A&P Chap 10

Aerobic metabolism normally provides ________ percent of the ATP demands of a resting muscle cell.

95%

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

A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?

A series of proteins that control calcium release.

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.

In rigor mortis

All of the above (muscles are inextensible. cross-bridge cycling is absent. ATP is depleted, the myosin heads are attached to actin)

To increase muscle tension, the nervous system can

All of these can increase muscle tension.

The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?

Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate.

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.

Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?

Calcium ions.

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.

Which of the following statements is false?

Cardiac muscle stimulation is neural.

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.

Region of sarcomere that only contains thick filament

H band

Contains only thin filament in sarcomere

I band

Point in sarcomere of connection for adjacent thick filaments

M line

The "rest and recovery" period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT

Pyruvic acid is converted back to lactic acid

Cycling of myosin cross-bridges results in

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

The muscle action potentials that initiate contraction are transmitted from the sarcolemma into the interior of the muscle fiber by

T-tubule

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

The energy comes from the hydrolysis of ATP.

Malignant hyperthermia (MH) is a rare genetic disease in which the sarcoplasmic reticulum leaks calcium when the patient is put under general anesthesia. Which of the following best describes how anesthesia would affect the skeletal muscles of a patient with MH?

The muscles would contract because of calcium binding to troponin.

What happens immediately after the myosin head binds to the active site on actin?

The myosin head pivots, moving the actin strand.

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

The sarcomere

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.

marks boundaries of sarcomere

Z line

Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why? The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients. The outside surface of the sarcolemma is negatively charged compared to the inside surface. Potassium ions diffuse outward along favorable chemical and electrical gradients. The outside surface of the sarcolemma is negatively charged compared to the inside surface. Sodium ions diffuse outward along favorable chemical and electrical gradients. The inside surface of the sarcolemma is negatively charged compared to the outside surface. Potassium ions diffuse inward along favorable chemical and electrical gradients.

a

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. Acetylcholine binds to its receptor in the junctional folds of the sarcolemma. Its receptor is linked to a G protein. Acetylcholine is released and moves across the synaptic cleft bound to a transport protein. When the action potential reaches the end of the axon terminal, voltage-gated sodium channels open and sodium ions diffuse into the terminal.

a

The skeletal muscle complex known as the triad consists of a transverse tubule and two terminal cisternae. filaments, myofibrils, and sarcomeres. A bands, H bands, and I bands. actin, myosin, and filaments. actin, myosin, and sarcomeres.

a

During neuromuscular transmission, the axon terminals release

acetylcholine

The cytoplasm of the neuromuscular terminal contains vesicles filled with molecules of the neurotransmitter

acetylcholine

In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?

acetylcholine (ACh)

How is acetylcholine (ACh) removed from the synaptic cleft?

acetylcholinesterase (AChE; an enzyme)

A myosin head binds to which molecule to form a cross bridge?

actin

Which of the following proteins contains the active site involved in cross-bridge formation?

actin

myosin molecules form cross-bridges when they attach to

actin

What causes the vesicles inside a neuron to fuse with the plasma membrane?

action potential in neuron

Creatine phosphate

acts as an energy reserve in muscle tissue

During the recovery period the body's need for oxygen is increased because

additional oxygen is required to restore energy reserves consumed during exercise

A resting muscle generates most of its ATP by

aerobic metabolism of fatty acids

When a skeletal muscle fiber contracts, the width of the A band remains constant. the zones of overlap get larger. the H bands and I bands get smaller. the Z lines get closer together. All of the answers are correct.

all

Which of the following is a recognized function of skeletal muscle? a.maintain posture b.guard body entrance/exit c. maintain body temp d.produce movement or all

all

Which statement about the microscopic anatomy of skeletal muscle fibers is true? Cross striations result from the lateral alignment of thick and thin filaments. Each fiber has many nuclei. Tubular extensions of the sarcolemma penetrate the fiber transversely. Muscle fibers are continuous from tendon to tendon. All of the answers are correct

all

When comparing slow muscle fibers to fast muscle fibers, slow fibers

all above

Which of the following statements is (are) true regarding human muscles?

all above

During anaerobic glycolysis

all above ( pyruvic acid produced, carbohydrate metabolized, atp produced, oxygen not consumed )

Which of these is true of cardiac muscle fibers?

all above ( single nucleus ,long twitch, fibers branch )

When contraction occurs,

all are correct (the Z lines move closer together. the width of the A band remains constant. the H bands get smaller.the I bands get smaller.)

Muscles are attached to bones by tendons or a.ligaments b.perimysium c.superficial fascia d.aponeuroses

aponeuroses

What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?

arrival of an action potential

Acetylcholine binds to its receptor in the sarcolemma and triggers the opening of voltage-gated calcium channels the opening of ligand-gated cation channels the opening of calcium-release channels the opening of ligand-gated anion channels

b

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? a.Acetylcholine is transported into the postsynaptic neuron by receptor-mediated endocytosis. b.Acetylcholine is degraded by acetylcholinesterase. c. Acetylcholine diffuses away from the cleft. d.Acetylcholine is transported back into the axon terminal by a reuptake mechanism.

b

Interactions between actin and myosin filaments of the sarcomere are responsible for a. muscle relaxation. b.muscle contraction. c.the striped appearance of skeletal muscle. d.muscle fatigue. e. the conduction of neural stimulation to the muscle fiber.

b

What causes the myosin head to disconnect from actin?

binding of ATP

Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons extend from the spinal cord to the sarcolemma of a skeletal muscle fiber arise in the epimysium of a skeletal muscle and extend to individual skeletal muscle fibers extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber extend from the brain to the sarcolemma of a skeletal muscle fiber

c

Calcium entry into the axon terminal triggers which of the following events? Cation channels open and sodium ions enter the axon terminal while potassium ions exit the axon terminal. Acetylcholine is released into the cleft by active transporters in the plasma membrane of the axon terminal. Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine. Acetylcholine binds to its receptor.

c

Which of the following best describes the term sarcomere? a.protein that accounts for elasticity of resting muscle b.storage site for calcium ions c.repeating unit of striated myofibrils d.thin filaments are anchored here e. largely made of myosin molecules

c

The sarcoplasmic reticulum contain

calcium

In response to action potentials arriving along the transverse tubules, the sarcoplasmic reticulum releases

calcium ions

A muscle producing its maximum tension is in

complete tetanus

Muscle tissue, one of the four basic tissue groups, consists chiefly of cells that are highly specialized for

contraction

What is the type of chemical reaction used to rebuild ADP into ATP?

dehydration synthesis

ATP binding leads to which of the following actions?

detaching and resetting cross-bridges

Which of the following best describes the term sarcoplasmic reticulum? (a-e) largely made of myosin molecules thin filaments are anchored here repeating unit of striated myofibrils protein that accounts for elasticity of resting muscle storage and release site for calcium ions

e

Titin is a(n) tropomyosin-binding protein thin filament protein elastic protein calcium-binding protein

elastic protein

The capillaries that wrap around each muscle fiber are located within the a. epimysium b.perimysium c.sarcolemma d.endomysium

endomysium

The dense layer of connective tissue that surrounds an entire skeletal muscle is the endomysium. epimysium. fascicle. tendon. perimysium.

epimysium

Synaptic vesicles contain neurotransmitters that are released by ________ when the action potential arrives.

exocytosis

What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?

exocytosis

Inside a muscle, bundles of single muscle fibers form

fascicles

The __________ type of muscle fiber has relatively few mitochondria.

fast

Large-diameter, densely packed myofibrils, large glycogen reserves, and few mitochondria are characteristics of

fast fibers

Which of the following most correctly describes excitation in the context of excitation-contraction coupling in skeletal muscle?

generation of an action potential in the sarcolemma

During the Cori cycle, in the liver

glucose from lactic acid

Which of the following processes produces molecules of ATP and has two pyruvic acid molecules as end products?

glycolysis

Muscle fibers differ from "typical cells" in that muscle fibers lack a plasma membrane. have large gaps in the cell membrane. are very small. have many nuclei. lack mitochondria.

have many nuclei

What is the function of the muscle cell feature indicated by the arrow? ( nucleus )

house genetic material

What energizes the power stroke?

hydrolysis or ATP

All of the following are found in both skeletal and cardiac muscle fibers except

intercalated disks

The type of contraction in which the muscle fibers do not shorten is called

isometric

Which of the following processes produces 36 ATP?

krebs cycle

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

lactic acid, decreases

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

large diameter

The muscle weakness of myasthenia gravis results from

loss of acetylcholine receptors in the end-plate membrane.

Myofibrils are

made of a series of sarcomeres

During activities requiring aerobic endurance

most of the muscle's energy is produced in mitochondria.

The neuromuscular junction is a connection between a neuron and a

muscle fiber

In an isotonic contraction

muscle tension exceeds the load and the muscle lifts the load

In which of the following would the motor units have the fewest muscle fibers?

muscles that control the eyes

Skeletal muscle fibers are formed from embryonic cells called myofibrils. myoblasts. myomeres. fascicles. sarcomeres.

myoblasts

Which of the following is involved in the power stroke?

myosin

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

myosin

Each skeletal muscle fiber is controlled by a motor neuron at a single

neuromuscular junction

Acetylcholine receptors are primarily located

on motor end nerve plate

The transverse tubules

part of coupling the action potential to contraction

A thin layer of connective tissue that surrounds a muscle fascicle is called the a.perimysium b.tendon c.epimysium d.endomysium

perimysium

Resting smooth muscle can be stretched without developing much tension because of its

plasticity

A patient takes a medication that blocks ACh receptors of skeletal muscle fibers. What is this drug's effect on skeletal muscle contraction?

reduces the muscle's ability for contraction

The role of acetylcholinesterase in the neuromuscular junction is to

remove acetylcholine from the synaptic cleft

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

The action potential in skeletal muscle fibers is generated by the sarcophagus sarcoplasm sarcolemma sarcoplasmic reticulum

sarcolemma

The plasma membrane of a skeletal muscle fiber is called the sarcoplasm. sarcolemma. sarcosome. sarcomere. sarcoplasmic reticulum.

sarcolemma

The repeating unit of a skeletal muscle fiber is the myofilament. myofibril. sarcomere. sarcolemma. sarcoplasmic reticulum.

sarcomere

Z lines define the edges of which of the following?

sarcomeres

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

sarcoplasmic reticulum

Which organelle completely surrounds each myofibril inside a muscle fiber?

sarcoplasmic reticulum

A single muscle action potential will normally be followed by

single pulse of calcium ion

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

skeletal

The type of muscle fiber that is most resistant to fatigue is the ________ fiber.

slow

What is the function of the muscle cell feature indicated by the arrow? ( sarcoplasmic reticulum) - houses the genetic material of the cell - part of coupling the action potential to contraction - making of ATP - the "power house" of the cell - storage of calcium

storage of calcium

The narrow space between the synaptic terminal and the muscle fiber is the

synaptic cleft

The end of a neuron, where acetylcholine-filled vesicles are located, is called the

synaptic terminal

At each end of the muscle, the collagen fibers of the epimysium, and each perimysium and endomysium, come together to form a tendon. ligament. sheath. tenosynovium. satellite cell.

tendon

The bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a(n) myofibril. tendon. fascicle. epimysium. ligament.

tendon

The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?

terminal cisternae of the sarcoplasmic reticulum

Which of the following acts as an ATPase during the contraction cycle of muscle?

the head portion of the myosin molecule

An action potential in the muscle fiber causes

the muscle fiber to contract

What is the synaptic cleft?

the space between the synaptic terminal and the motor end plate

Myosin molecules form what part of the sarcomere?

thick filament

Which of the following phrases best describes how excitation is coupled to contraction in skeletal muscle fibers?

through calcium release from the sarcoplasmic reticulum

What is name given to the regularly spaced infoldings of the sarcolemma?

transverse or T tubules

The muscle action potential penetrates into a fiber along the

transverse tubules

What is the contraction in graph (a) called?

treppe

T tubules and the terminal cisternae are clustered into structures called

triads

When the sarcomere is at rest, what is covering the active sites on actin?

tropomyosin

When calcium ion binds to troponin

tropomyosin moves into the groove between the helical actin strands.

Which of the following causes the active site on actin to be exposed or uncovered?

tropomyosin shifting position

To what regulatory protein does calcium bind during the initiation of the contraction cycle in skeletal muscle fibers?

troponin

When calcium is released inside a muscle cell, what does it bind to?

troponin

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

troponin

the binding of calcium to which molecule causes the myosin binding sites to be exposed?

troponin

Inside a neuron, acetylcholine is contained within

vesicles

When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?

voltage-gated calcium channels

When does cross bridge cycling end?

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

Which type of muscle fiber has a large quantity of glycogen and mainly uses glycolysis to synthesize ATP?

white fast twitch