ch 10.1 - 10.3, muscle tissue Flashcards
muscle tissue
primary tissue responsible for contraction and movement
types of muscle tissue
skeletal, cardiac, muscle
common properties of muscle tissue
excitability, contractility, extensibility, elasticity
excitability (responsiveness)
ability to receive and respond to stimuli
contractility
the ability of cells to shorten
extensibility
ability of the muscle to stretch
elasticity
ability of the muscle to recoil to its resting length
functions of skeletal muscle
- producing movement
-mainting posture and body position
skeletal muscle
muscles of the body that are attached to bones
3 layers of connective tissue in skeletal muscles
epimysium, perimysium, endomysium
epimysium
layer of collagen fibers that surrounds entire muscle and separates it from surrounding to tissues
- connected to the deep fascia (dense connective tissue layer)
perimysium
surrounds individual fascicles (muscle fiber bundles)
- contains collagen + elastic fibers, blood vessels and nerves
endomysium
surrounds individual muscle cells and loose interconnects them
what does endomysium contain
capillary networks
myosatellite cells (stem cells that repair damage)
nerve fibers
at the end of each muscle
collagen fibers of the epi,peri, and endomysium come together to form a tendon or broad sheet called an aponeurosis
what do tendons and aponeuroses do
attach skeletal muscles to bones
myofibrils
made of protein myofilaments (actin + myosin) that forms sarcomeres
muscle fibers
muscle cell
muscle fasicles
bundle of muscle fibers
skeletal muscle fiber (cells) characteristics
- large
- multinucleate
- striated
- develop by fusion of embryonic cells called myoblasts
sarcolemma
plasma membrane of a muscle fiber that surrounds the sarcoplasm (cytoplasm of muscle fiber)
what initiates a contraction in skeletal muscle fiber
a sudden change in the membrane potential
transverse tubules (t-tububles)
narrow tubes continuous w/ the sarcolemma, which extend deep into the sarcoplasm
t-tubules function
quickly transmit electrical impulses from the sarcolemma into the cell interior to ensure a coordinated contraction of the entire cell
sarcoplasmic reticulum (SR)
tubular network similar to smooth ER that surrounds each myofibril
sarcoplasmic reticulum (SR) function
- forms chambers (terminal cisternae) that attach to T tubules
- specialized for storage and release of calcium
triad
a pair of terminal cisternae plus a T tubule
myofibrils
organized collection of myofilaments that are responsible for muscle contraction
- surrounded by SR
myofilaments
bundles of contracticle protein filaments
- actin and myosin
2 types of myofilaments
thin - composed of actin
thick - composed of myosin
sacromeres
repeating structural and functional units of a myofibril
- smallest contractile units of muscle fiber
bands of the sacromere
A bands (dark bands)
I bands (light bands)
z disc
separates sarcomeres
A bands
dark bands which run the length of the thick filaments
subdivisions of A band
M line, H band, and zone of overlap
M line
vertical line in center of A band; contains proteins that stabilize the position of the thick filaments
H band
made only of thick filaments and extends on either side of the M line
zone of overlap
region where the thick and thin filaments overlap
I bands
light bands that contain only thin filaments
- extends from A band of one sarcomere to the A band of the next sarcomere
Z lines
bisect the I bands and mark the boundaries between adjacent sarcomeres
titin
elastic protein which extends from the tops of thick filaments to the Z line
titin function
- keeps filaments in proper alignment
- aids in restoring resting sarcomere length
thin filament contains what 4 proteins
F-actin
nebulin
tropomyosin
troponin
filamentous actin (F-actin)
twisted strand composed of 2 rows of globular G-actin molecules
nebulin
holds the F-actin strands together
tropomyosin
covers the active sites on G-actin and prevents actin-myosin interaction
troponin
globular protein that holds tropomyosin in place and binds to calcium ions
troponin
globular protein that holds tropomyosin in place and binds to calcium ions
thick filaments contain
myosin
each myosin molecule consists of
tail: binds to other myosin molecules, points towards the M line
head: made of 2 globular protein subunits, protects toward the nearest thin filament
sliding filament theory
during a contraction, the thin filament slides toward the center of the sarcomere (M line) alongside the thick filaments
- a sarcomere shortens as the thick and thin filaments slide past one another
steps of contraction
- brain stimulates muscle contraction + sends action potential
- terminal cisternae relases Ca to bind to troponin
- troponin becomes flat when Ca binds + tropomyosin slips off which activates exposed active sites on G- actin protein
- Myosin heads bind to exposed active sites
- power stroke/muscle contracts
