Chapter 10 - Muscle Tissue

Describe the three connective tissue layers associated with skeletal muscle tissue

- 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 - 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

The terminal cisternae that form a triad along with a T tubule are part of what organelle?

The terminal cisternae are part of the sarcoplasmic reticulum

A type of contraction in which the tension rises, but the load does not move is A. a wave summation B. a twitch C. an isotonic contraction D. an isometric contraction

D

An action potential can travel quickly from one cardiac muscle cell to another because of the presence of A. gap junctions B. tight junctions C. intercalated discs D. both a and c

D

An activity that would require anaerobic endurance is A. a 50 meter dash B. a pole vault C. a weight lifting competition D. all of these

D

The connective tissue coverings of skeletal muscle, listed from superficial to deep are A. endomysium, perimysium, and epimysium B. endomysium, epimysium, and perimysium C. epimysium, endomysium, and perimysium D. epimysium, perimysium, and endomysium

D

Describe muscle fatigue

Muscle fatigue is a muscle's reduced ability to contract due to low pH (hydrogen ion buildup), low ATP levels, or other problems

How do muscle fibers continuously synthesize ATP?

Muscle fibers 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 cytosol.

Define oxygen debt

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

Identify the structural characteristics of smooth muscle tissue

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

What is the calcium-binding protein in smooth muscle tissue?

The calcium-binding protein in smooth muscle tissue is calmodulin

Describe the neuromuscular junction

The neuromuscular 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

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

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

Identify the common properties shared by muscle tissues

1. Excitability = the ability to receive and respond to a stimulus 2. Contractility = the ability of a muscle cell to shorten when it is stimulated 3. Extensibility = stretching movement of a muscle 4. Elasticity = the ability of a muscle to recoil to its resting length

What three processes are involved in repaying the oxygen debt during a muscles recovery period?

1. O2 for aerobic metabolism is consumed by liver cells, which must make a great deal of ATP to convert lactate to pyruvate, and pyruvate to glucose 2. O2 for aerobic metabolism is consumed by skeletal muscles fibers as they restore ATP, creatine phosphate, and glycogen concentrations to their former leves 3. the normal O2 concentration in blood and peripheral tissues is replenished

Identify the three types of muscle tissue and cite their major functions

1. Skeletal muscle tissue moves the body by pulling on our bones 2. Cardiac muscle tissue pumps blood through the cardiovascular system 3. Smooth muscle tissue pushes fluids and solids along the digestive tract and other internal organs, and regulates the diameters of small arteries.

What three layers of connective tissue are part of each muscle? What functional role does each layer play?

1. epimysium: surrounds entire muscle 2. perimysium: surrounds bundles of muscle fibers (fascicles) 3. endomysium: surrounds individual skeletal muscle fibers (cells)

What five interlocking steps are involved in the contraction process?

1. exposure of active sites 2. attachment of cross-bridges 3. pivoting of myosin heads (power stroke) 4. detachment of cross-bridges 5. reactivation of myosin heads (recocking myosin head)

List the three types of muscle tissue in the body

1. skeletal muscle 2. cardiac muscle 3. smooth muscle

A muscle producing near-peak tension during rapid cycles of contraction and relaxation is said to be in A. incomplete tetanus B. treppe C. complete tetanus D. a twitch

A

During relaxation, muscles return to their original length because of all of the following except A. actin and myosin actively pushing away from one another B. the contraction of opposing muscles C. the pull of gravity D. the elastic nature of the sarcolemma E. elastic forces

A

The ____________ contains vesicles filled with acetylcholine A. axon terminal B. motor end plate C. neuromuscular junction D. synaptic cleft E. transverse tubule

A

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

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 cross-bridges would form and the muscle could not contract

Match the level of organization with the structure that surrounds it: Level of organization: skeletal muscle, muscle fascicle, muscle fiber, myofibril Surrounding structure: endomysium, epimysium, perimysium, sarcoplasmic reticulum

A skeletal muscle is surrounded by epimysium. A muscle fascicle is surrounded by perimysium. A muscle fiber is surrounded by endomysium. A myofibril is surrounded by sarcoplasmic reticulum

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

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

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

Acetylcholine (ACh) release from the axon terminal is necessary for skeletal muscle contraction, because it serves as the first step in the process that leads to 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

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

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.

Areas of the body where you would not expect to find slow fibers include the A. back and calf muscles B. eye and hand C. chest and abdomen D. all of these

B

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

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

What two factors affect the amount of tension produced when a skeletal muscle contracts?

Both the frequency of motor unit stimulation and the number of motor units involved affect the amount of tension produced when a skeletal muscle contracts

The detachment of the myosin cross-bridges is directly triggered by A. the repolarization of T tubules B. the attachment of ATP to myosin heads C. the hydrolysis of ATP D. Calcium ions

C

The signal to contract is distributed deep into a muscle fiber by the A. sarcolemma B. sarcomere C. transverse tubules D. myotubules E. myofibrils

C

Which of the following activities would employ isometric contractions? A. flexing the elbow B. chewing food C. maintaining an upright posture D. running E. writing

C

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

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)

Compare and contrast skeletal muscle tissue and cardiac muscle tissue

Compared to skeletal muscle tissue, cardiac muscle tissue (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

Which of the following statements about myofibrils is not correct? A. each skeletal muscle fiber contains hundreds to thousands of myofibrils B. Myofibrils contain repeating units called sarcomeres C. Myofibrils extend the length of a skeletal muscle fiber D. Filaments consist of bundles of myofibrils E. Myofibrils are attached to the plasma membrane at both ends of a muscle fiber

D

According to the length-tension relationship A. longer muscles can generate more tension than shorter muscles B. the greater the zone of overlap in the sarcomere, the greater the tension the muscle can develop C. the greatest tension is achieved in sarcomeres where actin and myosin initially do not overlap D. there is an optimum range of actin and myosin overlap that will produce the greatest amount of tension E. both b and d are correct

E

Describe general age-related effects on skeletal muscle tissue

General agerelated effects on skeletal muscles include decreased skeletal muscle fiber diameters, diminished muscle elasticity, decreased tolerance for exercise, and a decreased ability to recover from muscular injuries

What two mechanisms are used to generate ATP from glucose in muscle cells?

Glycolysis and aerobic metabolism generate ATP from glucose in muscle cells

Atracurium is a drug that blocks the binding of ACh to ACh receptors. Give an example of a site where such binding normally occurs, and predict the physiological effect of this drug

If atracurium blocked the binding of ACh to ACh receptors at the motor end plates of neuromuscular junctions, the muscles ability to contract would be inhibited

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

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 he 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.

For each portion of a myogram tracing a twitch in a simulated calf muscle fiber, describes the events that occur within the muscle fiber

In an initial period, an action potential generated in the muscle fiber triggers the release of calcium ions from the SR. In the contraction phase, calcium ions bind to troponin and tension begins to increase. In the relaxation phase, tension decreases because cross-bridges have detached and because calcium ion levels have decreased; the active sites are once again covered by the troponin-tropomyosin complex.

Explain why a murder victims time of death can be estimated according to the flexibility or rigidity of the body

In rigor mortis, the membranes of the dead cells are no longer selectively permeable; the SR is no longer able to retain calcium ions. As calcium ions enter to cytosol, a sustained contraction develops, making the body extremely stiff. COntraction persists because the dead muscle cells can no longer make the ATP required for cross-bridge detachment from the active sites. Rigor mortis begins a few hours after death and ends after one to six days, or when decomposition begins. Decomposition begins when the lysosomal enzymes released by autolysis break down the myofilaments

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?

People 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.

What forms of energy reserves do resting skeletal muscle fibers contain?

Resting skeletal muscle fibers contain ATP, creatine phosphate, and glycogen

Describe the components of a sarcomere

Sarcomeres, the smallest contractile units of a striated muscle cell, are segments of myofibrils. Each sarcomere has a dark A band 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.

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

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

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

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

Identify the primary functions of skeletal muscle

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

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

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

Identify the three types of skeletal muscle fibers

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).

How does cardiac muscle tissue contract without neural stimulation?

The timing of cardiac muscle contractions is determined by specialized cardiac muscle fibers called pacemaker cells; this property of cardiac muscle tissue is termed automaticity

What structural feature of a skeletal muscle fiber propagates action potentials into the interior of the cell?

The transverse T tubules propagate action potentials into the interior of the cell

Can a skeletal muscle contract without shortening? Explain.

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.

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

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