What is a motor neuron pool?
Collection of motor nerves innervating a muscle.
What is a motor unit?
One somatic motor neuron innervating multiple nerve fibers
What is motor unit recruitment?
Stimulation of more motor units at one time.
What are type I fibers?
Muscle fibers with slow myosin ATPase activity
What are type II fibers?
Muscle fibers with fast myosin ATPase activity
What is CREATINE PHOSPHATE?
A substance that donates phosphate in order to produce ATP.
What is OXIDATIVE PHOSPHORYLATION?
Metabolic pathway in mitochondria to produce ATP
What is glycolysis?
Metabolic pathway in cytosol to produce ATP
What molecule do all skeletal muscles use to produce ATP?
Creatine Phosphate
Give some characteristics of type I skeletal muscle fibers.
Slow myosin ATPase activityOxidative Phosphorylation (greatest
source for ATP)AEROBIC O2, mitonchondria
Give some characteristics of type IIb skeletal muscle
fibers.
Fast myosin ATPase activityGlycolysis (greatest source for
ATP)ANAEROBIC
Give some characteristics of type IIa skeletal muscle
fibers.
Fast myosin ATPase activity
Which muscle fiber type is recruited first during any physical
activity?
Type I Type IIa Type IIb
What is another name for Type I muscle fibers?
Slow Oxidative Fibers
What is another name for Type IIb muscle fibers?
Fast glycolytic Fibers
What is another name for Type IIa muscle fibers?
Fast oxidative glycolytic Fibers
What is FATIGUE?
Inability to maintain muscle tension
What cause muscle fatigue?
High ADP, Lactic Acid, and Potassium level
What is the effect of lactic acid on muscle fiber?
Inhibits Ca2+ ATPaseReduces affinity of troponin for Ca2+Reduces
myosin ATPase activityReduce Na+/K+ ATPase activity
How does potassium contribute to muscle fatigue?
Potassium buildup in T-tubules = CONDUCTION FAILURE OF Action
Potential
How does ADP contribute to muscle fatigue?
Increase ADP levels = decrease ATP levels, thus no ATP available
to release myosin from power stroke and set it in a relax
conformation.
Why are slow oxidative fibers (Type I fibers), fatigue
resistant?
Because they produce the lowest amount of tension in muscle
fibers
Why are fast glycolytic fibers (Type IIb fibers), fast
fatiguable?
Because they produce the greatest amount of tension in muscle
fibers.
What is ISOTONIC CONCENTRATION?
Muscle contracts and muscle length shortens
What is ISOMETRIC CONCENTRATION?
Muscle contracts but muscle length does not shorten
What is a TWITCH?
Mechanical response initiated by a single action potential
What is Tetanus?
Maintained contraction in response to repetitive stimulation
What is fused and unfused tetanus?
Fused tetanus is successive period of stimulation without
restUnfused tetanus is successive period of stimulation with
rest
What are two ways to increase force of contraction of skeletal
muscle?
Recruit more Motor UnitFrequency of Stimulation (summation of
contractile responses)
What is titin?
Protein that connects myosin filament to Z-line
What is passive tension or preload?
Non-stimulate force generated by stretching of titin
What is active tension or afterload?
Force generated by contractile proteins
When is active tension at its max?
At the optimal overlap of thick and thin filamentsHow is
skeletal muscle kept at its optimal preload? (Passive tension)
Skeletal muscle is set at the optimal stretched length by
tendons
What is total tension?
Passive tension + active tension
The following graph is a force-velocity curve.
At Y=0, What is that point on the x-axis indicate?
At y=0, the point on the x-axis indicates that no shortening of
muscle occurs at a force of more than 200 Newtons; THIS IS THE
ISOMETRIC POINT
At x=0, What is that point on the y-axis indicate?
At Y=0, this is the value of Vmax representing the activity of
myosin ATPase.
What does any point on the curve other than x=0, y=0
represents?
Isotonic Contraction