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A&P CH.9 Muscles and Muscle Tissue

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In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?

A) acetylcholine (ACh)
B) dopamine
C) serotonin
D) norepinephrine
A) acetylcholine
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?

A) chemically gated calcium channels
B) voltage-gated potassium channels
C) voltage-gated calcium channels
D) voltage-gated sodium channels
C) voltage-gated calcium channels
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
Exocytosis
The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?

A) Binding causes chemically gated potassium channels to open in the motor end plate.
B) Binding causes voltage-gated sodium channels to open in the motor end plate.
C) Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate.
D) Binding causes potassium voltage-gated channels to open in the motor end plate.
C
How is acetylcholine (ACh) removed from the synaptic cleft?

A) acetylcholinesterase (AChE; an enzyme)
B) diffusion away from the synaptic cleft
C) a reuptake pump on the axon terminal
B
The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?

A) cytosol
B) sarcolemma
C) T tubule
D) terminal cisternae of the sarcoplasmic reticulum
D
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?

A) calcium ion pump
B) ATP
C) troponin
D) arrival of an action potential
D) arrival of an action potential
The binding of calcium to which molecule causes the myosin binding sites to be exposed?
(This is a regulatory molecule)
Troponin
When calcium binds to ____, _____ releases tropomysoin, exposing the myosin binding sites
troponin
A myosin head binds to which molecule to form a cross bridge?
actin
What causes the myosin head to disconnected from actin?
Binding of ATP
What energizes the power stroke?
hydrolysis of ATP
Excitation- contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process.

A) Excitation refers to the shape change that occurs in voltage-sensitive proteins in the sarcolemma.

B) Excitation refers to the propagation of action potentials along the axon of a motor neuron.

C) Excitation refers to the release of calcium ions from the sarcoplasmic reticulum.

D) Excitation refers to propagation of action potentials along the sarcolemma.
D
Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction.

A) Sodium release from the sarcoplasmic reticulum initiates the contraction

B) voltage-gated proteins change shape.

C) calcium release from the sarcoplasmic reticulum initiates the contraction

D) Action potentials propagate into the interior of the skeletal muscle fiber.
C
A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?

A) potassium leak channels
B) myosin cross-bridge binding sites
C) a series of proteins that control calcium release
D) voltage-gated sodium channels
C) a series of proteins that control calcium release
What is the name given to the regularly spaced infoldings of the sarcolemma?
Transverse or t tubules
Which of the following is most directly resposible for the coupling of excitation to contraction of skeletal muscle fibers?
Calcium ions
What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?

A) motor neurons always innervated thousands of skeletal muscle fibers
B) a motor neuron typically innervates only one skeletal muscle fiber
C) hundreds of skeletal muscle fibers are innervated by a single motor neuron
D) A skeletal muscle fiber is innervated by multiple motor neurons
C
Contraction of skeletal muscle is controlled by ___ ___
somatic motor neurons
Skeletal muscle lacks the coarse connective tissue sheaths that are found in smooth muscle?
False
Skeletal muscle fibers tend to be shorter than smooth muscle fibers?
False
Skeletal muscle cells have one nucleus, but smooth muscle cells are multinucleated?
False
Skeletal muscle fibers contain sarcomeres; smooth muscle fibers do not.
True
Myasthenia gravis is sontimes treated medically by a treatment that involves
inhibiting the action of acetylcholinesterase
Skeletal muscle cells use creatine phosphate instead of ATP to do work
False
Skeletal muscle cells have T tubules
True
Skeletal muscle cells are multinucleated
True
Skeletal muscle cells contain myoglobin
true
Skeletal muscle cells have glycosomes
True
Outter most connective tissue sheath is continuous with what?
tendon
Which muscle characteristic describes the ability of muscle to respond to a stimulus?
A) extensibility
B) contractility
C) elasticity
D) excitability
D) excitability
The response of a motor unit to a single action potential of its motor neuron is called ________.
A) a muscle twitch
B) a tetanic contraction
C) wave summation
D) recruitment
A) a muscle twitch
Which of the following factors influence the velocity and duration of muscle contraction?
A) muscle fiber size
B) frequency of stimulation
C) load placed on the muscle
D) length of muscle fibers activated
C) load placed on the muscle
The distance between Z discs ________ during muscle contraction.
A) decreases
B) increases
C) decreases and then increases
D) stays the same
A) decreases
The sliding filament model of contraction states that ________.
A) during contraction the thin myofilaments slide past the thick myofilaments so that calcium ions can be released from the sarcoplasmic reticulum
B) during contraction the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments overlap to a greater degree
C) during contraction the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments no longer overlap
D) during contraction the thin myofilaments slide past T tubules so that the Z discs are overlapping
B
A muscle that is lengthening while it produces tension is performing a(an) ________ contraction.

A) eccentric
B) isometric
C) concentric
D) maximal
A) eccentric
Binding of calcium to calmodulin is a step in excitation-contraction coupling of ________ cells.

A) skeletal muscle
B) smooth muscle
C) cardiac and visceral smooth muscle
D) cardiac muscle
B) smooth muscle
What specific neurotransmitter is released from the axonal terminus via exocytosis
acetylcholine
When muscle cells break down glucose to generate ATP under oxygen deficient conditions, they will form ________.

A) glucose
B) lactic acid
C) glycogen
D) fatty acids
B) lactic acid
The major role of the sarcoplasmic reticulum is to regulate ________.

A) intracellular levels of Na+
B) intracellular levels of Ca2+
C) extracellular levels of Ca2+
D) extracellular levels of Na+
B) intracellular levels of Ca2+
Which type of muscle CANNOT contract without being stimulated by the nervous system?

A) skeletal
B) smooth
C) visceral
D) cardiac
A) skeletal
Which pathway for regenerating ATP provides the majority of the energy used for muscle activity during 30 minutes of light to moderate exercise?

A) direct phosphorylation of ADP by creatine phosphate
B) anaerobic glycolysis
C) use of stored ATP
D)aerobic respiration
D) aerobic respiration
Which event is most significant in initiating the "wave of depolarization"?

A) diffusion of acetylcholine into the muscle fiber
B) diffusion of acetylcholine down the length of the muscle fiber
C) diffusion of K+ out of the muscle fiber
D) diffusion of Na+ into the muscle fiber
D) diffusion of Na+ into the muscle fiber
Binding of acetylcholine to its receptor opens _______ that allow Na+ and K+ to diffuse across the sarcolemma.
Chemically gated ion channels
Duchenne muscular dystrophy could theoretically be cured if a technique was developed that would _________.

A) strengthen the dystrophin proteins that are present in the patient's muscle fibers
B) double the existing number of dystrophin molecules in the patient's muscle fibers
C) strengthen the thick and thin filaments in the patient's muscle fibers
D) none of the above
D) none of the above
The A band is occupied by the entire length of _____.
thick myofilaments
Slow oxidative muscle fibers are best suited for ________.

A) lifting heavy weights at the gym
B) running a 100-yard dash
C) running a marathon
D) hitting a baseball
C) running a marathon
The first step toward generating a skeletal muscle contraction is ________.

A) binding of the myosin heads to actin
B) a rise in intracellular Ca2+ levels
C) binding of ATP to the myosin heads
D) stimulation of the muscle by a nerve ending
D
The connective tissue sheaths of skeletal muscle, in order from internal to external, are the ________.
endomysium, perimysium, and epimysium
Which muscle fiber type is best suited for endurance activities, such as long-distance jogging?

A) fast glycolytic fibers
B) fast oxidative fibers
C) slow oxidative fibers
D) slow glycolytic fibers
C) slow oxidative fibers
A fascicle is an organized group of muscle fibers bounded by a ______.
perimysium
The smallest contractile unit of a muscle fiber is ________.

A) the elastic filament
B) the myofilament
C) the sarcomere
D) troponin
C) the sarcomere
If both of the neurons were activated, more muscle fibers would contract than if either neuron alone were active. This mechanism for control of the force of muscle contraction is known as ______.
recruitment
the smallest contractile unit of a muscle fiber.
sarcomere
The force of a muscle contraction is NOT affected by __________.

A) the frequency of the stimulation
B) the size of the muscle fibers stimulated
C) the amount of ATP stored in the muscle cells
D) the number of muscle fibers stimulated
E) the degree of muscle stretch
C
What is a cross bridge cycle?

A) It is the cycle in which motor units are recruited from small to large, in order to produce gradual increases in force.
B) It is the cycle in which an energized myosin head binds to actin and performs a power stroke, then binds to ATP in order to detach and re-energize.
C) It is the cycle by which the sarcolemma is repeatedly depolarized and repolarized.
D) It is a cycle of repeated stimuli resulting in summation of muscle twitches.
B
Thick myofilaments are made of ________.
A) troponin
B) tropomyosin
C) myosin
D)actin
C) myosin
Which of the following is the smallest structural unit in which the distinctive striated bands characteristic of skeletal muscle are observed?
myofibrils
Which organelle contains the contractile elements found in skeletal muscle?
myofibrils
In a bedridden patient recovering from a badly fractured femur, disuse atrophy in the thigh muscles is caused by _________.
A) decreased ability of muscle cells to produce ATP, resulting in decreased ability of the muscles to contract
B) decreased ability to synthesize acetylcholine in the neurons that innervate the thigh muscles
C) decreased synthesis of muscle proteins and/or increased breakdown of muscle proteins
D) none of the above
C
What event directly triggers the release of neurotransmitter from the synaptic vesicle in the axon terminal

A) diffusion of K+ into the axonal terminus
B) diffusion of Na+ out of the axonal terminus
C) diffusion of Ca2+ into the axonal terminus
D) diffusion of Na+ into the axonal terminus
diffusion of Ca2+ into the axonal terminus
Which protein inhibits interaction between actin and myosin to prevent skeletal muscle contraction; and which ions remove the inhibition?

A) myosin; sodium ions
B) troponin; sodium ions
C) tropomyosin; calcium ions
D) actin; calcium ions
C) tropomyosin; calcium ions
Cross bridge formation between myosin heads and actin molecules is caused by the elevation of calcium ion concentration in the cytosol. During rigor mortis, this elevation of calcium ion concentration in the cytosol is permanent because ________.

A) mitochondria stop producing ATP molecules required by the sarcoplasmic reticulum's calcium ion pumps
B) troponin molecules bind irreversibly to calcium ions to prevent them from being removed from the cytosol
C) tropomyosin molecules bind irreversibly to calcium ions to prevent them from being removed from the cytosol
D) acetylcholine continues to stimulate the release of calcium ions from the sarcoplasmic reticulum
A
Muscle tissue does NOT ________.

A) generate heat
B) produce movement
C) produce blood cells
D) maintain posture
E) stabilize joints
C) produce blood cells
Which of the following is CORRECTLY paired?

A) smooth muscle: striated
B) cardiac muscle: nonstriated
C) cardiac muscle: voluntary control
D) skeletal muscle: voluntary control
D) skeletal muscle: voluntary control
Excitation-contraction coupling includes all EXCEPT which of the following events?

A) release of acetylcholine from axon terminals at the neuromuscular junction
B) binding of calcium ions to troponin, which removes the blocking action of tropomyosin
C) release of calcium ions from the terminal cisterns
D) propagation of an action potential along the sarcolemma and down T tubules
A
The dense connective tissue of the epimysium is continuous with the ____ that connects the muscle to a bone.
tendon
_____ marathon runner
anaerobic pathway
______ weight lifting
aerobic pathway
______ 25 meter swim
direct phosphorylation
Muscle tissue has all of the following properties except ________.
secretion
extensibility
excitability
contractility
secretion
The force of muscle contraction is controlled by multiple motor unit summation or recruitment.
true
The muscle cell membrane is called the ________.
sarcolemma
What is the functional unit of a skeletal muscle called?
sarcomere
The end of the muscle that typically moves when a muscle contracts is called the ________.
insertion
Which of the choices below does not describe how excess postexercise oxygen consumption (oxygen deficit) restores metabolic conditions?

A) converts lactic acid back into glycogen stores in the liver
B) resynthesizes creatine phosphate and ATP in muscle fibers
C) replaces the oxygen removed from myoglobin
D) increases the level of lactic acid in the muscle
D
Once a motor neuron has fired, all the muscle fibers in a muscle contract.
False
Rigor mortis occurs because ________.

A) proteins are beginning to break down, thus preventing a flow of calcium ions
B) the cells are dead
C) no ATP is available to release attached actin and myosin molecules
D) sodium ions leak into the muscle causing continued contractions
C
_____stores oxygen in muscle cells
myoglobin
The thin filaments (actin) contain a polypeptide subunit G actin that bears active sites for myosin attachment.
True
Which of the following is the correct sequence of events for muscle contractions?

A) neurotransmitter release, motor neuron action potential, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke
B) motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments
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
B
Which of the following is not a component of the standard treatment for muscle strain?
rest of the muscle
elevation of the limb
stretching of the muscle
ice on the muscle
stretching of the muscle
A contraction in which the muscle does not shorten but its tension increases is called isometric contraction.
True
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 ________.
lactic acid
Cardiac muscle has a limited regenerative capacity.
True
The sliding filament model of contraction involves ________.

A) the Z discs sliding over the myofilaments
B) the shortening of thick filaments so that thin filaments slide past
C) actin and myosin sliding past each other and partially overlapping
D) actin and myosin lengthening in order to slide past each other
C
In an isotonic contraction, the muscle ________.

A) rapidly resynthesizes creatine phosphate and ATP
B) changes in length and moves the "load"
C) never converts pyruvate to lactate
D) does not change in length but increases tension
B
What is the primary function of wave summation?
increase muscle tension
prevent muscle relaxation
produce smooth, continuous muscle contraction
prevent muscle fatigue
produce smooth, continuous muscle contraction
Excitation-contraction coupling directly requires which of the following substances?
Ca2+ only
The oxygen-binding protein found in muscle cells is ________.
myoglobin
Which of the following is not a connective tissue sheath that wraps individual muscle fibers?
perimysium
endomysium
epimysium
aponeurosis
aponeurosis
Which muscle cells have the greatest ability to regenerate?
smooth
What is the role of calcium ions in muscle contraction?

A) reestablish glycogen stores
B) increase levels of myoglobin
C) form hydroxyapatite crystals
D) bind to regulatory sites on troponin to remove contraction inhibition
D
One of the important functions of skeletal muscle contraction is production of heat.
True
A motor neuron and all the muscle cells that it stimulates are referred to as a motor end plate.
False
Only ________ muscle cells are always multinucleated.
skeletal
What is the role of tropomyosin in skeletal muscles?

A) Tropomyosin serves as a contraction inhibitor by blocking the actin binding sites on the myosin molecules.
B) Tropomyosin is the chemical that activates the myosin heads.
C) Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.
D)Tropomyosin is the receptor for the motor neuron neurotransmitter.
C
Which of the following would be recruited later in muscle stimulation when contractile strength increases?

A) many small motor units with the ability to stimulate other motor units
B) large motor units with small, highly excitable neurons
C) motor units with larger, less excitable neurons
D) motor units with the longest muscle fibers
C
Muscle contraction will always promote movement of body parts regardless of how they are attached.
False
Eccentric contractions are more forceful than concentric contractions.
True
What does excess postexercise oxygen consumption represent?

A) the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used
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) amount of oxygen needed for aerobic activity to accomplish the same amount of work
A
The giant protein titin maintains the organization of the ________ assisting in muscle stretching.
A Band
Muscle cells store more creatine phosphate than ATP resulting in the muscle having a reserve source of energy.
True
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.
Latent
Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped, ________.
cross bridge attachment would be optimum because of all the free binding sites on actin
ATP consumption would increase because the sarcomere is "trying" to contract
maximum force production would result because the muscle has a maximum range of travel
no muscle tension could be generated
no muscle tension could be generated
What structure in skeletal muscle cells functions in calcium storage?
sarcoplasmic reticulum
What is the most distinguishing characteristic of muscle tissue?

A) the ability to transform chemical energy into mechanical energy
B) the ability to respond to nervous stimulation
C) the diversity of activity of muscle tissue
D) the design of the fibers
A
What is the role of tropomyosin in skeletal muscles?

A) Tropomyosin is the chemical that activates the myosin heads.
B) Tropomyosin serves as a contraction inhibitor by blocking the actin binding sites on the myosin molecules.
C) Tropomyosin is the receptor for the motor neuron neurotransmitter.
D)Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.
D
Muscle tone is ________.
a state of sustained partial contraction
When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods?
refractory period
Three discrete types of muscle fibers are identified on the basis of their size, speed, and endurance. Which of the following athletic endeavors best represents the use of red fibers?
a long relaxing swim
Cardiac muscle has a limited regenerative capacity.
True