A&p Chapter 10

Front 1

Identify the three types of muscle tissue.

Back 1

The three types of muscle tissue are skeletal muscle, cardiac muscle, and smooth muscle.

Front 2

Identify the six major functions of skeletal muscle.

Back 2

Skeletal muscles produce skeletal movement, maintain posture and body position, support soft tissues, guard body entrances and exits, maintain body temperature, and store nutrient reserves.

Front 3

Describe the three connective tissue layers associated with skeletal muscle tissue.

Back 3

The epimysium is a dense layer of collagen fibers that surrounds the entire muscle; the perimysium divides the skeletal muscle into a series of compartments, each containing a bundle of muscle fibers called a fascicle; and the endomysium surrounds individual skeletal muscle cells (muscle fibers). The collagen fibers of the epimysium, perimysium, and endomysium come together to form either bundles known as tendons, or broad sheets called aponeuroses. Tendons and aponeuroses generally attach skeletal muscles to bones.

Front 4

How would severing the tendon attached to a muscle affect the muscle’s ability to move a body part?

Back 4

Because tendons attach muscles to bones, severing the tendon would disconnect the muscle from the bone, and so the muscle could not move a body part.

Front 5

Describe the structural components of a sarcomere.

Back 5

Sarcomeres, the smallest contractile units of a striated muscle cell, are segments of myofibrils. Each sarcomere has dark A bands and light I bands. The A band contains the M line, the H band, and the zone of overlap. Each I band contains thin filaments, but not thick filaments. Z lines bisect the I bands and mark the boundaries between adjacent sarcomeres.

Front 6

Why do skeletal muscle fibers appear striated when viewed through a light microscope?

Back 6

Skeletal muscle appears striated when viewed through a light microscope because the Z lines and thick filaments of the myofibrils within the muscle fibers are aligned.

Front 7

Where would you expect to find the greatest concentration of Ca2+ in resting skeletal muscle?

Back 7

You would expect the greatest concentration of calcium ions in resting skeletal muscle to be in the terminal cisternae of the sarcoplasmic reticulum.

Front 8

Describe the neuromuscular junction.

Back 8

The neuromuscular junction, also known as the myoneural junction, is the synapse between a motor neuron and a skeletal muscle cell (fiber). This connection enables communication between the nervous system and a skeletal muscle fiber.

Front 9

How would a drug that blocks acetylcholine release affect muscle contraction?

Back 9

Acetylcholine (ACh) release is necessary for skeletal muscle contraction, because it serves as the first step in the process that enables the formation of cross-bridges in the sarcomeres. A muscle’s ability to contract depends on the formation of cross-bridges between the myosin heads and actin myofilaments. A drug that blocks ACh release would interfere with this cross-bridge formation and prevent muscle contraction.

Front 10

What would happen to a resting skeletal muscle if the sarcolemma suddenly became very permeable to calcium ions?

Back 10

If the sarcolemma of a resting skeletal muscle suddenly became permeable to Ca2+, the cytosolic concentration of Ca2+ would increase, and the muscle would contract. In addition, because the amount of calcium ions in the cytosol must decrease for relaxation to occur, the increased permeability of the sarcolemma to Ca2+ might prevent the muscle from relaxing completely.

Front 11

Predict what would happen to a muscle if the motor end plate failed to produce acetylcholinesterase (AChE).

Back 11

Without acetylcholinesterase (AChE), the motor end plate would be continuously stimulated by acetylcholine, locking the muscle in a state of contraction.

Front 12

Why does a muscle that has been overstretched produce less tension?

Back 12

A muscle’s ability to contract depends on the formation of cross-bridges between the myosin and actin myofilaments in the muscle. In a muscle that is overstretched, the myofilaments would overlap very little, so very few cross-bridges between myosin and actin could form, and thus the contraction would be weak. If the myofilaments did not overlap at all, then no crossbridges would form and the muscle could not contract.

Front 13

Can a skeletal muscle contract without shortening?

Back 13

Yes, a skeletal muscle can contract without shortening. The muscle can shorten (isotonic, concentric contraction), elongate (isotonic, eccentric contraction), or remain the same length (isometric contraction), depending on the relationship between the load (resistance) and the tension produced by actin–myosin interactions.

Front 14

How do muscle cells continuously synthesize ATP?

Back 14

Muscle cells synthesize ATP continuously by utilizing creatine phosphate (CP) and metabolizing glycogen and fatty acids. Most cells generate ATP only through aerobic metabolism in the mitochondria and through glycolysis in the cytoplasm.

Front 15

What is muscle fatigue?

Back 15

Muscle fatigue is a muscle’s reduced ability to contract due to low pH (lactic acid buildup and its dissociation to lactate and a hydrogen ion), low ATP levels, or other problems.

Front 16

Define oxygen debt.

Back 16

Oxygen debt is the amount of oxygen required to restore normal, pre-exertion conditions in muscle tissue.

Front 17

Identify the three types of skeletal muscle fibers.

Back 17

The three types of skeletal muscle fibers are (1) fast fibers (also called white muscle fibers, fast-twitch glycolytic fibers, Type II-B fibers, and fast fatigue fibers); (2) slow fibers (also called red muscle fibers, slow-twitch oxidative fibers, Type I fibers, and slow oxidative fibers); and (3) intermediate fibers (also called fast-twitch oxidative fibers, Type II-A fibers, and fast resistant fibers).

Front 18

Why would a sprinter experience muscle fatigue before a marathon runner would?

Back 18

A sprinter requires large amounts of energy for a short burst of activity. To supply this energy, the sprinter’s muscles rely on anaerobic metabolism. Anaerobic metabolism is less efficient in producing energy than aerobic metabolism, and the process also produces acidic wastes; this combination contributes to muscle fatigue. Conversely, marathon runners derive most of their energy from aerobic metabolism, which is more efficient and produces fewer wastes than anaerobic metabolism does.

Front 19

Which activity would be more likely to create an oxygen debt: swimming laps or lifting weights?

Back 19

Activities that require short periods of strenuous activity produce a greater oxygen debt, because such activities rely heavily on energy production by anaerobic metabolism. Because lifting weights is more strenuous over the short term than swimming laps, which is an aerobic activity, weight lifting would likely produce a greater oxygen debt than would swimming laps.

Front 20

Which type of muscle fibers would you expect to predominate in the leg muscles of someone who excels at endurance activities, such as cycling or long-distance running?

Back 20

Individuals who excel at endurance activities have a higher than normal percentage of slow fibers. Slow fibers are physiologically better adapted to this type of activity than are fast fibers, which are less vascular and fatigue faster.

Front 21

Compare and contrast skeletal muscle tissue and cardiac muscle tissue.

Back 21

Compared to skeletal muscle, cardiac muscle (1) has relatively small cells; (2) has cells with a centrally located nucleus (some may contain two or more nuclei); (3) has T tubules that are short and broad and do not form triads; (4) has an SR that lacks terminal cisternae and has tubules that contact the plasma membrane as well as the T tubules; (5) has cells that are nearly totally dependent on aerobic metabolism as an energy source; and (6) contains intercalated discs that assist in stabilizing tissue structure and spreading action potentials.

Front 22

What feature of cardiac muscle tissue allows the heart to act as a functional syncytium?

Back 22

Cardiac muscle cells are joined by gap junctions, which allow ions and small molecules to flow directly between cells. As a result, action potentials generated in one cell spread rapidly to adjacent cells. Thus, all the cells contract simultaneously, as if they were a single unit (a syncytium).

Front 23

Identify the structural characteristics of smooth muscle tissue.

Back 23

Smooth muscle cells lack sarcomeres, and thus smooth muscle tissue is nonstriated. Additionally, the thin filaments are anchored to dense bodies.

Front 24

Which type of muscle tissue is least affected by changes in extracellular Ca2+ concentration during contraction?

Back 24

Skeletal muscle contractions are least affected by changes in extracellular Ca2+ concentrations. In skeletal muscle, most of the calcium ions come from the sarcoplasmic reticulum. Most of the calcium ions that trigger a contraction in cardiac and smooth muscles come from the extracellular fluid.

Front 25

Why can smooth muscle contract over a wider range of resting lengths than skeletal muscle can?

Back 25

The looser organization of actin and myosin filaments in smooth muscle allows smooth muscle to contract over a wider range of resting lengths.