chapter 9: the muscular system Flashcards
Which of the following properties is most directly associated with changes to a muscle cell’s membrane potential (the voltage across the plasma membrane)?
A. elasticity
B. excitability
C. contractility
D. extensibility
B. excitability
Which type of muscle tissue is the only one that can respond to voluntary nervous stimulation in most people?
skeletal
Which of the following is NOT a normal function of muscle tissue?
A. producing movement
B. generating heat
C. secreting hormones
D. stabilizing joints
E. maintaining posture
C. secreting hormones
Which structure in the figure corresponds to a single skeletal muscle cell?
C
Which of the following corresponds to a single fascicle?
B
Which of the structures is surrounded by the connective tissue sheath known as the perimysium?
B
Which muscle cell structure stores calcium ions that are used to trigger the contraction?
the sarcoplasmic reticulum
The contractile, or functional, unit of a muscle fiber is __________.
the sarcomere
The __________ shorten(s) during muscle contraction
sarcomere
The sliding filament model of contraction states that __________.
during contraction, the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments overlap to a greater degree
What event directly triggers the release of neurotransmitter shown in A?
diffusion of Ca2+ into the axon terminal
Which statement accurately describes the event indicated by B?
A. Diffusion of acetylcholine into the muscle fiber triggers the opening of an ion channel.
B. The binding of acetylcholine directly causes the formation of a wave of depolarization.
C. Diffusion of Ca2+ into the muscle fiber triggers the diffusion of acetylcholine out of the muscle fiber.
D. Binding of acetylcholine to a receptor triggers the opening of an ion channel.
Binding of acetylcholine to a receptor triggers the opening of an ion channel.
A toxin released by certain bacteria can block the release of neurotransmitters into a neuromuscular synapse. What would result from such a block?
the loss of ability to contract the muscle
The interaction between which protein and ion initiates muscle coupling?
troponin and calcium ions
Which of the following events triggers the subsequent steps of excitation-contraction coupling?
A. binding of calcium ions to troponin, which removes the blocking action of tropomyosin
B. propagation of an action potential along the sarcolemma and T tubules
C. release of acetylcholine from axon terminals at the neuromuscular junction
D. release of calcium ions from the terminal cisterns of the sarcoplasmic reticulum
C. release of acetylcholine from axon terminals at the neuromuscular junction
Identify the correct sequence of the following events.
a. Myosin generates a power stroke.
b. Ca++ binds to troponin.
c. ATP recharges the myosin head.
d. Troponin removes tropomyosin from G actin.
e. The sarcomere shortens.
f. Myosin binds to actin.
b, d, f, a, e, c
Which of the following is most directly required to initiate the coupling of myosin to actin?
A. ACh
B. Ca++
C. glucose
D. ATP
B. Ca++
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 ________.
mitochondria stop producing ATP molecules required by the sarcoplasmic reticulum’s calcium ion pumps
What level of structural organization does the actin and myosin in a sarcomere of a muscle fiber represent?
Molecular
Each neuron shown in this figure innervates a group of muscle fibers. What is the term for a group of muscle fibers and the single neuron that innervates them?
motor unit
True or False:
Isometric contractions are important contractions that allow humans to hold their posture over time.
true
The energy reserves for which of the ATP regenerating pathways will be depleted first during an extended period of light to moderate exercise?
direct phosphorylation of ADP by creatine phosphate
The force of a muscle contraction is NOT affected by __________.
the amount of ATP stored in the muscle cells
Which of the following is true?
A. Skeletal muscle fibers tend to be shorter than smooth muscle fibers.
B. Skeletal muscle fibers contain sarcomeres; smooth muscle fibers do not.
C. Skeletal muscle lacks the coarse connective tissue sheaths that are found in smooth muscle.
D. Smooth muscle lacks the thin and thick filaments characteristic of skeletal muscle.
B. Skeletal muscle fibers contain sarcomeres; smooth muscle fibers do not.
Which type of muscle is found in the body wall of hollow organs?
Unitary smooth muscle
True or False:
The force of muscle contraction is controlled by multiple motor unit summation or recruitment.
True
In an isotonic contraction, the muscle ________.
a. never converts pyruvate to lactate
b. rapidly resynthesizes creatine phosphate and ATP
c. changes in length and moves the “load”
d. does not change in length but increases tension
c. changes in length and moves the “load”
An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________.
a. hydrolysis
b. the citric acid cycle
c. glycolysis
d. the electron transport chain
c. glycolysis
True or False:
A motor neuron and all the muscle cells that it stimulates are referred to as a motor end plate.
False
What produces the striations of a skeletal muscle cell?
a. the T tubules
b. a difference in the thickness of the sarcolemma
c. the sarcoplasmic reticulum
d. the arrangement of myofilaments
d. the arrangement of myofilaments
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. striated muscle
b. skeletal muscle
c. smooth muscle
d. cardiac muscle
c. smooth muscle
What is the functional unit of a skeletal muscle called?
a. a sarcomere
b. a myofilament
c. the sarcoplasmic reticulum
d. a myofibril
a. a sarcomere
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. motor units with the longest muscle fibers
c. motor units with larger, less excitable neurons
d. large motor units with small, highly excitable neurons
c. motor units with larger, less excitable neurons
Which muscle cells have the greatest ability to regenerate?
a. cardiac
b. no muscle can regenerate
c. smooth
d. skeletal
c. smooth
What is the role of calcium ions in muscle contraction?
a. form hydroxyapatite crystals
b. increase levels of myoglobin
c. bind to regulatory sites on troponin to remove contraction inhibition
d. reestablish glycogen stores
c. bind to regulatory sites on troponin to remove contraction inhibition
True or False:
Muscle contraction will always promote movement of body parts regardless of how they are attached.
False
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. slow oxidative fibers
d. fast oxidative fibers
b. fast glycolytic fibers
Which of the following is not a component of the standard treatment for muscle strain?
a. stretching of the muscle
b. rest of the muscle
c. ice on the muscle
d. elevation of the limb
a. stretching of the muscle
Reduction in blood flow to a muscle fiber would have the greatest effect on ________.
a. fast oxidative fibers
b. slow oxidative fibers
c. fast glycolytic
d. both slow and fast oxidative
b. slow oxidative fibers
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. dehydration with headache
b. coma and loss of voluntary muscle movement
c. seizures and uncontrollable muscle movement
d. weakness of muscle
d. weakness of muscle
Fatigued muscle cells that recover rapidly are the products of ________.
a. intense exercise of long duration
b. slow exercise of short duration
c. slow exercise of long duration
d. intense exercise of short duration
d. intense exercise of short duration
Approximately 80% of a muscle fiber’s volume are the myofibrils. This characteristic reflects muscles ability to ________.
a. produce movement through contractile force
b. store oxygen molecules that can be used in aerobic respiration
c. generate and propagate action potential
d. produce relatively high amounts of ATP
a. produce movement through contractile force
Excitation-contraction coupling requires which of the following substances?
a. ATP only
b. Ca2+ only
c. Ca2+ and ATP
d. ATP and glucose
c. Ca2+ and ATP
What is the primary function of wave summation?
a. produce smooth, continuous muscle contraction
b. prevent muscle fatigue
Incorrect
c. prevent muscle relaxation
d. increase muscle tension
a. produce smooth, continuous muscle contraction
The major function of the sarcoplasmic reticulum in muscle contraction is to ________.
a. provide a source of myosin for the contraction process
b. synthesize actin and myosin myofilaments
c. make and store phosphocreatine
d. regulate intracellular calcium concentration
d. regulate intracellular calcium concentration
