Lecture 6: Overview of the Musculoskeletal System (Hayward) Flashcards
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)
- elongation of the limbs
- disproportional growth of distal limbs
- 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?
- a change in stance - plantigrade vs. digitgrade vs. unguligrade
- a loss of digits - either in number or in functionality
- 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
- parallel
- fan shaped
- fusiform
- 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?
- the total cross-sectional area of the muscle
- the pennation of a muscle
- the muscle fiber type composition (fast twitch, type 2)
- 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