Lecture 6: Overview of the Musculoskeletal System (Hayward) Flashcards Preview

Undeleted > Lecture 6: Overview of the Musculoskeletal System (Hayward) > Flashcards

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

1. parallel
2. fan shaped
3. fusiform
4. pennate


what is an example of a parallel muscle?

hyoid muscle


fan shaped

ascending pectoral muscles


fusiform shape

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?)

pennate muscles


what type of muscle can shorten further and more rapidly but generate little force (parallel, fan-shaped, fusiform or pennate?)?

parallel muscles


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

force developed:
multipennate > bipennate > unipennate


muscles adapted for faster contraction have greater proportions of what type of muscle composition?

fast twitch, type 2 fibers


define hypertrophy

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


define hyperplasia

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


define flexion

the bending of a limb at a joint, thereby decreasing the angle around the joint


define extension

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

ex: wrist


what is a multiaxial joint

a joint with THREE degrees of freedom like a ball and socket joint

ex: shoulder and hip

Decks in Undeleted Class (134):