CH 10 HBOD MUSCLE TISSUE
True or false: A single myofibril runs the length of the muscle fiber.
True
True or false: In the absence of calcium, troponin attaches to tropomyosin to hold it in place on the surface of the F actin strand.
True
True or false: Playing the piano with your fingers uses very small motor units.
True
True or false: Smooth muscle cells lack transverse tubules.
True
When a muscle fiber contracts, which parts of the sarcomere maintain a constant length throughout contraction?
A band
What muscle type(s) would you expect to find in the cardiovascular system?
Cardiac & smooth
True or false: After diffusing across the synaptic cleft, ACh binds to receptors on the synaptic knob.
False
True or false: In smooth muscle contraction the thick and thin filaments slide past one another causing the Z lines to move closer together.
False
light band containing thin filaments only
I band
appears as a dark protein disc in center of H zone
M line
When calcium ions bind to troponin, which of the following then occurs?
The myosin-binding sites on actin are exposed.
After being generated, the muscle impulse continues to spread throughout the muscle fiber as long as ______ keeps the motor end plate receptors open.
acetylcholine
The motor end plate has large numbers of ______ receptors.
acetylcholine
Contraction of a muscle fiber requires that the myosin heads in the thick filament bind to active sites on ______ molecules within the thin filaments
actin
Each myosin head in a thick filament can bind to the protein in a thin filament called
actin
Which of the following proteins are found in a thin filament?
actin
binding site for myosin to shorten a sarcomere
actin
double-stranded contractile protein
actin
Which of the following proteins are found within a sarcomere?
actin connectin
Cardiac muscle cells use _________ respiration almost exclusively.
aerobic
For longer contractions, muscle cells obtain ATP by which process?
aerobic respiration
Smooth muscle cells generally generate ATP through which mechanism?
aerobic respiration
The endomysium is composed of what type of connective tissue?
areolar
The superficial fascia, composed of ______ and adipose connective tissue, separates muscle from skin.
areolar
Smooth muscle is found where in the respiratory system?
around the bronchioles
The connective tissue layers in muscle provide protection, distribution sites for blood vessels and nerves, and a means of ______ to the skeleton.
attachment
Cardiac muscle cells are ______.
autorhythmic
The ______ feature of cardiac muscle cells is responsible for the repetitious, rhythmic heartbeat.
autorhythmic
thick filament
bind to thin filaments and cause contraction
Cardiac muscle cells are ______ and contain ______ nuclei.
branched; 1-2
Which can cause muscle fatigue?
build up of intracellular Pi insufficient Ca2+ Na+ or K+ imbalances
At an NMJ, the influx of ______ ions into the synaptic knob causes the exocytosis of ACh into the synaptic cleft.
calcium
Functionally, troponin provides a binding site for ______ ions.
calcium
When an action potential travels down T-tubules to the terminal cisternae of the SR, what ion is released into the sarcoplasm?
calcium
When a nerve signal arrives at a synaptic knob, what type of channels open in the membrane?
calcium voltage-gated
During contraction of smooth muscle, ______ binds to calcium and activates myosin light chain kinase.
calmodulin
The sarcolemma of smooth muscle cells has small invaginations called ______.
caveolae
A muscle fiber is what level of organization in the body?
cellular
The long tails of the myosin molecules in the thick filaments point toward the ______ of the filament.
center
The shortening of muscle cells is called _______, a property that allows muscle cells to cause body movement.
contraction
The expansive sheet of dense irregular connective tissue that separates individual muscles is called the ______.
deep fascia
In an isometric contraction, the muscle ______ body movement.
does not produce
Muscle tissue demonstrates the property of _____ when it is done contracting and returns to its resting length.
elasticity
The motor neuron axon travels through the epimysium and perimysium and enters the ______, where it delivers a nerve impulse to an individual ______.
endomysium; muscle fiber
The synaptic knob of the neuron is a(n) ______ of an axon.
expanded tip
There is a(n) ______ network of blood vessels delivering blood to muscle tissue.
extensive
True or false: A muscle fiber that is partially shortened can produce a contraction stronger than the contraction it can produce when at its resting length.
false
perimysium covers the
fascicle
The majority of skeletal muscle fibers in the body are ______ fibers.
fast glycolytic
Which of the three skeletal muscle fiber types has the largest diameter and provides both power and speed?
fast glycolytic
If used repeatedly for endurance events, ______ fibers can develop the appearance and functional capabilities of ______ fibers.
fast; intermediate
In a normally functioning muscle, the inability to contract and produce tension is called muscle
fatigue
Type IIa fibers have a high resistance to ______.
fatigue
A skeletal muscle cell is also called a muscle
fiber
Smooth muscle is composed of short cells that have a ______ shape.
fusiform
With endurance training, it is possible for fast ______ fibers to take on characteristics of fast ______ fibers.
glycolytic; oxidative
Which are characteristics of oxidative fibers?
good for endurance red high concentration of myoglobin use aerobic respiration
lighter region in the middle of an A band
h zone
Each myosin strand has a free ______ and an attached tail.
head
What part of a myosin molecule does ATP bind to?
head
The diameter of a muscle fiber will predict ______.
how much power it will produce
The mechanism that allows smooth muscle to maintain muscle contraction without the use of additional ATP is the
latchbridge
muscle fiber
metabolic activities; contraction
Because muscle cells require a huge amount of ATP in order to contract, they have a large number of which organelle?
mitochondria
Slow fibers have a relatively large number of ______. This permits slow muscle fibers to produce a greater amount of ______ than fast muscle fibers while contractions are underway.
mitochondria; ATP
Upon release from the synaptic knob, acetylcholine attaches to receptors on the ______.
motor end plate
Skeletal muscle contraction is controlled by
motor neurons
Muscle tissue is distributed almost everywhere in the body; it is responsible for the _____ of materials within and throughout the body.
movement
Epimysium covers the
muscle
endomysium covers the
muscle cell
The sarcoplasm of a skeletal muscle fiber contains hundreds to thousands of long, cylindrical structures called _________that extend the length of the cell.
myofibrils
contain myofilaments that are responsible for muscle contraction
myofibrils
An extensive network of blood vessels and nerve fibers extends through both the epimysium and the _____ of a muscle.
perimysium
The connective tissue layer that surrounds each muscle fascicle is called ______.
perimysium
After stimulation of ACh receptors, a muscle impulse spreads quickly along the _________and into the muscle fiber along T-tubules.
sarcolemma
The motor end plate is a specialized region of the ______.
sarcolemma
The plasma membrane of a skeletal muscle fiber is called the
sarcolemma
regulates entry and exit of materials
sarcolemma
Within a myofibril, each ______ shortens as the muscle fiber contracts.
sarcomere
Within a myofibril, Z discs separate the functional contractile units known as
sarcomeres
The cytoplasm of a skeletal muscle cell has a specific name and is known as
sarcoplasm
site of metabolic processes for normal muscle fiber activities
sarcoplasm
At the end of muscle contraction, calcium ions are moved back into the _______reticulum by ATP-driven ion pumps.
sarcoplasmic
At the end of contraction, when the stimulation from the nerve impulse ceases, calcium ions are pumped back into the ______.
sarcoplasmic reticulum
According to the sliding filament theory, when a muscle contracts, thick and thin filaments_______ past each other, and the ______ shortens
slide sarcomere
the ______-filament theory explains how muscle fibers shorten during contraction.
sliding
An individual has better proficiency in performing repeated contractions under aerobic conditions if he or she has a greater percentage of ______ fibers in specific muscles.
slow
Smooth muscle contraction is ________ , resistant to_________, and usually sustained for an extended period of time.
slow fatigue
Over longer distances, runners who have higher proportions of ______ muscle fibers in their leg muscles are able to outperform runners who have a greater number of ______ muscle fibers in their leg muscles.
slow; fast
Type I muscle fibers contract more ______ than type IIa and IIb muscle fibers.
slowly
A "step-wise" increase in the force of contraction of a single muscle fiber or single motor unit due to repeated stimulation is called
summation
The narrow space separating the synaptic knob and the motor end plate is called the ______.
synaptic cleft
A nerve impulse travels through an axon to its ______.
synaptic knob
A thick cordlike structure that attaches a muscle to a bone is called a(n) ______.
tendon
The force generated when a skeletal muscle is stimulated to contract is muscle
tension
As a result of ACh stimulation, calcium ions are released from the ______ of the sarcoplasmic reticulum.
terminal cisternae
T-tubules are located adjacent to ______, which are reservoirs storing the calcium ions required for muscle contraction.
terminal cisternae
Slow-twitch and fast-twitch muscle fibers differ primarily in ______.
their ATPase which splits ATP
The H band (or H zone) is more lightly shaded because only ________filaments are present.
thick
in a sarcomere, the M line serves as an attachment site for the ______ filaments and keeps them aligned during contraction and relaxation.
thick
A cross section of a myofibril through the A band contains which myofilaments?
thick and thin
A cross section of a myofibril through the H zone contains which myofilaments?
thick only
In a sarcomere, Z discs serve as anchors for ______.
thin filaments
Single unit muscle cells contract ______.
together
As you sit there reading this your muscles, even your relaxed ones are not completely relaxed and soft. This is because they have some background tension called resting muscle ______.
tone
As the troponin changes shape (due to binding calcium), it moves the ______ molecule to which it is attached, thus exposing the active sites on the G-actin molecules.
tropomyosin
When a muscle fiber is in a relaxed state, the ______ molecules cover the G-actin active sites, preventing interaction between thick filaments and thin filaments.
tropomyosin
covers the active sites on actin when muscle cell is at rest
tropomyosin
double-stranded regulatory protein
tropomyosin
Thin filaments in smooth muscle cells contain which proteins?
tropomyosin actin
The two regulatory proteins associated with thin myofilaments are ______.
tropomyosin and troponin
Calcium ions bind to what protein in a thin myofilament?
troponin
Smooth muscle thin filaments do not contain ______ as in skeletal muscle.
troponin
Upon release from the terminal cisternae, some calcium ions bind to ______ causing it to change shape.
troponin
A single contraction and relaxation of a muscle fiber is referred to as a muscle
twitch
Each myosin protein molecule in a thick filament consists of ______ strands.
two
Thick filaments are about ______ the diameter of thin filaments.
two times
Skeletal muscle fibers are classified into three types based on what two characteristics?
type of contraction and ATP supply
Autonomic motor neurons that control smooth muscle contraction have bulbous swellings called ______ that contain synaptic vesicles.
varicosities
within a synaptic knob, synaptic ______ contain the neurotransmitter ACh
vesicles
Individual cardiac muscle cells can be stimulated to generate a muscle impulse ______ stimulation.
without nervous
The ______ line is a thin, transverse, protein meshwork structure in the center of the H zone of a sarcomere.
M
True or false: Most muscles contain a combination of all three muscle types, slow oxidative, fast oxidative, and fast glycolytic.
True
True or false: Postural muscles contract continuously when a person is awake to prevent collapse of the body.
True
True or false: Skeletal muscle is usually attached to the skeleton, but it is also found at the openings between the digestive tract and the external environment and the urinary tract and the opening to the external environment.
True
True or false: Your biceps brachii muscle in your arm is an organ.
True
In a neuromuscular junction, the enzyme _________ breaks down acetylcholine.
acetylcholinesterase
To stop motor end plate stimulation, usually acetylcholine is quickly broken down and removed from the receptor by ______.
acetylcholinesterase
A tropomyosin molecule is a short, thin, twisted filament that covers small sections of the ______ strands.
actin
Contractile proteins in smooth muscle are arranged ______.
between dense bodies and dense plaques
thin filament
bind to thick filaments and cause contraction
The ACh receptors on the motor end plate are ______ ion channels.
chemically
The enzyme acetylcholinesterase resides in the synaptic
cleft
The type of tetany in which a muscle cell is stimulated so frequently that it is not allowed to relax at all between stimuli is called _________ tetany
complete
A (An) _______ contraction of the arm muscles allows you to lift a book from the table, whereas a (an) ______ contraction of the arm muscles allows you to lower the book back down to the table.
concentric; eccentric
Muscles are considered organs because they are composed not only of muscle tissue but also ______ tissue and nervous tissue
connective
When smooth muscle is stretched, it responds by ______.
contracting then relaxing
In smooth muscle cells, thin filaments are attached to ______.
dense bodies
In a muscle, the perimysium is composed of what type of connective tissue?
dense irregular
The epimysium of a muscle is composed of ______ connective tissue.
dense irregular
Acetylcholine moves across the synaptic cleft by ______.
diffusion
Muscular dystrophy results from the lack of or an abnormal structure of which protein?
dystrophin
The epimysium of a muscle surrounds ______.
entire skeletal muscle
The three connective tissue layers surrounding the individual components of a muscle are the
epimysium perimysium endomysium
In a transverse section of a muscle, you can see that each skeletal muscle is actually composed of many __________, which are bundles of muscle fibers.
fascicles
Which of the following structures anchors adjacent cardiac muscle cells together?
intercalated disc
Cardiac muscle cells form Y-shaped branches and join to adjacent muscle cells at junctions called
intercalated discs
The calcium needed to activate smooth muscle contraction originates in the ______ around the cell.
interstitial fluid
When a nerve impulse reaches the end of an axon of a neuromuscular junction, calcium flows ______ the synaptic knob.
into
Smooth muscle contraction is under ______ control
involuntary
Multiunit smooth muscle is found in which of the following locations?
iris of the eye arrector pili muscles in the skin
Curare is a plant toxin used by indigenous people of South America in their blowguns to paralyze prey. What is a feasible mechanism of action for this drug?
it binds to and blocks ACh receptors on the motor end plate
Smooth muscle shows a different length-tension relationship than skeletal muscle because ______.
it lacks Z discs but has dense bodies the arrangement of the thick and thin filaments allows for contraction even when stretched
Big muscles like the "quads," which are used for power, have ______ motor units.
large
In order to predict how much tension a muscle can produce when contracting, it is important to consider the ______ relationship of thick and thin filaments.
length-tension
Eccentric contractions actively ______ a muscle.
lengthen
Athletes have more defined muscles than non-athletes even while at rest because they have ______ motor units contracting all the time.
more
The vascular supply to slow muscle fibers is ______ than the network of capillaries around fast muscle fibers.
more extensive
Where a motor neuron axon terminal and a muscle cell meet is called a ________ junction
neuromuscular
Synaptic knob, motor end plate, and synaptic cleft are parts of a ______.
neuromuscular junction
While observing skeletal muscle tissue under the microscope you note that it appears striated. You tell your lab partner this is because ______.
of the arrangement of myofilaments in each sarcomere
Contraction of specific skeletal muscles stabilizes joints and helps maintain the body's ________by holding the head and truck erect.
posture
As you hold a barbell and begin to flex your arm in a curl, your biceps brachii slowly lifts the weight by using more and more motor units. This phenomenon, which increases the strength of the contraction, is referred to as
recruitment
As you struggle to twist open a jar, more motor units are called into action until you finally generate enough force to open it. This is an example of ______.
recruitment
The endomysium contains ______ fibers to help bind together neighboring muscle fibers.
reticular
An internal membrane complex in skeletal muscle cells that is similar to the smooth endoplasmic reticulum of other cells is called the sarcoplasmic
reticulum
stores calcium ions needed for muscle contraction
sarcoplasmic reticulum
During the development of skeletal muscle cells, some myoblasts do not fuse and instead become ______ cells.
satellite
If a skeletal muscle is injured, surrounding _____ cells may be stimulated to differentiate and assist in its repair and regeneration.
satellite
Concentric isotonic contractions actively ______ a muscle.
shorten
Cardiac muscle cells are ______ and thicker than skeletal muscle cells, and they have only ______ nuclei.
shorter; 1-2
In which activities are muscles in an isometric contraction?
sitting up very straight pushing on a locked door holding a yoga pose
Approximately 40-50% of your body weight is _____ muscle.
skeletal
Attached to the skeleton and surrounding the openings of the urinary and gastrointestinal traces are locations of ______ muscle.
skeletal
Maintenance of posture and production of heat are functions of ______ muscle.
skeletal
Somatic motor neurons innervate ______ muscle.
skeletal
The length-tension relationship of ________ muscle cells is limited by the Z discs that are lacking in________ muscle cells.
skeletal smooth
The attachment of ACh to the receptor on the motor end plate causes the receptor to open, allowing _______ions to enter the muscle fiber.
sodium
The motor end plate has folds and indentations to increase the membrane surface area adjacent to the ______.
synaptic knob
In a muscle cell at rest, the myosin heads of a thick filament point ______ the sarcomere.
toward the ends of
You have hooked a frog calf muscle up to a myogram that records muscle tension. You notice that when you stimulate the muscle to contract, then stimulate it again before it can fully relax, the amount of tension generated in the second contraction is greater than the first contraction. This phenomenon is called ______.
wave summation
According to the sliding filament theory, the length of the ______ band remains constant, but the ______ zone disappears.
A; H
Acetylcholinesterase in the synaptic cleft is needed so that ______ will not continuously stimulate the cell to contract.
ACh
Muscle cells are said to have what characteristic because they can respond to stimulation from the nervous system?
Excitability
In a thin filament, individual G-actin molecules are strung together to form ______.
F-actin
In each helical strand of F-actin, many small, spherical molecules are connected to form a long filament resembling a string of beads. Each spherical molecule is called ______.
G-actin
At maximal contraction of a muscle fiber, the thin filaments are pulled into the ______ zone which disappears.
H
In a relaxed muscle fiber there are no thin filaments overlapping the thick filaments in the ______ zone.
H
In a sarcomere, the ______ zone (or band) is the light, central region of the A band.
H
The Z disc is a thin transverse protein structure in the center of the ______ band in a sarcomere.
I
Muscle cells store oxygen bound to a _________ molecule
Myoglobin
The muscle that surrounds the opening to your esophagus and opens reflexively to allow you to swallow food is what type of muscle?
Sphincter
The skeletal muscles arranged in layers along the walls of the abdominal cavity and the floor of the pelvic cavity perform what function?
Support Contraction Protection
transports the action potential from the sarcolemma throughout the entire muscle fiber
T-tubule
Deep invaginations of sarcolemma are called ______.
T-tubules
Once started, a muscle impulse will travel along the sarcolemma and into the muscle fiber via the ______.
T-tubules
______ distribute the muscle impulse throughout the inside of the muscle fiber.
T-tubules
Smooth muscle cells retains their mitotic ability.
True
made of dark proteins that create a zig-zag line
Z disc
As cross-bridges form, the myosin heads pivot toward the center of the sarcomere. This action pulls the thin filaments toward the sarcomere center, causing the ______ to move closer together as the sarcomere shortens.
Z discs
Smooth muscle cells have a ______ mechanism that allows them to contract with more power and use less ATP than a skeletal muscle cell.
latch bridge
Smooth muscle is found in which of the following locations?
in wall of the uterus around blood vessels in the wall of the small intestine
Multiunit smooth muscle cells are stimulated ______.
individually
Muscle fibers contain cylindrical structures called myofibrils, which are composed of ______.
myofilaments
Muscle fibers that rely on aerobic respiration for ATP synthesis contain a high concentration of _______, which gives them a reddish appearance.
myoglobin
Thick filaments are assembled from bundles of the protein called
myosin
After the cross bridges are formed, ATP is required to detach the ______ and complete the sequence of cyclic events.
myosin heads