A&P Chapter 10: Muscles (mastering A&P)

The first step in the contraction cycle in skeletal or cardiac muscles in when ____ binds to _____.

when calcium binds to troponin

Sarcomere is best defined as ____.

a repeating functional unit of striated muscle

What can happen when multiple stimuli are applied to a muscle fiber before it completely relaxes and tension production is gradually increasing? a. incomplete tetanus b. all of the listed answer c. wave summation d. complete tetanus

b. all of the listed answers

How does the release of calcium ions from the terminal cisternae initiate contraction?

it triggers the binding of myosin to actin

Which of the following is the dark band seen on myofibrils?

A band

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

ATP

___ is required to detach cross-bridges and reactivate the myosin head.

ATP

What allows the contraction cycle to repeat so that shortening of the sarcomere happens?

ATP is continuously supplied by the mitochondria; the active site on actin remains exposed; calcium levels remain high in the sarcomere

The H band contains which structures?

Only myosin in the thick filaments

Which structure in a muscle fiber or muscle cell is continuous with the sarcolemma and carries the signal to contract deep into the muscle cells?

T tubules

What causes the myosin head to release its attachment to actin?

a new ATP molecule binds to the myosin head

The thin filaments consist of _____.

a pair of F-actin molecules twisted together

A single stimulation-contraction-relaxation sequence in a muscle fiber is known as a what?

a twitch

The thick filaments consist of _______.

about 300 myosin molecules twisteed around one another

During neuromuscular transmission, the axon terminals release what?

acetylcholine

The sliding of __________ over ___________ causes shortening of skeletal muscle fibers.

actin; myosin

A blending of epimysium, perimysium, and endomysium that forms a broad sheet at the end of a muscle is known as __________.

an aponeurosis

Muscles are attached to bones by tendons or

aponeuroses

Which of the following is NOT found in a thin filament? a. tropononin b. myosin c tropomyosin d. actin

b. myosin

Which of these statements about skeletal muscle is FALSE? a. they store nutreint reserves b. their fibers branch c. they support soft tissues d. the pull on tendons

b. their fibers branch (this is false about skeletal muscle)

What is the function of troponin?

binds calcium and is site of movement - moves tropomyosin away from actin

Triads in skeletal muscle fibers function in _____.

calcium ion release

What must bind to troponin in order to expose the active sites on actin?

calcium ions

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

calcium, troponin

Depolarization of the skeletal muscles at the NMJ occurs as a result of acetylcholine binding and opening the _______.

chemically gated sodium channels

During _______, the muscle fiber is rapidly and continuously being stimulated and is never allowed to relax completely.

complete tetanus

During _______________ the muscle fiber is rapidly and continuously being stimulated and is never allowed to relax completely.

complete tetanus

The length of a sarcomere determines the degree of tension produced. For optimal contraction, the ideal range of the sarcomere length os 75-130% o fnormal length. This is because at this range, there is a maximal number of ____________ that can be formed during contraction.

cross-bridges

Which of the following situations could contribute to prolonged muscle contraction? a. infrequent neural stimulus b. limited availability of calcium ions c. cross-bridge formation being reduced d. acetylcholinesterase not being produced

d. acetylcholinesterase not being produced

Which is NOT found in the endomysium> a. capillary networks b. nerve fibers c. myosatellite cells d. all of these are present in the endomyisum

d. all are present in the endomysium

Characteristics of skeletal muscle fibers include all of the following EXCEPT: a. each fiber is multinucleated b. each fiber is striated c. skeletal muscle fibers are very large d. each fiber contains a single nucleus

d. each fiber contains a single nucleus (this is not true about skeletal muscle)

Skeletal muscle does each of these EXCEPT: a. store nutrients b. maintain posture c. produce movement d. pump blood

d. pump blood

After contraction, a muscle fiber returns to its original length because of _________.

elastic forces and the movement of opposing forces

Titan is a(n)

elastic protein

Excitation-contraction coupling forms the link between _______.

electrical activity in the sarcolemma and the initiation of contraction

Muscle fibers are directly surrounded by which thin layer of connective tissue?

endomysium

The capillaries that wrap around each muscle fiber are located within the what?

endomysium

The connective tissue layer that surrounds a single muscle fiber and joints it to other muscle fibers is _____.

endomysium

Which connective tissue layer wraps around the entire muscle?

epimysium

Nerves and blood vessels are contained within the connective tissues of the __________.

epimysium, perimysium, and endomysium

The perimysium surrounds a bundle of muscle fibers called a __________.

fasicle

Voluntary control over swallowing, defecation, and urination is provided by muscles that __________.

guard entrancs and exits

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

incomplete tetanus

What is the effect of acetylcholine on the motor end plate of the muscle cell membrane?

increasing permeablity to NA+, causing Na+ to diffuse into the muscle cell

The process of complete tetanus is reached by ______.

increasing the rate of stimulation until the relaxation phase is completely eliminated (not reached by applying a second stimulus before the relaxation phase has ended)

How does the release of calcium ions from the terminal cisterna intitiate contraction?

it triggers the binding of myosin to actin

Why is control over leg muscles LESS preceise than control over muscle of the eye?

many muscle dibers in the legs are controlled by a single motor neuron

Bacteria that cause tetanus release a neurotoxin. Which of the following components of the neuromuscular junction does this neurotoxin affect directly?

motor neurons

Inherited disorders that produce progressive muscle weakness and deterioration within muscles are called ______________.

muscular dystrophies

One of the distinct features of the skeletal muscle fibers is that they are multinucleated. The multinucleation is the result of the fusion of embryonic cells called __________.

myoblasts

Skeletal muscles develop from the conjoining of a group of embryonic cells knows as _______.

myoblasts

What area of the thick filament binds to actin once its active binding sites are exposed?

myosin cross-bridge (head)

The amount of tension produced by an individual muscle fiber ultimately depends on the:

number of pivoting cross-bridges

Skeletal muscle generate maximum tension when the maximum number of cross-brdges can form in the zone of _____.

overlap

The connective tissue layer that surrounds a bundle of skeletal muscle fibers is called __________.

perimysium

Myofibrils are formed as a result of repeating functional units called __________.

sarcomeres

The repeating functional units seen in the myofibrils are __________.

sarcomeres

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

sarcoplasmic reticulum

Where is the site of calcium storage in the skeletal muscle fibers?

sarcoplasmic reticulum

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

skeletal

What type of tissue is responsible for holding your head upright?

skeletal muscle tissue

What are the three types of muscle tissue?

skeletal, cardiac, and smooth

Which type of muscle tissue causes contraction of the urinary bladder, forcing urine out of the body?

smooth muscle tissue

What is the function of a triad?

storage of calcium

The connective tissue fibers of the epimysium, perimysum, and endoymysium extend beyond the skeletal muscle cells to form a bundle to connective tissue that joins muscle to bone. This bundle is called what?

tendon

The transmission of an action potential along the T tubule stimulates the release of calcium from which structure in the sarcomere?

terminal cisterna

Which of the following statements correctly describes the structure (band or line) of the sacromere indicated by the arrow? (z-line)

the boundary between adjacent sacromeres

What is happening during the contraction phase of a single twitch?

the muscle is producing tension; calcium binds to troponin, allowing cross-bridge to form

What structure below is part of the cross bridge?

the myosin head

What causes the myosin head to reenergize itself once the power stroke has occured?

the myosin head splits a fresh ATP molecule

Which of the following statements correctly describes the structure (band or line) of the sacromere indicated by the arrow? (M line)

the point of connection for adjacent tails of the thick filaments

Which of the following statements correctly describes the structure (band or line) of the sarcomere indicated by the arrow? (H line)

the region of the resting sarcomere that only contains thick filaments

Which of the following statements correctly describes the structure (band or line) of the sarcomere indicated by the arrow? (I band)

the region of the sarcomere that contains only thin filaments

What happens during the power stroke?

the thin filaments slide toward the M line

Why do the disease tetanus and the normal sustained muscle contraction called tetanus share the same name?

they both eliminate the relaxation phase in the affected muscle fiber

The regulatory protein responsible for elasticity of skeletal muscles is _________.

titin

The muscle action potential penetrates deep into a fiber along the what?

transverse tubules

The regulatory protein responsible for binding to calcium for contraction to proceed is ______.

troponin

What structures make up a triad?

two terminal cisternae and a T tubule

When would we use the contractile proteins in our skeletal muscle cells to provide energy?

when our diet contains too few proteins or calories