Tension Production Energy Use and Muscular Activity
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For sustained contractions you need
Asynchronous motor unit summation
Describe small motor units
precise control One motor neuron innervates a small number of muscle fibers
Describe large motor units
Gross movement control One motor neuron innervates a large number of muscle fibers
If you want precise control over a specific part of your body you don’t want to be contracting tons of cells at the same time. What type of motor unit will produce precise control?
Small motor units Found in hands eyes and speech muscles
Define muscle tone
Resting tension in a skeletal muscle
True or false, in any muscle some motor units are always active
True
Greater resting muscle tone causes
higher resting rate of metabolism
Why is it difficult to contract a muscle that has been overstretched?
Few, if any, myosin-actin cross bridges can form when sarcomeres are overextended
Define isotonic contractions
Tension rises, length of muscle changes
Define concentric
muscle tension exceeds resistance and muscle shortens
Define eccentric
Peak tension developed is less than the resistance, muscle elongates
Define isometric
tension rises, length of muscle remains
In isometric contractions
Tension produced never exceeds resistance Indiidual muscle fibers shorten until internal connective tissues are taut Cannot shorten further
True or false: there is an active mechanism for muscle fiber elongation
False
Why does a muscle return to resting length?
recoil in elastic components in connective tissue contraction of opposing muscle groups gravity
Muscle contraction requires large amounts of
ATP
Muscle cells store only enough high energy molecules to sustain contraction until
additional ATP can be generated
How long do ATP and Creatine phosphate reserves last during a contraction?
15 seconds
Muscle cells must generate ATP at approximately the same rate as its
used for remainder of contraction
CP reserves release stored energy in order to
Convert ADP to ATP when ATP is needed at start of contraction
______ pathway provides most ATP needed for resting muscle and moderate levels of muscle activity
Aerobic cellular respiration
At peak activity you need ______ pathway to generate additional ATP
Anaerobic glycolysis
Describe aerobic metabolism
Used at rest to moderate activity Uses O2 Releases CO2 Occurs in mitochondria
CO2 is produced in the
Citric acid cycle