A and P Chapter 10

In the neurons that innervate skeletal muscles, the cytoplasm of the synaptic terminal contains mitochondria and vesicles filled with molecules of the

Acetylcholine.

The most important factor in decreasing the intracellular concentration of calcium ion after contraction is

Active transport of calcium into the sarcoplasmic reticulum.

Creatine phosphate

Acts as an energy reserve in muscle tissue.

The sarcoplasmic reticulum stores

Calcium ions.

The delicate connective tissue that surrounds the skeletal muscle fibers and ties adjacent muscle fibers together is the

Endomysium.

In order for a muscle to contract properly, it requires

Energy. Oxygen. Nutrients. An adequate blood supply.

Large diameter, densely packed myofibrils, large glycogen reserves, and few mitochondria are characteristics of

Fast fibers.

When acetylcholine binds to receptors at the motor end plate, the muscle membrane becomes

More permeable to sodium ions.

Each skeletal muscle fiber is controlled by a neuron at a single

Neuromuscular junction.

Nerves and blood vessels that service the muscle fibers are located in the connective tissues of the

Perimysium.

The increase in muscle tension that is produced by increasing the number of active motor units is called

Recruitment

The cell membrane of skeletal muscle is called the

Sarcolemma.

The functional unit of a skeletal muscle fiber is the

Sarcomere.

Which of the following statements is incorrect

Sarcomeres can produce the most tension when stimulated over a relatively wide range of resting lengths

The series of membranous channels that surround each

Sarcoplasmic reticulum.

When contraction occurs,

The H and I bands get smaller. The width of the A band remains constant. The Z lines move closer together.

When a skeletal muscle fiber contracts,

The H zones and I bands get smaller. The zones of overlap get larger. The Z lines get closer together. The width of the A band gets constant.

The advantage of having many nuclei in a skeletal muscle fiber is

The ability to produce large amounts of the enzymes and structural proteins needed for contraction.

Action potentials are conducted into a skeletal muscle fiber by

Transverse tubules.

At rest, active sites on the actin are blocked by

Tropomyosin molecules.

When calcium ion binds to troponin

Tropomyosin moves out of the groove between the actin molecules

At rest, the tropomyosin molecule is held in place by

Troponin molecules.

Active sites on the actin become available for binding when

Calcium binds to troponin.

The pull called tension is a (n) ________ force.

active

Muscle tissue that is involuntary:

cardiac and smooth muscle

The ability of smooth muscle to function over a wide range of lengths is called

plasticity

fast muscle fibers can develop a larger number of mitochondria in response to

repeated, exhaustive stimulation

Which of the following is NOT a function of the muscular system:

hematopoiesis

Each skeletal muscle fiber contains ________ myofibrils.

hundreds to thousands

Which of the following is not a function of smooth muscle tissue

Forcing blood from the heart into the major arteries

The bacterium that causes tetanus produces a toxin that affects the central nervous system and skeletal muscles, producing powerful tetanic contractions of the skeletal muscles. The toxin probably acts by

Making the cell membranes more permeable to calcium ion.

Receptors for acetylcholine are located on the

Motor end plate.

Interactions between actin and myosin filaments of the sarcomere are responsible for

Muscle contraction.

Which of the following is not characteristic of smooth muscle?

Smooth muscle connective tissue forms tendons and aponeuroses.

The space between the neuron and the muscle is the

Synaptic cleft.

During muscle contraction, myosin cross bridges attach to active sites of:

actin filaments

contraction that utilize anaerobic ATP production

require maximal contraction of muscles for short periods of time

When energy reserves in a muscle are exhausted and lactic acid levels increase, ________ occurs.

fatigue

Which of the following acts as an ATPase during the contraction cycle of muscle?

myosin cross-bridges

The area of the sarcomere containing the thick filaments is the

A band.

Skeletal muscle contracts only under stimulation from

CNS

In response to action potentials arriving from the transverse tubules, the sarcoplasmic reticulum releases

Calcium ions

Physical evidence that supports the sliding filament theory of muscle contraction includes

Decreased distance between Z lines during contraction.

Differences between skeletal muscle cells and typical cells include which of the following?

Skeletal muscle cells are larger than normal cells. Skeletal muscle cells are multinucleate.

Which of the following statements is incorrect?

Skeletal muscles are responsible for the pumping action of the heart.

If a person was suffering from severe hyperkalemia, you would expect

Skeletal muscles to be unresponsive and the heart muscle would undergo cardiac arrest.

The bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a(n)

Tendon

In an isotonic contraction,

Tension rises and the skeletal muscle length changes.

When myosin cross-bridges bind to the active sites on actin,

They pivot toward the M line.

The type of contraction represented by a single stimulus/contraction/relaxation sequence is a(n)

Twitch.

Thin filaments at either end of the sarcomere are attached to the

Z line

Which of the following muscles would contract more forcefully?

a muscle receiving 10 to 15 action potentials per second

A motor unit consists of:

a neuron and all of the skeletal muscle fibers that it stimulates

Muscle tone is:

a state of sustained partial muscular contraction that is vital for the health of muscles

Which of the following is not a function of skeletal muscles

produce movement maintain posture maintain body temperature all of the above are functions of the skeletal muscle

Which of the following is greater?

the concentration of calcium ion in the sarcoplasmic reticulum of a resting muscle

Each thin filament consists of

A pair of protein strands wound together.

Because skeletal muscle contractions demand large quantities of ATP, skeletal muscles have

A rich vascular supply.

The skeletal muscle complex known as the triad consists of

A transverse tubule and terminal cisternae.

The area in the center of the A band that contains only thick filaments is the

H band.

Fast fibers

Have a low concentration of myoglobin and Produce powerful contractions

Muscle fibers differ from "typical cells" in that muscle fibers

Have many nuclei.

During muscle contraction, all of the following occur, except

Hemoglobin concentration in muscle fibers increases.

The area of the sarc.omere that contains only thin filaments is the

I band.

The type of contraction in which the muscle fibers produce increased tension but do not shorten is called

Isometric

How would a drug that competes with acetylcholine for receptors at the motor end plate affect skeletal muscle?

It would cause flaccid paralysis (muscles are relaxed and unable to contract).

How would blocking the activity of acetylcholinesterase affect skeletal muscle?

It would cause spastic paralysis (muscles are contracted and unable to relax).

Calcium ions are released from the sarcoplasmic reticulum during the ________ of contraction.

Latent period and Contraction phase

If a second stimulus arrives before the relaxation phase has ended, a second, more powerful contraction occurs. This is called

Wave summation.

When a muscle is stimulated repeatedly for several seconds with a constant stimulus, the amount of tension gradually increases to a maximum. This phenomenon is called

Wave summation.

Acetylcholine is:

a neurotransmitter

In a sarcomere, thick filaments are linked by the

M line.

ATP metabolism normally provides ________ percent of the ATP demands of a resting cell.

95

Increased oxygen consumption would accompany all of the following, except

Decreased ATP use.

Skeletal muscle fibers are formed from embryonic cells called

Myoblasts.

The type of muscle fiber that is most resistant to fatigue is the ________ fiber.

slow

During anaerobic glycolysis

A) ATP is produced. B) Pyruvic acid is produced. C) Lactic acid is produced if pyruvic acid accumulates.

During the recovery period the body's need for oxygen is increased because

Additional oxygen is required to metabolize the lactic acid produced during exercise.

A resting muscle generates most of its ATP by

Aerobic respiration.

Decreased blood flow to a muscle could result in all of the following, except

An increase in intracellular glycogen.

A muscle that is stimulated so frequently that the relaxation phase is completely eliminated is said to exhibit

Complete tetanus.

The dense layer of collagen fibers that surround an entire skeletal muscle is the

Epimysium.

Which of the following statements are true regarding human muscles?

Eye and hand muscles are composed of fast fibers. Back muscles are mostly composed of endurance fibers.

A muscle producing peak tension with rapid cycles of contraction and relaxation is said to be in

Incomplete tetanus.

Each of the following changes in the skeletal muscles is a consequence of aging except that

Muscle fibers increase their reserves of glycogen.

During the recovery period following exercise, all of the following are true, except

Muscle fibers remain contracted.

The contraction of a muscle exerts a pull on a bone because

Muscles are attached to bones by tendons.

Cross-bridges are portions of

Myosin molecules.

The cytoplasm of a skeletal muscle fiber is called the

Sarcoplasm

In which of the following would the ratio of motor neurons to muscle fibers be the greatest?

muscles that control the eye

which of the following is false A) cardiac muscle contraction cannot be summated B) skeletal muscle contraction may be summated C) skeletal muscle control is neural D) cardiac muscle control is neural only E) Cardiocytes are interconnected through intercalated discs

cardiac muscle control is neural only

Each of the following factors would increase the probability of skeletal muscles contracting, except one. Identify the exception.

increased permeability of the muscle membrane to potassium ion

Heat energy produced from muscle contraction is released through the ________ system.

integumentary

How would an elevated level of thyroid hormone in the body affect skeletal muscles?

it would stimulate metabolism

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

rigor mortis

Creatine phosphate functions in the muscle cell by:

storing energy that will be transferred to ADP to resynthesize ATP as needed

At each end of the muscle, the collagen fibers of the epimysium, perimysium, and endomysium come together to form either a bundle known as a ________, or a broad sheet called an aponeurosis.

tendon

Which of the following hormones directly stimulates growth of muscle tissue and increased muscle mass?

testosterone

A muscle twitch differs from a tetanic contraction in that:

the muscle twitch is a brief and jerky movement, while the tetanic contraction is prolonged and continuous

Athletes usually go through a "warm-up" period before engaging in an event. The reason for this "warm-up"

treppe