Chapter 9 (I) Flashcards
muscle tissue transforms ___(1)___ to ___(2)___ to exert force.
(1) chemical energy (ATP)
(2) mechanical energy
what are the 3 types of muscle tissue?
skeletal, cardiac, and smooth
skeletal muscles attach to ___(1)___ and ___(2)___.
(1) bones
(2) skin
muscle fibers
elongated cells
which muscles are striated, voluntary, contract rapidly, and tire easily?
skeletal muscles
which muscles require nervous system stimulation?
skeletal muscles
which muscles are only in the heart and are the bulk of heart walls?
cardiac muscles
which muscles are striated, involuntary, and can contract without nervous system stimulation?
cardiac muscles
which muscles are found in walls of hollow organs such as the stomach, urinary bladder, and airways?
smooth muscle
which muscles are not striated, involuntary, and can contract without nervous system stimulation?
smooth muscle
cell shape and appearance of ______: single, very long, cylindrical, multinucleate cells with obvious striations.
skeletal muscle cells
cell shape and appearance of ______: branching chains of cells; uni- or binucleate; striations.
cardiac muscle cells
cell shape and appearance of ______: single, fusiform, uninucleate; no striations.
smooth muscle cells
connective tissue components of skeletal muscles?
epimysium, perimysium, and endomysium
connective tissue components of cardiac muscle?
endomysium attached to fibrous skeleton of heart
what are the connective tissue components of smooth muscle?
endomysium
which muscles have the presence of myofibrils composed of sarcomeres? which muscles have the presence of T tubules?
skeletal and cardiac
where is the site of invagination of T tubules in the skeletal muscles? cardiac muscles?
skeletal:
2 in each A-I junction
cardiac:
1 in each sarcomere of Z disc
which muscle is the most organized? least organized?
most organized: skeletal
least organized: smooth
what has the most elaborate sarcoplasmic reticulum?
skeletal muscle
which muscles have the presence of gap junctions?
cardiac and smooth muscle
how do skeletal muscles regulate contractions?
voluntary contractions via axon terminals of the somatic nervous system
how do cardiac muscles regulate contractions?
involuntary
intrinsic system regulation and autonomic nervous system controls
hormones
how do smooth muscles regulate contractions?
involuntary
autonomic nerves
hormones
local chemicals
source of calcium for calcium pulse for skeletal, cardiac, and smooth muscle?
skeletal: sarcoplasmic reticulum (SR)
cardiac and smooth: SR and extracellular fluid
what is the site of calcium regulation for skeletal, cardiac, and smooth muscle?
skeletal and cardiac: troponin on actin-containing thin filaments
smooth: calmodulin in cytosol
which muscles have the presence of a pace maker?
cardiac and smooth
what are the effects of nervous system stimulation for skeletal, cardiac, and smooth muscle?
skeletal: excitation
cardiac and smooth: excitation or inhibition
speed of contraction for skeletal, cardiac, and smooth?
skeletal: slow to fast
cardiac: slow
smooth: very slow
which muscles have rhythmic contractions?
cardiac and smooth (in unitary muscle)
what kind of respiration does each muscle partake in?
skeletal: aerobic and anaerobic
cardiac: aerobic
smooth: mainly aerobic
what are the special characteristics of muscle tissue?
excitability
contractility
extensibility
elasticity
excitability
receive/respond to stimuli
contractility
ability to shorten forcibly when stimulated
extensibility
ability to be stretched
elasticity
ability to recoil to resting length
4 important functions of muscles
move bones/fluids
maintain posture/body position
stabilize joints
heat generation
what are the additional functions of muscle?
protect organs
forms valves
controls pupil size
cause goosebumps
which muscle is served by 1 artsy, 1 nerve, and 1/more veins?
skeletal muscle
where do arteries, nerves, and veins enter/exit through in skeletal muscle?
near central part and branch through connective tissue sheaths
skeletal muscle generates a large amount of what? what does this muscle need?
generates waste
needs nutrients/oxygen
what supports cells and reinforces whole muscle; connective tissue sheaths of skeletal muscle?
epimysium, perimysium, and endomysium
dense irregular connective tissue surrounding entire muscle; may blend with fascia
epimysium
fibrous connective tissue surrounding fascicles
perimysium
fine areolar connective tissue surrounding each muscle fiber
endomysium
skeletal muscle attaches in what 2 places?
insertion
origin
insertion
movable bone
origin
immovable (less movable bone)
attachments can be ______ or _______.
direct or indirect
direct
epimysium fused to periosteum of bine or perichondrium of cartilage
indirect
connective tissue wrappings extend beyond muscles as tendons/aponeurosis
fascicle
discrete bundle of muscle cells, segregated from rest of muscle by connective tissue sheath
what is muscle surrounded by? what is fascicle surrounded by?
muscle surrounded by epimysium
fascicle surrounded by perimysium
muscle fiber
elongated multinucleate cell; striated
what is muscle fiber surrounded by?
endomysium
myofibrils
rodlike contractile elements that occupy most of muscle cell volume
what are myofibrils composed of and how are they arranged?
sarcomeres arranged end to end
sarcomere
contractile unit composed of myofilaments made up of contractile proteins
what are the 2 types of myofilaments?
thick and thin
what do thick filaments contain?
bundled myosin molecules
what do thin filaments contain?
actin molecules
what produces muscle shortening?
sliding of thin filaments past thick
elastic filaments
maintain organization of A band and provide elastic recoil when muscle contractions end
long, cylindrical cell
multiple peripheral nuclei
what is the muscle fiber?
skeletal
sarcolemma
plasma membrane
sarcoplasm
cytoplasm
glycosomes
glycogen storage
myoglobin
O2 storage
densely packed, rodlike
80% cell volume
contain sarcomeres
exhibit striations
myofibrils
striations
perfectly aligned repeating series of dark A bands and light I bands
H zone
lighter region in midsection of dark A band where filaments don’t overlap
M line
line of protein myosin bisects H zone
Z disc (line)
coin-shaped sheet of proteins on midline of light I band
anchors thin filaments and connects myofibrils to one another
thick filaments
run entire length of A band
thin filaments
run length of I band and partway into A band
sarcomere
region between 2 successive Z discs
smallest contractile unit of muscle fiber
what is composed of thick and thin myofilaments made of contractile proteins?
sarcomere
what extend across I band and partway in A band and are anchored to Z discs?
actin myofilaments
what extend length of A band and connected at M line?
myosin myofilaments
what are composed of 2 heavy and 4 light polypeptide chains?
thick filament
myosin tails contain what?
2 interwoven heavy polypeptide chains
myosin heads contain what?
2 smaller, light polypeptide chains
2 smaller light polypeptide chains act as ______ during contraction.
cross bridges
myosin heads are binding sites for what?
actin of thin filaments
ATP
ultrastructure of thin filament
twisted double strand of fibrous protein F actin
F actin consists of ______ actin subunits.
G (globular)
what actin bears active sites for myosin head attachment during contraction?
G actin
tropomyosin and troponin
regulatory proteins bound to actin
what is elastic filament composed of?
titin
what holds thick filaments in place, helps recoil after stretch, and resists excessive stretching?
elastic filament
dystrophin
links thin filaments to proteins of sarcolemma
nebulin, myomesin, C proteins bind ___ or ___ together and maintain alignment.
filaments or sarcomeres
what is a network of smooth endoplasmic reticulum surrounding each myofibril?
sarcoplasmic reticulum
what is the function of sarcoplasmic reticulum?
regulate intracellular Ca2+ levels (stores/releases)
what are continuations of sarcolemma called?
T tubules
what is continuous with extracellular space?
lumen
T tubules increase muscle fiber’s ______
surface area
T tubules penetrate cell’s interior at each ______
A-I band junction
T tubules associate with paired terminal cisterns to form ___(1)___ that encircle each ___(2)___
(1) triads
(2) sarcomere
what conducts electric impulses deep into muscle fiber; into every sarcomere?
T tubules
integral proteins protrude into inter membrane space from T tubule and SR cistern membranes to act as _____
voltage sensors
SR foot proteins
gated channels that regulate Ca2+ release from SR cisterns
what occurs when tension generated by cross bridges on thin filaments exceeds forces opposing shortening?
shortening
in relaxed state, thin and thick filaments overlap only at ends of ______.
A band
cross bridges
myosin heads bind to actin
ratcheting pulls ______ toward _______
pulls Z disc toward M line
first step for skeletal muscle to contract
activation at neuromuscular junction
must generate action potential in sarcolemma
2nd step for skeletal muscle to contract
excitation-contraction coupling
action potential propagated along sarcolemma and intracellular Ca2+ levels rise
what stimulates skeletal muscles?
somatic motor neurons
axon of motor neurons travel from central nervous system via ______ to skeletal muscle.
nerves
each axon ending forms ______ with a single muscle fiber.
neuromuscular junction
ACh binding opens ion channels in the receptors that allow simultaneous passage of ___(1)___ into muscle fiber and ___(2)___ out of muscle fiber.
(1) Na+
(2) K+
what produces a local change in the membrane potential called end plate potential?
when more Na+ ions enter than K+ ions exit
how does ACh breakdown?
by acetylcholinesterase
where is the neuromuscular junction situated?
midway along length of muscle fiber
synaptic cleft
gel filled space that separates axon terminal and muscle fiber
acetylcholine
neurotransmitter in synaptic vesicles of axon terminal
what does the NMJ include?
axon terminals, synaptic cleft, junctional folds
events at the neuromuscular junction
- nerve impulse arrives at axon terminal > ACh released into synaptic cleft
- ACh diffuse across cleft and binds with receptors on sarcolemma
- electrical events generate action potential
what does breaking down ACh do?
prevents continued muscle fiber contraction in absence of additional stimulation
3 steps of generating action potential
end plate potential
depolarization
repolarization
local depolarization
ACh binding opens chemically (ligand) gated ion channels
simultaneous diffusion of Na+ in and K+ out
end plate potential
end plate potential spreads to adjacent membrane areas
voltage gated Na+ channels open
influx of Na+ decreases membrane voltage toward threshold
AP initiated and muscle fiber contraction starts
depolarization
restore electrical conditions of RMP
Na+ channels close and K+ channels open
K+ efflux restores resting polarity
resting state restored
depolarization
refractory period
fibers cannot be stimulated until depolarization complete
events that transmit AP along sarcolemma lead to what?
sliding of myofilaments
latent period
time when E-C coupling events occur
time between AP initiation and beginning of contraction
steps initiating muscle contraction (1st step)
nerve impulse reach axon terminal > voltage-gated calcium channels open > ACh released to synaptic cleft
steps initiating muscle contraction (2nd step)
ACh bind to receptors on sarcolemma > open ligand-gated Na+ and K+ channels > end plate potential
steps initiating muscle contraction (3rd step)
open voltage gated Na+ channels > AP propagation
steps initiating muscle contraction (4th step)
voltage sensitive proteins in T tubules change shape > SR release Ca2+ to cytosol
when do tropomyosin block active sites on actin, myosin heads cannot attach to actin, and muscle fibers relax?
when theres low intracellular Ca2+ concentration
when do Ca2+ bind to troponin and has troponin change shape, move tropomyosin away from myosin binding sites, and has myosin heads bind to actin causing sarcomere shortening and muscle contraction?
when theres a higher intracellular Ca2+ concentrations
what happens to Ca2+ when nervous stimulation ceases?
Ca2+ pumped back into SR and contraction ends
cross bridge cycle continues as long as ______ and ______ are present
Ca2+ signal and adequate ATP present
cross bridge formation
high energy myosin heads attach to thin filaments
working (power) stroke
myosin head pivots and pulls thin filament toward M line
cross bridge detachment
ATP attaches to myosin head and cross bridge detaches
cocking of myosin head
energy from hydrolysis of ATP cocks myosin head into high energy state
cross bridge cycle steps (1-4)
- cross bridge formation
- power (working) stroke
- cross bridge detachment
- cocking myosin head
3-4 hours after death muscles begin to stiffen with weak rigidity at 12 hours post mortem
rigor mortis
how do cross bridges form in rigor mortis?
dying cells take in calcium
is ATP generated to break cross bridges in rigor mortis?
no
