a delicate connective tiss called _____ covers ea muscle fiber
endomysium
muscle fibers are grouped in bundles called
fascicles
a sheath of tougher connective tiss called _____ surrounds the muscle as a whole and binds all the muscle fibers together.
epimysium
connective tiss called ____ surrounds the muscle outside the epimysium
fascia
____ _____ lies between muscles
deep fascia
__________ __________ resides just under the skin
superficial fascia
tendons rarely break but can be pulled
true
two ways skeletal muscle can attach to a bone
direct and indirect attachment
direct attachment is
muscle fibers merge with the periosteum of the bone, forming strong attachment
indirect attachment
epimysium extends past the muscle as a tendon that merges with the periosteum
the plasma membrane surrounding ea fiber is called
sarcolemma
cytoplasm of a cell is called
sarcoplasm
long protein bundles are called
myofibriles
what two thing do myfibriles store
glycogen and oxygen
the smooth endoplasmic reticulum of a muscle fiber that surrounds ea myofibrile
sarcoplasmic reticulum
where are calcium ions stored
sarcoplasmic reticulum
even finer fibers in the myofibriles are called
myofilaments
two types of myofilaments
thick and thin
myosin
think myofilaments made of protein
actin
thin
what gives skeletal muscle a striated appearance
arrangement of actin and myosin
a system of tubles is called
transverse tubules
what allows electrical impulses to travel deep into the cell
transverse tubules
sarcomeres
latticework of thin and thick myofilaments formed units
z disc
plate serves as an anchor pnt for thin myofilaments
muscle contraction occurs at the
sarcomere
section between the z discs is called
sarcomere
describe relaxed muscle
myosin and actin lie side by side, completely detached
describe muscle contraction
when myosin head latch onto actin. forms cross-bridge bw actin and myosin. myosin heads latch onto and release actin repeatedly, creating power strokes that propel actin forward toward the center of the sarcomere. pulls z discs closer together, shortening sarcomere. sliding-filament model
myofilaments don't shorten - they slide over top one another, sarcomere shortens
true
muscle contraction requires energy in the form of
atp
power strokes
series of gripping and releasing of myosin heads on actin filaments splitting atp for fuel
contraction requires two things
atp and calcium
motor neuron
stimulates a nerve to contract
axons
extensions from the cell bodies
4 stages of muscle fiber contraction
1 impulse releases neurotransmitters called ACh into synaptic cleft
2 ACh diffuses across cleft, stimulates receptors in the sarcolemma
3 sends electrical impulse over sarcolemma and inward along t tubules which causes sacs in the sarcoplasmic reticulum to release calcium
4 calcium binds w troponin on actin filament exposing attachment pnts where myosin heads grab onto
a connection bw a motor neuron and muscle fiber is called
neuromuscular junction
bw the end of motor neuron and muscle fiber is a narrow space called ____ ________
synaptic cleft
acetylcholine
ACh
a chemical messenger is called
neurotransmitter
two protein molecules entwined with actin filament
troponin and tropomyosin
how do muscles relax
acetylcholinesterase breaks down remaining ACh and calcium ions are pumped back into sarcoplasmic reticulum
how do muscles obtain energy at rest
oxygen uses aerobic respiration to break down fatty acids
aerobic means
with oxygen
how do muscles obtain energy during exercise
muscles break down cp
cp stands for
creatine phosphate
what is cp
high energy coumpound stored in muscle
cp can fuel a muscle for how long
20 sec high energy, a min of moderate
obtaining muscle energy with continued exercise
muscles switch to anaerobic respiration of glucose, generates energy quickly and produces lactic acid which leads to muscle fatigue
after 10 mins of moderate activity for energy levels
heart and lungs have had enough o2 and switch back to aerobic resp that produces more atp and carbon dioxide and water (less toxic than lactic acid)
"go for the burn"
strenous exercise causing lactic acid accumulation in anaerobic exercise
why do athletes focus on diet
body obtains energy from synthesis of atp and cp from food
main muscle triggering movement
prime mover
muscles that assist in movement
synergists
muslces balancing movement are
antagonists
how does antagonist work
they oppose action of prime mover. when pm contracts, antag relax.
works to moderate speed or range of movement.
prevent jnt injury
muscle enlargement from strength training
hypertrophy
muscle shrinking
atrophy
aerobic (endurance) exercise stimulates growth of blood vessels allowing
increased supply of o2 and glucose - for atp productuion
how many muscles and what % of wt
600 muscles, 40%
overly contracted fibers
weak contraction; myosin bumps into zdisc
overly stretched fibers
weak, myosin and actin have very little overlap
strongest contraction
myosin and actin are partially overlapped
muscle tone
continuous state of partial contraction , allows you to stand, react quick
motor unit
neuron and all the fibers it stimulates
motor units have how many fibers
a few to a few hundred
threshold
minimum voltage requried for a muscle fiber to contract
twitch
single, brief contraction
force of contraction is affected by 3 things
size of muscle, degree of stretch, # of muscle fibers contracting
smaller motor units found in muscles that
perform precise movement
larger motor units found
dont perform precise movement
rigor mortis
rigid muscles at time of death. atp stops, myosin heads remain locked onto actin filaments. no sliding occurs. peaks 12 h after death fades over 48 hrs
slow twitch type 1
respnd slowly to stimuli, efficient at using o2 to generate atp, fire for a long time, maarathon runner
