muscle contraction Flashcards
smooth muscle
involuntary
lines the hollow organs like the stomach and small intestines
cardiac muscle
involuntary
heart muscle
skeletal muscle
voluntary
attached to skeleton
entire muscle
surrounded with epimysium
-consists of many bundles (fasciculi)
fasciculi
surrounded by perimysium
-consists of individual muscle cells (fibers)
muscle fiber
surrounded by Endomysium
-myofibrils divided into sarcomeres
mysiums are all
connective tissues
size of skeletal muscle fibers (largest to smallest)
EPI, PERI, ENDO
sarcolemma
contains plasmalemma and basement membrane
-transmits force and is subjected to substantial stress during contractions
plasmalemma
surrounds individual muscle fibers, fuses with tendon which inserts into a bone, conducts action potential for muscle contraction
where does action potential happen
plasmamembrane
what is the working part of the sarcolemma of a muscle cell that maintains ph and transports nutrients
plasmamembrane
sarcoplasm
cytoplasm of muscle cell
what does the sarcoplasm have
stores glycogen, myoglobin
transverse tubules
extension of plasmalemma
- carry action potential deep into muscle fiber t get the sarcomeres to shorten inside which contracts the muscle
sarcoplasmic reticulum (SR)
CA2+ storage
myofibrils - built from sarcomeres
contractile unit of skeletal muscle
muscle = fasciculi = muscle fiber = myofibril
muscle
epimysium
fascicle
perimysium
muscle fiber
endomysium
myofilaments
thick and thin
sarcomeres
inside myofibrils
-run end to end of full myofibril length
-basic contractile element of skeletal muscle
alphabetical order of muscle from largest to smallest
fascicle, fiber, fibril, and filament
actin
thin myofilaments
- contains myosin binding sites
3 proteins that make up filaments
actin, troponin, tropomyosin
troponin
binds to calcium released from SR
-moves tropomyosin to expose myosin binding site
tropomyosin
covers myosin binding site enabling muscle to relax
- covers myosin binding site when calcium is within SR
myosin
thick myofilaments
-heads contain actin
-uses atp to “ratchet”
have ATPase enzyme
ATP
adenosine with 3 phosphate
ADP
adenosine with 2 phosphate
5 proteins in sarcomeres
- actin
- troponin
- myosin
- tropmyosin
- titin
myosin stabilizes by
titin
anchor points for myosin
m line (end to end) and titin
voluntary muscle contraction requires
nervous system, muscle cells, and interdependence
motor units
single alpha - motor unit + all fibers it innervates muscle fibers
(somatic nervous system)
-the more motor units the greater the contractile force
neuromuscular junction
site of communication between neuron and muscle
-consists of synapse between a motor neuron and muscle fiber
excitation-contraction coupling
rapid communication between electrical events occurring in the plasma membrane of skeletal muscle fibres and Ca2+ release from the SR, which leads to contraction.
action potential starts in the
brain
ap travels along alpha motor neuron towards
neuromuscular junction
ap arrives at NMJ, causes release of
acetylcholine
ACH crosses synapse, binds to ACH____ on plasmalemma (motor end plates)
receptors
ap travels down plasmalemma and into
T- Tubules as they come along
ap inside t- tubules, triggers Ca+2 release from the
sarcoplasmic reticulum
released _____ enables actin-myosin contraction
Ca+2
CA+2 binds to ______ that causes tropomyosin to uncover myosin binding sites
troponin
myosin binds to newly uncovered binding sites on actin and ratchets
contraction
role of Ca+2 in muscle fibers and contraction
AP arrives at the Axon terminal causing an influx of Ca+2 which causes the release of ACh into NMJ synapse
role of Ca+2 in muscle fibers and contraction 2.
ap arrives at myofibril SR via T-tubule
-SR arrives to electrical charge
-causes mass release of Ca+2 into sarcoplasm
role of Ca+2 in muscle fibers and contraction 3.
Ca+2 binds to troponin on thin filament
- at rest tropomyosin covers the binding sites
-troponin Ca+2 complex moves tropomyosin
- myosin binds to actin, contraction can occur
sliding filament theory: a relaxed state
no sarcoplasm Ca+2 stored in the SR in this state
-tropomyosin is covering myosin binding sites on actin
- no actin interaction at the binding site
sliding filament theory: contracted state
ap has caused SR to release Ca+2 into the sarcoplasm
Ca+2 binds to troponin which causes ____ to move off of myosin binding sites
tropomyosin
myosin head pulls actin toward sarcomere center =
power stroke
filaments slide past each other due to
ratcheting
type 1 muscle fiber
slow twitch, lower peak tension, slower ATPase, less developed SR, smaller motor units
type 2a muscle fiber
fast twitch oxydative
type 2b muscle fiber
fast twitch glycolic
type 2
fast twitch, higher peak tension, faster ATPase, more developed SR, larger motor units
type 1 is RED because
more mitochondria, and more hemoglobin
type 1
slow oxidative,
more mitochondria with Kreb’s,
less glycolytic enzymes,
peak tension in 110ms,
resist fatigue
slower ATPase, slower speed of contraction
slower Ca+2 release
type 2 is white because
less mitochondria, and less hemoglobin
type 2
about 25% of fibers in an average muscle
-fast glycolic fibers
-more glycolytic enzymes
-fewer mitochondria
-peak tension 50ms
-fatigues quicker
- more developed SR
-faster Ca+2 release
-larger motor units
muscle fiber types and power
- motor neuron
- fiber size
- SR development
endurance athlete
type 1
power athlete and sprinters
type 2
fast oxidative =
type 2a
fast glycolytic
type 2b
type 2a
faster fatigue
-more glycolytic that type 1 but less than 2x
-shorter high intensity endurance events
type 2x
very glycolytic, few mitochondria,
-used for everyday activities
-explosive movements
genetic factors
determines which motor neurons innervate fibers
- fibers become type 1, 2, 2x based on alpha motor neuron
training factors
type 1s can rarely become type 2s and vice versa
-but they can become more like another
all or none principle
when a motor neuron carries an AP to the muscle fibers, all or none of the fibers will be activated
principle of orderly recruitment
Type 1, type 2a, type 2x
-your body will only recruit what your body needs
size principle
the order of recruitment of motor units is directly related to the size of their motor neuron
-smaller motor units are recruited first
if minimal force is needed, then only type ____ recruited
type 1
if maximal force is needed, then ____ are recruited
ALL fiber types
concentric contraction
muscle shortens while producing force
-sarcomeres shorten, filaments side toward the center
-maximal force development decreases at higher speeds
eccentric contractions
muscle lengthens while producing force
-cross-bridges form but sarcomeres lengthens
-lowering heavyweight
-maximal force development increases at higher speeds
twitch
single electrical impulse (AP)
summation
a series of at least 3 successive stimuli before relaxation from the first
tetanus
continued stimulation
frequency of stimulation (rate coding)
twitch, summation, tetanus
lengthen tension relationship
optimal sarcomere length =optimal over lap
too short or too stretch =little or no force develops
