ANAT ch 10 text Qs

Why are some skeletal muscle fibers classified as "fast" and others are said to be "slow"?

"slow" because the ATPase in the myosin heads hydrolyzes ATP relatively slowly, and the contraction cycle proceeds at a slower pace than in "fast" fibers.

What are the three functions of ATP in muscle contraction?

(1) Its hydrolysis by an ATPase activates the myosin head so it can bind to actin and rotate (2) its binding to myosin causes detachment from actin after the power stroke; (3) it powers the pumps that transport Ca2+ from the sarcoplasm back into the sarcoplasmic reticulum.

In what order are the various types of skeletal muscle fibers recruited when you sprint to make it to the bus stop?

SO --> FOG --> FG

What features distinguish the three types of muscular tissue?

Skeletal: striated: Alternating light and dark protein bands (striations); voluntary Cardiac: striated, but its action is involuntary Smooth: nonstriated, which is why it is referred to as smooth; involuntary

Describe the four properties of muscular tissue

1. electrical excitability 2. contractibility 3. extensibility 4. elasticity

List the general functions of muscular tissue

1. produce body movement 2. stabilize body position 3. storing and moving substances in body 4. generating heat (thermogenesis)

What happens to the I band and H zone as muscle contracts? Do the lengths of the thick and thin filaments change?

The I bands and H zones disappear during muscle contraction; the lengths of the thin and thick filaments do not change.

How are the sizes of motor units related to the degree of muscular control they allow?

Because all of the muscle fibers of a motor unit contract and relax together, the total strength of a contraction depends, in part, on the size of the motor units and the number that are activated at a given time.

Why is a rich blood supply important for muscle contraction?

The blood capillaries bring in oxygen and nutrients and remove heat and the waste products of muscle metabolism. Especially during contraction, a muscle fiber synthesizes and uses considerable ATP. These reactions require oxygen, glucose, fatty acids, and other substances that are delivered to the muscle fiber in the blood.

What is motor unit recruitment?

The process in which the number of active motor units increases

How are the structures of thin and thick filaments different?

Thin filaments are 8 nm in diameter and 1-2 μm long and composed of the protein actin Thick filaments are 16 nm in diameter and 1-2 μm long and composed of the protein myosin.

How is the motor end plate different from other parts of the sarcolemma?

Within each motor end plate are 30 million to 40 million acetylcholine receptors, integral transmembrane proteins to which ACh specifically binds

Which proteins connect into the Z disc? Which proteins are present in the A band? In the I band?

Z disc: Actin and titin A band: myosin, actin, troponin, tropomyosin, and titin; I band: actin, troponin, tropomyosin, and titin

Which of the following is the smallest: muscle fiber, thick filament, or myofibril? Which is largest?

arranged from smallest to largest: thick filament, myofibril, muscle fiber

What types of fascia cover skeletal muscles?

epimysium, perimysium, endomysium

What type of contraction occurs in your neck muscles while you are walking?

isometric

Why is muscle tone important?

keeps skeletal muscles firm, but it does not result in a force strong enough to produce movement

How does sarcomere length influence the maximum tension that is possible during muscle contraction?

length-tension relationship for skeletal muscle indicates how the forcefulness of muscle contraction depends on the length of the sarcomeres within a muscle before contraction begins

What part of the sarcolemma contains acetylcholine receptors?

motor end plate

eccentric isotonic contraction

muscle lengthens

concentric isotonic contraction

muscle shortens

Which connective tissue coat surrounds groups of muscle fibers, separating them into fascicles?

perimysium

isometric contraction

tension is generated but does not shorten

What roles do contractile, regulatory, and structural proteins play in muscle contraction and relaxation?

Contractile: Muscle contraction occurs because myosin heads attach to and "walk" along the thin filaments at both ends of a sarcomere, progressively pulling the thin filaments toward the M line. As a result, the thin filaments slide inward and meet at the center of a sarcomere Regulatory: Ca2+ binds to troponin. Troponin then moves tropomyosin away from the myosin-binding sites on actin, beginning the contraction cycle Structural: the elastic titan returns the sarcomere to its original length

What would happen if ATP suddenly were not available after the sarcomere had started to shorten?

If ATP were not available, the cross-bridges would not be able to detach from actin. The muscles would remain in a state of rigidity, as occurs in rigor mortis

What is the effect of the size of a motor unit on its strength of contraction? (Assume that each muscle fiber can generate about the same amount of tension.)

Motor units having many muscle fibers are capable of more forceful contractions than those having only a few fibers

What events occur during the latent period?

During the latent period, the muscle action potential sweeps over the sarcolemma and calcium ions are released from the sarcoplasmic reticulum.