Heat released from contracting muscles functions to __________.

maintain body temperature

Voluntary control over swallowing, defecation, and urination is provided by muscles that __________.

guard entrances and exits

The perimysium surrounds a bundle of muscle fibers called a __________.

fascicle

Which connective tissue layer wraps the entire muscle?

epimysium

Which structure in a muscle fiber or muscle cell is continuous with the sarcolemma and carries the signal to contract deep into the muscle cells?

T tubules

Repeating functional units seen on the myofibrils are __________.

sarcomeres

Which of the following is NOT found in a thin filament?
actin
tropomyosin
myosin
troponin

myosin

Which of the following is the dark band seen on myofibrils?

A band

The neurotransmitter required to trigger skeletal muscle contraction is __________.

ACh

What must bind to troponin in order to expose the active sites on actin?

Ca++

In a twitch, what is the phase in which tension rises to a peak?

Contraction phase

All the muscle fibers and the single motor neuron that innervates them are called a __________.

motor unit

What is the type of contraction in which the muscle does NOT change length and the contraction does NOT produce tension that exceeds the load?

isometric

Which of the following produces ATP from glucose anaerobically?

glycolysis

When glycolysis produces pyruvic acid faster than it can be used by the mitochondria, pyruvic acid is converted to ________________, which lowers the pH of body fluids.

lactic acid

Which muscle fiber type contains abundant myoglobin and is specialized to contract for extended periods of time?

slow fiber

What is the name of the structure that contains gap junctions and desmosomes and joins the plasma membranes of two cardiac muscle cells together?

intercalated discs

What is the term for the ability of cardiac muscle cells to contract without neural stimulation?

automaticity

Which of the following is NOT a characteristic of smooth muscle tissue?
dense bodies
absence of sarcomeres
striations
spindle-shaped cells

striations

What is the term for the ability to function over a wide range of lengths?

plasticity

A slightly higher maximum tension produced by sequential stimulation.

Treppe

A single stimulus contraction-relaxation sequence in a muscle fiber.

Twitch

The addition of one wave to another, increasing overall tension.

Wave summation

Increased stimulation rate to the point where no relaxation phase is present.

Complete tetanus

Increasing rate of stimulation, with brief periods of incomplete relaxation.

Incomplete tetanus

Tension generated by myofibrils in contacted muscle.

Internal tension

Muscles surround the orifices that serve as openings to the digestive and urinary system and allow for voluntary control of actions such as swallowing, defecation, and urination.

Guarding entrances and exits

When body temperature falls below homeostatic levels, muscles contract and produce heat, which warms the body.

Maintenance of body temperature

Tension produced in skeletal muscles during contractions allows for sustained positions, such as holding the head up, standing, and sitting upright.

Maintenance of body posture and position

Contraction of muscles pull on tendons attached to bones, which creates motion in body parts such as raising an arm, swimming, and the coordinated movements of breathing.

Production of movement

Muscles in the abdominal wall and floor of the pelvic cavity support the weight of visceral organs in the abdominal and pelvic regions.

Support of soft tissues

Put in correct order:
Return to initial state
ACh binding at the motor end plate
Arrival of an action potential at the synaptic terminal
Appearance of an action potential in the sarcolemma
Release of acetylcholine

Arrival
Release
ACh
Appearance
Return

Skeletal muscle is responsible for all of the following EXCEPT __________.
maintenance of body temperature
production of vitamin D
movement
supporting soft tissues
guarding entrances and exits

production of vitamin D

Skeletal muscle functions in __________.
regulating the diameter of arteries
maintaining body temperature
pushing blood through the circulatory system
exhibiting plasticity

maintaining body temperature

What is the functional unit of the muscle fiber?

sarcomere

What is the membranous network that surrounds each myofibril?

sarcoplasmic reticulum

The command to contract is conducted throughout the muscle fiber by the __________.

transverse tubules

The part of the sarcomere that contains thick filaments but no thin filaments is the __________.

H zone

Z lines __________.

contain thick and thin filaments
contain thin filaments only
mark the boundaries between adjacent sarcomeres
stabilize the thick filaments

mark the boundaries between adjacent sarcomeres

For tropomyosin to be shifted off its position covering the active sites of G actin molecules, calcium ions must bind to which structure?

troponin

Which of the following descriptions of sarcomere components is FALSE?

The I band contains the Z line at its center.
Each sarcomere contains a Z line at each end.
Each sarcomere contains an M line at its center.
The I band contains the zone of overlap at its center.
The H zone contains the M line at its center.

The I band contains the zone of overlap at its center.

When Jennifer looks through the microscope at skeletal and cardiac muscles, she sees striations. What are these striations?

A bands and I bands

The junction between a muscle cell and the neuron innervating that cell is the __________.

neuromuscular junction

ACh is released from what structure?

synaptic terminal

Which of the following does NOT happen when the action potential reaches the synaptic terminal?
Exocytosis of ACh into the synaptic cleft occurs.
Vesicles in the synaptic terminal fuse with the membrane of the
neuron.
Potassium ions flood the intercellular space.

Potassium ions flood the intercellular space.

The binding of ACh to the motor end plate causes a change in membrane permeability to __________.

Sodium

Which of the following events in a muscle contraction marks the beginning of the relaxation of the muscle cell?

active-site exposure
detachment of cross-bridges
pivoting of the myosin heads
formation of cross-bridges

detachment of cross-bridges

What happens when the myosin head splits ATP into ADP and a phosphate group?

myosin reactivation

Which of the following represents the correct sequence of events in a contraction cycle?

cross-bridge attachment, active-site exposure, cross-bridge attachment, pivoting, cross-bridge detachment, myosin reactivation
active-site exposure, cross-bridge attachment, cross-bridge detachment, pivoting, myosin reactivation
active-site exposure, cross-bridge attachment, pivoting, cross-bridge detachment, myosin reactivation
active-site exposure, pivoting, cross-bridge attachment, pivoting, myosin reactivation

active-site exposure, cross-bridge attachment, pivoting, cross-bridge detachment, myosin reactivation

Action potentials must travel along which structure internal to the sarcolemma to cause the release of calcium ions from the sarcoplasmic reticulum?

T tubule

Which of the following statements about muscle contraction is FALSE?

Myosin cross-bridges remain in place until the myosin head binds an ATP molecule.
In the resting state, a myosin head is bound to an ADP and a phosphate molecule that have been produced by splitting an ATP molecule.
When Ca2+ binds to a myosin head, it triggers the formation of a cross-bridge between myosin and actin.
A troponin molecule that binds a calcium ion weakens its connection to a G actin molecule.

When Ca2+ binds to a myosin head, it triggers the formation of a cross-bridge between myosin and actin.

In __________ contraction, the peak tension developed is less than the resistance, and the muscle elongates as a result of the contraction of another muscle or the pull of gravity.

an eccentric

Pushing against a locked door is an example of __________.

an isometric contraction

In which part of the sarcomere are myosin heads able to form cross-bridges with actin?

zone of overlap

When pyruvic acid is produced by anaerobic metabolism faster than it can be utilized, the surplus is converted to __________.

lactic acid

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

fatigue

At peak levels of muscle exertion, mitochondrial activity can provide about only one-third of the ATP needed. The remainder is provided through __________.

glycolysis

Which of the following statements about muscle fatigue and the recovery period is FALSE?

Elevated oxygen demand in muscle tissue stops as soon as exercise activities cease.
Under moderate use and aerobic conditions, muscle fatigue occurs when all reserves of glycogen, lipids, and amino acids have been exhausted.
Muscles usually recover from moderate activity within several hours, but recovery from fatigue takes as long as a week.
A skeletal muscle is fatigued when it cannot contract any longer despite continued nervous stimulation.
The Cori cycle sends lactic acid produced through anaerobic muscle activity to the liver, which converts most of it to glucose that muscle fibers can pick up from circulating blood.
The formation of lactic acid is an anaerobic process.

Elevated oxygen demand in muscle tissue stops as soon as exercise activities cease.

During moderate and peak exertion of skeletal muscles, the body experiences a higher temperature because of which of the following?

the reduction of energy captured by skeletal muscles as ATP during moderate and peak exertion

Which type of muscle fiber allows for extremely quick contractions but fatigues quickly?

fast fibers

Which type of muscle fiber is supplied by extensive blood vessels?

slow fibers

What human muscles contain ONLY fast fibers?

hand muscles

The length of time muscular contraction can be supported by glycolysis is called __________.

anaerobic endurance

Which of the following features is found in cardiac muscle cells but NOT in skeletal and smooth muscle cells?

intercalated discs
troponin
dense bodies
calcium ions

intercalated discs

Unique features of smooth muscles include which of the following?

plasticity

True/False. Thick filaments are composed of myosin, troponin, and tropomyosin.

False. The thick filaments are composed of bundles of hundreds of myosin molecules.

True/False. Aerobic endurance is determined by the amount of glucose and oxygen available to fuel mitochondrial activity, while anaerobic endurance is determined by the amounts of ATP and CP already available.

True.

True/False. The duration of muscle contraction and the following relaxation are affected by levels of calcium ions in the sarcoplasm.

True.

True/False. In isometric contraction, the muscle does not change in length.

True.

True/False. The arrangement of myosin and actin fibers in skeletal, cardiac, and smooth muscles is identical.

False. Myosin and actin fibers are arranged similarly in skeletal and cardiac muscle; however, in smooth muscle the arrangement of myosin is scattered and actin fibers are loosely linked and incorporate the use of dense bodies.

The layer of connective tissue that surrounds an individual muscle fiber is called the ______.

endomysium

An individual contractile unit within a myofibril in a muscle fiber is called a(n) ____.

sarcomere

During a sarcomere contraction, the A band length does not change, while the _____ move closer together.

Z lines

What is the name of the enzyme in the synaptic cleft that breaks down the neurotransmitter that starts a muscle contraction?

AChE

When a muscle fiber has produced more ATP than it currently needs, the energy is transferred to form another high-energy compound called ____.

creatine phosphate

Muscle performance is considered in terms of power, the maximum amount of tension that can be produced by a muscle or muscle group, and_____ , the amount of time an individual can perform an activity.

endurance

While you sit at the computer reading this question, the postural muscles in your back are involved in contractions that produce tension but do not shorten muscle length. These are called _____ contractions.

isometric

Regular, repetitive, exhaustive stimulation of muscles leads to an increase in the number of mitochondria in those muscles. As a result, the muscles can be said to experience muscle _____ .

hypertrophy

A blending of epimysium, perimysium, and endomysium that forms a broad sheet at the end of a muscle is known as ________.

an aponeurosis

What are the three types of muscle tissue?

cardiac, smooth, skeletal

Why are skeletal muscles often called voluntary muscles?

They contract when stimulated by motor neurons of the central nervous system.

Repeating contractile units that make up a myofibril are called ________.

sarcomeres

Nerves and blood vessels are contained within the connective tissues of the ________.

epimysium, perimysium, and endomysium

The thinfilaments consist of ________.

a pair of F actin molecules twisted together

The thick filaments consist of ________.

about 300 myosin molecules twisted around one another

All of the muscle fibers controlled by a single motor neuron constitute a ________.

motor unit

Why is control over leg muscles LESS precise than control over the muscles of the eye?

Many muscle fibers are controlled by a single motor neuron.

According to the sliding filament theory, what is the physical change that takes place during contraction?

The thin filaments are sliding toward the center of the sarcomere alongside the thick filaments.

Troponin and tropomyosin are two proteins that can prevent the contractile process by ________.

covering the active site and blocking the actin–myosin interaction

The amount of tension produced by an individual muscle fiber ultimately depends on the ________.

number of pivoting cross-bridges

The transmission of an action potential along the T tubules stimulates the release of calcium from which structure in the sarcomere?

terminal cisterna

What determines the amount of tension produced in the skeletal muscle as a whole?

internal tension produced by the stimulated muscle fibers
external tension produced by the stimulated muscle fibers
total number of muscle fibers stimulated
all of the above

all of the above

Peak tension production occurs when all motor units in the muscle contract in a state of ________.

complete tetanus

In an isotonic contraction, ________.

cross-bridges must produce enough tension to exceed the load to be moved

Which of the following is an example of an isometric contraction?

holding a heavy stack of books above the ground

A high blood concentration of the enzyme creatine phosphokinase (CPK) usually indicates ________.

serious muscle damage

Mitochondrial activities are relatively efficient, but their rate of ATP generation is limited by the ________.

availability of oxygen

Which of the following has been correlated with muscle fatigue?

a decline in pH within the muscle, which alters enzyme activities

During the recovery period, the body's oxygen demand is ________.

elevated above normal resting levels

Which type of muscle fiber is dominant in a muscle such as the gastrocnemius, a calf muscle that contracts during standing and walking?

slow fibers

Extensive blood vessels, mitochondria, and myoglobin are found in the greatest concentration in ________.

slow fibers

The length of time a muscle can continue to contract while supported by mitochondrial activities is referred to as ________.

aerobic endurance

Which of the following may cause muscle atrophy?

wearing a cast on a broken limb
paralysis
a lack of regular stimulation of muscle fibers
all of the above

all of the above

What type(s) of muscle tissue do(es) NOT contain sarcomeres?

cardiac
skeletal
smooth
all of the above

smooth

Structurally, how do smooth muscle cells differ from skeletal muscle cells?

Smooth muscle cells lack myofibrils and sarcomeres.

Which of the following is necessary for smooth muscle contraction?

Calcium ions must interact with calmodulin to trigger muscle contraction.

Smooth muscle contractions in the respiratory passageways cause ________.

increased resistance to air flow

Layers of smooth muscle in the reproductive tract of the female are important in ________.

movement of oocytes
movement of sperm if present
expelling of the fetus at delivery
all of the above

all of the above

The cardiovascular system uses which types of muscle?

cardiac and smooth

The area of the A band in the sarcomere consists of ________.

M line, H band, and zone of overlap

The order of the sequential–cyclic reactions that occur at an active site during cross-bridging is ________.

attach, pivot, detach, return

Excitation–contraction coupling forms the link between ________.

electrical activity in the sarcolemma and the initiation of a contraction

Cardiac muscle has the feature of automaticity, which is the ability to contract without neural stimulation. Which of the following statements accurately explains this unique feature?

Specialized pacemaker cells within the heart determine the rate of contraction of heart muscle.
The heart is full of fast muscle fibers and can contract quickly enough not to require neural stimulation.
Calmodulin interacting with calcium and myosin light chain kinase triggers interactions between actin and myosin.
Because cardiac muscle is not under voluntary control, it does not respond to neural stimulation.
None of the listed responses is correct.

Specialized pacemaker cells within the heart determine the rate of contraction of heart muscle.

The phases of a single twitch, in sequential order, are ________.

latent period, contraction phase, relaxation phase

After contraction, a muscle fiber returns to its original length through ________.

elastic forces and the movement of opposing muscles

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

incomplete tetanus

The process of complete tetanus is reached by ________.

increasing the rate of stimulation until the relaxation phase is completely eliminated

The bacterium Clostridium tetani causes prolonged muscle contractions by doing which of the following?

inhibiting the mechanism that suppresses motor neuron activity

Which of the following would NOT be an effective source of energy for muscle contraction?

glycogen
creatine
DNA
ATP

DNA

What are the two mechanisms used to generate ATP from glucose?

aerobic respiration and anaerobic glycolysis
cytoplasm and mitochondria
ADP and creatine phosphate
None of the listed responses is correct

aerobic respiration and anaerobic glycolysis

In anaerobic glycolysis, glucose is broken down to pyruvic acid, which is converted to ________.

citric acid
glycogen
acetyl-CoA
lactic acid

lactic acid

Johnny, a 55-pound 6-year-old boy, wants to be as strong as some of the professional weight lifters he sees on television. He goes outside, grabs the front bumper of his mother's SUV, and attempts to raise it off the ground. The SUV does not move, but Johnny has succeeded in demonstrating which kind of muscle contraction?

isometric

On average, girls have smaller muscles and therefore less muscle mass than boys. Which hormones cause this difference between girls and boys?

growth hormone and testosterone

Which hormone is responsible for stimulating muscle metabolism and increasing the force of contraction during a sudden crisis?

epinephrine

Which type of skeletal muscle fibers has low fatigue resistance?

fast fiber

Which of the following is an example of an activity that requires anaerobic endurance?

a 50-yard dash

Athletes training to develop anaerobic endurance perform ________.

frequent, brief, intensive workouts

What is the major support that the muscular system gets from the cardiovascular system?

nutrient and oxygen delivery and carbon dioxide removal