Bio 3200 Ch.12-study dynaminc modules

When the arrival of an action potential at the muscle cell membrane triggers the release of calcium from the sarcoplasmic reticulum, this process does not go on indefinitely because __________.

the rising concentration of cytosolic calcium triggers the closure of calcium channels in the sarcoplasmic reticulum

The force generated by a muscle depends directly or indirectly on the __________.

force generated by individual muscle fibers, number of muscle fibers contracting, and number of active crossbridges formed

Muscle tension decreases at short muscle lengths because __________.

the thin filaments at opposite ends of the sarcomere overlap and the Z lines come into contact with the thick filaments

Which of the following is(are) true about small motor units?

They tend to be recruited first during a contraction and they generate less tension than large motor units.

During complete tetanus __________.

cytosolic calcium levels are high enough to saturate all the troponin molecules, action potential frequency is higher than the fused muscle twitch frequency, and action potential frequency is higher than the fused muscle twitch frequency

Muscle fibers can obtain energy from __________ when the oxygen supply for catabolism is too slow to meet the ATP demands of heavy exercise.

glucose that is metabolized to lactic acid

Which of the following statements about muscle contractions is(are) true?

The sarcomeres shorten during isometric and isotonic contractions.

Which of the following statements about muscle contraction is(are) true?

Each myosin head completes about five crossbridge cycles per second, but each thick filament has hundreds of myosin heads.

When an action potential travels along the sarcolemma of a muscle cell __________.

DHP receptors in the T-tubule undergo a conformational change and Ca2+ flows down its concentration gradient through the ryanodine receptors

During a prolonged bout of continuous exercise (longer than 30 minutes), ATP stores are replenished by __________.

fatty acids in the bloodstream

When myosin is bound to actin during the crossbridge cycle __________.

calcium is bound to the troponin complex and myosin is in its high-energy form

The latent period is due to the time it takes for __________.

excitation-contraction coupling

The A band contains __________.

an area of partial overlap between thick and thin filaments

Thick filaments have __________.

ATPase activity and actin binding sites

Muscle relaxation requires __________.

ATP

Put the events of the crossbridge cycle in the correct order, starting with the binding of myosin to actin: a. binding of ATP b. release of Pi c. release of ADP d. power stroke

b, d, c, a release of Pi->power stroke->release of ADP->binding of ATP

Molecules that are more likely to be found in higher concentrations in a fast glycolytic fiber include __________.

pyruvate and lactic acid

High capillary density, high myoglobin content, and high resistance to fatigue describe which of the following skeletal muscle types?

Red, slow oxidative muscle fibers

The functional unit within a muscle fiber is called a sarcomere. Which of the following does not make up part of the sarcomere?

myofibril

The troponin complex in thin filaments can bind __________.

tropomyosin, calcium, and actin

As the load on a muscle increases, which of the following also increase(s)?

Latent period

Skeletal muscles with the most endurance (resistance to fatigue) are __________ in color.

red

The neurotransmitter that signals the contraction of skeletal muscle fibers is __________.

acetylcholine

After the myosin ATPase hydrolyzes ATP into ADP + Pi, __________.

the two products stay attached to the myosin head, the myosin head is cocked and binds to a different G-actin molecule, ready for the power stroke

What triggers contraction in smooth muscle?

Calcium binds to calmodulin.

There is a high degree of overlap between the action potential and the contractile response in cardiac fibers. Why?

The overlap prevents summation of cardiac muscle contractions; it is critical that the heart have time to relax and fill with blood before the next contraction.

During skeletal muscle contraction, thick and thin filaments bind together forming __________.

crossbridges

Which type of muscle is subject to the greatest diversity of hormonal control?

Smooth muscle

The generation of a smooth, steady, maximum tension contraction by a muscle fiber, with no evidence of relaxation, due to a very rapid stimulation of the muscle fiber is known as __________.

complete (fused) tetanus

The amount of force a muscle can generate depends on __________.

the number of sarcomeres in parallel, the length of individual sarcomeres, and the cross-sectional diameter of the muscle fiber

In smooth muscle, the release of calcium from the sarcoplasmic reticulum is regulated by __________.

all answers are incorrect dihydropyridine receptor DAG receptor calcium-induced potassium release

Smooth muscle is similar to skeletal muscle in which of the following ways?

Both possess actin and myosin

Which of the following statements is true?

Eccentric contractions perform a lengthening action.

Which of these statements about smooth muscle is true?

There are two types: multi-unit, which lacks gap junctions, but has dense innervation; single-unit, which does have gap junctions, but sparse innervation.

In which type of muscle is the function of gap junctions of the greatest importance in maintaining life?

cardiac

Molecules common to both skeletal and smooth muscle crossbridge cycling include __________.

actin

Which of the following have a large muscle fiber diameter and a high force-generating capacity?

White, fast glycolytic fibers

What terminates smooth muscle contraction?

Dephosphorylation of myosin by a phosphatase

Which of the following statements is true about smooth muscle?

Actin and myosin generate force through the crossbridge cycle.

An increase in the force generated by a muscle is achieved by the __________ of more motor units.

recruitment

Put the following in order of largest to smallest: a. myofibril b. muscle fiber c. fascicle d. thick filament

c, b, a, d fascicle->muscle fiber->myofibril->thick filament

Thick and thin filaments overlap within the __________.

A band

Which is the fastest way that a skeletal muscle cell can generate ATP to power muscle contraction?

The high-energy phosphate on the creatine phosphate (phosphocreatine) is transferred to ADP creating more ATP.

In which types of muscle does myosin have an ATPase activity?

Smooth, cardiac, and skeletal

When a muscle is stimulated at a high frequency such that the twitches build on each other, __________ is observed.

summation

The burning sensation that is felt in muscles during exercise is due to the buildup of __________.

lactic acid

Which of the following statements is true?

The thin and thick filaments in smooth muscle have an oblique arrangement.

Which muscle fiber type experiences slow-wave potentials?

Smooth muscle

In what way(s) is cardiac muscle similar to smooth muscle?

It contains gap junctions, it possesses pacemaker cells, and it is innervated by autonomic neurons.

Which of the following statements comparing smooth muscles to skeletal muscles is false?

Smooth muscles have more sarcoplasmic reticulum than skeletal muscles.