L3 Flashcards
What is Henneman’s size principle
orderly recruitment is due to variations in motor neuron size
- with smaller motor neurons recruited first due to a smaller rheobase (less current needed to be activated)
what is rheobase
the amount of current needed to be used at the level of a MN to generate an AP
T or F: the order of recruitment is the same as the derecruitment
T: think of it as a pyramid slow are the first to be recruited and will thus be the last to be unrecruited
what is the positive reasons for recruitment in an orderly fashion
- sequence is predetermined, and brain doesn’t need to contend with all the switches, just the control of the level of input to the motor pool
- fine motor control
- the larger MUs near the end of a contraction will have a substantial effect on net force
what are the negative reasons for recruitment in an orderly fashion
inability to selectively activate motor units out of order
and limited in the rate of force development
what are the two ways muscle force is controlled
recruitment and rate coding
T or F: all muscle fibers within a motor unit are the same type
true
what is a twitch
the physiological response of a motor unit to a single stimulation
what is the discharge frequency
increase the discharge frequency of a motor neuron, and you increase the force output of the motor unit
degree of summation of twitches is dependent on…
the frequency at which the MUAPs are discharged
Slow twitch unit has ______ twitch contraction time, get summation at ______ rate but contribute ______ force
longer, lower, 4x less force
in a force-frequency curve why do we see the plateau or stabilization of the curve after a certain frequency
the force beings to stabilize due to reaching the maximum number of cross bridges available
what is the most accurate representation of the force-frequency relationship
a sigmoidal shape (bottom line = fast top = slow twitch)
