A&P Chapter 9 Muscles and Muscle Tissue - Practice Test

What would occur if a muscle became totally depleted of ATP?

The muscle would remain in a contracted state due to an inability to break actin-myosin cross bridges. ATP is needed to break actin-myosin cross bridges. If these bridges are not broken, the muscle remains in a contracted state.

The thin myofilaments of skeletal muscle are composed chiefly of __________.

actin Thick filaments are composed primarily of the protein myosin; thin filaments are composed primarily of the protein actin.

The most efficient means of producing ATP is __________.

aerobic respiration. Under aerobic conditions, muscle cells can carry out aerobic respiration, which is the most efficient metabolic pathway for ATP production.

The final "go" signal for skeletal muscle contraction is __________.

an increase in intracellular calcium ion levels. A short-lived rise in intracellular calcium ion levels (Ca2+) is the final trigger for contraction of skeletal muscle.

Acetylcholinesterase __________.

breaks down acetylcholine. After acetylcholine binds to its receptor, its effects are quickly stopped when it is enzymatically broken down by acetylcholinesterase.

Properly controlled skeletal muscle contractions produced by changing the frequency of stimulation or the strength of stimulation are accomplished by __________.

graded muscle response. Skeletal muscles respond to stimulation in a controlled and smooth manner. The variation needed in skeletal muscle contraction in order to have controlled movement is called a graded muscle response.

Myofibrils are composed of repeating contractile elements called __________.

sarcomeres Myofibrils are composed of repeating contractile units called sarcomeres. Sarcomeres are made of myofilaments. Myofilaments are made of thick myosin filaments and thin actin filaments.

Which of the following muscle types is both voluntary and striated?

skeletal muscle only. Skeletal muscle is striated and under voluntary control. Cardiac muscle is striated and under involuntary control. Smooth muscle is not striated and it is under involuntary control.

If a muscle is applied to a load that exceeds the muscle's maximum tension, __________.

the muscle length will not change during contraction. Isometric contraction does not lead to load movement. Tension may build to the muscle's peak tension, but the muscle does not lengthen or shorten. In isotonic contractions, the muscle will shorten, this will result in load movement.

When an action potential arrives at the neuromuscular junction, the most immediate result is __________.

the release of acetylcholine from the motor neuron. When an action potential arrives at the neuromuscular junction, acetylcholine (ACh) is released. ACh then binds to receptors on the sarcolemma of the muscle fiber. This binding event leads to depolarization of the sarcolemma.

Which of the following statements is false?

During contraction, thin filaments slide past thick filaments, so that actin and myosin filaments do not overlap. During contraction thin filaments slide past thick filaments, so that actin and myosin filaments overlap to a greater degree than in a relaxed muscle fiber.

Muscle cells initiate nerve impulses.

False While muscles can respond to nerve impulses and conduct impulses once stimulated, they do not initiate them. Neurons are responsible for initiating nerve impulses.

Which of the following is a special adaptation present in skeletal muscle cells, but absent in most other cells?

Muscle cells have myoglobin; most other cells do not. Myoglobin is a pigment found in skeletal muscle cells. It allows muscle cells to store oxygen.

Which of the following is false regarding smooth muscle?

Once damaged, smooth muscle is unable to regenerate. Smooth muscle is not striated in appearance, because it lacks sarcomeres. Smooth muscle contraction is under involuntary control. Unlike cardiac and skeletal muscle, smooth muscle is regenerative.

Match the muscle fiber to the appropriate characteristic.

Slow oxidative muscle fibers are best suited for endurance activities. (fatigue resistant) Fast oxidative fibers are best suited for sprinting. (moderately fatigue resistant) Fast glycolytic fibers are best suited for short-term powerful or intense movements. (fatigues quickly)

Choose the true statement.

Smooth muscle depends on the calcium-calmodulin system to regulate contraction while skeletal muscle relies on the calcium-troponin system to regulate contraction. Both muscles employ a sliding filament for contraction, and a rise in calcium to trigger contraction, and on ATP to fuel contraction.

The __________ are extensions of the sarcolemma, and serve as a rapid communication system that ensures that every myofibril in the muscle fiber contracts at virtually the same time.

T tubules. T tubules are continuations of the sarcolemma; they conduct impulses to the deepest regions of the muscle cell and to every sarcomere. Thus, T tubules serve as a communication network coordinating the contraction of each myofibril that makes up the muscle fiber.