7.3- whole skeletal muscle anatomy Flashcards
muscle fascicles (bundles of muscle fibers) are covered by this connective tissue layer called
the perimysium
the entire muscle is surrounded by a connective tissue layer called the
epimysium
Motor Neurons extend together with ____ and _____ thru the connective tissue and skeletal muscles
arteries and veins
skeletal muscle is ____- % of body weight
40
skeletal muscle is also called
striated muscle
a skeletal muscle consists of what 4 tissues?
skeletal muscle tissue, nervous tissue, connective tissue, and adipose tissue
each muscle cell is called a
muscle fiber
the skeletal muscle has three layers of connective tissue
- the epimysium
- the perimysium
- the endomysium
What forms a connective tissue sheath AROUND each skeletal muscle, and is the OUTER LAYER of the muscle?
the epimysium
bundles of muscle fibers (cells)
fascicles
what subdivides each whole muscle into fascicles, and serves as passageways for blood vessels and nerves to supply each fascicle ?
the perimysium
A delicate layer of connective tissue, separates individual muscle fibers WITHIN each fascicle, and serves as a passageway for nerve fivers an blood vessels that supply each separate muscle fiber.
The endomysium
Fibrous connective tissue layer surrounding a skeletal muscle
.epimysium
Fibrous sheath enveloping each of the skeletal muscle fascicles
perimysium
Fine connective tissue sheath surrounding a muscle fiber.
endomysium
the protein fibers of the three layers of connective tissue blend into one another and merges at the ends of most muscles forming
tendons
tendons
connect muscles to bones
the three muscle fiber components that respond to and transmit electrical signals
- the sarcolemma
- the transverse tubules
- the sarcoplasmic reticulum
the cell membrane of muscle fibers, surrounds fiber
outer to inner
endomysium, sarcolemma, sarcoplasm
sarcolemma
tubelike inward folds of the sarcolemma, carries electrical impulses into the center of the muscle fiber so the fiber contracts as a whole
transfers tubules ( T tubules) tubes
endoplasmic reticulum in skeletal muscle fivers that stores high levels of Ca 2+
sarcoplasmic reticulum- small yellow
release of _____ from the sarcoplasmic reticule is a switch for muscle contraction
Ca 2+
cytoplasm in muscle fibers
sarcoplasm - pink and liquid
enlarged portions of the sarcoplasmic reticulum
terminal cisternae - big yellow
two terminal cisternae and their associate T Tubule form a
triad (t tubule sandwich)
two main structures of contractibility in muscle fibers
myofibrils and myofilaments
BUNDLES of protein filaments ( actin and myosin)
myofibrils
Ultramicroscopic protein thread helping form myofibrils in skeletal muscle
myofilaments
two types of myofilaments
actin and myosin
thin myofilaments
actin
thick myofilaments, golf club
myosin
actin and myosin filaments are arranged into these highly ordered units.
sarcomeres
Sarcomeres join end to end, forming the _______
myofibrils
form a stationary anchor for actin myofilaments
Z disks
One _______ extends from one Z disk to the next Z disk
sarcomere
the regions of each sarcomere
i band (2 regions) and an A band
two lighter- stained regions
I bands
central darker-stained regions, center of each sarcomere. contains both actin and myosin filament overlapping (except in the center)
A band
the center of each A band has a smaller band called the __ _____. contains only myosin myofilaments.
H zone
the middle of each H zone has this dark line. it consists of delicate protein filaments that hold the myosin myofilaments in place
M line
three separate proteins of each actin myofilament
- actin
- tropomyosin
- troponin
______ act as receptor sites for a portion of the myosin myofilament, the myosin head.
Actin
long, fibrous protein that lies in the groove along the fibrous actin strand
tropomyosin
in a relaxed muscle, _________ is covering the attachment sites on the actin. A muscle cannot contract until it moves to uncover the active sites.
tropomyosin
has a 1. subunit that anchors the troponin to the actin, 2. a subunit that prevents the tropomyosin from uncovering the actin attachment sites, 3. and a subunit that binds Ca 2+
troponin
Myosin myosin filaments are composed of many elongated _______ molecules shaped like golf clubs
myosin
each myosin molecule consist of a _____ portion and ______ myosin heads.
rod, heads
What do myosin heads do?
bind to active sites on the actin to form cross-bridges to contract muscle, are attached to the rod portion that bends and straightens during contraction, and break down ATP, releasing energy
motor neurons carry electrical signals called
action potentials
The point of contact of motor neuron axon branches with the muscle fiber
synapse (neuromuscular junction)
A Synapse (neuromuscular junction) consist of what two things?
- axon terminals and 2. the area of the muscle fiber sarcolemma they innervate
each axon terminal is called the
presynaptic terminal
the space between the presynaptic terminal and the muscle fiber is the
synaptic cleft
the muscle cell membrane in the area of the junction is called the
motor end plate (postsynaptic membrane)
each presynaptic terminal contains numerous mitochondria and SMALL SPHERICAL SACS called
synaptic vesicles
the synaptic vesicles contain the neurotransmitter
acetylcholine
What is a molecule that allows a neuron to communicate with its target, and A chemical released at the distal end of an axon that either stimulates or inhibits an adjacent cell?
they cans simulate or inhibit the production of an action potential in the motor end plate (the sarcolemma) by binding to ligand gated ion channels
they are released from the presynaptic membrane and diffuse across the synaptic cleft to alter the activity of the muscle fiber.
neurotransmitter
specialized membrane transport proteins that are opened and closed by specific molecules, such as neurotransmitters. when opened, they allow ions to cross the cell membrane
Ligand ( or ligand gated ion channels)
Mechanism by which actin and myosin myofilaments slide over one another during muscle contraction.
sliding filament model
what forms when the myosin binds to the actin?
a cross-bridge
myofibrils appear ____ because of A bands and I bands
striated
what happens during the muscle fiber contraction ?
actin and myosin filaments slide past one another, shortening the sarcomeres
