The primary action of the biceps brachii muscle of the anterior arm is to flex the forearm at the elbow. However, when this muscle is inflamed, pain is felt in the shoulder. Explain this finding.

Some athletes will consume only protein for several days before a competition, which reduces the amount of glycogen in both the muscle fibers and the liver. What effect would this have on their ability to perform activities that require short, powerful bursts of activity? How would it affect their ability to perform endurance activities?

Ms. Sanchez was in a motorcycle accident in which she lost the use of her right upper limb muscles due to significant nerve damage. However, when an electrode is inserted into her muscles, they are able to contract. Explain specifically why nerve damage caused her to lose the use of her muscles. Why can they still respond to stimulation from an electrode?

Mr. Nasheed has cerebral palsy and suffers severe skeletal muscle spasms as a result of his condition. He is prescribed the drug dantrolene, which prevents the release of Ca²⁺ from the SR. Explain how this will treat his muscle spasms.

Jesse is a 2-year-old boy who presents with difficulty in walking and poor control of movements. When the doctor examines Jesse, she notices that when his muscles contract, they are very slow to relax and remain contracted well after the movement has been performed. She sends a sample of his tissue for genetic analysis, and the lab reports a genetic defect that causes the pumps in the SR to operate much more slowly than normal. How does a defect in DNA lead to a malfunctioning protein? How does this finding explain Jesse's symptoms?

Paola is a 3-year-old girl with a disease that reduces the ability of her mitochondria to generate ATP. Explain the specific effects of this disease on the ability of Paola's muscles to function properly. What other tissues and organs are likely to be especially affected by her disease, and why?

Which type of muscle fascicle pattern has an appearance similar to a feather?

a. Fusiform

b. Triangular

c. Pennate

d. Parallel

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

The plasma membrane of a muscle cell is called the sarcoplasmic reticulum.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

Muscle cells are contractile, conductive, distensible cells.

How does a skeletal muscle fiber differ structurally from typical cells?

Match the following terms with the correct definition.      

____Z-disc     

____Sarcomere     

____A band     

____H zone     

____I band     

____M line

a. The dark band containing the entire length of the thick filament

b. The band of proteins in the middle of the H zone

c. The boundary between sarcomeres

d. The functional unit of contraction

e. The middle region of the A band containing only thick filaments

f. The light band containing only thin filaments

What is the basic mechanism of contraction at the level of myofilaments?

Order the following events of excitation and excitation-contraction coupling. Put 1 by the first event, 2 by the second, and so on.

____ The motor end plate generates an end-plate potential.

____ The action potential spreads along the T-tubules, SR Ca²⁺ channels are pulled open, and Ca²⁺ floods the cytosol.

____ Acetylcholine binds to receptors on the motor end plate, and ligand-gated ion channels open.

____ Ca²⁺ bind troponin, which allows tropomyosin to move away from the actin active site, initiating a contraction cycle.

____ The action potential propagates through the sarcolemma and dives deeply into the cell along the T-tubules.

Which of the following statements accurately describes the role of ATP in a muscle contraction?

a. ATP is directly responsible for the power stroke.

b. ATP moves troponin and tropomyosin away from actin.

c. ATP breaks the actin/myosin attachment and 'cocks' the myosin head.

d. ATP causes the myofilaments to shorten.

A muscle fiber relaxes when:

a. The concentration of Ca²⁺ in the cytosol returns to resting levels.

b. The supply of ATP is exhausted.

c. Ca²⁺ flood the cytosol.

d. Acetylcholine is released from the axon terminal and the sarcolemma depolarizes.

Which of the following energy sources would provide the majority of the ATP for a person running a 26-mile marathon?

a. Stored ATP

b. Glycolytic catabolism

c. Oxidative catabolism

d. Creatine phosphate

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

Muscle fibers generate more tension if the starting length of their sarcomeres is very short.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

Stimulation by a motor neuron before a muscle fiber has fully relaxed results in a condition called wave summation.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

Muscles that require a great deal of precise control will have large motor units.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

A muscle fiber changes length during isotonic concentric and isotonic eccentric contractions.

Which of the following types of muscle fibers have low myosin ATPase activity and are classified as slow-twitch?

a. Type I fibers

b. Type IIa fibers

c. Type IIx fibers

d. Type III fibers

Muscle tone is:

a. The result of voluntary shortening of the muscle.

b. The result of a small amount of involuntary activation of motor units by the nervous system.

c. Abnormal—a person's muscles should be relaxed normally.

d. Present only where there is damage to the nervous system.

Resistance-type activities will likely rely on _______ energy sources, whereas endurance activities will probably rely on _____ energy sources.

Which of the following is not likely to result from endurance training alone?

a. Increase in oxidative enzymes in the muscle fiber

b. Increased numbers of mitochondria

c. Hypertrophy of the muscle fibers

d. Increase in blood supply to the muscle fibers

Which of the following factors is/are responsible for muscular fatigue?

a. Accumulation of chemicals, including calcium and phosphate ions & increased blood flow to the muscle

b. Decreased availability of oxygen

c. Psychological and environmental factors

d. Depletion of key metabolic fuels, such as creatine phosphate

What is thought to cause excess postexercise oxygen consumption?

List some of the functions of smooth muscle tissue.

Which of the following best describes single-unit smooth muscle tissue?

a. The fibers function individually.

b. It is found in organs that require precise control of contraction.

c. It contains gap junctions that couple the fibers electrically.

d. The amount of tension produced varies with the number of muscle cells recruited.

Mark the following statements as true for smooth muscle tissue, cardiac muscle tissue, and/or skeletal muscle tissue.          

a. _________ Actin attaches to dense bodies.          ​​​​

b. _________ Cells are joined by intercalated discs.          ​​​​

c. _________ The thick and thin filaments are arranged into sarcomeres.          ​​​​

d. _________ The thick filaments contain myosin heads along their entire length.          ​​​​

e. _________ The cells depolarize and contract as a unit.          ​​​​

f. _________ Ca²⁺ binding to troponin is the initiating event of contraction.          ​​​​

g. _________ Ca²⁺ binding to calmodulin is the initiating event of contraction.          ​​​​

h. _________ The sarcolemma has a distinct motor end plate.