Ch. 9

The contractile units of skeletal muscles are ________. microtubules mitochondria T tubules myofibrils

myofibrils

The oxygen-binding protein found in muscle cells is ________. immunoglobin ATP hemoglobin myoglobin

myoglobin

Muscle tone is ________. the ability of a muscle to efficiently cause skeletal movements he feeling of well-being following exercise a state of sustained partial contraction the condition of athletes after intensive training

a state of sustained partial contraction

Muscle contraction will always promote movement of body parts regardless of how they are attached. True False

False

Once a motor neuron has fired, all the muscle fibers in a muscle contract. True False

False

During isometric contraction, the energy used appears as movement. True False

False

Troponin, a major protein in thin filaments, is a globular protein with three polypeptide subunits. Which of the following is NOT a function of the troponin? One subunit binds tropomyosin and helps position it on actin. One subunit attaches troponin to actin. One subunit binds to potassium ions. One subunit binds to calcium ions.

One subunit binds to potassium ions.

The alternating contraction and relaxation of the longitudinal and circular layers mixing substances in the lumen and squeezing them through an organ's internal pathway is characteristic of smooth muscle. True False

True

Most skeletal muscles contain ________. a predominance of slow oxidative fibers a mixture of fiber types a predominance of fast oxidative fibers muscle fibers of the same type

a mixture of fiber types

Although all the anatomical parts of muscle work together to give it it's characteristics, which of the following proteins listed below would be most associated with the characteristics of excitability? elastic (titin) filaments the Na+-K+ pump acetylcholine receptors in the motor end plate actin of thin filaments

acetylcholine receptors in the motor end plate

During muscle contraction, myosin cross bridges attach to which active sites? actin filaments myosin filaments Z discs thick filaments

actin filaments

Sarcomeres are functional units of ________ muscle. smooth skeletal cardiac cardiac and skeletal only

cardiac and skeletal only

Addition of more myoglobin to a muscle fiber would have the largest effect on ________. fast glycolytic and fast oxidative fibers fast oxidative fibers only fast glycolytic fibers only fast oxidative and slow oxidative fibers

fast oxidative and slow oxidative fibers

The strongest muscle contractions are normally achieved by ________. increasing the stimulation up to the maximal stimulus a single stimulus above the threshold recruiting small and medium muscle fibers increasing stimulus above the threshold

increasing the stimulation up to the maximal stimulus

What part of the sarcolemma contains acetylcholine receptors? motor end plate end of the muscle fiber any part of the sarcolemma part adjacent to another muscle cell

motor end plate

During vigorous exercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to ________. stearic acid a strong base lactic acid hydrochloric acid

lactic acid

When a muscle fiber contracts, the I bands diminish in size, the H zones disappear, and the A bands do not diminish in length. True False

True

Of the following muscle types, which has the longest muscle cells and has obvious stripes called striations? skeletal muscle multiunit smooth muscle visceral smooth muscle cardiac muscle

skeletal muscle

Addition of more mitochondria to a muscle fiber will have the greatest effect on ________. both slow and fast oxidative fibers fast oxidative fibers slow oxidative fibers fast glycolytic fibers

slow oxidative fibers

The mechanism of contraction in smooth muscle is different from skeletal muscle in that ________. the site of calcium binding site differs actin and myosin interact by the sliding filament mechanism ATP energizes the sliding process the trigger for contraction is a rise in intracellular calcium

the site of calcium binding site differs

Which of the following is true about smooth muscle? Certain smooth muscle cells can actually divide to increase their numbers. Smooth muscle, in contrast to skeletal muscle, cannot synthesize or secrete any connective tissue elements. Smooth muscle cannot stretch as much as skeletal muscle. Smooth muscle has well-developed T tubules at the site of invagination.

Certain smooth muscle cells can actually divide to increase their numbers.

Curare is a poisonous plant extract. Curare molecules have a chemical structure like the neurotransmitter ACh. Curare can bind to the ACh receptor site on the chemically gated ion channels in the motor end plate. Even though curare will bind to the receptor site it will not open the ion channel and no ions will pass through. What do you think the symptoms of curare poisoning would look like? Muscles will respond too quickly and cause a severe tremor. Curare will only affect muscles with ACh receptors, paralyzing them. Curare will only affect cardiac muscle, causing fibrillations of the heart. Smooth muscles will become stimulated causing quick movement of nutrients through the digestive system.

Curare will only affect muscles with ACh receptors, paralyzing them.

The thin filaments (actin) contain a polypeptide subunit G actin that bears active sites for myosin attachment. True False

True

a muscle fiber were to suddenly and permanently stop producing ATP the fiber would no longer be able to actively transport calcium out of the cytoplasm (sarcoplasm) and the intracellular calcium concentration would rise. Which of the following would you expect to happen? The fiber would twitch uncontrollably due to excessive calcium bound to troponin. Calcium would be transported to the sarcoplasmic reticulum therefore contractions would cease. Myosin would be able to bind to the exposed binding sites on thin filaments but it would not be able to detach. No change would occur in a muscle that was relaxed to begin with.

Myosin would be able to bind to the exposed binding sites on thin filaments but it would not be able to detach.

Which of the following statements is true? Cardiac muscle cells are found in the heart and large blood vessels. Skeletal muscle cells are long and cylindrical with many nuclei. Smooth muscle cells have T tubules. Cardiac muscle cells have many nuclei.

Skeletal muscle cells are long and cylindrical with many nuclei.

Which of the following statements best illustrates the fact that skeletal muscle is voluntary muscle? Skeletal muscle appears striated due to the structure of the sarcomeres. Skeletal muscle is wrapped in several layers of connective tissue. The deepest layer being the endomysium. Skeletal muscle fibers are innervated by somatic motor neurons. The shivering reflex aids in maintaining body temperature.

Skeletal muscle fibers are innervated by somatic motor neurons.

Of the following items listed below, which is the best description for why skeletal muscle stores glycogen? Skeletal muscle is a heavy consumer of energy. Glycogen is part of muscles rigid supporting framework. The glycogen is an insulating layer that helps regulate body temperature. Glycogen provides a smooth surface for filaments to slide on.

Skeletal muscle is a heavy consumer of energy.

The force of muscle contraction is controlled by multiple motor unit summation or recruitment. True False

True

The 100-meter dash is a quick and short run requiring explosive speed. On completion of the dash, the runners will continue to breathe hard for several seconds to minutes even though they are no longer running. Which of the following is the best explanation for why this is so? The runners' fast oxidative muscles are so slow to utilize oxygen, they only begin aerobic respiration by the time the run has finished. The runners' use of stored oxygen, glucose, and creatine phosphate is being replenished and this requires a prolonged increase of oxygen intake. Slow oxidative fibers are recruited last and have only started to work at completion of the run. Since the exercise was mostly aerobic exercise, the runners' bodies have not yet realized the run is over.

The runners' use of stored oxygen, glucose, and creatine phosphate is being replenished and this requires a prolonged increase of oxygen intake.

Which of the following describes the cells of unitary smooth muscle? They exhibit spontaneous action potentials. They depend upon recruitment using the autonomic nervous system. They consist of muscle fibers that are structurally independent of each other. They are used for vision and hair raising.

They exhibit spontaneous action potentials.

What is the role of tropomyosin in skeletal muscles? Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules. Tropomyosin is the chemical that activates the myosin heads. Tropomyosin is the receptor for the motor neuron neurotransmitter. Tropomyosin serves as a contraction inhibitor by blocking the actin binding sites on the myosin molecules.

Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.

A contraction in which the muscle does not shorten but its tension increases is called isometric contraction. True False

True

A skeletal muscle contracts with varying force and length of time in response to the body's needs at the time. True False

True

Although there are no sarcomeres, smooth muscle still possesses thick and thin filaments. True False

True

An increase in the calcium ion level in the sarcoplasm starts the sliding of the thin filaments. When the level of calcium ions declines, sliding stops. True False

True

Cardiac muscle has a limited regenerative capacity. True False

True

Cells of unitary smooth muscle are found in the longitudinal and circular muscle layers of the intestine. True False

True

Excitability is the ability of a cell to receive and respond to stimulus by changing its membrane potential. True False

True

Muscle cells store more creatine phosphate than ATP resulting in the muscle having a reserve source of energy. True False

True

Muscle tone is the small amount of tautness or tension in the muscle due to weak, involuntary contractions of its motor units. True False

True

One of the functions of skeletal muscle contraction is production of heat. True False

True

Smooth muscles relax when intracellular Ca2+ levels drop but may not cease contractions. True False

True

The effect of a neurotransmitter on the muscle cell membrane is to modify its ion permeability properties temporarily. True False

True

After nervous stimulation stops, what prevents ACh in the synaptic cleft from continuing to stimulate contraction? the action potential stops going down the overloaded T tubules calcium ions returning to the terminal cisternae acetylcholinesterase breaks apart the ACh the tropomyosin blocking the myosin once full contraction is achieved

acetylcholinesterase breaks apart the ACh

The sliding filament model of contraction involves ________. the Z discs sliding over the myofilaments actin and myosin sliding past each other and partially overlapping actin and myosin lengthening in order to slide past each other the shortening of thick filaments so that thin filaments slide past

actin and myosin sliding past each other and partially overlapping

In an isotonic contraction, the muscle ________. does not change in length but increases tension changes in length and moves the "load" never converts pyruvate to lactate rapidly resynthesizes creatine phosphate and ATP

changes in length and moves the "load"

The ability of muscle to shorten forcibly when adequately stimulated is known as ________, and sets muscle apart from other tissue types. elasticity excitability extensibility contractilit

contractilit

Although all the anatomical parts of muscle work together to give it its characteristics, which of the following proteins listed below would be most associated with the characteristics of extensibility? potassium (K+) leak channels elastic (titin) filaments thick (myosin) filaments acetylcholine receptors in the motor end plate

elastic (titin) filaments

Which of the following surrounds an individual muscle cell? endomysium fascicle epimysium perimysium

endomysium

What is the functional role of the T tubules? hold cross bridges in place in a resting muscle stabilize the G and F actin enhance cellular communication during muscle contraction synthesize ATP to provide energy for muscle contraction

enhance cellular communication during muscle contraction

A motor neuron and all the muscle cells that it stimulates are referred to as a motor end plate. True False

false

Exhaustion of glycogen storage within a muscle fiber would have the biggest effect on ________. fast glycolytic fibers slow oxidative fibers fast oxidative fibers both slow and fast oxidative fibers

fast glycolytic fibers

An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________. the citric acid cycle the electron transport chain glycolysis hydrolysis

glycolysis

Immediately following the arrival of the stimulus at a skeletal muscle cell there is a short period called the ________ period during which the neurotransmitter is released by exocytosis, diffuses across the synaptic cleft, and binds to its receptors. refractory contraction latent relaxation

latent

Which of the following is the correct order for the phases of a muscle twitch? relaxation, contraction, latent contraction, relaxation, latent latent, contraction, relaxation latent, relaxation, contraction

latent, contraction, relaxation

Which of the following is a factor that affects the velocity and duration of muscle contraction? size of the muscle fibers stimulated load on the fiber number of muscle fibers stimulated muscle length

load on the fiber

Which of the following is the correct sequence of events for muscle contractions? neurotransmitter release, muscle cell action potential, motor neuron action potential, release of calcium ions from SR, sliding of myofilaments, ATP-driven power stroke neurotransmitter release, motor neuron action potential, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments muscle cell action potential, neurotransmitter release, ATP-driven power stroke, calcium ion release from SR, sliding of myofilaments

motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments

Which of the following would be recruited later in muscle stimulation when contractile strength increases? motor units with larger, less excitable neurons large motor units with small, highly excitable neurons motor units with the longest muscle fibers many small motor units with the ability to stimulate other motor units

motor units with larger, less excitable neurons

During development embryonic cells will fuse to form muscle fibers. This will result in ________. interlocking of cells that can prevent the filaments from sliding the striations that appear in skeletal and cardiac muscle tissues the coordination of nerve signals to muscle fibers multinucleated muscle fibers that can extend as long as 30 centimeters

multinucleated muscle fibers that can extend as long as 30 centimeters

Rigor mortis occurs because ________. no ATP is available to release attached actin and myosin molecules the cells are dead proteins are beginning to break down, thus preventing a flow of calcium ions sodium ions leak into the muscle causing continued contractions

no ATP is available to release attached actin and myosin molecules

Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped, ________. maximum force production would result because the muscle has a maximum range of travel ATP consumption would increase because the sarcomere is "trying" to contract cross bridge attachment would be optimum because of all the free binding sites on actin no muscle tension could be generated

no muscle tension could be generated

Approximately 80% of a muscle fiber's volume are the myofibrils. This characteristic reflects muscles ability to ________. produce movement through contractile force store oxygen molecules that can be used in aerobic respiration produce relatively high amounts of ATP generate and propagate action potential

produce movement through contractile force

What is the primary function of wave summation? produce smooth, continuous muscle contraction increase muscle tension prevent muscle relaxation prevent muscle fatigue

produce smooth, continuous muscle contraction

When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods? refractory period fatigue period relaxation period latent period

refractory period

What structure in skeletal muscle cells functions in calcium storage? myofibrillar network sarcoplasmic reticulum mitochondria intermediate filament network

sarcoplasmic reticulum

If given the exact same amount of ATP, which of the three fiber types would be able to contract for the longest amount of time? slow oxidative fibers fast oxidative fibers fast glycolytic fibers both fast glycolytic and fast oxidative fibers

slow oxidative fibers

Reduction in blood flow to a muscle fiber would have the greatest effect on ________. fast oxidative fibers slow oxidative fibers both slow and fast oxidative fast glycolytic

slow oxidative fibers

Which muscle cells have the greatest ability to regenerate? cardiac smooth skeletal no muscle can regenerate

smooth

Oxygen starved tissues can release chemical signals into the blood that can change the diameter of nearby blood vessels delivering oxygen and nutrients to the tissues. In doing so, the blood vessels will respond through vasodilation (widening of the vessel). Which muscle type is responsible for this vasodilation? cardiac muscle smooth muscle striated muscle skeletal muscle

smooth muscle

Myoglobin ________. is a protein involved in the direct phosphorylation of ADP breaks down glycogen produces the end plate potential stores oxygen in muscle cells

stores oxygen in muscle cells

Creatine phosphate functions in the muscle cell by ________. forming a chemical compound with actin inducing a conformational change in the myofilaments storing energy that will be transferred to ADP to resynthesize ATP forming a temporary chemical compound with myosin

storing energy that will be transferred to ADP to resynthesize ATP

When a sarcomere contracts and thin filaments move over thick filaments you would expect to see ________. the I bands to appear wider the H zone to appear wider the I bands to appear smaller the A band to appear darke

the I bands to appear smaller

What is the most distinguishing characteristic of muscle tissue? It is composed of multiple cells working together. the ability to respond to nervous stimulation the ability to transform chemical energy into mechanical energy to move the body its cells' inability to reproduce by mitosis

the ability to transform chemical energy into mechanical energy to move the body

What does excess postexercise oxygen consumption represent? amount of oxygen needed for aerobic activity to accomplish the same amount of work the amount of oxygen taken into the body immediately after the exertion the amount of oxygen equal to the oxygen already used the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used

the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used

Smooth muscle is characterized by all of the following EXCEPT ________. there are no sarcomeres there are noncontractile intermediate filaments that attach to dense bodies within the cell it appears to lack troponin there are more thick filaments than thin filaments

there are more thick filaments than thin filaments

Although all the anatomical parts of muscle work together to give it it's characteristics, which of the following proteins listed below would be most associated with the characteristics of contractility? voltage gated sodium channels thick (myosin) filaments potassium (K+) leak channels elastic (titin) filaments

thick (myosin) filaments

A potential benefit of recruiting slow oxidative fibers for contraction before recruiting fast oxidative and fast glycolytic fibers might be ________. to allow for fine control with delicate contractile force with a small stimulus because they are slower to respond, slow oxidative fibers must be stimulated first in order to contract simultaneously with the faster fibers recruiting slow oxidative fibers early helps to tire them out first so that they won't interfere with the more powerful contractions of fast glycolytic fibers There is little to no benefit from recruiting slow oxidative fibers first, and therefore it is in fact fast glycolytic fibers that will be recruited first.

to allow for fine control with delicate contractile force with a small stimulus

Myasthenia gravis is a disease that is believed to be caused by autoimmune disorder, resulting in the loss of ACh receptors at the motor end plate of muscle fibers. Which of the following is likely to be a symptom of myasthenia gravis? coma and loss of voluntary muscle movement dehydration with headache seizures and uncontrollable muscle movement weakness of muscle

weakness of muscle