BMS 507 - Mastering A&P Ch 10

Which of these is/are true of cardiac muscle fibers?

-Cardiac fibers branch -Cardiac fibers have a long twitch duration compared to skeletal fibers -Cardiac fibers have a single nucleus

When comparing slow muscle fibers to fast muscle fibers, slow fibers

-are rich in the red protein myoglobin -take about three times as long to reach peak tension -generate much less tension -have much smaller fiber diameters

Muscular force can be adjusted to match different loads by

-involving more muscle fibers in the contraction -recruiting larger motor units -varying the frequency of action potentials in motor neurons -recruiting more motor units

During anaerobic glycolysis,

-oxygen is not consumed -pyruvic acid is produced -ATP is produced -carbohydrate is metabolized

In rigor mortis

-sustained contractions occur -the myosin heads are attached to actin -ATP is depleted -calcium ions keep binding to troponin

Aerobic metabolism normally provides ________ percent of the ATP demands of a resting muscle cell

95

At what point during excitation contraction coupling does exocytosis play a role?

During acetylcholine release from the synaptic terminal

The area in the center of the A band that contains no thin filaments is the

H band

The region of the sarcomere that always contains thin filaments is the

I band

Which of the following best describes the term titin?

Protein that accounts for elasticity of resting muscle

A patient takes a medication that blocks ACh receptors of skeletal muscle fibers. What is this drug's effect on skeletal muscle contraction?

Reduces the muscle's ability for contraction

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

Skeletal

Which of the following types of muscle fibers are best adapted for prolonged contraction such as standing all day?

Slow fibers

What is the function of the triad?

Storage of calcium

Which of the following hormones directly stimulates growth of muscle tissue, leading to increased muscle mass?

Testosterone

Which region of the sarcomere gives rise to the structure (band or line) indicated by the arrow?

The region of the resting sarcomere that only contains thick filaments

Which of the following become connected by myosin cross-bridges during muscle contraction?

Thin filaments and thick filaments

Which of the following best describes the term Z line?

Thin filaments are anchored here

Sarcomere is best defined as ________

a repeating functional unit of striated muscle

The skeletal muscle complex known as the triad consists of

a transverse tubule and two terminal cisternae

Triggering of the muscle action potential occurs after

acetylcholine binds to chemically-gated channels in the motor end plate

Thin filaments are mostly made of the protein

actin

Creatine phosphate

acts as an energy reserve in muscle tissue

During the recovery period the body's need for oxygen is increased because

additional oxygen is required to restore energy reserves

A resting muscle generates most of its ATP by

aerobic metabolism of fatty acids

After heavy exercise, if energy reserves in a muscle are depleted, ________ occurs

an oxygen debt

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

aponeurosis

In response to action potentials arriving along the transverse tubules, the sarcoplasmic reticulum releases

calcium ions

Smooth muscle contracts when calcium binds to __________ and activates __________

calmodulin; myosin light chain kinase

Muscle tissue, one of the four basic tissue groups, consists chiefly of cells that are highly specialized for

contraction

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

endomysium

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

endomysium

The dense layer of connective tissue that surrounds an entire skeletal muscle is the

epimysium

Synaptic vesicles contain neurotransmitters that are released by ________ when the action potential arrives

exocytosis

Large-diameter, densely packed myofibrils, large glycogen reserves, and few mitochondria are characteristics of

fast fibers

In the liver, during the Cori cycle,

glucose is produced from lactic acid

Cardiac muscles cells have a sarcolemma that is more permeable to calcium, which causes them to __________

have contractions that last longer than skeletal muscle fibers

Fast fibers

have low resistance to fatigue and quick twitches

Muscle fibers differ from "typical cells" in that muscle fibers

have many nuclei

The muscle weakness of myasthenia gravis results from

loss of acetylcholine receptors in the end-plate membrane

When acetylcholine binds to receptors at the motor end plate, the sarcolemma becomes

more permeable to sodium ions

During activities requiring aerobic endurance,

most of the muscle's energy is produced in mitochondria

Receptors for acetylcholine are located on the

motor end plate

During the recovery period following exercise, all of the following are true except

muscle fibers are unable to contract

Skeletal muscle fibers are formed from embryonic cells called

myoblasts

Thick filaments are made of the protein

myosin

Cross-bridges are portions of

myosin molecules

Each skeletal muscle fiber is controlled by a motor neuron at a single

neuromuscular junction

At peak levels of muscle exertion the mitochondria can supply

only about one-third of the energy required by the muscle

Resting smooth muscle can be stretched without affecting tension development because of its __________

plasticity

The advantage of having many nuclei in a skeletal muscle fiber is the ability to

produce large amounts of muscle proteins

Fast muscle fibers can adapt to aerobic metabolism by generating more mitochondria in response to

repeated, exhaustive stimulation

After death, muscle fibers run out of ATP and calcium begins to leak from the sarcoplasmic reticulum into the sarcoplasm. This results in a condition known as

rigor mortis

The plasma membrane of a skeletal muscle fiber is called the

sarcolemma

The repeating unit of a skeletal muscle fiber is the

sarcomere

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

shortens

The structural theory that explains how a muscle fiber contracts is called the ________ theory

sliding filament

The narrow space between the synaptic terminal and the muscle fiber is the

synaptic cleft

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

tendon

The bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a(n)

tendon

An infection by the bacterium Clostridium tetani can cause the disease called

tetanus

The action potential is conducted into a skeletal muscle fiber by

transverse tubules

The complex of a transverse tubule and two adjacent terminal cisternae is known as a

triad

The protein that regulates muscle contraction by controlling the availability of active sites on actin is called

tropomyosin

At rest, active sites on the actin are blocked by

tropomyosin molecules

Active sites become exposed when calcium bind to

troponin

At rest, the tropomyosin molecule is held in place by

troponin molecules

The rapid rise and fall in force produced by a muscle fiber after a single action potential is a(n)

twitch

Each thin filament consists of

two actin protein strands coiled helically around each other

In a sarcomere, cross-bridge attachment occurs specifically in the

zone of overlap