Question 1

What does troponin bind to and what happens when it binds? A) Ca²⁺, tropomyosin shifts B) tropomyosin, the sarcomere relaxes C) acetylcholine, the sarcome shortens D) ATP, tropomyosin returns to normal position E) T tubules, the sarcomere shortens

Accepted Answer

Troponin binds to Ca²⁺ and this results in a shift of the tropomyosin threads, exposing myosin-binding sites.

Question 2

What ion is responsible for initiating muscle contraction? A) Mg²⁺ B) Ca²⁺ C) H⁺ D) Cl^- E) Na⁺

Accepted Answer

Calcium ions are released from the sarcoplasmic reticulum to initiate muscle contraction.

Question 3

Which of the following does not occur when a muscle fatigues?
A) Its energy reserves are depleted.
B) Stimulation continues.
C) Tetanus is achieved.
D) Acetylcholine is crossing the synaptic cleft.
E) The muscle relaxes.

Accepted Answer

Tetanus is maximal sustained contraction and does not occur during muscle fatigue.

Question 4

One motor neuron activates one muscle fiber.

Accepted Answer

One motor neuron can stimulate from a few to several muscle fibers of a muscle because each axon has several branches.

Question 5

Which of the following is not a phase of a single muscle twitch?
A) stimulation period
B) latent period
C) contraction period
D) relaxation period

Accepted Answer

A stimulation period is not a phase of a muscle twitch.

Question 6

When a muscle contracts,the H zone almost disappears.

Accepted Answer

The H zone is the area in the center of the sarcomere that almost disappears when the muscle contracts.

Question 7

When the nerve signal reaches the axon terminal what happens next? A) The muscle contracts. B) The synaptic vesicles release neurotransmitter. C) An electrical signal is formed that jumps the synaptic cleft. D) H⁺ is pumped into the synaptic cleft. E) Myosin is released from the axon terminal.

Accepted Answer

The synaptic vesicles release acetylcholine, a neurotransmitter, into the synaptic cleft.

Question 8

A muscle fiber is made up of many
A) muscle cells.
B) T tubules.
C) myofibrils.
D) fascicles.
E) bursa.

Accepted Answer

A muscle fiber is made up of many myofibrils divided into sarcomeres.

Question 9

Each actin molecule is shaped like a golf club,with a straight portion ending in a globular head.

Accepted Answer

Each myosin molecule is shaped like a golf club.

Question 10

One sarcomere
A) extends from Z line to Z line.
B) is composed of many myofibrils.
C) contains only actin fibers.
D) is composed of many muscle fibers.
E) surrounds each muscle in the body.

Accepted Answer

A sarcomere extends between two dark vertical lines called Z lines.

Question 11

Several of the structures in the muscle cell are given special names.For example,the cytoplasm of a muscle fiber is called the sarcoplasm.Which of the following is truly a unique structure to muscle cells (not just a renamed one)?
A) cytoplasm
B) nucleus
C) endoplasmic reticulum
D) transverse (T) system
E) plasma membrane

Accepted Answer

The T system is not found in other types of cells.

Question 12

In good muscle tone,how many motor units are contracted?
A) none
B) some
C) all

Accepted Answer

In good muscle tone, some motor units are always contracted, but not enough to cause movement.

Question 13

What does the word sarco mean?
A) large
B) short
C) muscle
D) tubule
E) smooth

Accepted Answer

The word sarco means muscle.

Question 14

What is happening during the latent period of a muscle twitch?
A) The muscle relaxes and returns to its former length.
B) Fresh ATP binds to the myosin causing it to return to its resting position.
C) ADP and phosphate are released, and the power stroke of the contraction occurs.
D) The myosin-actin cross-bridges are broken and the sarcomere shortens.
E) The neurotransmitter is diffusing across the synaptic cleft causing an electrical signal in the muscle cell.

Accepted Answer

All of the activities that begin a contraction are occurring.

Question 15

The actin and myosin filaments _______________ when a muscle contracts.
A) shorten
B) lengthen
C) stay the same length

Accepted Answer

The actin and myosin filaments stay the same length when a muscle contracts. They just slide past each other.

Question 16

What supplies the energy for muscle contraction? A) actin B) myosin C) tropomyosin D) ATP E) Ca²⁺

Accepted Answer

ATP supplies the energy necessary for muscle contraction.

Question 17

Why is the innervation ratio in the ocular muscles one motor axon per 23 muscle fibers,whereas in the gastrocnemius muscle it is one motor axon per 1000 muscle fibers?
A) There are more nerves in the upper body than in the lower extremities.
B) The ocular muscles require finer control than moving the legs.
C) The innervation ratio has to do with the overall size of the muscle--the bigger the muscle, the fewer the muscle fibers per motor axon.
D) The gastrocnemius muscle contracts much harder than the ocular muscles do.
E) There are fewer muscle fibers in the gastrocnemius muscle than in the ocular muscles.

Accepted Answer

The ocular muscles require much finer control than moving the legs.

Question 18

Contraction of a muscle requires all the motor units to be undergoing tetanic contraction.

Accepted Answer

Some motor units are contracting maximally while others are resting, allowing sustained contractions to occur.

Question 19

What is the name of the small gap that separates the axon terminal of a nerve from the sarcolemma?
A) T tubule
B) sliding filament
C) synaptic cleft
D) synaptic vesicle
E) sarcoplasmic reticulum

Accepted Answer

The small gap is called a synaptic cleft. The entire region is called a neuromuscular junction.

Question 20

One motor unit obeys a principle called the all-or-none law.

Accepted Answer

All the muscle fibers in a motor unit are stimulated at once. They all either contract or do not contract.

Quiz 12: Muscular System

What does troponin bind to and what happens when it binds?

What ion is responsible for initiating muscle contraction?

Which of the following does not occur when a muscle fatigues?

One motor neuron activates one muscle fiber.

Which of the following is not a phase of a single muscle twitch?

When a muscle contracts,the H zone almost disappears.

When the nerve signal reaches the axon terminal what happens next?

A muscle fiber is made up of many

Each actin molecule is shaped like a golf club,with a straight portion ending in a globular head.

One sarcomere

Several of the structures in the muscle cell are given special names.For example,the cytoplasm of a muscle fiber is called the sarcoplasm.Which of the following is truly a unique structure to muscle cells (not just a renamed one) ?

In good muscle tone,how many motor units are contracted?

What does the word sarco mean?

What is happening during the latent period of a muscle twitch?

The actin and myosin filaments _______________ when a muscle contracts.

What supplies the energy for muscle contraction?

Why is the innervation ratio in the ocular muscles one motor axon per 23 muscle fibers,whereas in the gastrocnemius muscle it is one motor axon per 1000 muscle fibers?

Contraction of a muscle requires all the motor units to be undergoing tetanic contraction.

What is the name of the small gap that separates the axon terminal of a nerve from the sarcolemma?

One motor unit obeys a principle called the all-or-none law.