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