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A&P - Ch 9

Muscle tissue

QuestionAnswer
skeletal muscles maintain __ posture
skeletal muscles __ joints stabilize
skeletal muscles generate __ heat
skeletal muscles __ __ but tires easily contracts rapidly
in skeletal muscles, each muscle is a(n) organ composed of muscle tissue, blood, & connective tissue
striated; involuntary; responsible for pumping blood through body; specialized muscle cardiac muscle
cardiac muscle contracts at steady rate set by __ __ heart’s pacemaker
neural controls, in cardiac muscles allow heart to respond to changes in body needs
spindle-shaped cells w/1 centrally located nucleus; no externally visible striations; involuntary; forces food, feces & other substances through internal body channels smooth muscles
smooth muscles are found walls of hollow visceral organs, such as stomach, urinary bladder, & respiratory passages
ability to recoil & resume resting length after being stretched elasticity
ability to be stretched/extended extensibility
muscle cell's ability to move by shortening contractility
ability to respond to stimuli excitability
most skeletal muscles __ __ & are attached to bone in at least __ places span joints; two
attachment of a muscle that remains relatively fixed during muscular contraction muscle’s origin
epimysium of muscle is fused to periosteum of a bone/perichondrium of cartilage direct or fleshy attachment
muscle's CT wrapping extends beyond muscle via tendons/aponeurosis indirect attachment
sheath of CT surrounding each muscle fiber; consists of fine areolar CT endomysium
connective tissue surrounding groups of fascicles perimysium
dense irregular connective tissue that surrounds entire muscle epimysium
sarcolemma plasma membrane os muscle cell
each __ __ is a long, cylindrical cell with multiple nuclei just beneath sarcolemma muscle fiber
sarcoplasm cytoplasm of muscle cell
contains glycosomes & myoglobin; abundant mitochondria; usual organelles sarcoplasm
myofibrils, sarcoplasmic reticulum, & T tubules are found in the muscle fiber's cytoplasm
made of hundreds of myofibrils muscle fiber (cell)
found within myofibril striations, sarcomere & myofilaments
striations of myofibril are due to arrangement of myofilaments
sarcomere is region of myofibril between 2 Z discs
banding pattern produced by thick myosin & thin actin filaments myofilaments
thin myofilaments; chiefly composed of the protein actin
thick myofilaments composed of protein myosin
each myosin molecule has rod-like tail & 2 globular heads
two interwoven, polypeptide chains are found in myosin molecule's tails
form cross bridges, found in myosin molecules heads
subunits of thin myofilaments contain active sites to which myosin heads attach during contraction
regulatory subunits bound to actin tropomyosin & troponin
sarcoplasmic reticulum is elaborate smooth __ __ that runs longitudinally & surrounds each myofibril endoplasmic reticulum
sarcoplasmic reticulum has paired terminal cisternae form perpendicular cross channels
sarcoplasmic reticulum stores __ __ & releases them when muscle is stimulated to contract calcium ions
extensions of sarcolemma, penetrate deep into cell’s interior T tubules
T tubules associate w/paired terminal cisternae to form __ triads
upon __ __, myosin heads bind to active sites on actin & sliding begins nerve stimulation
thin filaments __ __ thick ones so that actin & myosin filaments __ to greater degree slide past; overlap
in the __ __, thin & thick filaments overlap only slightly relaxed state
as muscles relax, sarcomeres __ & muscle cell __ shorten; shortens
stimulated by a nerve ending; electrical current or action potential is propagated along its sarcolemma; results in a rise in intracellular Ca2+ levels skeletal muscle contraction
the final trigger for skeletal muscle contraction rise in intracellular Ca2+ levels
sequence of events by which transmission of an action potential along the sarcolemma leads to the sliding of myofilaments; linking electrical signal to contraction is called excitation-contraction coupling
skeletal muscles are stimulated by motor neurons
__ of motor neurons branch as they enter muscles axons
each __ __ forms a neuromuscular junction w/muscle fiber axonal terminal
axon branch; folds of sarcolemma at motor end plate w/acetyl choline receptors; synaptic vesicles in axon terminal; synaptic cleft; are all components of a(n) neuromuscular junction (NMJ)
__ __ reaches axon terminal at NMJ nerve impulse
at NMJ, voltage-gated __ __ in axon terminal open, allowing __ enter axon calcium channels; Ca++
at NMJ, Ca++ inside axon terminal causes synaptic vesicles to fuse with __ __ axonal membrane
at NMJ, fusion of synaptic vessels w/axonal membrane releases ACh into synaptic cleft via __ exocytosis
at NMJ, binding of ACh to its receptors on sarcolemma opens Na/K __ __ gated channels
at NMJ, more Na+ diffuses in & interior of sarcolemma becomes less negative (depolarization), which initiates a(n) action potential in muscle
at NMJ, ACh is quickly destroyed by __ acetylcholinesterase enzyme
predominant extracellular ion is Na+; predominant intracellular ion is K+ resting state
in resting cell inside of sarcolemma is negative compared to outside
difference in charge of sarcolemma, negative compared to outside, is known as resting membrane potential
action potential, depolarization, takes place when ACh binds to its receptors on sarcolemma Na/K channels open
once ACh binds to its receptors on sarcolemma Na/K channels open, sodium channels open first- Na+ diffuses in & causes a patch of sarcolemma to become less negative
change in resting potential is depolarization
initially, depolarization, is a local electrical event called end plate potential
if stimulus is strong enough, a(n) __ __ is initiated action potential/propagation
if action potential initiated, voltage-gated Na+ channels open in adjacent areas of sarcolemma causing it to depolarize
action potential travels across sarcolemma
ultimately action potential results in contraction of a muscle
in action potential/repolarization, sarcolemma permeability changes
in action potential/repolarization, Na+ channels __ & K+ channels __ close; open
in action potential/repolarization, K+ __ out from cell, restoring __ membrane potential (becoming negative again) diffuses; resting
occurs in same direction as depolarization repolarization
in excitation/contraction coupling, action potential propagates along sarcolemma to T-tubules
in excitation/contraction coupling, action potential propagated along sarcolemma to T-tubules triggers Ca2+ release from terminal cisternae
in excitation/contraction coupling, Ca++ bind to __; blocking action of tropomyosin released- actin binding sites __ troponin; exposed
in excitation/contraction coupling, myosin heads attach forming a __ __; power stroke of myosin head causes sliding of __ __ toward center of sarcomere cross bridge; thin filaments
binding of ATP to myosin heads results in their detachment from actin during excitation/contraction coupling
during excitation/contraction coupling, as action potential ends, removal of Ca+2 by __ __ active transport
stiffening of muscles after death; cross bridge detachment requires ATP rigor mortis
because of lack of __ after breathing stops- actin & myosin irreversibly cross linked causing rigor mortis ATP
refers to activation of cross bridges contraction
force exerted by contracting muscle on an object muscle tension
opposing force exerted on muscle by weight of object load
occurs when tension generated by cross bridges exceeds forces opposing it shortening
when cross bridges become inactive, tension declines & relaxation occurs contraction ends
contraction in which muscle does not shorten (load is too heavy) but its internal tension increases; load not moved isometric contraction
isometric contraction is used in standing, sitting, posture
muscle changes in length; muscle tension overcomes load & moves load isotonic contraction
isotonic contraction are used in walking/moving any part of body
motor neuron & all muscle fibers it supplies motor unit
muscles that control fine precise movements e.g. fingers, eyes (few muscle fibers) have small motor units
large weight-bearing muscles (many muscle fibers) e.g. thighs, hips have large motor units
muscle contraction in response to a single stimulus muscle twitch
phase of a muscle twitch; first few m/sec after stimulus; no response seen yet latent period
phase of a muscle twitch when cross bridges form period of contraction
phase of a muscle twitch when Ca2+ re-enters SR; muscle tension decreases period of relaxation
factor affecting muscle tension in which muscle stimulated rapidly, contractions are summed up become stronger frequency of stimulation
factor affecting muscle tension in which the more the motor fibers are contracting (by recruitment of more motor units) the stronger the contraction number of muscle fibers contracting
factor affecting muscle tension in which muscles contract strongest when muscle fibers are moderately stretched before contraction degree of muscle stretch
degree of muscle stretch is optimum muscle length at which they can generate maximum force of contraction
degree of muscle stretch, number of muscle fibers contracting, & frequency of stimulation factors that affect muscle tension
single stimulus results in a single contractile response a muscle twitch
with increased frequency of stimulus muscle does not relax completely; contraction force increasing wave summation
shorter & shorter relaxation incomplete tetanus
smooth continuous contraction without any relaxation complete tetanus
produces weak contraction because overlapping thin filaments interfere with each other unstretched sarcomere
cross bridges too far apart to cycle overstretched sarcomere
maximum tension develops at this optimum overlap of thick & thin filaments; all cross bridges can cycle moderately stretched sarcomere
constant, partial state of muscle contraction which does not produce active movements muscle tone
muscle tone keeps muscles __ & ready to __ to stimulus firm; respond
account for muscle tone by responding to stretch receptors in muscles & tendons spinal reflexes
ATP in muscle contraction is used for energizing power stroke of myosin head
ATP in muscle contraction is used for ___ myosin head from actin detaching
ATP in muscle contraction is used for pumping __ back into sarcoplasmic reticulum calcium
creatine phosphate (CP), anaerobic glycolysis of glucose, & aerobic respiration are sources of ATP regeneration
during contraction: hydrolysisphosphate group combines w/ADP to form ATP (immediate source) creatine phosphate (CP)
during contraction: when muscle contractile activity reaches 70% of maximum, bulging muscles compress blood vessels; impaired O2 delivery anaerobic glycolysis of glucose
during contraction, largest amount of ATP formed aerobic respiration
muscle is being stimulated but is in a state of physiological inability to contract muscle fatigue
muscle fatigue can be due to __ ATP production low
muscle fatigue can be due to __ __ accumulation lactic acid
a functional characteristic of muscle fiber type, slow & fast fibers on basis of speed of contraction
a functional characteristic of muscle fiber type, according to ATP-forming pathways oxidative or glycolytic fibers
cells that rely on oxygen-using aerobic pathways for ATP generation oxidative fibers
cells that rely more on anaerobic glycolysis pathways for ATP generation glycolytic fibers
characteristics intermediate btwn oxidative & glycolytic fibers fast oxidative fibers
red fibers; depend on aerobic ATP production; have more myoglobin, capillaries, mitochondria, low glycogen; contract slowly, are fatigue resistant & have high endurance slow oxidative fibers
example of slow oxidative fibers muscles maintaining posture; activities- running a marathon
white fibers; mainly use glycolysis for ATP production; large diameter fibers, have abundant glycogen, but few capillaries, mitochondria & low myoglobin; contract quickly, and are easily fatigued; muscles used for short time in powerful activities fast glycolytic fibers
example of fast glycolytic fibers hitting baseball, pushing piano
most muscles contain a(n) __ of fiber types mixture
shrinkage of muscle due to decrease in size of cells atrophy
example of disuse atrophy immobilization
example of atrophy due to loss of nerve supply paralysis
enlargement of a muscle; more capillaries & more mitochondria; greater bulk through increase in size, but not in number of cells hypertrophy
example of hypertrophy strenuous exercise in body builders
composed of spindle-shaped fibers w/central nuclei smooth muscle
smooth muscle is found in walls of blood vessels, digestive, urinary, respiratory & reproductive tracts
smooth muscle is organized in two layers of sheets
organized sheets of smooth muscle are sheets of longitudinal & circular
smooth muscle lack the __ __ junctions of skeletal muscle structures neuromuscular
smooth muscles autonomic nerve fibers have __ that release neurotransmitters varicosities
smooth muscle sarcoplasmic reticulum is less developed
smooth muscle T tubules are absent
in smooth muscle, actin & myosin filaments are present but there are no sarcomeres
in smooth muscle, there is no troponin complex
slow & prolonged; has low energy requirements smooth muscle contraction
mostly whole sheets of smooth muscle contract together, because of __ __, as __ __ spread from cell to cell gap junctions; action potentials
each skeletal muscle fiber is stimulated to __ by its own NMJ contract
in smooth muscle, actin & myosin interact by the sliding filament mechanism
in smooth muscle, final trigger for contractions is a(n) rise in intracellular Ca2+
in smooth muscle, sliding filament mechanism requires ATP
in smooth muscle, Ca2+ enter mainly from the __ __ extracellular space
in smooth muscle, some Ca2+ is __ __ SR released from
when stretched to an optimal length contract more strongly cardiac & skeletal muscles
smooth muscle responds to stretch briefly by __ __ then adapts to its new length & relaxes increased contraction
enables organs such as the stomach and bladder to be able to store contents without strong contractions expelling contents stress-relaxation response of smooth muscles
found in walls of hollow visceral organs; cells contract as a unit (have gap junctions); arranged in sheets; show stress-relaxation response smooth muscle single unit
found in airways, large arteries, internal eye muscles; have individual NMJs & muscle fibers independent of each other smooth muscle multiunit
increase in cell numbers hyperplasia
smooth muscles can undergo hyperplasia when stimulated
examples of smooth muscle hyperplasia stimulation is estrogen’s effect on the uterus
during pregnancy, estrogen stimulates uterine growth to accommodate the increasing size of the growing fetus, causing smooth muscle hyperplasia
because skeletal & smooth muscles are __ they are called muscle fibers elongated
whenever you see prefixes myo-/mys- or sarco- the reference is to muscle
word root means muscle myo-/mys-
word root means flesh sarco-
word root means husk -lemma
muscle composed of cylindrical, multinucleate cells w/obvious striations; attached to skeleton; voluntary muscle skeletal muscle tissue
skeletal muscle tissue is packaged; organs that attach to & cover bony skeleton; responsible for body movements skeletal muscles
cardiac muscles tissue constitutes bulk of __ __ heart walls
allow heart to speed up for brief periods of exertion neural controls
response to stimuli; generation of electrical impulse that passes along plasma membrane of muscle cell & causes cell to contract conductivity
produces movement, maintains posture, stabilizes joints, generates heat, etc. muscle functions
skeletal muscles are responsible for all __ & __ locomotion; manipulation
skeletal muscles enable you to __ __ to changes in external environment respond quickly
cardiac muscle of heart & smooth muscle in walls of blood vessels help to maintain blood pressure
skeletal muscles account for at least 40% of body mass
skeletal muscles are muscle type most responsible for generating heat
form valves to regulate passage of substances through internal body openings, dilate/constrict pupils of eyes, & forms arrector pili muscles attached to hair follicles smooth muscles
predominately muscle fibers, but also blood vessels, nerve fibers, & CT composition of skeletal muscles
in general, __ __ is served by one nerve, artery, & 1/more veins each muscle
only cardiac & smooth muscles can contract in without nerve stimulation
long & winding w/numerous cross-links, which is feature that accommodates changes in muscle length muscle capillaries
muscle capillaries __ when muscle is stretched straighten
muscle capillaries __ when muscle contracts contort
support each muscle cell & reinforce muscle as a whole; prevents bulging muscle from bursting during strong contractions CT sheaths
bundle of nerve/muscle fibers bound together by CT fascicles
CT sheaths contribute to __ of muscle tissue elasticity
CT sheaths provide entry & exit routes for blood vessels & nerve fibers serving muscle
movable attachment of a muscle muscle's insertion
when muscle contracts movable bone, __ moves towards immovable/less movable bone insertion
cord of dense fibrous tissue attaching muscle to bone tendon
fibrous/membranous sheet connecting muscle & part it moves aponeurosis
anchors muscle to CT covering of skeletal element or fascia of other muscles aponeurosis/tendon
indirect attachments are more common because of their durability & size
more __ than fleshy muscle can pass over __ tendons; joint
granules of stored glycogen that provide glucose during periods of muscle cell activity glycosomes
oxygen-binding, red pigment in muscle myoglobin
myoglobin is similar to hemoglobin
rod-like bundle of contractile filaments (myofilaments) found in muscle fibers (cells) myofibril
myofibrils account for about 80% of cellular volume
repeating series of dark & light bands, evident along length of each myofibril striations
dark striations within muscle cells A bands
light striations within muscle cells I bands
lighter region in midsection of A band H zone
dark line that bisects each H zone vertically; formed by molecules of protein myomesin M line
darker, midline interruption in I bands; coin-shaped sheet composed largely of protein alpha-actinin; anchors thin filaments Z disc
smallest contractile unit of muscle; extends from 1 Z disc to next sarcomere
sarcomere is __ __ of skeletal muscle functional unit
sarcomere contains __ band flanked by 1/2 __ band A; I
located in center; contain myosin; extend entire length of A band thick filaments
more lateral; contain actin; extend across I band & partway into A band thin filaments
contain desmin; extend from Z disc; connect each myofibril to next throughout width of muscle cell intermediate filaments
consists of 2 heavy & 4 light polypeptide chains; has rod-like tail attached by flexible hinge to 2 globular heads myosin molecule
rod-shaped protein, spiral about actin core & hep stiffen & stabilize it tropomyosin
in relaxed muscle fiber, tropomyosin __ myosin-binding sites on actin block
globular, three-polypeptide complex troponin
troponin & tropomyosin help control __ __ involved in contraction myosin-actin interactions
composed of titin elastic filament
protein extending from Z disc to thick filament, & then runs within thick filament to attach to M line titin
titin forms __ of thick filament core
titin holds thick filaments in place, thus maintaining organization of A band
titin holds thick filaments in place, helping muscle cell to spring back into shape after being stretched
titin does not resist stretching in ordinary range of extension
titin stiffens as it uncoils, helping muscle to resist excessive stretching
structural protein that links thin filaments to integral proteins of sarcolemma dystrophin
nebulin, myomesin, & C proteins are other proteins that act to bind filaments or sarcomeres together & maintain their alignment
SR & T tubules are two sets of intracellular tubules that participate in regulation of muscle contractions
tubules of SR run longitudinally along myofibril communicating at H zone
major role of SR is to regulate intercellular levels of ionic calcium
T tubules increase muscle fiber's __ __ surface area
successive groupings of 2 membranous structures (terminal cisterna, T tubule, & terminal cisterna triads (definition)
because T tubules are extensions of sarcolemma they conduct impulses to deepest regions of muscle cell to every sarcomere
protruding integral proteins of T tubules act as voltage sensors
form gated channels through which Ca2+ can be released from SR cisternae foot proteins
term contraction refers to activation of myosin's cross bridges
states that during contraction thin filaments slide past thick ones so that actin & myosin filaments overlap to greater degree sliding filament model of contraction
for skeletal muscle to contract it must be stimulated by nerve ending so change in membrane potential occurs
large transient depolarization event, including polarity reversal, that is conducted along membrane of muscle cell/nerve fiber action potential
for skeletal muscle to contract it must be activated, then must generate & propagate action potential along its sarcolemma
for skeletal muscle to contract it must be activated, generate/propagate action potential, then final trigger is short-lived rise in intracellular calcium ion levels
nerve cells that activate skeletal muscle fibers are called somatic motor neurons
long thread-like extensions of somatic motor neurons axons
synaptic connection of axon of motor neuron with muscle fiber neuromuscular junction
when axon of motor neuron divides when entering muscle, the short curling branches it gives off are collectively called elliptical neuromuscular junctions
each muscle fiber has only one neuromuscular junction
fluid-filled (with ACh) space at a synapse synaptic cleft
chemical transmitter substance released by some nerve endings; neurotransmitter acetylcholine (ACh)
trough-like part of muscle fiber's sarcolemma junctional folds
junctional folds provide __ __ __ for location for millions of ACh receptors large surface area
neuromuscular junction includes axonal endings, synaptic cleft, junctional folds
enzyme present at NMJ & synapses that degrades acetylcholine & terminates its action acetylcholinesterase
disease characterized by drooping upper eyelids, difficulty swallowing & talking, & generalized muscle weakness, involves shortage of ACh receptor myasthenia gravis
resting sarcolemma is polarized
loss of a state of polarity; loss/reduction of negative membrane potential depolarization
depolarizations of skeletal muscle fibers caused by neurotransmitters binding to post-synaptic membrane in NMJ end plate potential
movement of membrane potential to initial resting state repolarization
period of time it takes for an excitable membrane to be ready for 2nd stimulus once it returns to its resting state following an excitation refractory period
repolarization only restores __ __ of resting state electrical conditions
ATP-dependent sodium-ion pump restores __ __ of resting state ionic conditions
once initiated, the action potential is __ unstoppable
events of excitation-contraction coupling take place during __ __ btwn action potential initiation & beginning of mechanical activity latent period
intracellular Ca levels low & active (myosin-binding) sites on actin are physically blocked by tropomyosin muscle is relaxed
tropomyosin is __ when sufficient Ca is present removed
continues as long as Ca signal & adequate ATP are present sliding of thin filament
when impulses delivered rapidly, intracellular Ca2_ levels __ __ due to successive rounds of Ca2_ released from SR increase greatly
except for brief period following muscle cell __, Ca ion concentrations in cytosol are kept low excitation
graphic recording of mechanical contractile activity produced by apparatus that measures muscle contraction myogram
latent period period of time btwn stimulation & onset of muscle contraction; excitation-contraction coupling occurs here
period of contraction when cross bridges are active, from onset-peak tension development, myogram tracing rises to peak
period of relaxation final phase; initiated by reentry of Ca2+ into SR
muscle twitches may result from some neuromuscular problems
relatively smooth; vary in strength as different demands placed on them healthy muscle contractions
variations in degree of muscle contraction by changing either frequency/strength of stimulus graded muscle responses
nervous system achieves __ __ __ by increasing firing rate of motor neurons greater muscular force
occurs in transmission of nerve impulses when volley of impulses arrives at synapse so that duration of impulses is briefer than post-synaptic potential & their deliveries of transmitter are combined to create larger than normal response temporal/wave summation
each stimulus causes contraction to be initiated when muscle has only partly relaxed from previous contraction unfused/incomplete tetanus
sustained muscular contraction caused by series of nerve stimuli repeated so rapidly that individual muscular responses are fused complete tetanus
fused/complete tetanus happens __ in real world infrequently
__ tetanus eventually leads to muscle __ prolonged; fatigue
wave summation contributes to __ force contractile
is to produce smooth, continuous muscle contractions by rapidly stimulating specific number of muscle cells primary function of wave summation
smooth but steady increase in muscular tension produced by increasing number of active motor units recruitment/multiple motor unit summation
stimulus too weak to evoke a response subthreshold stimulus
one stimulus just strong enough to excite; weakest stimulus capable of producing response in irritable tissue threshold stimulus
stimulus strong enough to evoke greatest possible response; represents point at which all muscle's motor units are recruited maximal stimulus
increasing stimulus intensity beyond maximal stimulus does not produce stronger contraction
recruitment process is __ by size principle dictated
motor units of small, highly excitable motor neurons (found in smallest muscle fibers) tend to be activated first; as motor units w/larger & larger muscle fibers begin to excited, contractile strength increases size principle
size principle dictates that largest motor units containing large, coarse muscle fibers controlled by largest least excitable neurons & are activated only when most powerful contraction is necessary
size principle is important because it allows for increases in force during weak contractions to occur in small steps
according to size principle, gradations in muscle force are __ __ when large amounts of force are needed progressively greater
although all motor unit of a muscle may be recruited simultaneously to produce strong contraction, they are more commonly activated __ in body asynchronously
even __ muscles are almost always __ relaxed; contracted
muscle contraction that occurs while muscle is shortening as it develops tension & contracts to move resistance concentric contraction
type of muscle contraction that occurs as muscle fibers lengthen; contractile force generated by muscle is weaker than opposing force, which causes muscle to stretch eccentric contraction
eccentric contractions are about 50% __ __ than concentric ones more forceful
eccentric contractions put body in position to contract concentrically
CP-ADP reaction is catalyzed by creatine kinase
initial phase of glucose breakdown; anaerobic pathways; glucose broken down into pyruvic acid molecules releasing enough energy to form small amount of ATP glycolysis
2 ATP produce per glucose broken down
product of anaerobic metabolism, especially in muscle lactic acid
lactic acid is produced when bulging muscles (from vigorous activity) compress blood vessels within them causing impaired blood flow & O2 delivery
energy-yielding conversion of glucose to lactic acid in muscle, when sufficient oxygen is not available anaerobic glycolysis
during __ __, lactic acid is end product of cellular metabolism of glucose oxygen deficit
95% of ATP used for muscle activity from from aerobic respiration
when ATP demands are within capacity os aerobic pathway, light to moderate muscular activity can continue for several hours in well-conditioned person
when exercise demands begin to exceed ability of muscle cells to carry out necessary reactions quickly enough, glycolysis contributes more & more of total ATP generated
length of time muscle can continue to contract using aerobic pathways aerobic endurance
point at which muscle metabolism converts to anaerobic glycolysis anaerobic threshold
activities requiring surge of power lasting only few seconds (i.e. weight lighting, diving, etc.) rely entirely on ATP & CP stores
more on-and-off or burst-like activities (i.e. tennis, soccer, etc.) appear to be fueled almost entirely by anaerobic glycolysis
prolonged activities (i.e. marathons, jogging) where endurance over power is goal, depend mainly on aerobic respiration
levels of CP & ATP do not change much during __ __ because ATP is generated at same rate it is use prolonged exercise
states of continuous contraction because cross bridges are unable to detach contractures
example of temporary contracture writer's cramp
several __ __contribute to muscle fatigue ionic imbalances
lactic acid is more important in provoking __ fatigue than __ fatigue central; physiological
excessive intracellular accumulation of lactic acid raises concentration of H+ and alters __ __ contractile proteins
lactic acid has been shown to __ high K+ levels, which do lead to muscle fatigue counteract
intense exercise of short duration produces fatigue rapidly via disturbances that alter E-P coupling
short-duration exercise damages SR, interfering with Ca2+ __ & __, and thus with muscle activation regulation; release
O2-requiring muscle metabolism activities occur more slowly & are deferred until O2 is again available during anaerobic muscle contraction
volume of O2 required after exercise to replenish stores of O_2, ATP, creatine phosphate, & glycogen & oxidize lactic acid formed during exercise oxygen deficit (definition)
oxygen deficit represents difference btwn amount of oxygen __ for totally aerobic muscle activity & amount __ __ need; actually used
only about 40% of energy released during muscle activity is converted to useful work
greater muscle's __ __, more tension can develop & greater its strength cross-sectional area
force generated by cross bridges, inside contracting muscle fibers internal tension
force generated in extracellular fibers external tension
length at which muscle can generate maximum force optimal operating length
relationship btwn length of fiber & force that fiber produces at that length; permits sliding along nearly entire length of thin filaments ideal length-tension relationship
in slow/fast fibers, difference in speed reflects how fast their myosin ATPases __ __ split ATP
in slow/fast fibers, difference in speed reflects on pattern of __ __ of motor neurons electrical activity
depending on pathways for forming ATP, skeletal muscles cells can be classified as slow oxidative (SO), fast oxidative (FO), or fast glycolytic (FG) fibers
exercise that increases the need for oxygen aerobic exercise
moderately weak but sustained muscle activity endurance exercise
high-intensity exercise in which the muscles are pitted against high resistance or immovable forces and, as a result, muscle cells increase in size resistance exercise
smooth muscle fibers run parallel to long axis of organ; when muscle contracts organ dilates & shortens longitudinal layer
smooth muscle fibers run around circumference of organ; contraction constricts lumen causing it to elongate circular layer
junction of varicosities & synaptic cleft of smooth muscle cells diffuse junctions
epimysium surround entire muscle
endomysium surround each muscle fiber
perimysium surround each muscle bundle
deep fascia bind muscles into functional groups
sarcolemma plasma membrane of skeletal muscle fiber
sarcoplasm cytoplasm of a skeletal muscle fiber
sarcoplasmic reticulum series of membranous channels (modified ER) that surround each myofibril
myofibril rod-like contractile elements within a muscle fiber
sarcomere functional unit of a skeletal muscle fiber
A band area of the sarcomere with overlapping thick and thin filaments
I band area of sarcomere containing only thin filaments
H band are in center of A band containing only thick filaments
myosin molecules cross bridges
synaptic knob contains vesicles filled w/ACh
synaptic cleft space btwn neuron & muscle
motor end plate contains receptors for ACh
twitch type of contraction represented by a single stimulus/contraction/relaxation sequence
incomplete tetanus muscle producing peak tensions with visible relaxation during rapid cycles of contraction and relaxation
complete tetanus muscle that is stimulated so frequently that the relaxation phase is completely eliminated
wave summation when muscle is stimulated repeatedly for several seconds with a constant stimulus, the amount of tensions gradually increases to a maximum
endurance-type activities best suited for slow oxidative fibers
400M or 800M sprint best suited for fast oxidative fibers
short-term intense movements best suited for fast glycolytic fibers
skeletal muscle fibers single, very long, cylindrical, multinucleate cells with striations
cardiac muscle cells branching chains of cells; uni- or binucleate striations; intercalated discs
smooth muscle cells single, fusiform, uninucleate; no striations
excitability ability to receive and respond to a stimulus
contractility ability to shorten forcibly when adequately stimulated
extensibility ability to be stretched or extended
elasticity ability of a muscle to resume its resting length after being stretched
isotonic contraction contraction of muscle during which the muscle changes in length and the tension remains constant through most of the contractile period
isometric contraction contraction of muscle during which the tension continues to increase but the muscle neither shortens nor lengthens
concentric contraction contraction of the muscle in which the muscle shortens and does work
eccentric contraction contraction of muscle in which the muscle contracts as it lengthens
skeletal muscle voluntary via __ __ of the somatic nervous system axonal endings
involuntary; intrinsic system regulation, hormones and autonomic nervous system controls cardiac muscles
involuntary, autonomic nerves, hormones, local chemicals smooth muscles
acetylcholine (ACh) neurotransmitter at the neuromuscular junction
creatine phosphate high-energy compound in muscle
myoglobin O2 storage molecules in muscles
lactic acid product of anaerobic glycolysis
fast oxidative fibers muscle fibers that contract quickly and rely on aerobic respiration for ATP
slow oxidative fibers muscle fibers that are most resistant to fatigue
fast glycolytic fibers muscle fibers that have few mitochondria
sustained spasm, or tetanic contraction cramp
inflammation of a muscle, its connective tissue coverings and tendons, and capsules of nearby joints fibromyositis
muscle pain resulting from any muscle disorder myalgia
excessive stretching and possible tearing of a muscle caused by muscle overuse or abuse strain
latent period time btwn stimulus/electrical event & mechanical event of contraction
contraction period time during which the muscle is shortening
relaxation period time during which the muscle is returning to its original length
refractory period very brief time after one stimulus during which the muscle is unresponsive to a second stimulus
action potential propagation of an electrical current along sarcolemma
resting potential initial polarized state
repolarization restoration of membrane potential to resting potential
refractory period time when fiber cannot be stimulated until repolarization is complete
end plate potential electrical event occurring only at neuromuscular junction
Ca2+ released by terminal cisternae into the sarcoplasm to bind with troponin
acetylcholinesterase enzyme released into neuromuscular junction to break down acetylcholine
calmodulin cytoplasmic, calcium-binding protein
electrical conditions of a resting sarcolemma outside positive relative to the inside
depolarization & generation of action potential production of an end plate potential at the motor end plate and consequent depolarization of adjacent areas
propagation of action potential increased positive charge inside sarcolemma changes permeability of adjacent areas, opening voltage-regulated Na+ channels
repolarization change in sarcolemma after the wave of depolarization; Na+ channels close and K+ channels open, allowing K+ to create a positive charge outside the membrane
producing movement pulling on something to change its position
maintaining posture development of tension to prevent movement, as in keeping the vertebral column upright
stabilizing joints attaching to bones and keeping them in close proximity to one another
generation of heat release of energy during metabolism
myosin changes shape during the contraction cycle
actin slides toward the M line during a contraction
tropomyosin covers the binding site
troponin binds Ca2+ and starts the contraction cycle
__ skeletal muscle is surrounded by epimysium entire
as an axon enters a muscle, it branches into a number of axonal terminals, each of which forms a neuromuscular junction with a single muscle fiber. A motor neuron and all the muscle fibers it supplies is called a(n) motor unit
What is the ion released from the terminal cisternae that combines with troponin and removes the blocking action of tropomyosin, resulting in the formation of cross bridges? Ca2+
each skeletal muscle fiber is controlled by a neuron at a single NMJ
terminal cisterna, transverse tubule, and terminal cistern composition of the structure known as a triad in a skeletal muscle fiber
In the __ __ __ of muscle contraction, the myofilaments slide over each other, resulting in the overlapping of actin and myosin sliding filament model
epimysium is the dense layer of collagen fibers that surround an entire skeletal muscle
muscle tone means a continued mild or partial contraction of an entire muscle is muscle
isometric type of muscle contraction in which the muscle fibers produce increased tension, but the muscle neither shortens nor lengthens
lactic acid substance that increases in quantity during repetitive muscle contraction
action potential sequence of electrical changes that occurs along the sarcolemma when a muscle fiber is stimulated
calmodulin binds calcium ions in a smooth muscle, causing contraction
sarcomere is part of a myofibril
"cross bridges" that link between the thick and thin filaments are formed by the globular heads of thick filaments
refractory period in which the muscle will not contract if stimulated occurs during refractory period of muscle cell
cause of rigor mortis calcium influx into the cell after death
95% of the energy needed for contraction during moderate exercise comes from ATOP
T-tubules serve as a communication network that coordinates the contraction of each myofibril that makes up the muscle fiber
actin myofilaments are composed chiefly of
when an action potential arrives at the neuromuscular junction, the most immediate result is release of acetylcholine
if a muscle is applied to a load that exceeds the muscle's maximum tension muscle length will not change during contraction
graded muscle response variation of stimulation needed in skeletal muscle contraction in order to have controlled movement
aerobic respiration most efficient means of producing ATP
if muscle became totally depleted of ATP muscle would remain in a contracted state due to an inability to break actin-myosin cross bridges
smooth muscle depends on the __ system to regulate contraction calcium-calmodulin
skeletal muscle relies on the __ __ system to regulate contraction calcium-troponin
peristalsis progressive, wavelike contractions that move foodstuffs through alimentary tube organs/move other substances through other hollow body organs
smooth muscle lacks highly structured, __ __ of skeletal muscles specific NMJs
smooth muscles are controlled by innervating nerve fibers, part of autonomic nervous system
varicosities knob-like swellings of certain autonomic axons containing mitochondria and synaptic vesicles
diffuse junctions wide synaptic cleft in general area of smooth muscles
smooth muscles have __ __ SR less developed
some SR tubules of smooth muscle touch __ at several sites, forming what resembles __ sarcolemma; half-triads
pouch-like infoldings that sequester bits of extracellular fluid containing high concentration of Ca2+ close to membrane caveolae
when calcium channels in caveolae open, Ca2+ influx occurs rapidly
in smooth muscles, SR does release some calcium that triggers contraction, but most enters through the calcium channels
contraction of smooth muscle ends when calcium is actively transported to SR & out of cell
smooth muscles contain interdigitating thick & thin filaments
in smooth muscle, __ filament are fewer, but have __ __ along their entire length thick; myosin heads
in smooth muscle, there is no __ __ in thin filaments troponin complex
in smooth muscle, thick & thin filaments are __ __ allowing muscles to contract in __ __; thus peristalsis arranged diagonally; twisting way
in smooth muscles, the lattice-like arrangement of non-contractile __ filaments attach to __ __ intermediate; dense bodies
cytoplasmic structures; tethered to sarcolemma; act as anchoring points for thin filaments; correspond to Z discs of skeletal muscles dense bodies
forms strong, cable-like intracellular cytoskeleton that harnesses pull generated by sliding of thick & thin filaments in smooth muscles intermediate filament-dense body network
dense bodies, of smooth muscles, bind muscle cell to endomysium & adjacent cells
synchronizistic contraction of smooth muscles reflects electrical coupling by gap junctions
allow smooth muscles to transmit action potentials from fiber to fiber gap junctions
some smooth muscles in stomach & small intestines are pacemaker cells
smooth muscle's pacemaker cells have fluctuating __ __ & are __ membrane potentials; self-excitatory
smooth muscle's pacemaker cells __ __ in absence of stimuli depolarize spontaneously
rate & intensity of smooth muscle contraction may be modified by neural & chemical stimuli
in order to phosphorylate myosin, calmodulin interacts with myosin kinase/myosin light chain kinase
smooth muscle takes 30x longer to contract & relax than skeletal muscle
smooth muscle myofilaments may __ __ during prolonged contractions, saving energy latch together
smooth muscle cells may maintain __ __ even after dephosphorylation of myosin latch state
__ __ of smooth muscle is extremely important to overall body homeostasis ATP-efficient contraction
graded contraction depends on level of calcium and # of cross bridges formed smooth muscle tone
smooth muscle makes ATP through __ __ aerobic pathways
some smooth muscles respond to neural stimulation with __ __ only graded potentials
smooth muscles react to __ __ in different ways depending on receptors present different neurotransmitters
smooth muscles without nerve supply depolarize __ or in response to chemical stimuli that bind to __ __ receptors spontaneously; G protein-linked
certain hormones, lack of O2, histamine, excess CO2, & low pH are different chemical factors that cause smooth muscle contraction & relaxation without an action potential
smooth muscle responds differently to stretch
smooth muscle can __ more than other muscle types shorten
stretch of smooth muscle provokes contraction, but soon muscle adapts to length & relaxes with retaining ability to contract on demand
lack of sarcomeres & irregular, overlapping arrangement of smooth muscle filaments allow them to generate considerable force, even when they are substantially stretched
smooth muscle can contract when it is anywhere from twice to half its resting length
smooth muscles are categorized as single-unit or multiunit
type of smooth muscle; cells contract as unit & rhythmically, are electrically coupled by gap junctions; often exhibit spontaneous action potentials visceral muscle
visceral muscle is also known as single-unit smooth muscle
visceral muscle is found in walls of all hollow organs except the heart
smooth muscles in large airways to lungs & in large arteries, arrector pili muscle attached to hair follicles, & internal eye muscles are examples of multiunit smooth muscle
in multiunit smooth muscle gap junctions are rare & spontaneous synchronous depolarization are rare
multiunit smooth muscle is innervated by autonomic nervous system
embryonic mesoderm cells from which all muscle fibers develop myoblasts
Created by: lfrancois