Chapter 10: Skeletal Muscle Tissue

The central part of the "A band" of a sarcomere is known as the __________.

"H zone"

Which of the following are important similarities among skeletal, cardiac, and smooth muscle?

- All three depend on myofilaments for contraction. - Their plasma membrane is called a sarcolemma.

T tubules ____________.

- Are deep invaginations of the sarcolemma - Conduct impulses into the deepest region of muscle fibers

Slow oxidative muscle fibers ____________.

- Are prevalent in postural muscles of the back - Have abundant myoglobin and numerous mitochondria

Thin Filaments:

- Contains actin - Does not lie in the H zone - Attaches to a Z disc

Thick Filaments:

- Contains myosin heads - Contains myosin - Does not lie in the I band

What muscles attach to the hyoid bone?

- Geniohyoid - Stylohyoid - Mylohyoid - Sternohyoid - Thyrohyoid

Which bands narrow when a skeletal muscle fiber contracts?

- H band - I band

Muscle tissue has which of the following functions?

- Heat generation - Joint stabilization - Movement

Skeletal Muscle Fascicle:

- Is surrounded by perimysium - A bundle of cells

What are the muscles of mastication?

- Masseter - Temporalis - Lateral pterygoid - Medial pterygoid

Skeletal Muscle Fiber:

- Multinucleated contractile cell that runs the length of a skeletal muscle

Myofilaments:

- Myofilaments are composed of the contractile proteins actin and myosin. - In striated muscle, the myofilaments are arranged into sarcomeres, the smallest contractile unit in striated muscle.

Smooth Muscle:

- Not striated and involuntary - Is present in wall of bladder - The individual muscle cells are called muscle fibers - Has no A or I bands - It is located in the walls of hollow body organs - Its extranuclear materials are called sarcoplasm instead of cytoplasm, and the plasma membrane is called the sarcolemma

Skeletal Muscle Myofibril:

- Rod-shaped organelle - Made of sarcomeres

Cardiac Muscle:

- Striated and involuntary - Is located only in the heart - Its extranuclear materials are called sarcoplasm instead of cytoplasm, and the plasma membrane is called the sarcolemma

Skeletal Muscle:

- Striated and voluntary - Its fibers are giant, multinucleate cells - The individual muscle cells are called muscle fibers - Its extranuclear materials are called sarcoplasm instead of cytoplasm, and the plasma membrane is called the sarcolemma

What are the functions of the terminal cistern and the T tubules?

- The terminal cistern stores Ca2+. - The T tubules carry the stimulus to contract from the surface sarcolemma to the deeper regions of the muscle fiber, initiating the release of Ca2+ from the terminal cistern.

Skeletal muscle cells have which of the following characteristics?

- They are long and cylindrical. - Their diameter is 10-100µm. - They are multinucleate. - They are long and cylindrical and multinucleate.

Which one of the following describes A band sarcomere?

Full length of thick filaments, including overlapping inner ends of thin filaments

Which of the following is the definition of muscular dystrophy?

It is a group of inherited muscle-destroying diseases that generally appear in childhood. The affected muscles enlarge with fat and connective tissue.

Which of the following is the definition of myofascial pain syndrome?

It is associated with overused or strained postural muscles in "reference zones."

Which of the following describes the functional characteristic of muscle called elasticity?

After being stretched, muscle tissue can passively recoil and resume its resting length.

Titin is a protein that does all of the following except ____________.

Aid in diffusion of acetylcholine across the synaptic cleft

Skeletal Muscle:

An organ

What fiber type would be the most useful in the leg muscles of a long-distance runner?

Fast oxidative

Which portion of the sarcomere creates the light portions of the light-dark pattern of striations seen along the length of a muscle fiber?

I band

Which of the following is the definition of fibromyalgia?

It is a chronic pain syndrome of unknown cause that includes musculoskeletal pain, fatigue, sleep abnormalities, and headache.

Which of the following is the definition of myotonic dystrophy?

It is an inherited, slowly progressing disease that consists of muscle spasms, followed by muscle weakness and abnormal heart rhythm.

During contraction of a sarcomere, what happens to the A band?

It remains the same length.

Another name for muscle cells is __________.

Muscle fibers

Which of the following is the definition of Duchenne muscular dystrophy?

Muscle fibers lack a submembrane protein called dystrophin, which links the cytoskeleton of the muscle fiber to the extracellular matrix.

Which of the following describes the functional characteristic of muscle called extensibility?

Muscle tissue can be stretched by the contraction of an opposing muscle.

What type of embryological cell gives rise to muscle fibers?

Myoblasts

Slow oxidative fibers are dark red because of what pigment?

Myoglobin

Slow oxidative (SO) fibers (slow-twitch fibers) have more _______ and less ________ than fast glycolytic (FG) fibers (fast-twitch fibers).

Myoglobin, glycogen

How does the sliding filament mechanism result in concentric contraction of skeletal muscle?

Myosin heads of thick filaments attach to thin filaments at both ends of a sarcomere and pull the thin filaments toward the center of the sarcomere.

Which of the following describes functional characteristic of muscle called excitability?

Nerve signals or other factors cause electrical impulses to travel along the cell's sarcolemma, stimulating the cells to contract.

What is a motor unit?

One motor neuron and all the muscle fibers it innervates

In general, each skeletal muscle is supplied by __________.

One nerve, one artery, and one or more veins

A motor unit is:

One neuronal axon and all the muscle fibers innervated by it.

In muscle fibers, fascicles are surrounded by a layer of fibrous connective tissue called __________.

Perimysium

Myofilaments are ____________.

Protein filaments that are responsible for shortening muscle cells

Which of the following describes an I band sarcomere?

Region of thin filaments only; part of two adjacent sarcomeres

What structure stores calcium ions that trigger contraction?

Sarcoplasmic reticulum

Why are skeletal muscle fibers (skeletal muscle cells) multinucleate?

Skeletal muscle fibers are formed by the fusion of embryonic myoblasts.

Posture is maintained by _____ fibers.

Slow oxidative (SO)

Which skeletal muscle fibers are extremely resistant to fatigue, as long as enough oxygen is present, and deliver prolonged contractions?

Slow oxidative fibers (SO)

Which skeletal muscle fibers are relatively thin, and are red due to their abundant myoglobin content?

Slow oxidative fibers (SO)

Which of the following describes myofilament?

There are two types of this structure, thick and thin, which slide against each other to cause muscle shortening.

Which of the following describes the events that occur during a muscle contraction of H zones?

These structures disappear completely.

Which of the following describes the events that occur during a muscle contraction of Z discs?

These structures move closer together, causing the sarcomere to shorten.

Which of the following describes the events that occur during a muscle contraction of I bands?

These structures shorten as the muscle contracts.

Which of the following describes the events that occur during a muscle contraction of A bands?

These structures stay the same length.

Which protein is a springlike molecule in sarcomeres that prevents overstretching, extending in a sarcomere from the Z disc to a filament and running within the filament to attach to the M line?

Titin

The function of T tubules in muscle contraction is to:

Transmit an impulse deep into the muscle cell

Which of the following describes the functional characteristic of muscle called contractility?

When muscle cells shorten, they generate a strong pulling force.

During contraction, which of the following occur(s) in a sarcomere?

Z discs move closer together and the lengths of the I bands and the H zone decrease.

Muscle Fiber:

A muscle fiber is a muscle cell.

Muscles may change due to exercise in all the following ways:

- Through satellite cells fusing with muscle fibers, contributing additional nuclei - By increasing the production of contractile proteins - By the conversion of fast glycolytic fibers to fast oxidative fibers, particularly through resistance training - By increasing in diameter

Titin is a protein that does:

- Unfold when a muscle cell is stretched - Hold thick filaments in place, thus maintaining the organization of the A band - Refold when stretching force is released

An adult human female's skeletal muscles make up what percentage of body mass, on average?

36%

Each end of a sarcomere is marked by:

A Z disc

The region of a sarcomere where actin and myosin overlap is:

A band

A fascicle is:

A bundle of muscle cells enclosed by a connective tissue sheath

When a muscle joins a bone and has no visible tendon, it is said to have:

A direct attachment

Skeletal Muscle Myofilament:

A group of large molecules

Myfibril:

A myofibril is an organelle within a muscle cell made up of repeating sarcomeres.

Endomysium, perimysium, and epimysium __________.

Are each continuous with tendons and are the connective tissue sheaths around skeletal muscle fibers, muscle fascicles, and whole muscles, respectively

Sarcoplasmic reticulum tubules called "terminal cisterns" form large, perpendicular cross-channels over which junction?

Between each A band in a myofibril and its adjacent I bands

Which of the following describes the Z disc of the sarcomere?

Boundary of an individual sarcomere; connected to thin filaments and titin

Muscles may change due to exercise in all the following ways, except ____________.

By increasing in number through dividing mitotically

The ions that first enter the cytosol of a muscle cell when an impulse passes over its sarcolemma and then trigger muscle contraction are:

Calcium

The sarcoplasmic reticulum stores large quantities of which ion?

Calcium

What ion binds to troponin during excitation-contraction coupling?

Calcium

The "sliding filament mechanism" explains which type of muscle contraction?

Concentric contraction

Regarding muscle attachments, which term(s) indicate(s) that the strands of connective tissue are so short that the muscle fascicles appear to attach directly to the bone?

Direct attachments and fleshy attachments

Which of the following describes a fascicle?

Discrete bundles of muscle cells, segregated from the rest of the muscle by a connective tissue sheath

Which is not a function of skeletal muscle? A. Movement B. Heat production C. Stability D. Communication E. All of these are functions of skeletal muscle.

E. All of these are functions of skeletal muscle.

In contrast to skeletal muscle, smooth muscle has all of the following properties except: A. One nucleus in each cell. B. A lack of striations. C. A lack of Z discs. D. Ability to regenerate through the process of mitosis. E. An increased number of T tubules.

E. An increased number of T tubules.

Which of the following is an autoimmune disorder that leads to destruction of acetylcholine receptors? A. Duchenne muscular dystrophy B. Atrophy C. Crush syndrome D. Rhabdomyoma E. Myasthenia gravis

E. Myasthenia gravis

After being stretched, muscle tissue can recoil passively and resume its resting length. This is known as __________.

Elasticity

Which of the following describes a skeletal muscle fiber?

Elongated, multinucleate cell that has a striated appearance

The connective tissue that lies just outside the sarcolemma of an individual muscle cell is called the:

Endomysium

An "overcoat" of dense, irregular connective tissue surrounding the whole skeletal muscle, and sometimes blending with the deep fascia, is known as __________.

Epimysium

The functional characteristic of muscles that allows electrical impulses to travel along the cells' sarcolemma, leading to contraction, is __________.

Excitability

In muscle tissue, the characteristic that is defined as "the ability to be stretched by contraction of an antagonist (opposing muscle)" is known as __________.

Extensibility

Place the following structures in order from smallest to largest, and define each: myofibril, muscle fiber, myofilament, sarcomere.

Smallest to largest: myofilament, sarcomere, myofibril, muscle fiber. Myofilaments are composed of the contractile proteins actin and myosin. In striated muscle, the myofilaments are arranged into sarcomeres, the smallest contractile unit in striated muscle. A myofibril is an organelle within a muscle cell made up of repeating sarcomeres. A muscle fiber is a muscle cell.

Which of the following describes titin sarcomere?

Springy molecule that resists overstretching

Nerve-generated impulses in the sarcolemma are conducted by deep invaginations of the sarcolemma that run between each pair of terminal cisternae. These deep invaginations are called __________.

T tubules

Action potentials are propagated from the surface to the interior of a muscle fiber by way of:

The T tubules

Which one of the following describes the H zone sarcomere?

The central portion of an A band, where no thin filaments reach

Which of the following describes an M line sarcomere?

The central portion of the H zone that contains tiny rods that hold the thick filaments together

Which of the following describes a sarcomere?

The contractile unit, composed of myofilaments

In a sarcomere, the I band is ____________.

The region containing only thin filaments

Which of the following is considered to be the "functional unit" of skeletal muscle fibers?

The sarcomere