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ch 9

Terms in this set (91)

Nearly half of body's mass
muscle tissue
Transforms chemical energy (ATP) to directed mechanical energy
exerts force
Three types of muscle
Skeletal
Cardiac
Smooth
Skeletal and smooth muscles cells are elongated
muscle fibers
Myo, mys, and sarco
prefixes for muscle
Organs attached to and cover bony skeleton
skeletal muscle
Elongated cells called
muscle fibers
conscious control
Voluntary
Responsible for overall motility
skeletal muscle
Contract rapidly; tire easily; powerful
skeletal muscle
Require nervous system stimulation
skeletal muscle
Only in heart; bulk of heart walls
cardiac muscle
striated
cardiac muscle
Can contract without nervous system stimulation
cardiac muscle
Involuntary
cardiac muscle
In walls of hollow organs, e.g., stomach, urinary bladder, and airways
smooth muscle
Not striated
smooth muscle
Can contract without nervous system stimulation
smooth muscle
Involuntary
smooth muscle
ability to receive and respond to stimuli
Excitability (responsiveness)
ability to shorten forcibly when stimulated
Contractility
ability to be stretched
Extensibility
ability to recoil to resting length
elasticity
Movement of bones or fluids (e.g., blood)
Maintaining posture and body position
Stabilizing joints
Heat generation (especially skeletal muscle)
four important muscle functions
Protects organs, forms valves, controls pupil size, causes "goosebumps"
additional muscle functions
Predominantly muscle fibers however blood vessels, nerve fibers, and connective tissue are present
gross anatomy
Each muscle served by one artery, one nerve, and one or more veins
Skeletal Muscle
Skeletal muscle- Enter/exit near central part
branch through connective tissue sheaths
Every skeletal muscle fiber supplied by
nerve ending that controls its activity
Huge nutrient and oxygen need
generates large amount of waste
Connective tissue sheaths wrap individual fibers
skeletal muscle
Support cells of skeletal
reinforce whole muscle (prevent bursting during contraction)
Epimusium, perimysium, endomysium
External to internal
ense irregular connective tissue surrounding entire muscle; may blend with fascia
epimusium
fibrous connective tissue surrounding fascicles (groups of muscle fibers)
perimysium
fine areolar connective tissue surrounding each muscle fiber
Endomysium
movable bone
insertion
immovable (less movable) bone
origin
epimysium fused to periosteum of bone or perichondrium of cartilage
direct
connective tissue wrappings extend beyond muscle as ropelike tendon or sheetlike aponeurosis
indirect
skeletal muscle anatomy
Long, cylindrical cell
10 to 100 µm in diameter; up to 30 cm long

Multiple peripheral nuclei
plasma membrane (skeletal muscle)
Sarcolemma
cytoplasm (skeletal muscle)
Sarcoplasm
Contains large amounts of Glycosomes for glycogen storage, myoglobin for O2 storage
sarcoplasm
myofibrils, sarcoplasmic reticulum, and T tubules
Modified structures of skeletal muscle
Densely packed, rodlike elements
myofibrils
~80% of cell volume
myofibrils
Contain sarcomeres
myofibrils
contractile units
sarcomeres
perfectly aligned repeating series of dark A bands and light I bands
Exhibit striations
lighter region in midsection of dark A band where filaments do not overlap
h zone
line of protein myomesin bisects H zone
M line
coin-shaped sheet of proteins on midline of light I band that anchors thin filaments and connects myofibrils to one another
Z disc (line)
run entire length of an A band
thick filaments
run length of I band and partway into A band
thin filaments
region between two successive Z discs
sarcomere
Smallest contractile unit (functional unit) of muscle fiber
Sarcomere
Align along myofibril like boxcars of train
Sarcomere
Contains A band with ½ I band at each end (Z disc to Z disc)
Sarcomere
Composed of thick and thin myofilaments made of contractile proteins
Sarcomere
Orderly arrangement of actin and myosin myofilaments within sarcomere
Myofibril Banding Pattern
thin filaments
Extend across I band and partway in A band
Anchored to Z discs
actin myofilaments
thick filaments
Extend length of A band
Connected at M line
Myosin myofilaments
Composed of protein myosin
Ultrastructure of Thick Filament
Each composed of 2 heavy and four light polypeptide chains
Ultrastructure of Thick Filament
2 interwoven, heavy polypeptide chains
Myosin tails contain
2 smaller, light polypeptide chains that act as cross bridges during contraction
Myosin heads contain
Binding sites for actin of thin filaments
Binding sites for ATP
ATPase enzymes
cross bridges during contraction
Twisted double strand of fibrous protein F actin
Ultrastructure of Thin Filament
F actin consists of
G (globular) actin subunits
G actin bears active sites for
myosin head attachment during contraction
regulatory proteins bound to actin
Tropomyosin and troponin
Network of smooth endoplasmic reticulum surrounding each myofibril
Sarcoplasmic Reticulum (SR)
Pairs of terminal cisterns form
perpendicular cross channels
Functions in regulation of intracellular Ca2+ levels
Stores and releases Ca2+
Continuations of sarcolemma
Lumen continuous with extracellular space
Increase muscle fiber's surface area
Penetrate cell's interior at each A band-I band junction
T Tubules
Associate with paired terminal cisterns to form
triads that encircle each sarcomere
T tubules conduct impulses deep into muscle fiber
every sarcomere
Integral proteins protrude into intermembrane space from T tubule and SR cistern membranes
connect with each other
T tubule integral proteins act as voltage sensors and
change shape in response to voltage changes
SR integral proteins are channels that release Ca2+ from SR cisterns when voltage sensors
change shape
Generation of force
Does not necessarily cause shortening of fiber
Sliding Filament Model of Contraction
tension generated by cross bridges on thin filaments exceeds forces opposing shortening
Shortening occurs when
Shortens if
enough force
thin and thick filaments overlap only at ends of A band
In relaxed state
During contraction, thin filaments slide past thick filaments
actin and myosin overlap more
Occurs when myosin heads bind to actin
cross bridges
Myosin heads bind to actin
sliding begins
Cross bridges form and break several times
ratcheting thin filaments toward center of sarcomere
Causes shortening of muscle fiber
Pulls Z discs toward M line
ratcheting thin filaments toward center of sarcomere
I bands shorten; Z discs closer; H zones disappear; A bands move closer (length stays same)
Pulls Z discs toward M line
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