Chapter 9 Quiz and Test
What would occur if a contracting muscle became totally depleted of ATP? The muscle would relax and lengthen because of an inability to sustain actin-myosin cross bridges. The muscle would exhibit isotonic contraction. The muscle would remain in a contracted state because of an inability to break actin-myosin cross bridges. The muscle would exhibit isometric contraction.
The muscle would remain in a contracted state because of an inability to break actin-myosin cross bridges. wrong answer feedback:ATP is needed to break actin-myosin cross bridges. If these bridges are not broken, the muscle remains in a contracted state.
The thin myofilaments of skeletal muscle are composed chiefly of __________. troponin tropomyosin actin myosin
actin wrong answer feedback:Thick filaments are composed primarily of the protein myosin; thin filaments are composed primarily of the protein actin.
The sequence of electrical changes that occurs along the sarcolemma when a muscle fiber is stimulated is known as the __________. action potential receptor potential motor end plate potential resting membrane potential generator potential
action potential An action potential is the result of a predictable sequence of electrical changes that occurs along the length of the sarcolemma.
Where does 95% of the energy needed for contraction come from during moderate exercise? creatine phosphate anaerobic glycolysis lactic acid aerobic respiration
aerobic respiration right answer feedback:Aerobic respiration provides 95% of energy during moderate exercise.
The most efficient means of producing ATP for muscle contraction is __________. aerobic respiration lactic acid formation anaerobic respiration anaerobic glycolysis
aerobic respiration wrong answer feedback:Under aerobic conditions, muscle cells can carry out aerobic respiration, which is the most efficient metabolic pathway for ATP production. Under anaerobic conditions (oxygen deficient conditions), most of the pyruvic acid produced in glycolysis will be converted to lactic acid to ensure that the muscle cell maintains a supply of ATP. While lactic acid can subsequently be used by some cells to make ATP, the process is not efficient; ATP yields per glucose molecule are extremely low in anaerobic glycolysis.
Which of the following is FALSE regarding smooth muscle? Smooth muscle tends to be organized in sheets. Contraction of smooth muscle is regulated by the autonomic nervous system. Smooth muscle is not striated. Once damaged, smooth muscle is unable to regenerate.
Once damaged, smooth muscle is unable to regenerate. wrong answer feedback:Smooth muscle is not striated in appearance, because it lacks sarcomeres. Additionally, smooth muscle tends to be organized in sheets. These sheets are present in all but the smallest blood vessels and in the walls of hollow organs of the respiratory, digestive, reproductive, and urinary systems. The alternating contraction and relaxation of these layers is regulated by the autonomic nervous system. Thus, smooth muscle contraction is under involuntary control. Unlike cardiac and skeletal muscle, smooth muscle is regenerative.
Which of the following is NOT a characteristic of skeletal muscle contraction? It can perform both anaerobic and aerobic metabolism. It can contract for long periods of time without tiring. It contracts rapidly. It can exert tremendous power.
It can contract for long periods of time without tiring. right answer feedback:Skeletal muscle tires easily.
Which of the following is present in muscle cells but absent in most other cell types? Muscle cells have myoglobin; most other cells do not. Muscle cells have a nucleus; most other cells do not. Muscle cells have mitochondria; most other cells do not. Muscle cells use ATP to do work; most other cells do not.
Muscle cells have myoglobin; most other cells do not. wrong answer feedback:Myoglobin is a pigment found in muscle cells. It allows muscle cells to store oxygen.
The final "go" signal for skeletal muscle contraction is __________. a decrease in extracellular calcium ion levels an increase in extracellular calcium ion levels a decrease in intracellular calcium ion levels an increase in intracellular calcium ion levels
an increase in intracellular calcium ion levels wrong answer feedback:A short-lived rise in intracellular calcium ion levels (Ca2+) is the final trigger for contraction of skeletal muscle.
Acetylcholinesterase __________. activates acetylcholine is another name for acetylcholine breaks down acetylcholine helps acetylcholine bind to its receptor
breaks down acetylcholine wrong answer feedback:After acetylcholine binds to its receptor, its effects are quickly stopped when it is enzymatically broken down by acetylcholinesterase.
What is the cause of rigor mortis? breakdown of protein in the cell after death high levels of sodium in the cell after death diffusion of potassium out of the cell after death calcium influx into the sarcoplasm after death
calcium influx into the sarcoplasm after death right answer feedback:Calcium influx into the cell after death promotes the formation of myosin cross bridges and stiffening of muscles after death, which is known as rigor mortis.
Which one of the following binds calcium ions in a smooth muscle, causing contraction? troponin actin myosin tropomyosin calmodulin
calmodulin right answer feedback:Calmodulin causes smooth muscle contractions. Question19 Question 19:
All of the following terms refer to the ability to receive and respond to a stimulus EXCEPT __________. responsiveness excitability contractility irritability
contractility right answer feedback:Contractility is the ability of a muscle to shorten forcibly when adequately stimulated.
Which of the following allows recoil of the muscle fiber when contraction ends? myosin actin troponin elastic filaments tropomyosin
elastic filaments right answer feedback:Elastic filaments maintain the organization of the A band and provide for elastic recoil when muscle contraction ends.
An entire skeletal muscle is surrounded by __________. tendon sheath endomysium epimysium sarcolemma perimysium
epimysium right answer feedback:Perimysium surrounds bundles of fibers (fasciculi), and endomysium surrounds each fiber. The entire muscle is surrounded by epimysium.
Duchenne muscular dystrophy is more common in females than in males. True False
false wrong answer feedback:Since Duchenne muscular dystrophy is inherited as an X-linked recessive trait, the disease tends to affect males more frequently than females.
Muscle cells initiate nerve impulses
false wrong answer feedback:While muscles can respond to nerve impulses and conduct impulses once stimulated, they do not initiate them. Neurons are responsible for initiating nerve impulses.
Which type of skeletal muscle contains abundant quantities of glycogen? fast glycolytic fibers fast oxidative fibers slow oxidative fibers slow glycolytic fibers
fast glycolytic fibers right answer feedback:Glycogen stores are abundant in fast glycolytic fibers.
Match the muscle fiber to the appropriate characteristic. Using the drop-down menus, match each numbered item on the left with a lettered item on the right. fast glycolytic muscle fiber fast oxidative muscle fiber slow oxidative muscle fiber fatigue resistant moderately fatigue resistant fatigues quickly
fast glycolytic muscle fiber --> fatigues quickly fast oxidative muscle fiber --> moderately fatigue resistant slow oxidative muscle fiber --> fatigue resistant
Which of the following substances increases in quantity during repetitive muscle contraction during oxygen deficit? lactic acid glucose adenosine triphosphate (ATP) oxygen creatine phosphate
lactic acid right answer feedback:ATP, CP, glucose, and oxygen all decrease during muscle contraction.
A motor neuron along with all the muscle fibers it supplies is called a(n) __________. neuromuscular junction axon terminal motor unit motor end plate synaptic cleft
motor unit right answer feedback:A motor unit is a nerve-muscle functional unit, with a motor neuron supplying all the muscle fibers within the motor unit.
Which of the following is thought to be an autoimmune disease of acetylcholine receptors? myotonic dystrophy fibromyalgia muscular dystrophy myasthenia gravis
myasthenia gravis right answer feedback:Myasthenia gravis is thought to be an autoimmune disease of the acetylcholine receptors on the skeletal muscle cell because antibodies that destroy these receptors can be detected in the patients.
In the sliding filament model of muscle contraction, the myofilaments slide over each other, resulting in the overlapping of actin and __________. actin tropomyosin troponin myosin thin filaments
myosin
Myofilament cross bridges form when which two structures bond? myosin tails and myosin heads myosin heads and globular actin globular actin and troponin troponin and tropomyosin
myosin heads and globular actin right answer feedback:The bonds between the globular heads of thick filaments (myosin) and the globular protein actin are responsible for the formation of cross bridges between the thick and thin filaments.
The alternating contraction and relaxation of opposing layers of smooth muscle is referred to as __________. peristalsis isometric contraction isotonic contraction automatic contraction
peristalsis right answer feedback:Peristalsis is the term used to describe the squeezing action produced when opposing layers of smooth muscle alternate contraction and relaxation.
Each skeletal muscle fiber is controlled by a neuron at a single __________. sarcomere varicosity synaptic knob neuromuscular junction transverse tubule
neuromuscular junction right answer feedback:The axon of each motor neuron divides as it enters the muscle, and each of these axonal endings forms a branching neuromuscular junction with a single muscle fiber. As a rule, each muscle fiber has only one neuromuscular junction.
The refractory period in which the muscle will NOT contract if stimulated occurs during __________ of the muscle cell. depolarization hyperpolarization polarization repolarization
repolarization right answer feedback:The refractory period occurs during repolarization.
The functional unit of contraction in a skeletal muscle fiber is the __________. sarcolemma myofilament myofibril sarcomere sarcoplasmic reticulum
sarcomere A sarcomere is the smallest contractile unit of a skeletal muscle fiber.
Myofibrils are composed of repeating contractile elements called __________. myofilaments actin myosin sarcomeres
sarcomeres wrong answer feedback:Myofibrils are composed of repeating contractile units called sarcomeres. Sarcomeres are composed of myofilaments, which are made up of contractile proteins, myosin and actin.
Which of the following muscle types is/are both voluntary and striated? skeletal muscle only cardiac muscle only cardiac muscle and skeletal muscle smooth muscle only Question2 Question 2:
skeletal muscle only wrong answer feedback:Skeletal muscle is striated and under voluntary control. Cardiac muscle is striated and under involuntary control. Smooth muscle is not striated and it is under involuntary control.
The space between the axon terminus of the neuron and the sarcolemma of the muscle fiber is the __________. synaptic knob motor unit M line synaptic cleft motor end plate
synaptic cleft right answer feedback:The axonal terminus and the muscle fiber do not actually touch and remain separated by a space called the synaptic cleft, which is filled with a gel-like substance rich in glycoprotein.
Which of the following best describes the composition of the structure known as a triad in a skeletal muscle fiber? terminal cisterna, transverse tubule, and terminal cisterna actin, troponin, and tropomyosin A band, I band, and H band ATP, CP, and glycogen sarcolemma, sarcoplasm, and sarcoplasmic reticulum
terminal cisterna, transverse tubule, and terminal cisterna right answer feedback:The triad refers to a set of three membranous channels and is formed by a single transverse tubule and two terminal cisternae, which are elements of the sarcoplasmic reticulum.
Which of the following characteristics is unique to smooth muscle? presence of gap junctions presence of sarcoplasmic reticulum the absence of striations the ability of ATP to energize the sliding process
the absence of striations right answer feedback:Only smooth muscle is non-striated.
Which of the following statements is INCORRECT? The contractions of skeletal muscles pull on tendons and move elements of the skeleton. Skeletal muscles support the weight of some internal organs. Skeletal muscles are responsible for the pumping action of the heart. Skeletal muscle contractions help maintain body temperature. Smooth muscles form valves regulating the passage of substances through internal openings of the digestive and urinary tracts.
Skeletal muscles are responsible for the pumping action of the heart. right answer feedback:Cardiac muscle is responsible for the pumping action of the heart.
What is the ion released from the terminal cisternae that combines with troponin and removes the blocking action of tropomyosin, resulting in the formation of cross bridges? Na+ H+ K+ Cl- Ca2+
Ca2+ right answer feedback:Ca2+ combines with troponin, causing troponin to change shape which removes the blocking action of tropomyosin, allowing cross bridges to form.
Which of the following does NOT occur during skeletal muscle contraction? The I bands shorten, and H zones disappear. Calcium concentration in the sarcoplasm increases. Myosin heads bind to actin. ATP is hydrolyzed. Calcium binds to myosin heads.
Calcium binds to myosin heads right answer feedback:Increase of hemoglobin concentration in muscle fibers is not a process that occurs during muscle contraction.
Which of the following statements is FALSE? During contraction, thin filaments slide past thick filaments so that actin and myosin filaments overlap. During contraction, thin filaments slide past thick filaments so that actin and myosin filaments do not overlap. During contraction, the distance between Z discs of a sarcomere decreases. During contraction, actin-myosin cross bridges form.
During contraction, thin filaments slide past thick filaments so that actin and myosin filaments do not overlap. wrong answer feedback:The sliding filament model of contraction states that during contraction, thin filaments slide past thick filaments so that actin and myosin filaments overlap to a greater degree than in a relaxed muscle fiber. When the muscle relaxes, the thick and thin filaments overlap only at the ends of the A band. The sliding of the filaments is accomplished by the formation of actin-myosin cross bridges. As the sliding occurs, Z discs of the sarcomere are brought closer together.
Which of the following statements about smooth muscle is true? Fibers are small and spindle-shaped. Smooth muscle is striated and involuntary. Contractions are rapid and forceful. It has branching fibers. Nuclei are peripherally located in the fibers.
Fibers are small and spindle-shaped. Smooth muscle fibers are small and spindle-shaped. Cardiac muscle has branching fibers and is striated and involuntary. Skeletal muscle has peripherally located nuclei and has rapid and forceful contractions.
Choose the true statement. The final signal for contraction in smooth muscle is a rise in extracellular calcium, while the final signal for contraction in skeletal muscle is a rise in intracellular calcium. Smooth muscle depends on the calcium-calmodulin system to regulate contraction, while skeletal muscle relies on the calcium-troponin system to regulate contraction. Unlike skeletal muscle, smooth muscle does not depend on ATP to fuel contractions. Unlike skeletal muscle, contraction in smooth muscle does not involve a sliding filament mechanism.
Smooth muscle depends on the calcium-calmodulin system to regulate contraction, while skeletal muscle relies on the calcium-troponin system to regulate contraction. wrong answer feedback:Skeletal muscle and smooth muscle both employ a sliding filament mechanism for contraction, they both depend upon a rise in intracellular calcium to trigger contraction, and they both depend on ATP to fuel contraction. Unlike skeletal muscle, smooth muscle depends on the calcium-calmodulin system to regulate contraction. Skeletal muscle utilizes a calcium-troponin regulation mechanism.
The __________ are inward invaginations of the sarcolemma that run deep into the cell and ensure that every myofibril in the muscle fiber contracts at virtually the same time. T tubules thin filaments Z discs A bands
T tubules wrong answer feedback:T tubules are continuations of the sarcolemma; they conduct impulses to the deepest regions of the muscle cell and to every sarcomere. Thus, T tubules serve as a communication network coordinating the contraction of each myofibril that makes up the muscle fiber.
During the phase of excitation-contraction coupling of skeletal muscle, what occurs immediately after the action potential spreads down the T tubule? The sarcoplasmic reticulum releases calcium. The cross bridge forms. The power stroke takes place. Acetylcholine is released from the axon terminus.
The sarcoplasmic reticulum releases calcium. right answer feedback:Transmission of the action potential along the T tubules of the triads causes the voltage-sensitive tubule proteins of the sarcoplasmic reticulum to change shape, releasing calcium into the cytosol.
Properly controlled skeletal muscle contractions produced by changing the frequency of stimulation and the strength of stimulation are referred to as __________. wave summation multiple motor unit summation graded muscle responses muscle
graded muscle responses wrong answer feedback:The response of a motor unit to a single action potential of its motor neuron is called a muscle twitch. Muscle twitches are single jerking contractions. However, skeletal muscles normally respond to stimulation in a controlled and smooth manner. The variation needed in skeletal muscle contraction in order to have controlled movement is called a graded muscle response. The term wave summation describes how a muscle response changes with respect to changes in stimulus frequency. The term multiple motor unit summation describes how a muscle response changes with respect to changes in stimulus strength.
Myoglobin __________. is an oxygen-storage molecule activates myosin kinase in smooth muscle contraction is a sugar-storage molecule is released into the sarcoplasm by the sarcoplasmic reticulum is a byproduct of glycolysis
is an oxygen-storage molecule right answer feedback:Myoglobin is a red pigment that provides oxygen for cellular respiration in skeletal muscle fibers.
The type of muscle contraction in which the muscle fibers produce increased tension although the muscle neither shortens nor lengthens is called __________. treppe isometric isotonic concentric tetany
isometric right answer feedback:Muscles that maintain upright posture are contracting isometrically.
If a muscle is applied to a load that exceeds the muscle's maximum tension, __________. the contraction is isotonic the muscle length will shorten during contraction the muscle length will not change during contraction the load will be moved by the contraction
the muscle length will not change during contraction wrong answer feedback:Isometric contraction does not lead to load movement. In contrast, isotonic contractions will result in load movement. In isometric contractions, tension may build to the muscle's peak tension-producing capacity, but the muscle does not lengthen or shorten. In isotonic contractions, the muscle will shorten.
Which of the following muscles is voluntary? the muscle of the stomach the muscle in the wall of the urinary bladder the muscle in the wall of the heart the muscle that extends the arm at the elbow
the muscle that extends the arm at the elbow right answer feedback:The muscle that extends the arm at the elbow is skeletal muscle, and it is a voluntary muscl
When an action potential arrives at the neuromuscular junction, the most immediate result is __________. the depolarization of the sarcolemma a rise in intracellular Ca2+ levels in the muscle fiber the release of acetylcholine from the motor neuron the formation of actin-myosin cross bridges
the release of acetylcholine from the motor neuron wrong answer feedback:The first step toward generating a skeletal muscle fiber contraction is nervous stimulation of the muscle fiber. When an action potential arrives at the neuromuscular junction, acetylcholine (ACh) is released. ACh then binds to receptors on the sarcolemma of the muscle fiber. This binding event leads to depolarization of the sarcolemma. As depolarization occurs, a muscle action potential is propagated along the sarcolemma and down the T tubules. The sarcoplasmic reticulum then releases Ca2+ ions into the intracellular environment, and the Ca2+ ions bind to troponin in order to facilitate the formation of actin-myosin cross bridges.
Continued mild or partial contraction of a muscle that keeps it healthy and ready to respond is known as muscle __________. tone summation stimulation tetanus twitch Question12 Question 12:
tone right answer feedback:Muscle tone is a state of partial, sustained contraction in a muscle that results from tetanic contraction of about 10% of the muscle fibers on a rotating basis. Tetanic contraction is sustained and forceful contraction that results from high-frequency stimulation from the nervous system. A muscle twitch is a brief, maximum contraction of a muscle in response to a stimulus.
