muscles

The following is a list of the events that occur during a muscle contraction. What is the correct sequence of these events? 1. Myosin cross-bridges bind to the actin. 2. The free myosin head splits ATP. 3. Calcium ion is released from the sarcoplasmic reticulum. 4. The myosin head pivots toward the center of the sarcomere. 5. Calcium ion binds to troponin. 6. The myosin head binds an ATP molecule and detaches from the actin. 5, 1, 4, 6, 2, 3 3, 5, 1, 4, 6, 2 1, 3, 5, 4, 6, 2 3, 5, 1, 2, 4, 6 1, 4, 6, 2, 3, 5

3, 5, 1, 4, 6, 2

The characteristic muscle stiffness associated with rigor mortis is due to the inability of myosin filaments to detach from the active site on actin filaments. What molecule is essential for this detachment?

ATP

For a weight to be lifted, which of the following must occur? An isometric muscle contraction with a force less than the load. An isotonic muscle contraction with a force less than the load. An isotonic muscle contraction with a force greater than the load. An isometric muscle contraction with a force greater than the load.

An isotonic muscle contraction with a force greater than the load.

The resting length of the muscle _______. 40) A) describes the length of the muscle during contraction. B) occurs when the muscle is relaxed. C) occurs when peak tension develops. D) describes the muscle during stimulation.

B) occurs when the muscle is relaxed.

When does cross bridge cycling end? Cross bridge cycling ends when calcium ions are passively transported back into the sarcoplasmic reticulum. Cross bridge cycling ends when calcium release channels in the sarcoplasmic reticulum open. Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin. Cross bridge cycling ends when ATP binds to the myosin head. Submit

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

The delicate connective tissue that surrounds the skeletal muscle fibers and ties adjacent muscle fibers together is the

Endomysium

At each end of the muscle, the collagen fibers of the epimysium, perimysium, and endomysium, come together to form a

Tendon

What happens immediately after the myosin head binds to the active site on actin? The myosin head pivots, moving the actin strand. Tropomyosin moves away from the active site on actin. The myosin head detaches from the active site on actin. ATP binds to the myosin head.

The myosin head pivots, moving the actin strand.

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

Troponin

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? troponin tropomyosin myosin actin

actin

Myosin molecules form cross-bridges when they attach to __________.

actin.

A(n) ________ can be described as a broad tendinous sheet.

aponeurosis

What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell? calcium ion pump troponin ATP arrival of an action potential

arrival of an action potential

What causes the myosin head to disconnect from actin?

binding of ATP

Muscle twitches overlap with _______. fused tetanus only unfused tetanus only threshold voltage applied both fused and unfused tetanus

both fused and unfused tetanus

The muscle that generates the most power during elbow flexion is the __________.

brachialis

Triggering of the muscle action potential occurs after acetylcholinesterase is released from synaptic vesicles into the synaptic cleft. acetylcholine binds to chemically-gated channels in the motor end plate. the action potential jumps across the neuromuscular junction. calcium ion binds to channels on the motor end plate. Any of these can produce an action potential in the muscle cell.

calcium ion binds to channels on the motor end plate.

Interactions between the thick and thin filaments are prevented by tropomyosin. To make the active sites accessible, __________ ions must bind to __________.

calcium;troponin

Physical evidence that supports the sliding filament theory of muscle contraction includes decreased width of the H band during contraction. constant distance between Z lines during contraction. decreased width of the A band during contraction. the I band + H band distance is constant during contraction. increased width of the I band during contraction.

decreased width of the H band during contraction.

ATP binding leads to which of the following actions? cross-bridge formation exposure of active sites on actin detaching and resetting cross-bridges pivoting of the myosin head

detaching and resetting cross-bridges

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

elastic protein

The origin of the external obliques includes ribs __________. eight through twelve six through twelve five through twelve seven through twelve

five through twelve

A muscle that assists another by stabilizing its origin is called its __________. agonist antagonist fixator synergist

fixator

Both heads of the biceps femoris muscle __________. flex the leg at the knee flex the hip extend the hip extend the leg at the knee

flex the leg at the knee

The soleus muscle __________ the foot at the ankle and is innervated by the __________.

flexes;tibial nerve

The brachioradialis is a strong forearm __________.

flexor

The actions of the internal intercostals are most important during __________. forced inspiration normal expiration normal inspiration forced expiration

forced expiration

The soleus muscle shares an insertion with the __________.

gastrocnemius

The infraspinatus inserts on the ____________ of the humerus.

greater tubercle of the humerus

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

incomplete tetanus

A weight-lifter strains to lift a heavy weight and there is no movement of the person's arms holding on to the weight. This type of contraction is called a(n) ________ contraction.

isometric

Muscle fatigue occurs because of a buildup of __________ and a(n) __________ in pH.

lactic acid; decrease.

Myofibrils are __________. made of a series of sarcomeres bundles of muscle cells inside a whole muscle proteins that cover active sites on actin connections between actin and myosin

made of a series of sarcomeres

The insertion of the extensor carpi radialis longus muscle is on __________.

metacarpal 2

When acetylcholine binds to receptors at the motor end plate, the sarcolemma becomes less permeable to sodium ions. less permeable to potassium ions. less permeable to potassium and sodium ions. more permeable to calcium ions. more permeable to sodium ions.

more permeable to sodium ions.

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

muscle contraction.

In an isotonic contraction, tension rises and falls but the muscle length is constant .postural muscles stabilize the vertebrae. many twitches always fuse into one. muscle tension exceeds the load and the muscle lifts the load. the peak tension is less than the load.

muscle tension exceeds the load and the muscle lifts the load.

Which of the following is involved in the power stroke? tropomyosin myofibrils Z lines myosin

myosin

Each skeletal muscle fiber is controlled by a motor neuron at a single transverse tubule. synaptic knob. sarcomere. synaptic cleft. neuromuscular junction.

neuromuscular junction.

The latissimus dorsi inserts __________.

on the intertubercular groove of the humerus

The origins of the rectus abdominus muscle are on the __________. ischial bone sacral bone pubic bone ileum bone

pubic bone

The two heads of the biceps brachii combine to insert on the __________. radial tuberosity ulnar notch olecranon process radial notch

radial tuberosity

Where does the acetylcholine that stimulates muscle contraction bind? receptors in troponin receptors in the axon terminal receptors in the sarcoplasmic reticulum receptors in the motor end plate

receptors in the motor end plate

You try to pick up an object and discover that it is much heavier than you expected. Which process must occur in the muscle to increase tension so you can pick up the object?

recruitment

A patient takes a medication that blocks ACh receptors of skeletal muscle fibers. What is this drug's effect on skeletal muscle contraction? increases the muscle's excitability causes a strong contraction similar to a "charlie horse" cramp increases tone in the muscle reduces the muscle's ability for contraction produces a strong, continuous state of contraction

reduces the muscle's ability for contraction

What causes the power stroke? release of ADP and Pi calcium binding of ATP hydrolysis of ATP

release of ADP and Pi

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

sarcolemma.

Z lines define the edges of which of the following? sarcomeres cross-bridges myosin myofibrils

sarcomeres

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 nuclei. Calcium ions are stored in the mitochondria. Calcium ions are stored in the transverse tubules. Calcium ions are stored in the sarcoplasmic reticulum.

sarcoplasmic reticulum

In response to an action potential along the transverse tubules, the __________ release(s) calcium ions into the sarcoplasm. motor-end plate sarcoplasmic reticulum troponin molecules sarcomere

sarcoplasmic reticulum

Stem cells located between the endomysium and sarcolemma that function in the repair of damaged muscle tissue are called creatinocytes. myocytes. sarcocytes. endocytes. satellite cells.

satellite cells.

Which of the following is NOT a phase of a muscle twitch? relaxation phase latent period contraction phase shortening phase

shortening phase

Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber

shortens.

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

slow

What is the function of the structure indicated by the arrow?

storage of calcium

When acetylcholine binds to its receptors, it results in __________. a graded depolarization the end plate potential, a graded depolarization, and a change in ion permeability a change in ion permeability the end plate potential

the end plate potential, a graded depolarization, and a change in ion permeability

Which region of the sarcomere gives rise to the structure (band or line) indicated by the arrow? the region of the sarcomere that contains only thin filaments the region of the resting sarcomere that only contains thick filaments the point of connection for adjacent thick filaments the boundary between adjacent sarcomeres

the region of the resting sarcomere that only contains thick filaments

Myosin molecules form what part of the sarcomere?

thick filament.

The biceps brachii-radius arrangement represents a __________-class lever system.

third

The prime mover of elbow extension is the __________.

triceps brachii

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

tropmyosin

The binding of calcium to which molecule causes the myosin binding sites to be exposed? tropomyosin actin troponin

troponin

At rest, the tropomyosin molecule is held in place by...

troponin molecules.

The actions of the extensor carpi radialis brevis are localized to the __________.

wrist