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