Properties of Whole Muscle Contraction Flashcards
What is a motor unit?
One motor neuron and all the muscle fibers it supplies
Fine control muscles have…
smaller motor units
Large, weight-bearing muscles have…
larger motor units
Every muscle fiber has ______ innervation
its own innervation
Name the two ways muscle responses are graded
frequency of stimulation # of motor units recruited (strength)
What does it indicate about the motor units if a muscle contraction reached its maximum?
All the motor units would be activated
What size muscle fibers are recruited for large amounts of force?
small, medium, AND large-fiber motor units are recruited
Hypotonia (lack of muscle tone) indicates a problem with what?
spinal reflexes; could be due to lack of oxygen during birth, cerebral palsy, problems with brain development or formation in womb
What is muscle tension?
The force exerted on object to be moved
what is a load?
the opposing force exerted on the muscle by the object being moved
What is the same during an isometric and isotonic contraction
both have cross-bridge cycling, both create tension, contraction, both doing work, both going to fatigue
What is different about isotonic contraction versus isometric?
isotonic- tension great enough to move load, muscle shortens, filaments slide
isometric- tension not enough to move load, muscle does not shorten, filaments not sliding
What are the two types of isotonic contractions?
concentric- muscle contracts
and eccentric- muscle elongates
What happens during direct phosphorylation
Who knows?
No but seriously, what happens during direct phosphorylation?
Creatine kinase pulls phosphate off CP to make ADP–>ATP, only good for about 15 seconds of energy
How many ATP per glucose does an anaerobic pathway create?
2, and it’s only good for 30-40 seconds or so
How many ATP per glucose does aerobic pathway create?
32, good for multiple hours of activity
Why is there excess postexercise oxygen consumption (EPOC)?
the body needs to replenish stored ATP
& oxygen, and convert lactic acid –> pyruvic; aka oxygen “debt”
Muscle fatigue is caused by lack of ATP. True or false?
FALSE; muscle fatigue can be due to ionic imbalances that disrupt membrane potential, too much inorganic phosphate that prevents calcium release, too much magnesium, or too much lactic acid
Name two of the four factors affecting the number of cross-bridges that are formed (force of contraction)
frequency of stimulation
number of muscle fibers recruited
size of muscle fibers
amount of stretch (a little over 100% is ideal)
What are the three muscle fiber types?
Slow oxidative
Fast oxidative
Fast glycolytic
Which fiber types use aerobic metabolism?
Oxidative (not glycolytic)
Which fiber types hydrolyze ATP quickly?
Fast fibers (not slow)
What’s the recruitment order for the three muscle fiber types?
first-slow oxidative
second-fast oxidative
third-fast glycolytic
which muscle fiber type has the fewest mitochondria?
fast glycolytic
Which is the least fatigue-resistant muscle fiber type?
fast glycolytic muscle fibers
Small load and high recruitment –> ___ velocity and ___duration
high velocity, high duration
What happens to the muscles of people who do a lot of endurance training? Name a few things.
more capillary &mitochondrial density more activity of aerobic metabolic pathways more capacity to use fat for energy less lactate accumulation more myocardial efficiency more oxygen delivery weakened stress hormone responses
What happens to the muscles of people who do a lot of isometric exercise?
More immediate ATP energy delivery more glycolytic energy delivery More force and power output larger muscle fibers (NOT more muscle fibers) more movement efficiency
When does disuse atrophy happen?
immobilization or loss of neural stimulation (to maintain muscle tone)
At what point is regeneration of muscle impossible?
If there is only 25% of muscle mass left, paralysis is imminent
