Lecture 6: Overview of the Musculoskeletal System (Hayward)

Question 1

what is the formula for speed in reference to the musculoskeletal system?

Answer 1

stride length x rate of stride

distance/time = (distance/stride) x (strides/time)

Question 2

what are some adaptations that have been made to improve speed (3 things)

Answer 2

1. elongation of the limbs
2. disproportional growth of distal limbs
3. flexibility of spine

Question 3

if the frequency of oscillation (rate of stride) remains constant, how would you increase speed?

Answer 3

by increasing stride length

Question 4

longer limbs equals _____?

Answer 4

equals longer strides

Question 5

how do you increase the frequency of oscillation (rate of stride)

Answer 5

by disproportional, proximal distribution of muscle mass, the center of gravity of the limb must reside in the proximal portion

Question 6

what would increase both the rate of oscillation and stride length?

Answer 6

disproportional growth of distal bones

Question 7

what would increase stride length?

Answer 7

longer limbs (increasing the length of the pendulum)

Question 8

what are the 3 functional modifications associated with disproportional growth of the distal limb?

Answer 8

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

Question 9

what is the difference between plantigrade, digitgrade and unguilgrade?

Answer 9

plantigrade = flat footed like beavers and humans

digitgrade = walking on toes like cats and dogs

unguligrade = walking on toenails like horses and ruminants

Question 10

how does flexibility of the spine increase stride length?

Answer 10

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

Question 11

define the origin of a muscle

Answer 11

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

Question 12

define the insertion of a muscle

Answer 12

the most distal attachment of the muscle, most moveable part and may have multiple insertions

Question 13

what are the 4 descriptions/type of muslce fibers

Answer 13

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

Question 14

what is an example of a parallel muscle?

Answer 14

hyoid muscle

Question 15

fan shaped

Answer 15

ascending pectoral muscles

Question 16

fusiform shape

Answer 16

spindle shaped muscles where the fibres converge on tendons at both ends of the muscle like the rectus femoris

Question 17

pennate muscle fibers

Answer 17

parallel muscle fibers attached to the tendon at an angle

Question 18

what determines the amount of force a muscle can generate?

Answer 18

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)

Question 19

what type of muscle generates lare amounts of force but allow little shortening? (parallel, fan-shaped, fusiform or pennate?)

Answer 19

pennate muscles

Question 20

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

Answer 20

parallel muscles

Question 21

range of contraction (degree of shortening) varies with _______? what are the three variations of pennation?

Answer 21

pennation of muscle

unipennate, bipennate and multipennate

Question 22

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?

Answer 22

range of shortening:
unipennate > bipennate > multipennate

force developed:
multipennate > bipennate > unipennate

Question 23

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

Answer 23

fast twitch, type 2 fibers

Question 24

define hypertrophy

Answer 24

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

Question 25

define hyperplasia

Answer 25

the formation of more muscle cells. this increases the force generating capacity of muscle. however the ability to form new cells is limited.

Question 26

agonist vs antagonist muscles

Answer 26

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

Question 27

isometric contraction vs isotonic contraction

Answer 27

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

Question 28

concentric contraction vs. eccentric contraction

Answer 28

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.

Question 29

which type of contraction generates the most force? (eccentric, concentric or isometric?)

Answer 29

eccentric contractions generate the most force.

eccentric > isometric > concentric

Question 30

define flexion

Answer 30

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

Question 31

define extension

Answer 31

the straightening of a limb which increases the angle around a joint

Question 32

define moment arm

Answer 32

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

Question 33

what is the formula for torque

Answer 33

torque = force x moment arm

Question 34

the torque a muscle group can generate about a joint is a function of what?

Answer 34

the force generated by the muscle

the moment arm of the muscle insertion

Question 35

the larger the moment arm then the _____ the torque (greater/lesser)

Answer 35

the GREATER the torque

larger the moment arm = greater torque

Question 36

insertion of a muscle closer to a joint allows for _______ range of motion (greater/lesser)

Answer 36

GREATER range of motion

insertion closer to a joint = greater range of motion

Question 37

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?

Answer 37

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

Question 38

what is a uniaxial joint

Answer 38

a joint with ONE degree of freedom. it moves in only one plane like a “hinge joint”

ex: elbow and knee

Question 39

what is a biaxial joint

Answer 39

a joint with TWO degrees of freedom and can move in two planes

ex: wrist

Question 40

what is a multiaxial joint

Answer 40

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

ex: shoulder and hip