Muscle physiology 3 Flashcards
what are the 2 ways to increase strength of a contraction?
- More motor units (synchronization)
- Increase frequency of stimulation to motor unit neuron
_______ motor units recruited first, then _________ recruited
Slow-twitch/weak, fas-twitcht/strong
______ twitch is not strong, but resistant to fatigue
Slow
______ twitch is strong but fatigue easily
Fast
Synchronous activation of motor units increases strength by _____ effect
additive
_______ units are usually inhibited but can be activated in rare conditions
Largest/Very strong
Nerve bundle is stimulated with _________________, and this recruits more and more motor units
increased amount of current
______ means “same load/tension”. the weight on your muscles stays constant and this measures shortening. these type of exercises involve movement where weight isnt changing (squat, bench press, walking, swimming)
Isotonic
In isotonic contraction, the ________ helps to stretch elastic properties of skeletal muscle
Latent period
does muscle shortening occur during the latency period?
YES that’s what builds up tension. This period is due to elastic properties prior to you noticing the weight is moving
does mass change in isotonic movements?
NO
Work = (______)( ______)
(Force)(distance)
if you move an object you are creating ______
work
if you have the same amount of load, but double the amount moved, what happens to work? (EX: moving 10kg 1cm vs 2cm)
this doubles the work!
(10x1) vs (10x2)
Same load = _____ tension = _____ force (but work can change dependent on distance)
same, same
How can you increase the force needed to lift a heavier load?
Recruit more motor units.
If you recruit more → displacement is faster with same weight → more force
Force = number of _________
crossbridges in parallel
Force = (______)(_______)
mass, acceleration
Mass doesn’t change in isotonic system, so if you ______ you produce MORE force
accelerate
How would recruitment of more motor units affect speed of contraction?
it would increase the speed of contraction (increase units/same mass = inc force = inc acceleration)
How can marathon runners keep running so long but sprinters are exhausted after a short length?
long distance runners use ~⅓ of max force while sprinters use up max force in small amount of time
what are the Factors influencing force generation?
inertia, force/velocity relationship
Object must be accelerated to overcome ________ for it to be moved, and movement continues after contraction because the moving object has _____
inertia
More inertia to overcome = prolonged ______
latency period
Relaxation following contraction for a bigger object = relaxation is _____ (slowed down or accelerated?)
accelerated
when is there maximum velocity to move an object?
when theres no weight! (you can jump faster/higher holding nothing rather than holding 50lbs)
Increasing the load ________ velocity of shortening
decreases
Power = (_______)(______)
(force)(velocity)
Velocity = (_______)/(________)
(distance)/(time)
Faster object is moving = _____ power it has
more
maximum power output is at _______ Fmax
1/3 (33%)
______ muscle contraction is when muscle length does NOT change. it measures tension/force (tension produced but no displacement). Joints do not move
Isometric
______ exercises are static, and contract your muscles without changing their length (think planks, wall-sits, anything that is static and not moving)
isometric
do you stretch elastic properties during isometric exercises?
there is NO slack, so you don’t need to stretch elastic properties
__________ is when you summate mechanical events which increases cross bridges which increases force produced
Wave summation
More tension = _____ resistance
more
how does latency period for isometric compare to isotonic?
Latency period for isometric is very small compared to isotonic.
why is latency period for isometric so much shorter than isotonic?
-You don’t need to overcome inertia/build up tension, because elastic component is stretched out prior to the contraction
-Object does not move = no inertia to overcome = force buildup is rapid
if weight doesn’t change but you move faster, you add more _____
force
_______ must be stretched by muscle contraction prior to moving the bone
Series elastic
______ system is useful to measure summation of contraction
isometric
do electrical events have a refractory period? do mechanical events?
-Electrical events in nerve/muscle DO have refractory period
-Mechanical events do NOT have refractory period and will continue as long as Ca+ is there
_____ occurs when all sarcomeres are contracting at once in recruited motor units
Tetanus
Can you tetanize muscle groups at various tensions/weights?
yes! you still experience tetanus when you are holding up a pencil and when you are holding a 50lb weight. You recruit more motor units for heavier object
