Tortora 15e Anatomy Chapter 10: Muscle Tissue Structure and Function

What is the ability of muscular tissue to contract forcefully when stimulated?

Contractility

What is the ability of muscular tissue to be stretched without being damaged?

Extensibility

Which statement is FALSE regarding skeletal muscle fibers?

The myofibrils are arranged at right angles to the long axis of the cell, creating cross striations.

What is TRUE of myosin?

It forms thick filaments.

What does the sarcoplasmic reticulum (SR) release to trigger contraction in skeletal muscle?

Ca2+

What does the close association of a transverse (T) tubule and two terminal cisterns form?

Triad

During contraction in a skeletal muscle fiber, what happens to the myosin cross-bridges?

They move the thin filaments so that their ends meet or overlap in the center of the sarcomere.

What is the correct order of events during muscle contraction?

4, 2, 1, 5, 3

What causes an increase (hypertrophy) or decrease (atrophy) in muscle size?

Increased or decreased size of skeletal muscle fibers.

Which skeletal muscle fibers fatigue most easily?

Fast glycolytic (type IIb) fibers.

How does cardiac muscle differ from skeletal muscle?

It has branching cells.

What are the two types of smooth muscle tissue?

Visceral (single-unit) and multiunit.

What does NOT occur as skeletal muscle ages after age 30?

Decrease in the relative number of slow oxidative fibers.

Where are neurotransmitter receptors found on the sarcolemma?

Motor end plate.

Which statement about muscle fibers is FALSE?

The darker, middle band of a sarcomere is called the I band.

Which protein has direct contact with actin in a muscle at rest?

Tropomyosin.

What does one sarcomere NOT contain?

Myofibrils.

During an isotonic contraction, what happens to the muscle?

The muscle shortens while the tension increases.

What is a somatic motor neuron?

A nerve cell that stimulates a skeletal muscle fiber to contract.

What separates a bundle of skeletal muscle fibers from neighboring bundles?

Perimysium.

What is the thick connective tissue around the periphery of a muscle called?

Epimysium.

What is a motor unit?

A somatic motor neuron together with all the skeletal muscle fibers it stimulates.

What is the lighter area in the sarcomere that contains only thin filaments?

I band.

What are the contractile elements of skeletal muscle fibers?

Myofibrils.

What is the importance of skeletal muscle components?

They are essential for understanding the microanatomy of a skeletal muscle fiber.

Do cardiac muscle fibers contain more mitochondria than skeletal muscle fibers?

True

Can cardiac muscle tissue be classified as either visceral or multiunit?

False

What are myoblasts that persist in mature skeletal muscle called?

Satellite cells

What separates the motor neuron and the muscle fiber?

Synaptic cleft

What are four functions of muscle tissue?

1. Producing body movements; 2. Stabilizing body positions; 3. Storing and moving substances; 4. Heat production.

What structural protein wraps around the length of a thin filament?

Nebulin

What are the four steps of the contraction cycle?

Formation of cross-bridges, roles of ATP and calcium, role of troponin, movement of actin filaments.

Which type of muscle fiber has the least amount of myoglobin?

Fast glycolytic fibers

What is the ability to generate spontaneous action potentials called?

Autorhythmicity

In which muscle tissues are striations visible?

Cardiac and skeletal muscle tissues.

What are large dense irregular connective tissue sheets that wrap around groups of skeletal muscles called?

Fascia.

What is the connective tissue that surrounds and separates individual skeletal muscle fibers called?

Endomysium

What is a tube-shaped invagination of the sarcolemma?

T-tubule

What neurotransmitter is released at a neuromuscular junction in skeletal muscle?

Acetylcholine

What is the term for a small amount of tautness or tension in a skeletal muscle due to weak, involuntary contractions?

Muscle tone

What type(s) of cell junctions do intercalated discs in cardiac muscle contain?

Desmosomes and gap junctions

Which kind of muscle fibers do NOT contain sarcomeres?

Smooth muscle fibers

Which muscle fibers are oxidative and the most resistant to fatigue?

Slow oxidative fibers

What type of tissue is endomysium made of?

Loose connective tissue (mostly reticular fibers)

What type of tissue is epimysium made of?

Dense irregular connective tissue

What type of tissue is perimysium made of?

Dense irregular connective tissue

What are the characteristics of skeletal muscle tissue?

Voluntary, striated

What are the characteristics of smooth muscle tissue?

Involuntary, nonstriated

What are some characteristics of smooth muscle tissue?

No transverse tubules

What connects muscle fibers?

Fibers connect by gap junctions.

What is a synaptic vesicle?

A membrane-enclosed sac that stores neurotransmitter.

What is a motor end plate?

Region of sarcolemma at the neuromuscular junction.

What are acetylcholine receptors?

Integral transmembrane proteins of motor end plate that bind with acetylcholine.

What are fast oxidative-glycolytic fibers?

The largest in diameter among muscle fibers.

What are slow oxidative fibers adapted for?

Maintaining posture and endurance-type activities.

What is the connective tissue covering labeled A?

Tendon.

What is the connective tissue covering labeled B?

Perimysium.

What is the connective tissue covering labeled C?

Endomysium.

What organelle is labeled A in a muscle fiber?

Sarcoplasmic reticulum.

What is the function of mitochondrion in skeletal muscle fibers?

Energy production

Which feature is NOT associated with muscle fiber structure labeled C?

Cytoplasm of a muscle fiber

Will the band labeled A shorten during muscle contraction?

True

Will the band labeled B shorten during muscle contraction?

False

Does the structure labeled C extend from M-line to M-line?

False

What proteins are found in the A band of a sarcomere?

Actin, myosin, titin, troponin, and tropomyosin

What event must occur at the sarcolemma for muscle contraction to begin?

Acetylcholine binding and opening of sodium channels

Which types of muscle tissues exhibit autorhythmicity?

Cardiac and smooth

Which type of muscle fiber is isolated during strength training for explosive power?

Fast glycolytic fibers

What changes occur in muscle fiber types after long distance runs?

Fast glycolytic fibers into fast oxidative glycolytic fibers

What type of muscle fiber does bodybuilding increase in size and strength?

Fast glycolytic fibers

Which of the following does strength training NOT positively impact?

Decreasing amount of time for lactic acid to be produced in the muscle

What is the best way to increase flexibility of muscles before a workout?

Stretching may cause injury to a cold muscle and won't increase flexibility of muscles.

From which embryonic layer are most muscles of the body derived?

Mesoderm.

What are paired, cube-like structures that give rise to the skeletal muscles of the thoracic and abdominal walls?

Somites.

Is age associated muscle decline reversible?

False.

Which type of muscle develops from mesodermal cells that envelope the developing gastrointestinal tract?

Smooth muscle.

Which group of muscles usually weaken first in individuals over 65?

Muscles of the lower limb.

What does acetylcholinesterase do?

It breaks down acetylcholine.

Which protein is the main component of thick filaments in muscle tissue?

Myosin.

What is the correct organization of skeletal muscle from largest to smallest?

Skeletal muscle, muscle fascicle, muscle fiber, myofibril, myofilament.

What occurs in excitation-contraction coupling when an action potential travels along a T-tubule?

The release of Ca2+ into the sarcoplasm.

What might a patient experience if they have never received the tetanus vaccine and are infected?

Rigidity of the muscles leading to difficulty breathing.

What type of muscle contraction occurs when lifting a weight during bicep curls?

Concentric isotonic contraction.

What type of muscle contraction is holding a book with an outstretched arm?

Isometric contraction.

Which of the following is NOT a characteristic of muscular dystrophy?

Mostly affects females.