A potential benefit of recruiting slow oxidative fibers for contraction before recruiting fast oxidative and fast glycolytic fibers might be ________.
A. to allow for fine control with delicate contractile force with a small stimulus
B. because they are slower to respond, slow oxidative fibers must be stimulated first in order to contract simultaneously with the faster fibers
C. 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
D. 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.
Addition of more mitochondria to a muscle fiber will have the greatest effect on ________.
A. both slow and fast oxidative fibers
B. slow oxidative fibers
C. fast oxidative fibers
D. fast glycolytic fibers
Addition of more myoglobin to a muscle fiber would have the largest effect on ________.
A. fast glycolytic and fast oxidative fibers
B. fast oxidative and slow oxidative fibers
C. fast glycolytic fibers only
D. fast oxidative fibers only
After nervous stimulation stops, what prevents ACh in the synaptic cleft from continuing to stimulate contraction?
A. the tropomyosin blocking the myosin once full contraction is achieved
B. the action potential stops going down the overloaded T tubules
C. calcium ions returning to the terminal cisternae
D. acetylcholinesterase breaks apart the ACh
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?
A. acetylcholine receptors in the motor end plate
B. actin of thin filaments
C. the Na+-K+ pump
D. elastic (titin) 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?
A. voltage gated sodium channels
B. thick (myosin) filaments
C. elastic (titin) filaments
D. potassium (K+) leak channels
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?
A. thick (myosin) filaments
B. elastic (titin) filaments
C. potassium (K+) leak channels
D. acetylcholine receptors in the motor end plate
An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________.
A. the citric acid cycle
B. the electron transport chain
Approximately 80% of a muscle fiber's volume are the myofibrils. This characteristic reflects muscles ability to ________.
A. store oxygen molecules that can be used in aerobic respiration
B. produce relatively high amounts of ATP
C. produce movement through contractile force
D. generate and propagate action potential
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?
A. Muscles will respond too quickly and cause a severe tremor.
B. Curare will only affect cardiac muscle, causing fibrillations of the heart.
C. Curare will only affect muscles with ACh receptors, paralyzing them.
D. Smooth muscles will become stimulated causing quick movement of nutrients through the digestive system.
Creatine phosphate functions in the muscle cell by ________.
A. storing energy that will be transferred to ADP to resynthesize ATP
B. forming a temporary chemical compound with myosin
C. inducing a conformational change in the myofilaments
D. forming a chemical compound with actin
During development embryonic cells will fuse to form muscle fibers. This will result in ________.
A. the striations that appear in skeletal and cardiac muscle tissues
B. the coordination of nerve signals to muscle fibers
C. multinucleated muscle fibers that can extend as long as 30 centimeters
D. Interlocking of cells that can prevent the filaments from sliding
During muscle contraction, myosin cross bridges attach to which
A. actin filaments
B. myosin filaments
C. Z discs
D. thick filaments
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 ________.
A. lactic acid
B. stearic acid
C. hydrochloric acid
D. a strong base
Exhaustion of glycogen storage within a muscle fiber would have the biggest effect on ________.
A. both slow and fast oxidative fibers
B. fast glycolytic fibers
C. fast oxidative fibers
D. slow oxidative fibers
Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped, ________.
A. no muscle tension could be generated
B. maximum force production would result because the muscle has a maximum range of travel
C. ATP consumption would increase because the sarcomere is "trying" to contract
D. cross bridge attachment would be optimum because of all the free binding sites on actin
If 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?
A. Myosin would be able to bind to the exposed binding sites on thin filaments but it would not be able to detach.
B. The fiber would twitch uncontrollably due to excessive calcium bound to troponin.
C. Calcium would be transported to the sarcoplasmic reticulum therefore contractions would cease.
D.No change would occur in a muscle that was relaxed to begin with.
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?
A. slow oxidative fibers
B. fast oxidative fibers
C. both fast glycolytic and fast oxidative fibers
D. fast glycolytic fibers
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.
In an isotonic contraction, the muscle ________.
A. rapidly resynthesizes creatine phosphate and ATP
B. never converts pyruvate to lactate
C. changes in length and moves the "load"
D. does not change in length but increases tension
Most skeletal muscles contain ________.
A. a predominance of fast oxidative fibers
B. a mixture of fiber types
C. muscle fibers of the same type
D. a predominance of slow oxidative fibers
Muscle tone is ________.
A. the ability of a muscle to efficiently cause skeletal movements
B. the feeling of well-being following exercise
C. the condition of athletes after intensive training
D. a state of sustained partial contraction
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?
A. seizures and uncontrollable muscle movement
B. coma and loss of voluntary muscle movement
C. dehydration with headache
D. weakness of muscle
A. is a protein involved in the direct phosphorylation of ADP
B. produces the end plate potential
C. breaks down glycogen
D. stores oxygen in muscle cells
Of the following items listed below, which is the best description for why skeletal muscle stores glycogen?
A. The glycogen is an insulating layer that helps regulate body temperature.
B. Glycogen is part of muscles rigid supporting framework.
C. Glycogen provides a smooth surface for filaments to slide on.
D. Skeletal muscle is a heavy consumer of energy.
Of the following muscle types, which has the longest muscle cells and has obvious stripes called striations?
A. multiunit smooth muscle
B. skeletal muscle
C. cardiac muscle
D. visceral smooth muscle
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?
A. skeletal muscle
B. striated muscle
C. smooth muscle
D. cardiac muscle
Reduction in blood flow to a muscle fiber would have the greatest effect on ________.
A. fast glycolytic
B. fast oxidative fibers
C. slow oxidative fibers
D. both slow and fast oxidative
Rigor mortis occurs because ________.
A. sodium ions leak into the muscle causing continued contractions
B. the cells are dead
C. proteins are beginning to break down, thus preventing a flow of calcium ions
D. no ATP is available to release attached actin and myosin molecules
Sarcomeres are functional units of ________ muscle.
D. B and C only
Smooth muscle is characterized by all of the following EXCEPT ________.
A. there are noncontractile intermediate filaments that attach to dense bodies within the cell
B. there are no sarcomeres
C. there are more thick filaments than thin filaments
D. it appears to lack troponin
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?
A. Since the exercise was mostly aerobic exercise, the runners' bodies have not yet realized the run is over.
B. The runners' fast oxidative muscles are so slow to utilize oxygen, they only begin aerobic respiration by the time the run has finished.
C. Slow oxidative fibers are recruited last and have only started to work at completion of the run.
D. The runners' use of stored oxygen, glucose, and creatine phosphate is being replenished and this requires a prolonged increase of oxygen intake.
The ability of muscle to shorten forcibly when adequately stimulated is known as ________, and sets muscle apart from other tissue types.
The contractile units of skeletal muscles are ________.
A. T tubules
The mechanism of contraction in smooth muscle is different from skeletal muscle in that ________.
A. actin and myosin interact by the sliding filament mechanism
B. ATP energizes the sliding process
C. the site of calcium binding site differs
D. the trigger for contraction is a rise in intracellular calcium
The oxygen-binding protein found in muscle cells is ________.
The sliding filament model of contraction involves ________.
A. actin and myosin sliding past each other and partially overlapping
B. the Z discs sliding over the myofilaments
C. actin and myosin lengthening in order to slide past each other
D. the shortening of thick filaments so that thin filaments slide past
The strongest muscle contractions are normally achieved by ________.
A. increasing stimulus above the treppe stimulus
B. increasing the stimulation up to the maximal stimulus
C. increasing stimulus above the threshold
D. recruiting small and medium muscle fibers
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?
A. One subunit binds tropomyosin and helps position it on actin.
B. One subunit binds to calcium ions.
C. One subunit attaches troponin to actin.
D. One subunit binds to potassium ions.
What does excess postexercise oxygen consumption represent?
A. amount of oxygen needed for aerobic activity to accomplish the same amount of work
B. the amount of oxygen taken into the body immediately after the exertion
C. the amount of oxygen equal to the oxygen already used
D. the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used
What is the functional role of the T tubules?
A. enhance cellular communication during muscle contraction
B. synthesize ATP to provide energy for muscle contraction
C. hold cross bridges in place in a resting muscle
D. stabilize the G and F actin
What is the most distinguishing characteristic of muscle tissue?
A. It is composed of multiple cells working together.
B. the ability to respond to nervous stimulation
C. its cells' inability to reproduce by mitosis
D. the ability to transform chemical energy into mechanical energy to move the body
What is the primary function of wave summation?
A. prevent muscle fatigue
B. produce smooth, continuous muscle contraction
C. prevent muscle relaxation
D. increase muscle tension
What is the role of tropomyosin in skeletal muscles?
A. Tropomyosin is the receptor for the motor neuron
B. Tropomyosin serves as a contraction inhibitor by blocking the actin binding sites on the myosin molecules.
C. Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.
D. Tropomyosin is the chemical that activates the myosin heads.
What part of the sarcolemma contains acetylcholine receptors?
A. motor end plate
B. end of the muscle fiber
C. part adjacent to another muscle cell
D. any part of the sarcolemma
What structure in skeletal muscle cells functions in calcium storage?
B. sarcoplasmic reticulum
C. intermediate filament network
D. myofibrillar network
When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods?
A. relaxation period
B. refractory period
C. fatigue period
D. latent period
When a sarcomere contracts and thin filaments move over thick filaments you would expect to see ________.
A. the H zone to appear wider
B. the A band to appear darker
C. the I bands to appear smaller
D. the I bands to appear wider
Which muscle cells have the greatest ability to regenerate?
D. no muscle can regenerate
Which of the following describes the cells of unitary smooth muscle?
A. They exhibit spontaneous action potentials.
B. They consist of muscle fibers that are structurally independent of each other.
C. They depend upon recruitment using the autonomic nervous system.
D. They are used for vision and hair raising.
Which of the following is a factor that affects the velocity and duration of muscle contraction?
A. number of muscle fibers stimulated
B. load on the fiber
C. size of the muscle fibers stimulated
D. muscle length
Which of the following is the correct order for the phases of a muscle twitch?
A. contraction, relaxation, latent
B. relaxation, contraction, latent
C. latent, relaxation, contraction
D. latent, contraction, relaxation
Which of the following is the correct sequence of events for muscle contractions?
A. motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments
B. neurotransmitter release, motor neuron action potential, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke
C. muscle cell action potential, neurotransmitter release, ATP- driven power stroke, calcium ion release from SR, sliding of myofilaments
D. neurotransmitter release, muscle cell action potential, motor neuron action potential, release of calcium ions from SR, sliding of myofilaments, ATP-driven power stroke
Which of the following is true about smooth muscle?
A. Smooth muscle, in contrast to skeletal muscle, cannot synthesize or secrete any connective tissue elements.
B. Certain smooth muscle cells can actually divide to increase their numbers.
C. Smooth muscle has well-developed T tubules at the site of invagination.
D. Smooth muscle cannot stretch as much as skeletal muscle.
Which of the following statements best illustrates the fact that skeletal muscle is voluntary muscle?
A. The shivering reflex aids in maintaining body temperature.
B. Skeletal muscle appears striated due to the structure of the sarcomeres.
C. Skeletal muscle fibers are innervated by somatic motor neurons.
D. Skeletal muscle is wrapped in several layers of connective tissue. The deepest layer being the endomysium.
Which of the following statements is true?
Cardiac muscle cells have many nuclei.
Striated muscle cells are long and cylindrical with many nuclei. Smooth muscle cells have T tubules.
Cardiac muscle cells are found in the heart and large blood vessels.
Which of the following surrounds an individual muscle cell? A. fascicle
Which of the following would be recruited later in muscle stimulation when contractile strength increases?
A. motor units with larger, less excitable neurons
B. many small motor units with the ability to stimulate other motor units
C. large motor units with small, highly excitable neurons
D. motor units with the longest muscle fibers