Chapter 9 Practice Quiz Questions

What features are not present in smooth muscle?

Tranverse tubules and striations

Muscle fibers generally have only one motor end plate, but a single motor neuron can innervate many different muscle fibers in a group. How does this arrangement affect muscle contraction?

A signal from one motor neuron can potentially stimulate multiple fibers in a group to contract, generating more force.

Where is the location of the vesicles containing neurotransmitter molecules?

At distal end of motor axon

What type of muscle fiber is large in diameter and contains abundant glycogen and relatively few mitochondria?

Fast glycolytic fiber

After finishing a sprint, a runner experienced painful cramps in their calf muscles. A deficit in which molecule would explain the cramping?

ATP

Which of these options lists the structures in order, from deepest to most superficial?

Endomysium, perimysium, epimysium, fascia

What is a function of transverse tubules?

To transmit action potentials (impulses) into the cell interior

A runner collapses during their 800-meter race. A medical exam finds that they have lost the ability to plantar flex at the ankle. What muscle has most likely been injured?

Gastrocnemius

As a muscle fiber is stimulated with increasing frequency, individual twitches begin to summate. If no relaxation occurs between twitches, the contraction is called __________

fused tetany

What muscle originates at the transverse processes of the cervical vertebrae and inserts at the medial border of the scapula?

Levator scapulae

What change occurs with aging?

Decreased supply of myoglobin

True or False: Endomysium separates individual muscle fibers from each other.

True

During a muscle contraction, why is ATP required?

To allow myofilament movement

What is the location of the buccinator muscle?

Cheek

Why does oxygen debt develop?

The respiratory and circulatory systems are unable to supply enough oxygen for skeletal muscles to work strenuously for a minute or two.

In a laboratory that studies muscle function, a group of rats are bred that, due to a genetic defect, produce a non-functional version of troponin. As a result, the rats are paralyzed. What explains the impact of this defect on muscle?

Troponin can’t bind calcium ions and, thus, will not change shape nor cause tropomyosin to move away from the binding sites on the thin filament.

Which of the following is unique in that its insertion is onto fascia and not bone?

palmaris longus

What happens in a muscle as it undergoes atrophy in response to disuse?

The size of actin and myosin filaments decreases.

True or False: A motor neuron and the muscle fibers that it innervates form a motor unit.

True

Why are athletes typically able to exercise longer before developing muscle fatigue than non-athletes?

Due to training, athletes have a better blood supply and more mitochondria in their muscles than do non-athletes.

What muscle causes movement at the temporomandibular joint (TMJ)?

masseter

Curare is a poison that binds to acetycholine receptors at the motor end plate. What is the result of curare poisoning?

Inability of the muscle fiber to respond to nervous stimulation

What is the main component of thin filaments?

Actin

What neurotransmitter(s) can stimulate smooth muscle cells?

Both norepinephrine and acetylcholine

Since the action of the rectus femoris and the biceps femoris muscles oppose each other at the knee, functionally these muscles can be described as __________ to each other.

antagonists

The soleus muscle forms part of the __________

calf

During walking, the gastrocnemius muscle (calf muscle) contracts, shortening and causing plantar flexion. This type of muscle contraction is called a(n) __________ contraction.

concentric

Regina began an exercise program six months ago, and the muscles of her upper limbs and lower limbs have become more prominent. How does exercise lead to formation of new muscle?

By stimulating muscle cells to release IL-6, which stimulates satellite cells to divide

The origin of the occipitalis muscle is the __________ bone of the skull.

occipital

Consider a muscle that originates on the posterior femur and inserts on the posterior tibia. What is the action of this muscle?

To flex the knee

The amount of oxygen that liver cells require to support the conversion of lactic acid to glucose or glycogen is called the __________

oxygen debt

What is the function of acetylecholinesterase?

To break down acetylcholine

Which connective tissue layer is comprised of loose connective tissue?

endomysium

What term describes the more movable end of a muscle?

Insertion

Which of these events occurs first in muscle fiber contraction?

Acetylcholine is released from the axon of the motor neuron

What is the linea alba?

A band of tough connective tissue on the midline of the abdomen

What term describes a muscle that opposes a particular action?

Antagonist

How do skeletal muscles help maintain body temperature?

Muscle contraction releases heat.

What binds to the exposed cross-bridges on actin?

Myosin

A broad sheet of dense connective tissue that attaches a muscle to bone, skin, or other muscles is called a(n) __________

aponeurosis

Bones and muscles function together as mechanical devices called __________

levers

Arrange the steps of muscle fiber contraction in the correct order:

1. The muscle impulse reaches the sarcoplasmic reticulum and calcium is released.

2. Thin filaments are pulled over the thick filaments.

3. Calcium floods the sarcoplasm and binds to troponin molecules leaving active sites.

4. The impulse arrives at the synapse and travels through the transverse tubules.

5. The muscle fiber shortens and contracts.

6. Myosin heads bind to exposed active sites on actin, forming cross-bridges.

4, 1, 3, 6, 2, 5

Following stenuous exercise, levels of ATP, creatine phosphate, oxygen, and glucose must be returned to normal levels. This situation, called __________ may take several hours to complete.

Oxygen debt

What are fascicles?

Bundles of muscle fibers

What term refers to an increase in the number of motor units activated as a result of more intense stimulation?

Recruitment

Which of the following is the functional connection between a neuron and a skeletal muscle fiber?

Synapse

The pigment responsible for the reddish brown color of skeletal muscle is __________

myoglobin

In a laboratory that studies muscle function, a group of rats are bred that, due to a genetic defect, have myosin heads which bind ADP irreversibly. As a result, the rats are paralyzed. What explains the impact of this defect on muscle?

Because ADP is permanently bound, the myosin heads will be irreversibly cross-bridged with the actin binding sites on the thin filament.

What is the cause of rigor mortis that occurs in skeletal muscles a few hours after death?

A decrease in ATP and increased membrane permeability to calcium.

The structures that anchor cardiac muscle cells to each other are called __________

intercalated discs

Many muscles are named for their location in the body, particularly in relation to bones. In what body region would you expect to find the frontalis muscle?

The cranial region

What is the functional unit of muscle contraction?

Sarcomere

True or False: Acetylcholine released by a myofibril crosses the synaptic cleft to bind to the motor end plate.

False

A forceful, sustained muscle contraction is called a(n) __________ contraction.

tetanus

What enzyme degrades acetylcholine, keeping it from accumulating in the synapse?

Acetylcholinesterase

Instead of using troponin to bind calcium ions, smooth muscle cells use __________

calmodulin

How does smooth muscle compare to skeletal muscle?

Smooth muscle contracts more slowly and relaxes more slowly.

Name the area of the sarcolemma that is part of a neuromuscular junction.

Motor end plate

In producing a movement, the muscle that causes an action is acting as the __________

agonist

What is a threshold stimulus?

Minimum stimulus strength required to contract a muscle fiber

Accumulation of lactic acid or depletion of ATP, most likely causes muscle __________

fatigue

What occurs during excitation-contraction coupling?

SR cisternae release calcium ions into the cytosol

Myofibrils are composed primarily of __________

actin and myosin

True or False: ATP is necessary for muscle relaxation.

True

During the motion that extends the upper limb at the elbow, the elbow joint represents which part of the lever?

Fulcrum

True or False: Recruitment refers to increasing the number of motor units involved in a muscle contraction.

True

When acetylcholine binds to its receptors at the motor end plate, the muscle fiber membrane becomes more permeable to __________

sodium

In a recording of a muscle twitch, a delay occurs between the time a stimulus is applied and the time the muscle responds. What is this delay called?

Latent period

Muscles that assist an agonist are acting as __________

synergists

Since the action of the rectus femoris and the vastus lateralis muscles produce the same action at the knee, functionally these muscles can be described as __________ to each other.

synergists

What makes up the cross-bridges that form during a contraction?

Myosin heads binding to actin

A tendon is __________, whereas an aponeurosis is __________.

cordlike and connects muscles to bones; a broad sheet of dense connective tissue that connects muscles to muscles

Which statement describes a sarcomere?

A segment of a muscle fiber

Since many muscles are named for their location, it can be assumed that the zygomaticus muscles originate on the __________ bones of the skull. 

zygomatic

What makes up muscle fibers?

sarcomeres

As a worker carries a heavy box, their arm muscles contract, but the box doesn't shift its position. The arm muscles are undergoing __________ contractions.

isometric

True or False: The myosin heads function as ATPase enzymes.

True

Botulism results from ingestion of a toxin produced by a type of bacterium. Along with other symptoms, it causes a type of paralysis in which the muscles cannot contract. Why does this paralysis occur?

The toxin prevents release of acetylcholine.

In a muscle twitch, the period of time during which the force of contraction is increasing is the ___________ period.

contraction

True or False: During cross-bridge cycling, calcium ions bind to tropomyosin, exposing active sites on actin for cross-bridge formation.

False

What is an example of a partial but sustained contraction?

Muscle tone

Certain natural plant poisons and animal venoms contain substances that inhibit the function of acetylcholinesterase. If a person is poisoned by one of these substances, which of the following will be the cause of their symptoms?

Muscles will be in a constant state of contraction because acetylcholine won't be broken down and cleared from the neuromuscular junction. 

What characteristics would be found in the muscle fibers stimulated during activities such as distance swimming and distance running?

Slow contracting and fatigue-resistant

A muscle that will adduct the thigh (moving it toward the midline of the body) will be located in what area?

Inner thigh

Consider a muscle that originates on the anterior forearm and inserts on the palm of the hand. What is the action of this muscle?

To flex the wrist

What muscle originates on the proximal tibia, inserts on the foot, and causes dorsiflexion and inversion of the foot.

Tibialis anterior

How do slow-twitch fibers (type I) compare to fast-twitch fibers (type IIb)?

Type I fibers have more mitochondria than type IIb fibers.

A muscular contraction in which the muscle shortens, moving an object, is called a(n) __________ contraction.

concentric

The triangle of auscultation, commonly used to hear sounds of respiratory organs, is bounded by what muscles?

Trapezius, rhomboid major, and latissimus dorsi

What is the function of creatine phosphate?

In many movements, the agonist is assisted by other muscles. A muscle that assists the agonist is called a(n) __________

syngerist

What causes the striated appearance of skeletal muscle fibers?

Organization of components of the sarcomeres

What muscle cells are short in length and have centrally located nuclei?

Smooth muscle cells

The rectus femoris originates on the ___________ and inserts on the ___________.

anterior superior iliac spine; tibial tuberosity

Increased frequency of stimulation results in the combining of a series of twitches to produce a more forceful contraction in a process called __________

summation

What structures connect cardiac muscle cells together?

Intercalated discs

The rhythmic, wavelike motion produced by smooth muscles in tubular organs is called __________

peristalsis

In skeletal muscle fibers, what is the source of the calcium ions that are released into the sarcoplasm to bind with troponin, resulting in contraction?

Sarcoplasmic reticulum

During strenuous exercise, when muscles are not being supplied with enough oxygen, a shift in metabolism results in the breakdown of pyruvic acid to lactic acid. What is this change in metabolism called?

Lactic acid threshold

The characteristic reddish brown color of skeletal muscle is due to the presence of which substance?

myoglobin