range of motion
Where is effort applied in mechanical disadvantaged speed lever?
effert is very near fulcrum (joint)
what does a lever allow for?
move a heavier load or a load farther or faster than otherwise.
what are the classes of lever?
first class, second class, third class
where is fulcrum in first class lever?
Between effort and load, its in the middle
example of first class lever?
atlanto occipital joint
What is second class lever?
The load lies between fulcrum and effort, just like wheel barrow
Advantage of second class lever?
great strength, althogh there is less speed and range of motion.
example of second class lever?
plantar flexion,
What type of mechanical advantage does a second class lever work at
It works at mechanical advantage
what type of lever are most in the body?
third class levers
What is the third class lever?
effort is applied between load and fulcrum, like arm curl.
what is the advantage of third class?
fast large movement with little effort.
What is the mechanical advantage type of third class lever?
mechanical disadvantage lever, like a speed lever.
hat would differences in positioning of effort, load and fulcrum change?
speed, range of motion, weight that can be moved
Mechanical disadvantage lever
Third Class , effort close to fulcrum, force not strong, speed, range of motion
Mechanical advantage lever
second class, effort farther than load from fulcrum, strong, slower, less ranger, greater stability
