Mastering Ch. 10

To increase muscle tension, the nervous system can __________.

All of these can increase muscle tension.

Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?

Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.

The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?

A myosin head bound to actin

After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?

ATP binds to the myosin head.

Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine?

Acetylcholine is degraded by acetylcholinesterase.

The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction?

Acetylcholine is released by axon terminals of the motor neuron.

Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber?

Calcium ions are stored in the sarcoplasmic reticulum.

What specific event triggers the uncovering of the myosin binding site on actin?

Calcium ions bind to troponin and change its shape.

Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?

Calcium release from the sarcoplasmic reticulum initiates the contraction.

When does cross bridge cycling end?

Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.

Cycling of myosin cross-bridges results in ___________.

Repeated cycling of cross-bridges causes all of these effects.

Calcium entry into the axon terminal triggers which of the following events?

Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.

How does the myosin head obtain the energy required for activation?

The energy comes from the hydrolysis of ATP.

What structure is the functional unit of contraction in a skeletal muscle fiber?

The sarcomere

Which of these statements about skeletal muscles is false?

Their fibers branch.

The soleus muscle is very red in color. Which of these statements about soleus muscle fibers is false?

They are large in diameter.

Which of these is not a property of slow muscle fibers?

They are large in diameter.

What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?

Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron. Submit

Muscles are attached to bones by tendons or __________.

aponeuroses

Triads in skeletal muscle fibers function in __________.

calcium ion release

A muscle producing its maximum tension is in __________.

complete tetanus

The capillaries that wrap around each muscle fiber are located within the __________.

endomysium

Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________.

extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber

The __________ type of muscle fiber has relatively few mitochondria.

fast

When a muscle contraction develops tension but doesn't shorten the muscle, the contraction is called __________.

isometeric

Muscle fatigue occurs due to a buildup of __________ and __________ in pH

lactic acid; decrease

Which thick filament binds to actin once its active binding sites are exposed?

myosin

What is the function of the muscle cell feature indicated by the arrows?

part of coupling the action potential to contraction

A thin layer of connective tissue that surrounds a muscle fascicle is called the __________.

perimysium

Skeletal muscle does each of these except __________.

pump blood

In response to an action potential along the transverse tubules, the __________ release(s) calcium ions into the sarcoplasm

sarcoplasmic reticulum

Which type of muscle tissue has the greatest effect on the body's heat production?

skeletal

Which arrangement of the sarcomere gives rise to the structure (band or line) indicated by the arrow?

the boundary between adjacent sarcomeres

Which component of a thin filament binds to calcium once the calcium ion is released from the sarcoplasmic reticulum?

troponin