Muscle tissue, one of the four basic tissue groups, consists chiefly of cells that are highly specialized for
Which of the following is a recognized function of skeletal muscle?
maintain body temperature
guard body entrances and exits
At each end of the muscle, the collagen fibers of the epimysium, and each perimysium and endomysium, come together to form a
Nerves and blood vessels that service a muscle fiber are located in the connective tissues of its
The delicate connective tissue that surrounds the skeletal muscle fibers and ties adjacent muscle fibers together is the
The bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a(n)
Put the following structures in order from superficial to deep:
1. muscle fiber
6, 2, 4, 5, 1, 3
Interactions between actin and myosin filaments of the sarcomere are responsible for
The advantage of having many nuclei in a skeletal muscle fiber is
the ability to produce large amounts of the muscle proteins needed for growth and repair.
Which of the following best describes the term sarcoplasmic reticulum?
storage and release site for calcium ions
The skeletal muscle complex known as the triad consists of
a transverse tubule and two terminal cisternae.
Which of the following best describes the term titin?
protein that accounts for elasticity of resting muscle
Which statement about the microscopic anatomy of skeletal muscle fibers is true?
Tubular extensions of the sarcolemma penetrate the fiber transversely.; Cross striations result from the lateral alignment of thick and thin filaments.; Each fiber has many nuclei.;Muscle fibers are continuous from tendon to tendon.
The thin filaments of striated muscle are made primarily of which protein(s)?
actin; tropomyosin; troponin; nebulin
When a skeletal muscle fiber contracts,
the H bands and I bands get smaller. ; the zones of overlap get larger.; the Z lines get closer together.; the width of the A band remains constant.
Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber
In response to action potentials arriving along the transverse tubules, the sarcoplasmic reticulum releases
The most important factor in decreasing the intracellular concentration of calcium ion after contraction is
active transport of calcium into the sarcoplasmic reticulum.
Which of the following acts as an ATPase during the contraction cycle of muscle?
the head portion of the myosin molecule
When calcium ion binds to troponin,
tropomyosin moves into the groove between the helical actin strands.
Which of the following become connected by myosin cross-bridges during muscle contraction?
thin filaments and thick filaments
After death, muscle fibers run out of ATP and calcium begins to leak from the sarcoplasmic reticulum into the sarcoplasm. This results in a condition known as
In rigor mortis....
the myosin heads are attached to actin.; ATP is depleted.; muscles are inextensible; cross-bridge cycling is absent.
Physical evidence that supports the sliding filament theory of muscle contraction includes
decreased width of the H band during contraction.
Triggering of the muscle action potential occurs after
acetylcholine binds to chemically-gated channels in the end plate membrane.
The following is a list of the events that occur during a muscle contraction.
1. Myosin cross-bridges bind to the actin.
2. The free myosin head splits ATP.
3. Calcium ion is released from the sarcoplasmic reticulum.
4. The myosin head pivots toward the center of the sarcomere.
5. Calcium ion binds to troponin.
6. The myosin head binds an ATP molecule and detaches from the actin.
The correct sequence of these events is
3, 5, 1, 4, 6, 2.
How would the loss of acetylcholinesterase from the motor end plate affect skeletal muscle?
It would cause spastic paralysis (muscles are contracted and unable to relax).
When acetylcholine binds to receptors at the motor end plate, the end plate membrane becomes
more permeable to sodium ions.
The cytoplasm of the neuromuscular terminal contains vesicles filled with molecules of the neurotransmitter
When contraction occurs,
the H bands get smaller.; the Z lines move closer together.; the width of the A band remains constant. ; the I bands get smaller.
Which statement about excitation-contraction coupling is incorrect
Calcium ion is released from the transverse tubule.
Synaptic vesicles contain neurotransmitters that are released by ________ when the action potential arrives.
The muscle weakness of myasthenia gravis results from
loss of acetylcholine receptors in the end-plate membrane.
A patient takes a medication that blocks ACh receptors of skeletal muscle fibers. What is this drug's effect on skeletal muscle contraction?
reduces the muscle's ability for contraction
The rapid rise and fall in force produced by a muscle fiber after a single action potential is
When a muscle is stimulated repeatedly at a high rate, the amount of tension gradually increases to a steady maximum tension. This is called
A muscle producing tension that peaks and falls at intermediate stimulus rates is said to be in
If a second stimulus arrives before the relaxation phase has ended, a second, more powerful contraction occurs. This is called
The contraction of a muscle exerts a pull on a bone because
muscles are attached to bones by tendons.
The increase in muscle tension that is produced by increasing the number of active motor units is called
A weight-lifter strains to lift a heavy weight and there is no movement of the person's arms holding on to the weight. This type of contraction is called a/an ________ contraction.
Suppose that you try to pick up an object and discover that it is much heavier than you expected. Which process must occur in the muscle to increase tension so you can pick up the object?
In which of the following would the motor units have the fewest muscle fibers?
muscles that control the eyes
During the recovery period the body's need for oxygen is increased because
additional oxygen is required to restore energy reserves consumed during exercise.
During anaerobic glycolysis
ATP is produced.; pyruvic acid is produced. oxygen is not consumed.; carbohydrate is metabolized
Aerobic metabolism normally provides ________ percent of the ATP demands of a resting muscle cell.
During the recovery period following exercise, all of the following are true, except
muscle fibers are unable to contract.
At peak levels of muscle exertion the mitochondria can supply
only about one-third of the energy required by the muscle.
Which of the following hormones directly stimulates growth of muscle tissue, leading to increased muscle mass?
Which of these would lead to increased oxygen consumption?
increased heat production; increased conversion of lactic acid to glucose; increased aerobic respiration by muscle cells; increased muscle activity
Because skeletal muscle contractions demand large quantities of ATP, skeletal muscles have
many mitochondria and a rich blood supply.
Decreased blood flow to a muscle could result in all of the following, except
an increase in intracellular glycogen.
How would an elevated level of thyroid hormone in the body affect skeletal muscles?
It would stimulate energy use and heat production.
During activities requiring aerobic endurance
most of the muscle's energy is produced in mitochondria.
Fast muscle fibers can adapt to aerobic metabolism by generating more mitochondria in response to
repeated, exhaustive stimulation
Which of the following statements is (are) true regarding human muscles?
A) Most have both slow and fast fibers.
B) Slow fibers are abundant in the calf muscles.
C) Eye muscles are composed entirely of fast fibers.
D) Slow fibers are abundant in the back muscles.
When comparing slow muscle fibers to fast muscle fibers, slow fibers
take about three times as long to reach peak tension.
B) have much smaller fiber diameters.
C) generate much less tension.
D) are rich in the red protein myoglobin.
Large-diameter, densely packed myofibrils, large glycogen reserves, and few mitochondria are characteristics of
Which type of muscle fibers are best adapted for prolonged contraction such as standing all day?
Muscular force can be adjusted to match different loads by
varying the frequency of action potentials in motor neurons.
B) recruiting larger motor units.
C) recruiting more motor units.
D) involving more muscle fibers in the contraction.
Which of the following is not characteristic of smooth muscle?
Smooth muscle connective tissue forms tendons and aponeuroses.