Flashcards in Lecture 6: Overview of the Musculoskeletal System (Hayward) Deck (40):
what is the formula for speed in reference to the musculoskeletal system?
stride length x rate of stride
distance/time = (distance/stride) x (strides/time)
what are some adaptations that have been made to improve speed (3 things)
1. elongation of the limbs
2. disproportional growth of distal limbs
3. flexibility of spine
if the frequency of oscillation (rate of stride) remains constant, how would you increase speed?
by increasing stride length
longer limbs equals _____?
equals longer strides
how do you increase the frequency of oscillation (rate of stride)
by disproportional, proximal distribution of muscle mass, the center of gravity of the limb must reside in the proximal portion
what would increase both the rate of oscillation and stride length?
disproportional growth of distal bones
what would increase stride length?
longer limbs (increasing the length of the pendulum)
what are the 3 functional modifications associated with disproportional growth of the distal limb?
1. a change in stance - plantigrade vs. digitgrade vs. unguligrade
2. a loss of digits - either in number or in functionality
3. a loss of manipulative skills - man > dog > horse
what is the difference between plantigrade, digitgrade and unguilgrade?
plantigrade = flat footed like beavers and humans
digitgrade = walking on toes like cats and dogs
unguligrade = walking on toenails like horses and ruminants
how does flexibility of the spine increase stride length?
by providing an extra pivot point through the vertebral column.
the cheetah and the horse have similar stride length, but the cheetah has a more flexible spine and has a stride rate greater than the horse
define the origin of a muscle
is the most proximal attachment of the muscle and usually has no tendon or a small aponeurotic tendon. it is usually the least moveable part of the muscle
define the insertion of a muscle
the most distal attachment of the muscle, most moveable part and may have multiple insertions
what are the 4 descriptions/type of muslce fibers
2. fan shaped
what is an example of a parallel muscle?
ascending pectoral muscles
spindle shaped muscles where the fibres converge on tendons at both ends of the muscle like the rectus femoris
pennate muscle fibers
parallel muscle fibers attached to the tendon at an angle
what determines the amount of force a muscle can generate?
1. the total cross-sectional area of the muscle
2. the pennation of a muscle
3. the muscle fiber type composition (fast twitch, type 2)
4. the size and number of the muscle fibers (hypertrophy vs. hyperplasia)
what type of muscle generates lare amounts of force but allow little shortening? (parallel, fan-shaped, fusiform or pennate?)
what type of muscle can shorten further and more rapidly but generate little force (parallel, fan-shaped, fusiform or pennate?)?
range of contraction (degree of shortening) varies with _______? what are the three variations of pennation?
pennation of muscle
unipennate, bipennate and multipennate
what is the range of shortening in pennate muscles? which variation shortens the most vs the least? which creates the most force vs the least?
range of shortening:
unipennate > bipennate > multipennate
multipennate > bipennate > unipennate
muscles adapted for faster contraction have greater proportions of what type of muscle composition?
fast twitch, type 2 fibers
increasing the diameter of a muscle fiber through the synthesis of new myofibrils.
increasing the diameter will increase the force-generating capacity of the muscle
the formation of more muscle cells. this increases the force generating capacity of muscle. however the ability to form new cells is limited.
agonist vs antagonist muscles
agonist (generates the helping movement) = muscles that produce similarly directed movements at a joint
antagonist (generates the opposing movement) = muscles that produce opposite directed movements at a joint
ex: when you flex your elbow, the bicep is the agonist and the tricep is the antagonist
isometric contraction vs isotonic contraction
isometric = "same length" force generated at a constant length
meaning the muscle contracts but does not shorten
isotonic = "same tone/tension" when the internal force exceeds the external force the muscle shortens at a constant velocity.
meaning the muscle contracts and shortens
concentric contraction vs. eccentric contraction
concentric contraction - isotonic contraction in the shortening direction.
--> meaning it shortens when it contracts
eccentric contraction - lengthening of a contracting muscle or "lengthening contraction"
--> this contraction is "weird" or "eccentric"because it actually lengthens during contraction.
which type of contraction generates the most force? (eccentric, concentric or isometric?)
eccentric contractions generate the most force.
eccentric > isometric > concentric
the bending of a limb at a joint, thereby decreasing the angle around the joint
the straightening of a limb which increases the angle around a joint
define moment arm
it is the muscle that is a perpendicular distance from an axis to the line of application of a force
ex: the bicep would be the moment arm for the elbow joint
what is the formula for torque
torque = force x moment arm
the torque a muscle group can generate about a joint is a function of what?
the force generated by the muscle
the moment arm of the muscle insertion
the larger the moment arm then the _____ the torque (greater/lesser)
the GREATER the torque
larger the moment arm = greater torque
insertion of a muscle closer to a joint allows for _______ range of motion (greater/lesser)
GREATER range of motion
insertion closer to a joint = greater range of motion
torque ______ when muscle is extended (increases/decreases)
think in reference to your moment arm. what does it do when a muscle extends? does it increase or decrease?
torque decreases when muscle is extended.
the distance perpendicular from the angle of muscle pull or the moment arm decreases as the limb goes into extension. thus the torque that the same muscle can generate in extension is less than that which it can generate when the joint is in a more flexed position
what is a uniaxial joint
a joint with ONE degree of freedom. it moves in only one plane like a "hinge joint"
ex: elbow and knee
what is a biaxial joint
a joint with TWO degrees of freedom and can move in two planes