Chapter 9 Practice Quiz

Bones and muscles function together as mechanical devices called __________

levers

True or False: The myosin heads function as ATPase enzymes.

True

What is the function of acetylecholinesterase?

To breakdown acetylcholine

In a laboratory that studies muscle function, a group of rats are bred that, due to a genetic defect, have myosin heads which bind ADP irreversibly. As a result, the rats are paralyzed. What explains the impact of this defect on muscle?

Because ADP is permanently bound, the myosin heads will be irreversibly cross-bridged with the actin binding sites on the thin filament.

During a muscle contraction, why is ATP required?

To allow myofilament movement

What change occurs with aging?

Decreased supply of myoglobin

What is the linea alba?

A band of tough connective tissue on the midline of the abdomen

Consider a muscle that originates on the posterior femur and inserts on the posterior tibia. What is the action of this muscle?

To flex the knee

Accumulation of lactic acid or depletion of ATP, most likely causes muscle __________

fatigue

In many movements, the agonist is assisted by other muscles. A muscle that assists the agonist is called a(n) __________

synergist

What term describes the more movable end of a muscle?

insertion

What features are not present in smooth muscle?

Transverse tubules and striations

Following stenuous exercise, levels of ATP, creatine phosphate, oxygen, and glucose must be returned to normal levels. This situation, called __________, may take several hours to complete.

oxygen debt

What characteristics would be found in the muscle fibers stimulated during activities such as distance swimming and distance running?

Slow contracting and fatigue-resistant

Certain natural plant poisons and animal venoms contain substances that inhibit the function of acetylcholinesterase. If a person is poisoned by one of these substances, which of the following will be the cause of their symptoms?

Muscles will be in a constant state of contraction because acetylcholine won’t be broken down and cleared from the neuromuscular junction.

True or False: Troponin, tropomyosin and actin are all parts of the thin filaments.

True

What type of muscle cells lack transverse tubules, have a single nucleus, and are under involuntary control?

smooth muscle

The triangle of auscultation, commonly used to hear sounds of respiratory organs, is bounded by what muscles?

Trapezius, rhomboid major, and latissimus dorsi

Arrange the steps of muscle fiber contraction in the correct order:

1. The muscle impulse reaches the sarcoplasmic reticulum and calcium is released.

2. Thin filaments are pulled over the thick filaments.

3. Calcium floods the sarcoplasm and binds to troponin molecules leaving active sites.

4. The impulse arrives at the synapse and travels through the transverse tubules.

5. The muscle fiber shortens and contracts.

6. Myosin heads bind to exposed active sites on actin, forming cross-bridges.

4, 1, 3, 6, 2, 5

What is the relationship between ATP and creatine phosphate?

Creatine phosphate supplies energy to produce ATP from ADP and phosphate.

What makes up the cross-bridges that form during a contraction?

Myosin heads binding to actin

What happens in a muscle as it undergoes atrophy in response to disuse?

The size of actin and myosin filaments decreases.

How do slow-twitch fibers (type I) compare to fast-twitch fibers (type IIb)?

Type I fibers have more mitochondria than type IIb fibers.

A muscle that will adduct the thigh (moving it toward the midline of the body) will be located in what area?

inner thigh

The characteristic reddish brown color of skeletal muscle is due to the presence of which substance?

myoglobin

While examining a sample of muscle tissue under a microscope, you notice that the cells have a single nucleus. The fibers are striated and heavily branched. Which muscle type does this sample contain?

Cardiac muscle

What occurs at a neuromuscular junction?

Neurotransmitters are released.

When acetylcholine binds to its receptors at the motor end plate, the muscle fiber membrane becomes more permeable to __________

sodium

What is the cause of rigor mortis that occurs in skeletal muscles a few hours after death?

A decrease in ATP and increased membrane permeability to calcium

The pigment responsible for the reddish brown color of skeletal muscle is __________

myoglobin