Ch. 12

QRS complex

Abnormally slow conduction through the ventricles would change the ________ in an ECG tracing.

during the latter part of the P wave.

Atrial contraction begins

crossbridges

Most of the time, the parallel thick and thin filaments of the myofibrils are connected by ________ that span the space between myosin and actin molecules.

fewer

Motor units that control skeletal muscles involved with fine motor movements (eye muscles or the hands) have ________ muscle fibers than motor units that control more gross movements (gastrocnemius muscle of the lower leg).

ECGs

show the summed electrical activity generated by all cells of the heart.

True

A motor unit consists of a motor neuron and all of the muscle fibers it innervates.

Ca2+-ATPase

The relaxation of skeletal muscle relies on the activity of the ________, which decreases cytoplasmic calcium concentration.

isotonic, isometric

A contraction that generates force and moves a load is known as an _________ contraction , whereas one that generates force without movements is known as an ___________ contraction .

tachycardia.

A heart rate of 125 beats per minute could be correctly termed

a normal resting heart rate.

A heart rate of 70 beats per minute could be

the progressive wave of ventricular depolarization.

The QRS complex of an ECG represents

Motor unit recruitment

By increasing the number of active motor units, we can produce a steady increase in muscle force, a process called

the ventricles will beat more slowly.

If the connection between the AV node and bundle of His becomes blocked,

True

Passive force is generated by stretching the muscle and result form the elastic recoil of the tissue itself.

more P waves than QRS complexes per minute.

The ECG of a person with complete heart block would show

depolarization of the atria.

The P wave of an ECG corresponds to

Latent period

The brief period of time between the action potential in the muscle and the beginning of contraction is referred to as the

latent period.

The brief period of time between the action potential in the muscle and the beginning of contraction is referred to as the

depletion of glycogen stores.

The cause of skeletal muscle fatigue during extended submaximal exercise is primarily a(n)

frequency of action potentials only.

The force generated by a single muscle fiber can be increased by increasing

stabilize the position of the contractile filaments.

The function of the titin protein is to

rapidly move action potentials to the interior of the muscle fiber.

The function of transverse tubules is to

release of ADP from the myosin.

The molecular event that occurs immediately after the power stroke is the

True

Total force is the sum of passive and active forces.

just after the Q wave.

Ventricular contraction begins

the sarcomere and the I band will shorten.

When a skeletal muscle generates enough force during contraction to shorten,

Complete tetanus involves development of maximum tension.

When comparing fused (complete) tetanus with unfused (incomplete) tetanus, which is true? Complete tetanus involves some relaxation between twitches. Complete tetanus involves development of maximum tension. Complete tetanus occurs at a lower frequency of stimulation than unfused tetanus. Complete tetanus would occur when there is more time between twitch contractions.

Treppe

Which of the following is the progressive increase in force generated when a muscle is stimulated in succession, such that muscle twitches follow one another closely, with each successive twitch peaking slightly higher than the one before?