10/21 Class Lecture Chapter 9 Flashcards
how much muscle tissue makes up the body mass
half of bodys mass
prefixes for muscle
Myo, mys, and sarco
skeletal muscle characteristics
Organs attached to bones and skin Elongated cells called muscle fibers striated voluntary Contract rapidly; tire easily; powerful Require nervous system stimulation
special characteristics of muscle tissues
excitability
contractility
extensibility
elasticity
excitability
(responsiveness): ability to receive and respond to stimuli electricity, causes muscles to “jump”
contractility
ability to shorten forcibly when stimulated responds through contractility, shorts with force- why muscle is usefull
extensibility
ability to be stretched, expands but not forcibly (muscle pulls, it does not push)
elasticity
ability to recoil to resting length, flexible tissue
what are the reasons for the muscle characteristics
the muscle functions
Functions of muscles
Movement of bones or fluids (e.g., blood)
Maintaining posture and body position
stabilizing joints
heat generation
Protects organs, forms valves, controls pupil size, causes “goosebumps”
what is a skeletal muscle served by
one artery, one nerve, and one or more veins
how are skeletal muscles structured
connective tissue sheaths of skeletal muscle
epimysium
dense irregular connective tissue surrounding entire muscle; may blend with fascia (broad sheet of muscle)
perimysium
fibrous connective tissue surrounding fascicles (groups of muscle fibers)
endomysium
fine areolar connective tissue surrounding each muscle fiber, most microscopic
skeletal muscle attachments
insertion
origin
action
innervation
insertion
moveable bone
origin
immovable (less movable) bone
action
what is does (ex. Flexes forearm)
innervation
what nerve
direct skeletal muscle attachment
epimysium fused to periosteum of bone or perichondrium of cartilage
indirect skeletal attachment
connective tissue wrappings extend beyond muscle as ropelike tendon or sheetlike aponeurosis
sarcolemma
plasma membrane
sarcoplasm
cytoplasm
what is in sarcoplasm
glycosomes
myoglobin
glycosomes
glycogen storage for energy
myloglobin
for O2 storage (store a few minutes worth) as you get in shape they can store more to a degree
modified structures of skeletal muscle fibers
myofibrils, sarcoplasmic reticulum, and T tubules
what does the skeleton need for contract
calcium
what are myofibrils
Densely packed, rodlike elements
~80% of cell volume bascially 2 proteins
Contain sarcomeres
Exhibit striations
sarcomeres
contractile units
What are the striations
- perfectly aligned repeating series of dark A bands and light I bands A is the dArk band, I is the lIght band
Parts of muscle tissues striations
H Zone, M Line, Z disc, thick and thin filaments, sacromeres, myosin, actin
H zone
lighter region in midsection of dark A band where filaments do not overlap
M line
line of protein myomesin bisects H zone, m as in middle, anchoring point for the thick filaments
z discs
coin-shaped sheet of proteins on midline of light I band that anchors thin filaments and connects myofibrils to one another tube shaped strucutres, anchoring point for thin filaments
thick filaments
run entire length of an A band
thin filaments
run length of I band and partway into A band
myosin
proteins fibers darker filaments
actin
lighter filaments
sarcomere characteristics
Smallest contractile unit (functional unit) of muscle fiber
Align along myofibril like boxcars of train, all next to eachother linked together
Contains A band with ½ I band at each end
Composed of thick and thin myofilaments made of contractile proteins
actin myofilaments
thin filaments
Extend across I band and partway in A band
Anchored to Z discs
myosin myofilaments
thick filaments
Extend length of A band
Connected at M line
Sarcoplasmic reticulum
Network of smooth endoplasmic reticulum surrounding each myofibril
Most run longitudinally
Pairs of terminal cisterns form perpendicular cross channels
Highly organized
Functions in regulation of intracellular Ca2+ levels
Stores and releases Ca2+ and reabsorb it which allows the muscle to contract
what is contained in T Tubules
triads and transverse
characteristics of T Tubules
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
Associate with paired terminal cisterns to form triads that encircle each sarcomere
