Studied by 2 people
components of muscular system
muscles and tendons
what type of tissue are tendons
dense regular connective tissue
Muscle tissue consists of elongated muscle cells specialized for _____________--
contraction
Three types of muscle tissue
skeletal, cardiac, smooth
During embryonic development, What tissue layer are muscle tissues derived from?
mesoderm
Where is the mesoderm located?
between ectoderm and endoderm
skeletal muscles are ___________ composed of skeletal muscle tissue, connective tissues, nerves, and blood
organs
How are skeletal muscles attached to bones?
directly or indirectly via tendons
How many skeletal muscles are there?
~700(majority of our muscles are skeletal muscles)
five functions of skeletal muscle
Movement Maintain posture and body position Support soft tissues Guard entrances and exits Maintain body temperature
how do skeletal muscles move the skeleton
skeletal muscle pull on tendons that then move bones
Where do skeletal muscles support soft tissue
abdominal wall and pelvic cavity
How do skeletal muscles guard entrances and exit
by encircling openings of the digestive and urinary tracts, voluntarily controlling swallowing, defecation, and urination
skeletal muscles that encircle openings of digestive and urinary tracts are
sphincters
how do skeletal muscles maintain body temp
muscle contractions generate heat
skeletal muscle tissues are composed of skeletal muscles that encircle openings of digestive and urinary tracts are
muscle fiber
why are skeletal muscles called muscle fibers
long and slender
three CONNECTIVE tissue layers of skeletal muscles
epimysium, perimysium, endomysium
Epimysium
surrounds entire muscle
Perimysium
divides muscle into fascicles
What are fascicles?
bundles of muscle fibers
perimysium contains ______________ and ____________ supplying fascicles
blood vessels, nerves
Endomysium
Surrounds individual muscle fibers and ties them tog
endomysium contains _________ and ______________
capillaries and nerve fibers(axons); myosatellite cells
capillaries in endomysium deliver ___________ to skeletal muscle cells
blood
what do nerve fibers(axons) in endomysium do
allow muscles to move
myosatellite cells
stem cells that help repair damaged muscle tissue by fusing with damaged skeletal muscle cells
collagen fibers from all three skeletal muscle connective tissue layers come together to form 1____________ 2____________
tendon; aponeurosis
what is a tendon
bundle of fibers that attaches muscle to bone
What is aponeurosis?
broad sheet of fibers (broad tendon) that connects muscles to EACH OTHER
skeletal muscles have ____________ that provide them w/ enough oxygen to make atp needed for them to contract
blood vessels
skeletal muscles require stimulation of central nervous system and are under__________control
voluntary
among the muscle cells, which is the largest in diameter and the longest
skeletal muscle fibers
skeletal muscle fibers are ___________(multi or uninucleate) and __________(striated or nonstriated)
multinucleate; striated
how are multinucleate skeletal muscle cells formed
during development, embryonic cells called myoblasts(containing ONE nucleus) fuse together to form multinucleate skeletal muscle cells
some myoblasts don't fuse and remain as____________ cells in adult skeletal muscle tissue
myosatellite
What is the name of muscle cell's membrane
sarcolemma
what does sarcolemma surround
sarcoplasm or cytoplasm
What does sarcoplasm have
cytosol + organelles
sarcolemma contains openings that lead into network of tubules called
transverse tubules or T tubules
Why are T-tubules important?
bc they allow electrical impulses or action potentials from sarcoplasm to reach cell's interior; allowing entire skeletal muscle cell to contract
what are the cylinder shaped structures inside the skeletal muscle fiber
myofibrils
what are myofibrils encircled by
T tubules
myofibrils are bundles of ______________- and _____________
thick and thin myofilaments
the sliding of thick and thin myofilaments causes muscle fibers to ________________
contract
during contraction, ____________________ shortens but ___________-- and ____________--stay the same
myofibril; thick and thin
what is the terminal cisterna and what does it contain a high conc. of?
expanded portions on either side of T tubules; calcium ions
conc of calcium ions is much higher in ____________than in the cytosol
sarcoplasmic reticulum
conc of calcium ions is much higher _________-- the cell than inside(intracellular fluid or cytosol)
outside(extracellular fluid)
Triad (sarcoplasmic reticulum)
area where 2 terminal cisternae and 1 t tubule come together
what is the smallest functional unit of skeletal muscle fiber
sarcomere
sarcomeres are repeating functional units of ________________
myofilaments
why do skeletal muscle fibers appear striated
the arrangement of thick and thin filaments in sarcomeres
thick filaments are found in the ________ of sarcomere while thin are found on ___________________of sarcomere
middle;; both sides
thin filaments are attached to the _____________--
z line
What mark the boundaries of sarcomeres?
z lines
thick filaments are attached to the z lines via strands of the protein_________________---
titin
M lines are located at the ______________ of each sarcomere
center
M line is made of proteins that connect central portions of the ________________-
thick filaments
What band (A,I,H) is the darker region containing thick filaments
A band
__________band includes zone of overlap containing BOTH thick and thin filaments
A
What band (A,I,H) is the lighter region containing thin filaments
I band
________band includes the Z line
I
What band (A,I,H) contains ONLY thick filaments when fiber is relaxed
H band
___________band includes the M line and light regions on either side
H
Thin twisted strand of actin molecules
thin(actin) filaments
active sites on actin interact with __________
myosin
At rest active sites are covered by strands of ___________
tropomyosin
how are tropomyosin strands held in position
by troponin
what is tropomyosin
a protein that prevents myosin-actin interaction
What is troponin?
a protein that consists of three globular subunits
first globular subunit of troponin interacts w/ ______________ forming troponin-tropomyosin complex
tropomyosin
Second globular subunit of troponin binds to one of the ___________molecules
actin
Third globular subunit of troponin has the ______which binds calcium ions
receptor
troponin and tropomyosin are proteins associated w _________ but NOT myosin
actin
THICK(myosin) filaments are composed of ____________ molecules
myosin
Each myosin molecule consists of
-Tail: binds to other myosin molecules -Head: made of two globular protein subunits and projects toward nearest thin filament
the globular head of myosin molecule has ___________subunits
two
myosin tails point toward
M line(center of sarcomere)
myosin tails point ____________ heads project ___________
INWARD; OUTWARD
During contraction, myosin heads interact with ____________on actin
active sites
In order for myosin heads to interact active sites on actin, the movement of what two proteins is required?
troponin and tropomyosin
what theory explains sarcomere contraction
sliding filament theory
sliding filament theory is based on observed ___________in sarcomere
changes
sliding filament theory
theory that actin(thin) filaments slide toward each other during muscle contraction, while the myosin(thick) filaments don't move
during contraction, the width of I and H bands
decreases
during contraction the width of A bands
stays the same (bc thick filaments dont move)
during contraction the distance b/w z lines
decreases
during contraction the zone of overlap
increases
the binding of thick filaments to active sites produces
cross bridges
cross bridge formation is followed by the myosin head
pivoting
myosin head pivots toward
m line(center of sarcomere), pulling thin filament in that direction
what happens as a result of thin filament being pulled toward the center of sarcomere(m line)
sarcomere and myofibril shorten and skeletal muscle cell contracts
the neuromuscular junction is a specialized connection b/w a________ and a skeletal muscle fiber
intercellular; motor neuron
the neuromuscular junction consists of __________________ and _________
axon terminal; motor end plate
axon terminal of neuron contains _vesicles, which contain
synaptic; neurotransmitters(acetylcholine)
one of the most common neurotransmitters found in the body
acetylcholine
What is a neurotransmitter?
chemical signal that is produced mainly by the nerve cells
motor end plate is a portion of ____________
muscle sarcolemma
how is motor end plate separated from the axon terminal
by the synaptic cleft(or synaptic gap)
Note 
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