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110 terms

Muscle Chapt. 10

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the following is a function of skeletal muscle
produce movement, maintain posture.
the contractions of skeletal muscles pull on tendons and move bones of the skeleton, skeletal muscles are responsible for
controlling the openings of the digestive and urinary tracts
skeletal muscles support the weight of some internal organs, muscle contractions help maintain body temperature
the dense layer of collagen fibers that surround an entire skeletal muscle is the
epimysium
nerves and blood vessels that service the muscle fibers are located in the connective tissues of the
perimysium
the delicate connective tissue that surrounds the skeletal muscle fibers and ties adjacent muscle fibers together is the
edomysium
the bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a
tendon
muscle fibers differ from "typical" cells in that muscle fibers
have many nuclei
the advantage of having many nuclei in a skeletal muscle fiber is
the ability to produce large amounts of the enzymes and structural proteins needed for contraction
skeletal muscle fibers are formed from embryonic cells called
myoblasts
the cell membrane of skeletal muscle is called the
sarclemma
the cytoplasm of a skeletal muscle fiber is called the
sarcoplasm
the series of membranous channels that surround each myofibril is the
sarcoplasmic reticulum
the functional unit of a skeletal muscle fiber is the
sarcomere
interactions between actin and myosin filaments of the sarcomere are responsible for
muscle contraction
in a sarcomere, thick fillaments are linked laterally by filaments of the
M line
thin filaments at either end of the sarcomere are attached to the
Z line
the area of the sarcomere containing the thick filaments is the
A band
the area of the sarcomere that contains only thin filaments is the
I band
the area in the center of the A band that contains only thick filaments is the
H band
each thin filament consists of
a pair of protein strands wound together
the sarcoplasmic reticulum stores
calcium ions
the skeletal muscle complex known as the triad consists of
a transverse tubule and terminal cisternae
cross-bridges are portions of
myosin molecules
at rest, active sites on the actin are blocked by
tropomyosin molecules
at rest, the tropomyosin molecule is held in place by
troponin molecules
each skeletal muscle fiber is controlled by a neuron at a single
neuromuscular junction
the space between the neuron and the muscle is the
synaptic cleft
receptors for acetylcholine are located on the
motor end plate
action potentials are conducted into a skeletal muscle fiber by
transverse tubules
active sites on the actin become available for binding when
calcium binds to troponin
in response to action potentials arriving from the transverse tubules, the sarcoplasmic reticulum releases
calcium ions
which of the following acts as an ATPase during the contraction cycle of muscle?
myosin cross-bridges
when calcium ion binds to troponin,
tropomyosin moves out of the groove between the actin molecules.
the most important factor in decreasing the intracellular concentration of calcium ion after contraction is
active transport of calcium into the sarcoplasmic reticulum
when sarcomeres are fully shortened, contraction cannot occur, when sarcomeres are slightly less than fully shortened, contraction connot occur
when the muscle is fully stretched, contraction cannot occur, all sarcomeres in a muscle fiber contract and relax together.
calcium ions are released from the sarcoplasmic reticulum during the
latent period and the contraction phase
the type of contraction represented by a single stimulus/contraction/relaxation sequence is
a twitch
when a muscle is stimulated repeatedly for several seconds with a constant stimulus, the amount of tension gradually increases to a maximum. This phenomenon is called
wave summation
a muscle producing peak tension with rapid cycles of contraction and relaxation is said to be in
incomplete tetanus
if a second stimulus arrives before the relaxation stage has ended, a second, more powerful contraction occurs. This is called
wave summation
a muscle that is stimulated so frequently that the relaxation phase is completely eliminated is said to exhibit
complete tetanus
the increase in muscle tension that is produced by increasing the number of active motor units is called
recruitment
the type of contraction in which the muscle fibers produce increased tension but do not shorten is called
isometric
a resting muscle generates most of its ATP by
aerobic respiration
creatine phosphate
acts as an energy reserve in muscle tissue
during anaerobic glycolysis
ATP is produced, pyruvic acid is produced, lactic acid is produced if pyruvic acid accumulates.
at peak levels of muscle exertion the mitochondria can supply
only about 1/3 of the energy required by the muscle
when energy reserves in a muscle are exhausted and lactic acid levels increase,
fatigue occurs
during the recovery period following exercise, all of the following is true:
lactic acid is removed from muscle cells, the muscle actively produces ATP, oxygen is consumed, heat is generated
during the Cori cycle in the liver,
glucose is produced from lactic acid
during the recovery period the body's need for oxygen is increased because
additional oxygen is required to metabolize the lactic acid produced during exercise
fast fibers
produce powerful contractions
the type of muscle fiber that is most resistant to fatigue is the
slow fiber
contractions that utilize anaerobic ATP production
require maximal contraction of muscles for short periods of time
during activities requiring aerobic endurance
most of the muscle's energy is produced in mitochondria
fast muscle fibers can develop a larger number of mitochondria in response to
repeated, exhaustive stimulation
which of the following statements are true regarding human muscles:
eye and hand muscles are composed of fast fibers, back muscles are mostly composed of endurance fibers.
Each of the following changes in the skeletal muscles is a consequence of aging
muscle fibers become smaller, less elastic, fatigue more rapidly, and there is a steady decrease in number of satellite cells
heat energy produced from muscle contraction is released through the
integumentary system
cardiac muscle cannot be summated, skeletal muscle contractions may be summated, skeletal muscle control is neutral, cardiocytes are interconnected through intercalated discs
...
Neurons that innervate smooth muscle are under involuntary control, smooth muscles are uninucleate
smooth muscles do not contain sarcomeres, the thin filaments of smooth muscle fibers are attached to dense bodies
functions of smooth muscle: altering diameter of respiratory passageways, elevating hairs on the arm,
moving food materials along digestive tract, forcing urine out of urinary tract
the ability of smooth muscle to function over a wide range of lengths is called
plasticity
muscle tissue, one of four primary types of tissue, consists chiefly of muscle cells that are highly specialized for
contraction
the types of muscle tissue include all of the following: striated, cardiac, smooth
...
at each end of the muscle, the collagen fibers of the epimysium, perimysium, and endomysium come together to form either a bundle known as
a tendon or a broad sheet called a aponeurosis
in order for a muscle to contract properly, it requires
energy, oxygen, nutrients, adequate blood supply
skeletal muscle contracts only under stimulation from
the central nervous system
differences between skeletal muscle cells and typical cells include
sketetal muscle cells are larger than normal cells, and are multinucleate
each skeletal muscle fiber contains
hundreds to thousands myofibrils
when a skeletal muscle fiber contracts
the H zones and I bands get smaller, the zones of overlap get larger, the Z lines get closer together, the width of the A band gets constant
knowing that the myofibrils are attached at the Z line of the sarcolemma and at either end of the muscle fiber, when myofibrils get shorter, the muscle fiber
shortens
the pull called tension is
an active force
The cytoplasm of the synaptic terminal contains mitochondria and vesicles filled with molecules of the neurotransmitter
acetylcholine
knowing the five steps that occur causing a neuron to stimulate a muscle fiber, if there is a problem with the release of calcium ions in the third step,
the acetylcholine does not bind to the motor end plate
ATP metabolism normally provides
95% of the ATP demands of a resting cell.
in a isotonic contraction
tension rises and the skeletal muscle length changes
the contraction of a muscle exerts a pull on a bone because
muscles are attached to bones by tendons
large diameter, densith packed myofibrils, large glycogen reserves, and a few mitochondria are characteristics of
fast fibers
when contraction occur,
the H and I bands get smaller, the Z lines move closer together, the width of the A band remains constant.
which of the following hormones directly stimulates growth of muscle tissue and increased muscle mass
testosterone
because skeletal muscle contractions demand large quanities demand large qualities of ATP, skeletal muscles have
a rich vascular supply
during muscle contraction, all of the following occur, except
hemoglobin concentration in muscle fibers increases
Physical evidence that supports the sliding filament theory of muscle contraction includes
decreased distance between Z lines during contraction
when myosin cross-bridges bind to the active sites on actin,
they pivot toward the M line.
the following is a list of the events that occur during a muscle contraction
calcium ion is released from the sarcoplasmic reticulum, calcium ion binds to troponin, myosin cross-bridges bind to the actin, the myosin head pivots toward the center of the sarcomere, the myosin head binds an ATP molecules and detaches from the actin, the free myosin head splits ATP
after death, muscle fibers run out of ATP and calcium begins to leak from the sarcoplasm reticulum into the sarcoplasm. This results in a condition known as
rigor mortis
how would blocking the activity of acetylcholinesterase affect skeletal muscle--
it would cause spastic paralysis (muscles are contracted and unable to relax)
when acetylcholine binds to receptors at the motor end plate, the muscle membrane becomes
more permeable to sodium ions
each of the following factors would increase the probability of skeletal muscles contracting:
increased permeability of the muscle membrane to calcium ions, increased amounts of acetylcholine in the synaptic cleft, increased permability of the muscle membrane to sodium ion, increased numbers of acetylcholine receptors at the motor end plate
the following ratio of neurons to muscle fibers are the greatest :
muscles that control the eye
which of the following muscles would contract more forcefully-
a muscle receiving 10 to 15 action potentials per second
a muscle with 20 motor units active
would produce the greater tension
increased blood flow to a muscle could result in all of the following:
fatigue, oxygen debt, shift to more anaerobic glycolysis in the muscle, an increase in intracellular lactate
increased oxygen consumption would accompany all of the following:
increased heat production, increased conversion of lactate to glucose, increased aerobic respiration by muscle cells, increased muscle activity
how would an elevated level of thyroid hormone in the body affect skeletal muscles:
it would simulate atrophy, hypertrophy, decrease heat production by muscle tissue, increase muscle mass
How does a drug that competes with acetylcholine for receptors at the motor end plate affect skeletal muscle--
it would cause flaccid paralysis (relaxed and unable to contract)
if a person is suffering from severe hyperkalemia, you would expect
the potassium ion concentration of the interstital fluid to be less than normal, muscle weakness and increased strength of twitch contractions
The bacterium that causes tetanus produces a toxin that affects the central nervous system and skeletal muscles producing a powerful tetanic contractions of the skeletal muscles. the toxin probably acts by
making the cell membranes more permeable to calcium ions
athletes go through a warmup period before engaging in an event. the reason for this is to take advantage of
wave summation
satellite cells
are scattered between the endomysium and muscle fibers and function in the repair of damaged muscle tissue
communication between nerve and muscle fibers occur at specialized junctions called
neuromuscular junctions
on either side of a transverse tubule, the individual tubules of the sarcoplasmic reticulum fuse, and form expanded chambers called the
terminal cisternae
the theory that explains how a muscle fiber contracts is called the
sliding filament theory
the sequence of events that forms the link between electrical activity in the sarcolemma and the initiation of a contraction is called
excitation-contraction coupling
thyroid hormone
elevates the rate of energy consumption in resting and active skeletal muscles
testosterone
primary sex hormone in males
epinephrine
stimulates muscle metabolism and increases duration and stimulation of the force of contraction
myoglobin
gives red pigment to slow fibers
calmodulin
interacts with calcium ions and activates myosin light chain kinase