Exam 2 Flashcards
Chapter 9 Part 1
major functions of muscles
- body movement
- posture
- respiration
- body heat production
- communication
- constriction of blood vessels and organs
- heart contraction
characteristics of muscles
excitable
contractable
extensible
elasticity
excitable =
responds to stimuli
contractable=
shortens with height, muscles pull, not push
extensible=
stretch, beyond original resting length
elasticity=
recoil
3 muscle types
smooth, skeletal, cardiac
each myoblast has its own
nucleus
long, cylindrical cells formed by fusion of hundreds of embryonic cells =
myoblasts in myogenesis
Stem cells in Skeletal muscle, Usually Quiescent, Activate by Muscle damage
Stimulated to divide and fuse with existing muscle fibers
satellite cells
hypertrophy=
enlarge
what do skeletal muscles not do
undergo mitosis
what control localized region
nuclear domains
muscular compositon consists of
75% water
20% protein (actin, myosin, troponin, tropomyosin)
5% organic and inorganic compounds
muscular hierachy is
muscle fibers= muscle cell= myocyte
parallel and connect to one another by
endomysium
endomysium is what kind of CT
loose areolar
wrapped into unit called
fascicle
fascicles are connected by
perimysium
perimysium is what CT
dense irregular CT
entire unit is wrapped in a CT overcoat called
epimysium
epimysium is what CT
dense irregular CT
joins with deep muscular fascia=
separate structures
muscle anchored to bone via tendon (strap) or
aponeurosis (sheet)
can direct or indirect muscle to bone withstand more friction
indirect
what surround each muscle fiber and fascicle
bv and nerves
each what has its own nerve ending that control activity
muscle fiber
Specialized nerve cells that stimulate skeletal muscle contraction
motor neurons
each muscle fiver surrounded by plasma membrane=
sarcolemma
cytoplasm with xs glycogen and myoglobin=
sarcoplasm
Each Muscle Fiber (Cell) consists of Bundled
Contractile Elements
myofibrils
each myofibril is surrounded by
sarcoplasmic reticulum
the sarcoplasmic reticulum is highly
modified er
highly modified er regulates
calcium
Each Myofibril consists of Bundles Contractile
Elements ….. in sarcomere units
myofilaments
smallest contractile unit
sarcomere
sarcomere stretches from
z line to z line
dark band =
a band
light band=
I band
2 contractile proteins=
myofilaments
thick A vand connect at m line =
myosin
thin I band connect at z line
actin
globular=
polypeptide subunits
atp binding site is
myosin atpase
Rod Shape, Stiffens F actin. Spans 7 Actin, Blocks Myosin – Actin Interaction
tropomyosin
3 Polypeptide subunits = 3 Binding Sites
troponin
Tnl=
actin
TnT=
tropomyosin
TnC=
calcium
what does troponin do
interact with calcium to regulate tropomyosin’s position of blocking of actin-myosin interaction
when calcium moves tropomyosin away, actin and myosin=
cross bridge and power stroke begins
holds thick filaments in place and are extensible. composed of protein= titan
elastic filament
Helps Muscle cell spring back into shape after stretching
elastic filament
Stiffens as Uncoils to Resist Excessive Stretch. Largest Protein in Humans.
elastic filament
Links Thin Filaments to Integral Proteins on Sarcolemma
dystrophin
Mechanical Support to keep Sarcolemma Intact, NO Calcium Leak
dystrophin
defective gene (sex linked recessive)=
duchenne muscular dystrophy
S&S of duchenne muscular dystrophy
Frequent Falls, NOT rise from Lying/Sitting, Waddling Gait, Walk on toes
treatment for duchenne muscular dystrophy
to sustain mobility & Respiratory function. OT, PT.
Steroids
no cure
when do people with duchenne muscular dystrophy usually die
in 30s, respiratory failure
weakening if skeletal muscles and adipose is what
duchenne muscular dystrophy
when are you Dx for duchenne muscular dystrophy, and due to what
at birth
due to elevated CK levels, genetic tests
what does elevated CK levels indicate
damage to muscle fibers
in duchenne muscular dystrophy what tears during contraction and excessive calcium enters and damages contractile fibers
sarcolemma
does the muscle regenerate in duchenne muscular dystrophy
no
muscle fiber’s PM
transmits electrical impulses to muscle interior
sarcolemma
tubelike infold of sarcolemma.
carry electrical impulses into center or muscle fiber- every muscle fiber sarcomere contracts together
transverse tubules
SER in skeletal muscle fibers that store calcium
sarcoplasmic retuculum
temrinal cisternae- t tubule- terminal cisternae
triad
nervous stimulation
quick response
motor neuron does what
message to muscle; voltage regulated calcium channels open and influx
where do muscular contractions meet
neuromuscular junction
ACh released from vesicles at synapse
stimulation
what diffuses across synaptic cleft and binds to receptors
ACh
muscular contraction stimulates what release
Na
Na release and depolarization past threshold generate
action potential
action potential goes along sarcolemma and down what
t tubule
calcium release from
sarcoplasmic reticulum
what binds troponin
calcium
binding of calcium on troponin causes
conformational change
after the conformational change
troponin attaches to tropomyosin
after troponin attaches to tropomyosin what happens
tropomyosin moves no longer locking actin and myosin
once tropomyosin moves
actin and myosin interact
once actin and myosin interact
myosin pulls actin to center of sarcomere
after myosin pulls actin to the center of the sarcomere
it shortens sarcomere length and muscle fiber length
once sarcomere and muscle fiber length shorten what happens
Ca goes back to SR
once Ca goes back to SR
troponin and tropomyosin go back to resting position
power stroke steps
- myosin head cocks into position
- myosin binds to actin
- power stroke (push actin)
- detach from actin and new atp binds
- repeat
Need calcium and atp