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NOT FINISHED YET. School: Chamberlain College of Nursing, Addison, Illinois. Class: BIOS252 - 68623 & 68624, Anatomy and Physiology II. Text: Principles of Anatomy and Physiology, 13th edition, Gerard J. Tortora and Bryan Derrickson. Instructor: Dr. Matthew Bruder. Subject: Chapter 10.2 - Skeletal Muscle Tissue.

Each skeletal muscle is a separate what?


What is a skeletal muscle composed of?

Muscle fibers (cells).

What is a muscle fiber (muscle cell)?

Elongated cells that make up a skeletal muscle.

What does skeletal muscle contain?

Connective tissues, blood vessels, and nerves.

What is the function of connective tissue in a skeletal muscle?

It surrounds and protects muscular tissue.

What is the subcutaneous layer (hypodermis)?

A layer of connective tissue that separates muscle from skin.

What two tissues is the subcutaneous layer (hypodermis) composed of?

Areolar and adipose.

What is the function of the subcutaneous layer (hypodermis)?

It provides a pathway for nerves, blood vessels, and lymphatic vessels to enter and exit muscles.

What are the functions of the subcutaneous layer's (hypodermis) adipose tissue?

1. Stores most of the body's triglycerides.
2. Serves as an insulating layer that reduces heat loss.
3. Protects muscles from physical trauma.

What is fascia?

A dense sheet or broad band of irregular connective tissue that lines the body wall and limbs and supports and surrounds muscles and other organs of the body.

How is fascia organized around muscles?

It holds muscles with similar functions together.

What are the functions of fascia?

1. Allows free movement of muscles.
2. Carries nerves, blood vessels, and lymphatic vessels.
3. Fills spaces between muscles.

What are the three layers of connective tissue in a skeletal muscle?

1. Epimysium.
2. Perimysium.
3. Endomysium.

Epimysium, perimysium, and endomysium extend from what?

The fascia.

What are the functions of epimysium, perimysium, and endomysium?

They protect and strengthen skeletal muscle.

What is epimysium?

The outermost layer of dense, irregular connective tissue that encircles the entire muscle.

What is perimysium?

The middle layer of dense, irregular connective tissue that surrounds groups of 10 to 100 or more muscle fibers and separates them into fascicles.

What is a fascicle?

A small bundle or cluster, especially of nerve or muscle fibers (cells).

If you tear a piece of meat, it rips apart along the what?


What is endomysium?

The innermost layer of connective tissue that penetrates the interior of each fascicle and separates individual muscle fibers from one another.

What is endomysium mostly composed of?

Reticular fibers.

What is the outermost layer of connective tissue in a skeletal muscle?


What is the middle layer of connective tissue in a skeletal muscle?


What is the innermost layer of connective tissue in a skeletal muscle?


What layer of connective tissue encircles the entire muscle?


What layer of connective tissue surrounds fascicles?


What layer of connective tissue surrounds individual muscle fibers?


What are epimysium, perimysium, and endomysium all continuous with?

The connective tissue that attaches a skeletal muscle to other structures, such as bone or another muscle.

All three connective tissue layers may extend beyond the muscle fibers to form what?

A tendon.

What is a tendon?

A white fibrous cord of dense regular connective tissue that attaches muscle to the bone.

What is an aponeurosis?

The connective tissue elements extended as a broad, flat, sheetlike tendon, joining one muscle with another or with bone.

What is fibromyalgia?

A chronic, painful, nonarticular rheumatic disorder that affects the fibrous connective tissue components of muscles, tendons, and ligaments.

What is a striking sign of fibromyalgia?

Pain that results from gentle pressure at specific tender points.

What are some symptoms of fibromyalgia?

1. Even without pressure, there is pain, tenderness, and stiffness of muscles, tendons, and surrounding soft tissues.
2. Severe fatigue.
3. Poor sleep.
3. Headaches.
4. Depression.
5. Irritable bowel syndrome.
6. Inability to carry out daily activities.

What is the cause of fibromyalgia?

There is no specific identifiable cause.

What are some treatments for fibromyalgia?

1. Stress reduction.
2. Regular exercise.
3. Application of heat.
4. Gentle massage.
5. Physical therapy.
6. Medication for pain.
7. Low-dose antidepressant to help improve sleep.

Skeletal muscles are well supplied with what?

Nerves and blood vessels.

Generally, how many arteries and veins accompany each nerve that penetrates a skeletal muscle?

An artery and one or two veins.

What is a somatic motor neuron?

A neuron that stimulates skeletal muscle to contract.

Where does the threadlike axon of a somatic motor neuron extend from and go to?

Its axon extends from the brain or spinal cord to a group of skeletal muscle fibers.

How many times does the axon of a somatic motor neuron branch?

Many times.

What does each branch of the axon of a somatic motor neuron extend to?

A different skeletal muscle fiber.

What are capillaries?

Microscopic blood vessels.

Are there capillaries in muscular tissue?

Yes. They are plentiful in muscular tissue.

Each muscle fiber is in close contact with how many capillaries?

One or more.

What is the function of blood capillaries?

They bring in oxygen and nutrients and remove heat and the waste products of muscle metabolism.

How do capillaries aid in the process of muscle contraction?

Especially during contraction, a muscle fiber synthesizes and uses considerable ATP (adenosine triphosphate). These reactions require oxygen, glucose, fatty acids, and other substances that are delivered to the muscle fiber in the blood.

What are the most important components of a skeletal muscle?

Muscle fibers.

What is the diameter of a mature skeletal muscle fiber?

10 to 100 μm.

What is the length of a mature skeletal muscle fiber?

10cm (4in).

How long can some mature skeletal muscle fibers be?

30cm (12in).

When do skeletal muscle fibers arise?

During embryonic development.

How do skeletal muscle fibers arise?

From the fusion of a hundred or more myoblasts.

What is a myoblast?

A small mesodermal cell that creates a skeletal muscle fiber when it fuses with other myoblasts during embryonic development.

How many nuclei do mature skeletal muscle fibers have?

A hundred or more.

What happens to a skeletal muscle fiber once fusion occurs?

It loses its ability to undergo cell division.

Does your body create more skeletal muscle fibers after birth?

No. The number of skeletal muscle fibers is set before you are born.

How long do most skeletal muscle fibers last?

A lifetime.

Why can't more skeletal muscle fibers be created after birth?

Because once fusion occurs, skeletal muscle fibers lose their ability to undergo cell division.

What is the sarcolemma?

The plasma membrane of a muscle cell.

Where are the multiple nuclei of a skeletal muscle fiber located?

Just beneath the sarcolemma.

What are transverse (T) tubules?

Small, cylindrical invaginations of the sarcolemma of striated muscle fibers (cells) that conduct muscle action potentials toward the center of the muscle fiber.

What are transverse (T) tubules filled with?

Interstitial fluid.

How do muscle action potentials spread throughout a muscle fiber?

They travel along the sarcolemma and through the T tubules.

What is the sarcoplasm?

The cytoplasm of a muscle fiber.

What are some structures found in the sarcoplasm of a muscle fiber?

Glycogen and myoglobin

What is glycogen?

A large molecule composed of many glucose molecules.

What can glycogen be used for?

Synthesis of ATP.

What is myoglobin?

The oxygen-binding, iron-containing protein present in the sarcoplasm of muscle fibers (cells); contributes the red color to muscles.

Myoglobin are found only in what?


What is the function of myoglobin?

It binds oxygen molecules that diffuse into muscle fibers from interstitial fluid. It then releases this oxygen when it is needed by the mitochondria for ATP production.

Where are the mitochondria located in a skeletal muscle fiber?

They lie in rows throughout the muscle fiber, strategically close to the contractile muscle proteins that use ATP during contraction so that ATP can be produced as quickly as needed.

What is a myofibril?

A threadlike structure, extending longitudinally through a muscle fiber (cell), consisting mainly of thick filaments (myosin) and thin filaments (actin, troponin, and tropomyosin). The contractile organelles of skeletal muscle.

What is the diameter of a myofibril?


What is the length of a myofibril?

It extends the entire length of a muscle fiber.

What makes a skeletal muscle appear striped (striated)?

The prominent striations on a myofibril.

What is the sarcoplasmic reticulum (SR)?

A network of saccules and tubes surrounding myofibrils of a muscle fiber (cell), comparable to endoplasmic reticulum; functions to reabsorb calcium ions during relaxation and to release them to cause contraction.

What does the sarcoplasmic reticulum do in a relaxed muscle fiber?

It stores calcium ions (Ca2+).

How does the sarcoplasmic reticulum trigger muscle contraction?

By releasing calcium ions (Ca2+) from its terminal cisterns.

What are terminal cisterns?

Dilated end sacs of the sarcoplasmic reticulum that butt against the T tubules from both sides.

How do terminal cisterns trigger muscle contraction?

The sarcoplasmic reticulum triggers it to release calcium ions (Ca2+).

What is a triad?

A transverse (T) tubule and the two terminal cisterns on either side of it.

What are filaments (myofilaments)?

Small protein structures within myofibrils.

What are the two filaments in a myofibril?

Thin filaments and thick filaments.

What is the diameter of a thin filament?


What is the length of a thin filament?


What protein is a thin filament mostly composed of?


What is the diameter of a thick filament?


What is the length of a thick filament?


What protein is a thick filament mostly composed of?


What are filaments arranged in?


What process are both thin and thick filaments directly involved in?

The contractile process.

In the regions of filament overlap, how many thin filaments are there for every thick filament?

There are two thin filaments for every thick filament.

Do filaments extend the entire length of a muscle fiber?

No. They are arranged in sarcomeres.

What is a sarcomere?

A contractile unit in a striated muscle fiber (cell), especially of a skeletal muscle fiber; the basic functional unit of a myofibril.

A sarcomere extends from where to where?

From one Z disc to the next Z disc.

What are Z discs?

Narrow, plate-shaped regions of dense material that separates one sarcomere from the next.

What does the extent of overlap of the thick and thin filaments depend on?

On whether the muscle is contracted, relaxed, or stretched.

What creates the visible striations in single myofibrils and whole muscle fibers?

The overlap patterns of the thick and thin filaments.

What is the A band?

The dark, middle part of sarcomere that extends the entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments.

What is the zone of overlap?

Where the thick and thin filaments lie side by side toward each end of the A band.

What is the I band?

The lighter, less dense area of sarcomere that contains a remainder of thin filaments but no thick filaments; a Z disc passes through the center of each I band.

What is the H zone?

The narrow region in center of each A band that contains thick filaments but no thin filaments.

What is the M line?

The region in center of H zone that contains proteins that hold thick filaments together at center of sarcomere.

What is muscular hypertrophy?

An enlargement of existing muscle fibers.

What kind of muscle growth occurs after birth?

Muscular hypertrophy.

How do existing muscle fibers enlarge through muscular hypertrophy?

From increased production of myofibrils, mitochondria, sarcoplasmic reticulum, and other organelles.

How does muscular hypertrophy occur?

From very forceful, repetitive muscular activity, such as strength training.

What are hypertrophied muscles capable of more forceful contractions?

Because there are more myofibrils.

What stimulates an increase in the size of skeletal muscle fibers during childhood?

Human growth hormone, testosterone, and other hormones.

What is muscular hyperplasia?

An increase in the number of muscle fibers.

Can skeletal muscle tissue be regenerated?

Yes, but it is limited.

What are satellite cells?

Flat, neuroglial cells that surround cell bodies of peripheral nervous system ganglia to provide structural support and regulate the exchange of material between a neuronal cell body and interstitial fluid.

How can functional muscle fibers be regenerated?

Satellite cells can fuse with one another or with damaged muscle fibers, but the number of new skeletal muscle fibers that satellite cells can form is not enough to compensate for significant skeletal muscle damage or degeneration.

How do skeletal muscle fibers regenerate when satellite cells aren't enough?

Skeletal muscle tissue undergoes fibrosis.

What is fibrosis?

The process by which fibroblasts synthesize collagen fibers and other extracellular matrix materials that aggregate to form scar tissue. It replaces damaged skeletal muscle fibers with fibrous scar tissue.

What is muscular atrophy?

A wasting away of muscles.

How does muscular atrophy occur?

Individual muscle fibers decrease in size as a result of progressive loss of myofibrils.

What are the two types of muscular atrophy?

1. Disuse atrophy.
2. Denervation atrophy.

What is disuse atrophy?

Muscular atrophy that occurs because muscles are not used.

What can cause disuse atrophy?

Bedridden individuals and people with casts experience this because the flow of nerve impulses (nerve action potentials) to inactive skeletal muscle is greatly reduced.

Which type of muscular atrophy is reversible?

Disuse atrophy.

What is denervation atrophy?

Muscular atrophy that occurs because a nerve supply to a muscle is disrupted or cut.

What happens to a muscle when it is atrophied by denervation atrophy?

Over a period of six months to two years, the muscle shrinks to about one-fourth its original size, and the muscle fibers are irreversibly replaced by fibrous connective tissue.

What is exercise-induced muscle damage?

Torn sarcolemmas in some muscle fibers, damaged myofibrils, and disrupted Z discs after intense exercise. There is also an increase in blood levels of proteins, such as myoglobin and the enzyme creatine kinase, that are normally confined within muscle fibers.

What is delayed onset muscle soreness (DOMS)?

Stiffness, tenderness, and swelling of skeletal muscles 12 to 48 hours after a period of strenuous exercise.

What are the causes of delayed onset muscle soreness?

Causes are not completely understood, but microscopic muscle damage appears to be a major factor.

What happens to muscle fibers in response to exercise-induced muscle damage?

Muscle fibers undergo repair. New regions of sarcolemma are formed to replace torn sarcolemmas, and more muscle proteins (including those of the myofibrils) are synthesized in the sarcoplasm of the muscle fibers.

Myofibrils are built from what three kinds of proteins?

1. Contractile proteins.
2. Regulatory proteins.
3. Structural proteins.

What are contractile proteins?

Proteins that generate force during muscle contractions.

What are regulatory proteins?

Proteins that help switch the muscle contraction process on and off.

What are structural proteins?

Proteins that:
1. Keep the thick and thin filaments of myofibrils in the proper alignment.
2. Give the myofibril elasticity and extensibility.
3. Link the myofibrils to the sarcolemma and extracellular matrix.

What are the two contractile proteins in muscles?

1. Myosin.
2. Actin.

What contractile protein makes up the thick filament?


What is myosin?

A contractile protein that makes up thick filament; molecule consists of a tail and two myosin heads, which bind to myosin-binding sites on actin molecules of thin filaments.

Where does a myosin molecule bind to?

Myosin-binding sites on actin molecules of thin filaments.

What kind of protein does myosin function as in all three types of muscle tissue?

A motor protein.

What is a motor protein?

A protein that pulls various cellular structures to achieve movement by converting chemical energy in ATP to the mechanical energy of motion, that is, the production of force.

In skeletal muscle, how many molecules of myosin form a single thick filament?


What is a myosin molecule shaped like?

Two golf clubs twisted together.

What part of a myosin molecule is a myosin tail?

The twisted golf club handles.

Where is a myosin tail located?

It points toward the M line in the center of the sarcomere.

What part of the thick filament do the parallel myosin tails of a myosin molecule form?

The shaft of the thick filament.

What part of a myosin molecule is the molecule heads?

The twisted golf club heads.

What are myosin heads?

The two projections of each myosin molecule.

Where are the myosin heads located?

They project outward from the shaft in a spiraling fashion, each extending toward one of the six thin filaments that surround each thick filament.

What are thin filaments anchored to?

Z discs.

What is actin?

A contractile protein that is the main component of thin filament; each actin molecule has a myosin-binding site where myosin head of thick filament binds during muscle contraction; individual actin molecules join to form an actin filament that is twisted into a helix.

What contractile protein makes up the thin filament?


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