Chapter 9 - Muscles/Nerves
The smallest contractile unit within skeletal muscle would correspond to the distance between which two points in the figure? 1 and 7 3 and 5 1 and 3 2 and 6
1 and 7
The smallest contractile unit within skeletal muscle would correspond to the distance between which two points in the figure
1 and 7 The distance between points 1 and 7 spans a sarcomere, the smallest contractile unit of a muscle fiber.
Between which two points would there be substantial amounts of both the proteins actin and myosin? 2 and 3 1 and 2 3 and 5 None of the listed responses is correct.
2 and 3
The region between which two points corresponds to the entire A band? 2 and 6 3 and 5 2 and 3 1 and 2
2 and 6
The region between which two points corresponds to the entire A (dark) band?
2 and 6 The A band, also know as the dark band, is occupied by the entire length of thick myofilaments
Arrange the following steps for contraction in the correct sequence. 1. The muscle impulse reaches the sarcoplasmic reticulum and calcium is released 2. Thin filaments are pulled over the thick filaments 3. Calcium floods the sarcoplasm and binds to troponin molecules leaving active sites 4. The impulse arrives at the synapse and travels through the transverse tubules 5. The muscle fiber shortens and contracts 6. Tropomyosin molecules bind to exposed active sites, linking actin and myosin
4,1,3,6,2,5
The smallest contractile unit within skeletal muscle would correspond to the distance between which two points in the figure? (img 1) >3 and 5 >1 and 3 >1 and 7 >2 and 6
>1 and 7. The distance between points 1 and 7 spans a sarcomere, the smallest contractile unit of a muscle fiber.
The region between which two points corresponds to the entire A (dark) band? (img 1) Relationship between fibers composing a sarcomere. >1 and 2 >2 and 3 >3 and 5 >2 and 6
>2 and 6 The A band, also know as the dark band, is occupied by the entire length of thick myofilaments.
The molecular interaction described as a cross bridge involves the binding of which two proteins? (img 5) >A and C >B and D >A and D >A and B
>A and C. Cross bridges between thin and thick myofilaments are formed by the specific interaction between actin (A) and myosin head groups (C).
Which step precedes all of the other listed steps? >The sarcoplasmic reticulum is activated. >An action potential starts on the sarcolemma. >Na+ rushes into the cell. >ACh is released by the motor neuron.
>ACh is released by the motor neuron. The first step toward generating a skeletal muscle contraction is nervous stimulation of the muscle fiber in order to generate an action potential. The site of muscle stimulation, where the nerve ending communicates with the muscle fiber, is called the neuromuscular junction.
Which of the following interactions must occur first so that the others can take place? (Refer to img 5) Interaction between thick and thin filaments during muscle contraction. >B binds to troponin. >D is shifted from actin's binding sites. >C binds to actin. >C releases ADP and P.
>B binds to troponin. Binding of calcium (B) to troponin removes the blocking action of tropomyosin along the thin myofilament. This allows myosin to bind to actin and form the cross bridge illustrated in this figure.
Which of the following corresponds to a single fascicle? (img 4) >A >B >C >D
>B. A fascicle is an organized group of muscle fibers (cells) bounded by a perimysium.
Which of the structures is surrounded by the connective tissue sheath known as the perimysium? (img 4) A B C D
>B. The structure at B is covered by the perimysium. Remember that the word root peri means "around," as in "perimeter."
Which statement accurately describes the event indicated by B? (img 2) >The binding of acetylcholine directly causes the formation of a wave of depolarization. >Diffusion of acetylcholine into the muscle fiber triggers the opening of an ion channel. >Binding of acetylcholine to a receptor triggers the opening of an ion channel. >Diffusion of Ca2+ into the muscle fiber triggers the diffusion of acetylcholine out of the muscle fiber.
>Binding of acetylcholine to a receptor triggers the opening of an ion channel. Binding of acetylcholine to its receptor opens chemically (ligand) gated ion channels that allow Na+ and K+ to diffuse across the sarcolemma.
Which structure in the figure corresponds to a single skeletal muscle cell? (img 4) >A >B >C >D
>C. Note that a skeletal muscle cell is commonly termed a muscle fiber.
Which protein functions as a motor protein that applies the power stroke during muscle contraction? (img 5) >A >B >C >D
>C. The myosin head groups (C) hydrolyze ATP to power molecular movement along the actin subunits of the thin myofilaments.
If the cell could no longer produce ATP, what would be the effect on the sarcoplasmic reticulum? >It would be unable to concentrate Ca+ in the sarcoplasmic reticulum. >Ca+ would leak out of the cell. >The muscle would not contract. >Ca+ would build up in the sarcoplasmic reticulum.
>It would be unable to concentrate Ca+ in the sarcoplasmic reticulum. To concentrate Ca+ in the sarcoplasmic reticulum, active transport must occur. With no ATP, there would be no active transport.
Based on what you know of the relationship between the thick and the thin filaments, what would happen if a disorder existed that caused a person to produce no tropomyosin? >The muscle tissues would never be able to relax. >The muscle would be weaker than normal. >Actin will spontaneously fall apart. >The muscle would never contract.
>The muscle tissues would never be able to relax. The tropomyosin covers the myosin binding site on actin. Without tropomyosin, the myosin would constantly have access to those binding sites.
In the muscles of the limbs, the origin is usually the immobile muscle attachment. >True >False
>True. In the muscles of the limbs, the insertion is pulled toward the immobile origin.
Which protein is indicated by the letter A? (img 5) >actin >troponin >myosin >keratin
>actin. Actin is the chief component of the thin myofilaments.
What event directly triggers the release of neurotransmitter shown in A? (img 2) Summary of events at a neuromuscular synapse. >diffusion of Na+ into the axon terminal >diffusion of Na+ out of the axon terminal >diffusion of Ca2+ into the axon terminal >diffusion of K+ into the axon terminal
>diffusion of Ca2+ into the axon terminal. A nerve impulse arrives at the axon terminal triggering the opening of Ca2+ channels, which allows for the diffusion of Ca2+ into the terminal. This in turn leads directly to the release of neurotransmitters by exocytosis.
An enzyme known as acetylcholinesterase is present in the synaptic cleft. What is its role? >to facilitated transport of acetylcholine across the cleft >to pump Ca2+ back out of the axon terminal >to facilitate the entrance of acetylcholine into the muscle cell >to break down acetylcholine
>to break down acetylcholine. Acetylcholinesterase breaks acetylcholine apart, terminating the synaptic transmission. Choline can be taken back into the axon terminal and reused.
The interaction between which protein and ion initiates contraction of skeletal muscle? >tropomyosin; calcium ions >troponin; calcium ions >myosin; sodium ions >troponin; sodium ions
>troponin; calcium ions. When calcium ions bind to troponin, troponin changes shape and moves tropomyosin away from its inhibitory position. As a result, the energized myosin heads can bind to the actin molecules and begin the cross bridge cycle, which shortens the muscle fiber.
Which of the following corresponds to a single fascicle?
A fascicle is an organized group of muscle fibers (cells) bounded by a perimysium.
This muscle compresses the cheek when you whistle. A. buccinator B. depressor labii inferioris C. masseter D. levator labii superioris
A. buccinator
Muscles are named based on all the criteria below except ________. A. color of the muscle B. direction of muscle fibers C. action of the muscle D. number of origins
A. color of the muscle
This powerful muscle is the prime mover of arm extension. A. latissimus dorsi B. rhomboids C. supraspinatus D. teres minor
A. latissimus dorsi
Tawanda finishes a sprint and suffers great pain in her calf muscles. Her muscle cramps are most likely due to a temporary deficit of
ATP
Which of the following statements is correct?
Actin filaments slide along myosin filaments
Which structure corresponds to a single fascicle? A B C D
B
Which of the structures is surrounded by the connective tissue sheath known as the perimysium?
B The structure at B is covered by the perimysium. Remember that the word root peri means "around," as in "perimeter.
What is the correct order of structures as you move from outside a muscle cell, to deep inside it? A. myofibril, myofilament, fiber B. fiber, myofibril, myofilament C. myofilament, fiber, myofibril D. myofilament, myofibril, fiber
B. fiber, myofibril, myofilament
In the figure above, which structure corresponds to a single skeletal muscle cell? A, B, C, D?
C
In which phase in the figure would the net movement of Ca2+ into the sarcoplasmic reticulum (SR) be greatest?
C During the period of relaxation (C), Ca2+ is transported by active transport into the SR. Decreased Ca2+ concentrations in the sarcoplasm leads to detachment of cross bridges and, consequently, decreased contractile force.
A prime mover (agonist) ________. A. opposes or reverses a movement B. aids the action of the muscle primarily responsible for the movement C. is primarily responsible for a movement D. immobilizes the origin of the prime mover
C. is primarily responsible for a movement
The actual contractile units of muscles extend from Z disc to Z disc. They are ________. A. myofibrils B. thick filaments C. sarcomeres D. sarcoplasmic reticulum
C. sarcomeres
When both muscles of this pair are contracted simultaneously, they flex the neck forward. A. semispinalis B. platysma C. sternocleidomastoid D. trapezius
C. sternocleidomastoid
Which of the following is the smallest structural unit in which the distinctive striated bands characteristic of skeletal muscle are observed? A B C D
D
A neuron and all the muscle fibers it stimulates is called a ________. A. myoneural junction B. fascicle C. synaptic cleft D. motor unit
D. motor unit
The neuromuscular junction consists of ________. the end branch of a single nerve fiber touching a muscle a nerve touching a muscle a nerve coming into close proximity to a muscle fiber D. the axon terminal coming into close proximity to a muscle fiber
D. the axon terminal coming into close proximity to a muscle fiber
Duchenne muscular dystrophy could theoretically be cured if a technique was developed that would
Duchenne muscular dystrophy is caused by a mutation in the dystrophin gene. Without a normal copy of DNA for transcription, there can never be a normal protein translated. This genetic mutation causes the protein to be either abnormal in structure or completely absent.
Which of the following statements is FALSE? >Skeletal muscle cells have T tubules. >Skeletal muscle cells use creatine phosphate instead of ATP to do work. >Skeletal muscle cells are multinucleated. >Skeletal muscle cells contain myoglobin. >Skeletal muscle cells have glycosomes
Muscle cells, just like other cells, use ATP to do work. Creatine phosphate is used by muscle cells to directly phosphorylate (i.e., donate a high-energy phosphate group to) ADP to resynthesize ATP.
The region between which two points corresponds to the I band? 3 and 5 2 and 5 2 and 3 None of the listed responses is correct.
None of the listed responses is correct.
What is the function of the filaments found in ranges 1-2 and 6-7 but no other ranges?
Protection from overstretching Elastic (titin) filaments help to protect the muscle from overstretching and also aid in returning it to normal length.
If both of the neurons in the figure 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 Recruitment refers to the increased force generated by the activation of increasing numbers of motor units
This indentation of the sarcolemma carries electrical signals deep into the muscle cells.
T tubule
The connective tissue that covers structure A is continuous with which of the following?
Tendons The dense connective tissue at A is continuous with the tendon that connects the muscle to a bone or, in some cases, to another muscle or to the skin.
What result would be expected if an additional stimulus, equal in intensity to the first, were to be applied to the muscle at the 60 millisecond (ms) time point?
The muscle would increase in tension to a level greater than that measured at the beginning of phase C The second, more forceful contraction that would occur by adding another stimulus before the muscle has completely relaxed is an example of wave summation.
The linea alba is
a band of tough connective tissue to which abdominal wall muscles attach
A motor unit is
a motor neuron and the muscle fibers connected to it
A myogram is
a recording of the events of a twitch
Which is not true of skeletal muscle? a. It enables you to manipulate your environment. b. If influences the body's contours and shape. c. It is one of the major components of hollow organs. d. It provides a means of locomotion.
a. It enables you to manipulate your environment
a prime mover or ________ produces a particular type of movement. a. agonist b. antagonist c. fixator d. synergist
a. agonist
The two headed muscle bulges, when the forearm is flexed. It is the most familiar muscle of the anterior humerus. It is the ___________. a. biceps brachii b. flexor carpi radialis c. extensor digitorum d. triceps brachii
a. biceps brachii
Because the cells of skeletal muscle are relatively large and cylindrical in shape, they are also known as __________. a. fibers b. tubules
a. fibers
Muscles that act on the _________ cause movement at the hip, knee, and foot joints. a. lower limb b. trunk c. upper limb
a. lower limb
deltoid
abduct arm
gluteus maximus
abduct leg and extend hip
People with myasthenia gravis lack
about two-thirds of the normal number of acetylcholine receptors
___ degrades acetylcholine, keeping it from accumulating in the synapse
acetlycholinesterase
The first event in muscle fiber contraction is that
acetylcholine is released from the end of the motor neuron
Myofibrils are composed primarily of
actin and myosin
The two contractile proteins that make up the myofilaments of skeletal muscle are _________ and _______.
actin, myosin
pectoralis
adduct arm anteriorly
gracilis
adduct leg
Which pathway for regenerating ATP provides the majority of the energy used for muscle activity during 30 minutes of light to moderate exercise?
aerobic respiration
Cardiac muscle
all of the above (is only in the heart, responds in an all-or-none manner, contracts as a syncytium, excites itself)
Functions of muscles are for
all of the above (moving bones, the heartbeat, muscle tone, distribution of heat)
Temporomandibular joint (TMJ) syndrome causes
all of the above (ringing in the ears, clicking sound from the jaw, insomnia, backache)
Muscle atrophy that progresses with aging is caused by reduction in
all of the above (the sizes of muscle fibers, ATP, creatine phosphate, myoglobin)
Myasthenia gravis is
an autoimmune disorder
A shift in metabolism that breaks down pyruvic acid to lactic acid is called
anaerobic threshold
In which phase of the muscle twitch shown in the figure would the maximum amount of ATP be consumed by myosin head groups
b Myosin heads catalyze the hydrolysis of ATP to power the sliding of myofilaments. This event would be at a maximum during the period of contraction (B).
A cordlike structure that connect a muscle to another muscle or bone is: a. a fascicle b. a tendon c. deep fascia
b. a tendon
This lower limb muscle, which attaches to the calcaneus via the calcaneal tendon and plantar flexes the foot when the knee is extended, is the ___________. a. tibialis anterior b. gastrocnemius
b. gastrocnemius
These abdominal muscles are responsible for giving me my "six pack." They also stabilize my pelvis when walking. They are the ________ muscles. a. internal intercostal b. rectus abdominis c. quadriceps d. triceps femoris
b. rectus abdominis
The contractile unit of muscle is the: a. sarcolemma b. sarcomere
b. sarcomere
Acetylcholine (ACh) is the neurotransmitter of axon terminals at the neuromuscular junction. It ________.
binds to receptors on the muscle membrane
The dark band of skeletal muscle consists of ________.
both thick and thin filaments
Each muscle cell is surrounded by thin connective tissue called the: a. aponeuroses b. epimysium c. endomysium d. perimysium
c. endomysium
The ______ is the largest and most superficial of the gluteal muscles. a. gluteus internus b. gluteus medius c. gluteus maximus d. gluteus minimus
c. gluteus maximus
The _________ musculature includes muscles that move the vertebral column and muscles that move the ribs. a. head and neck b. lower limb c. trunk
c. trunk
gastrocnemius insertion
calcaneus
The soleus is a muscle that forms part of the
calf
Smooth muscle has ___ and not troponin
calmodulin
At the neuromuscular junction, the electrical signal of the nerve
causes the axon terminal to release acetylcholine (ACh)
The buccinator muscle is in the
cheek
Compared to skeletal muscle, smooth muscle
contracts more slowly and relaxes more slowly
The function of the neuromuscular junction is to ________.
convey a signal from the nervous system to skeletal muscle
The muscle that adducts and flexes the arm is the
coracobrachialis
A tendon is ___, whereas an aponeurosis is ___
cordlike and connects muscles to bones; a broad, fibrous sheet of connective tissue that connects muscles to muscles
The relationship between ATP and creatine phosphate is that
creatine phosphate supplies energy to regenerate ATP from ADP and phosphate
A band in cardiac muscle
dark
A band in skeletal muscle
dark
The enzyme acetylecholinesterase cause acetylcholine to
decompose
Rigor mortis affects skeletal muscles a few hours after death, due to
decreased ATP and increased permeability to calcium
A sign of aging of the muscular system is
decreased supplies of myoglobin to muscles
In a bedridden patient recovering from a badly fractured femur, disuse atrophy in the thigh muscles is caused by
decreased synthesis of muscle proteins and/or increased breakdown of muscle proteins Muscle tissue grows and heals in response to stress. Without the stress of exercise and normal daily activities, muscle tissue degenerates
What event directly triggers the release of neurotransmitter shown in A?
diffusion of Ca2+ into the axonal terminus A nerve impulse arrives at the axon terminal triggering the opening of Ca2+ channels, which allows for the diffusion of Ca2+ into the terminal. This in turn leads directly to the release of neurotransmitters by exocytosis.
antagonist to masseter
digastric
Skeletal muscles are named on the basis of many criteria, name one
direction of fibers or size or location or shape or action
The outermost layer of connective tissue surrounding a skeletal muscle is the
epimysium
What cellular event is indicated by A?
exocytosis Neurotransmitters stored in synaptic vesicles are released into the synaptic cleft by exocytosis.
triceps brachii
extend elbow
True or false: the biceps femoris is located in the anterior compartment of the thigh.
false
True or false: Larger, more powerful muscles have relatively less connective tissue than smaller muscle.
false, more
Each of the elements that make up a skeletal muscle is surrounded by connective tissue. Which words below correctly pair the connective tissue layer with the corresponding muscle structure?
fascicle: perimysium
What is the correct order of structures as you move from outside a muscle cell, to deep inside it?
fiber, myofibril, myofilament
biceps brachii
flex elbow
sternocleidomastoid
flex neck
rectus abdominis
flex trunk (body)
A gluteal gait, in which a person walks with a waddling limp, is usually caused by a disorder of the
gluteus medius and gluteus minimus
latissimus dorsi insertion
humerus
Myasthenia gravis is sometimes treated medically by a treatment that involves ________
inhibiting the action of acetylcholinerase This enzyme breaks down acetylcholine into acetic acid and choline.
The movable end of a muscle is its
insertion
The structures that connect cardiac muscle cells are
intercalated discs
origin of hamstring group
ischium
A plank position is part of a yoga/Pilates workout. The person supports the body on the floor in a prone position with the arms and feet supporting the body. It is a little like the "up" position of a push-up, held for 30 to 60 seconds. Contraction of the abdominal muscles in a plank is most likely
isometric
In a recording of a muscle twitch, the delay between the time a stimulus is applied and the time the muscle responds is called the
latent period
antagonist to pectoralis group
latissimus dorsi
Bones and muscles function as mechanical devices called
levers
I band in cardiac muscle
light
I band in skeletal muscle
light
digastric
lower mandible
origin of external oblique
lumbodorsal fascia
masseter insertion
mandible
Which of the following is not a muscle of mastication?
mandibular
sternocleidomastoid insertion
mastoid process
Fibers of muscles whose motor neurons are severed
may be replaced by fat or fibrous connective tissue
Threshold stimulus is the
minimal amount of energy required to contract a muscle fiber
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 sacrcoplasmic reticulum's calcium ion pumps A pump is considered an active transport process. Active transport moves molecules against their concentration gradient, which requires energy in the form of ATP
At a neuromuscular junction, the muscle fiber membrane folds, forming a
motor end plate
Neurotransmitters are stored in vesicles in
motor neuron endings
Weightlifting, in which a muscle exerts more than 75% of its maximum tension, stimulates
muscle fibers developing new filaments of actin and myosin
An example of a partial but sustained contraction is
muscle tone
From gross to microscopic, the parts of a muscle are ________.
muscle, fascicle, fiber
In muscle contraction ATP supplies energy for
myofilament movement
This contractile protein is shaped like a golf club.
myosin
The thick and thin filaments are made up of ________, respectively.
myosin and actin
The junction between an axon and a muscle fiber is called a ______________
neuromuscular
At a neuromuscular junction
neurotransmitters are released
The amount of oxygen liver cells require to react lactic acid to produce glucose or the glycogen glycogen is the
oxygen debt
Which of the following is unique in that its insertion is to fascia and not bone?
palmaris longus
The toxin that causes botulism
prevents release of acetylcholine
The muscle primarily responsible for an action is the
prime mover
Athletes usually experience muscle fatigue less quickly than nonathletes because they
produce less lactic acid
antagonist to hamstring group
quadriceps group
masseter
raise mandible
Which of the following is not true?
red fibers have fewer mitochondria than white
The very brief moment following stimulation when a muscle remains unresponsive to additional stimulation is called the
refractory period
antagonist to serratus ventralis
rhomboideus
intercostals insertion
ribs
The discoloration and swelling of a muscle strain is due to
ruptured blood vessels
The striated appearance of skeletal muscles results from the
sarcomere organization
Muscle fibers are basically a collection of
sarcomeres
The actual contractile units of muscles extend from Z disc to Z disc. They are ________.
sarcomeres
origin of supraspinatus
scapula
Transverse tubules and sarcoplasmic reticulum are well developed in
skeletal muscle fibers
The type of muscle cell that lacks transverse tubules, has a single nucleus, and is under involuntary control is
smooth muscle
Both acetylcholine and norepinephrine can affect
smooth muscle contraction
Short muscle cells with centrally located nuclei are
smooth muscle fibers
antagonist to splenius
sternocleidomastoid
origin of pectoralis major
sternum
Regina began an exercise program six months ago, and the muscles of her upper limbs and lower limbs are more prominent. Exercise can lead to formation of new muscle by
stimulating skeletal muscle cells to release IL-6, which stimulates satellite cells to divide, producing more muscle cells
Aponeurosis
strong sheet of tissue that acts as a tendon to attach muscles to bone
Creatine phosphate
supplies energy for the synthesis of ATP
The functional connection between a neuron and a skeletal muscle fiber is a
synapse
The space between the axon terminal and the sarcolemma of a muscle fiber is called the ________.
synaptic cleft
A muscle that assists a prime mover is a(n)
synergist
origin of temporalis
temporal
The connective tissue that covers structure A is continuous with which of the following?
tendon
This strong, cord-like structure attaches muscles to bones.
tendon
Tendons differ from ligaments in that ________.
tendons bind muscle to bone and ligaments bind bone to bone
A triad consists of ________.
terminal cisternae and T-tubules
Oxygen debt in muscles may develop because of
the inability of respiratory and circulatory systems to supply enough oxygen to skeletal muscles when used strenuously for a minute or two
Skeletal muscles help maintain body temperature in that
the more active they are, the more heat is released
The functional unit of muscle contraction is
the sarcomere
The I-band consists of ________.
thin filaments
antagonist to gastrocnemius
tibialis anterior
The severe pain of compartment syndrome is caused by
too much fluid in the compartment
Transverse tubules
transmit muscle impulses into the cell interior
Smooth muscle lacks
transverse tubules and striations
The triangle of auscultation, commonly used to hear sounds of respiratory organs, is located near the border of the
trapezius and latissimus dorsi
antagonist to biceps brachii
triceps brachii
Which protein inhibits interaction between actin and myosin to prevent skeletal muscle contraction; and which ions remove the inhibition?
tropomysin, calcium ions
True or False: Muscles of facial expression differ fro most skeletal muscles because they usually do not insert into a bone.
true
True or false: skeletal muscle cells have more than one nucleus.
true
triceps brachii insertion
ulna
origin of rhomboideus
vertebrae
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 no longer overlap >during contraction, the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments overlap to a greater degree >during contraction, the thin myofilaments slide past the thick myofilaments so that calcium ions can be released from the sarcoplasmic reticulum >during contraction, the thin myofilaments slide past T tubules so that the Z discs are overlapping
>during contraction, the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments overlap to a greater degree. The sliding filament model of contraction states that during contraction, the thin myofilaments slide past the thick myofilaments so that actin and myosin myofilaments overlap to a greater degree. In a relaxed muscle fiber, the thick and thin myofilaments overlap only at the ends of the A band.
Muscle tissue can be stimulated by the nervous system. This is because of the membrane potential in the muscle cell. Cells with a membrane potential have what property? >excitability >extensibility >elasticity >contractility
>excitability. Excitability, also termed responsiveness, is the ability to receive and respond to a stimulus. For example, skeletal muscle contracts in response to receiving chemical stimulation from the central nervous system.
What cellular event is indicated by A? >endocytosis >facilitated diffusion >active transport >exocytosis
>exocytosis. Neurotransmitters stored in synaptic vesicles are released into the synaptic cleft by exocytosis.
Which term best identifies a muscle cell? >sarcomere >muscle fascicle >myofibril >muscle fiber
>muscle fiber. Skeletal muscle cells fuse during development to form the mature, multinucleated muscle fibers.
Which term best identifies a muscle cell? >sarcomere >myofibril >muscle fiber >muscle fascicle
>muscle fiber. Skeletal muscle cells fuse during development to form the mature, multinucleated muscle fibers.
Which protein is indicated by the letter E? (img 5) >tropomyosin >troponin >actin >myosin
>myosin. Myosin tail groups form the extended regions of the thick myofilament.
What is the function of the filaments found in ranges 1-2 and 6-7 but no other ranges? (Refer to img 1) Relationship between fibers composing a sarcomere. >neurological sensing of the muscle's tension >a connection between the myosin fibers and a calcium source >adding strength to contraction >protection from overstretching
>protection from overstretching. Elastic (titin) filaments help to protect the muscle from overstretching and also aid in returning it to normal length.
Excitation-contraction coupling includes all EXCEPT which of the following events? >release of acetylcholine from axon terminals at the neuromuscular junction >binding of calcium ions to troponin, which removes the blocking action of tropomyosin >propagation of an action potential along the sarcolemma and down T tubules >release of calcium ions from the terminal cisterns
>release of acetylcholine from axon terminals at the neuromuscular junction. Release of acetylcholine from axon terminals at the neuromuscular junction is an event that precedes excitation-contraction coupling, which begins with excitation of the T-tubules.
The __________ shorten(s) during muscle contraction >Z lines >thick filament >actin >sarcomere
>sarcomere. As actin slides over myosin, the z lines are pulled closer together, shortening the sarcomere.
Which of the following is NOT a normal function of muscle tissue? >secreting hormones >generating heat >stabilizing joints >maintaining posture >producing movement
>secreting hormones. Secreting hormones is a function of the endocrine system.
Which of the following are correctly paired? >smooth muscle; striated >skeletal muscle; voluntary control >cardiac muscle; nonstriated >cardiac muscle; voluntary control
>skeletal muscle; voluntary control.
Which type of muscle requires voluntary nervous stimulation for activation? >skeletal >smooth >cardiac >visceral
>skeletal. In order to contract, skeletal muscle fibers must be voluntarily stimulated by the nervous system. The site of muscle stimulation, where the nerve fiber communicates with the muscle fiber, is called the neuromuscular junction.
The connective tissue that covers structure A is continuous with which of the following? >ligament >synovial membrane >endomysium >tendon
>tendon. The dense connective tissue at A is continuous with the tendon that connects the muscle to a bone or, in some cases, to another muscle or to the skin.
A toxin released by certain bacteria can block the release of neurotransmitters into a neuromuscular synapse. What would result from such a block? >The muscle would become permanently contracted. >The muscle would remain fixed at the length it was when the toxin contacted it. >the loss of ability to contract the muscle
>the loss of ability to contract the muscle. Without acetylcholine, the muscle would not be able to contract or even maintain tone.
Which of the following regions best identifies where myosin would have maximum cross-bridge access to actin? (img 1) >the region between 1 and 2 >4 >the region between 3 and 5 >the region between 2 and 3
>the region between 2 and 3. Actin and myosin are components of thin and thick filaments, respectively. The region between points 2 and 3 includes the area of overlap between thin and thick filaments.
The contractile, or functional, unit of a muscle fiber is __________. >the myofilament >troponin >the sarcomere >the elastic filament
>the sarcomere. The sarcomere is the contractile unit of a muscle fiber and the smallest functional unit of muscle. A sarcomere is the region of a myofibril between two successive Z discs; it primarily consists of thin and thick myofilaments.
Which organelle can chemically regulate the shortening of the muscle? >the sarcolemma >the sarcoplasmic reticulum >the myofibril >glycosome
>the sarcoplasmic reticulum