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Muscular System Annabel Quintero Period: 7 (Names of muscles (vastus…
Muscular System Annabel Quintero Period: 7
sliding filament theory
The sliding filament theory is the explanation for how muscles contract to produce force. The actin and myosin filaments within the sarcomeres of muscle fibers bind to create cross-bridges and slide past one another, creating a contraction.
myosin head attaches to actin, forming actin/myosin filaments
myosin head moves toward M line of sarcomere, pulling actin filaments past myosin
Ca++ binds to actin myofilament, exposing the myosin binding site
this action is repeated many times powered by ATP (ATP needed to release myosin heads from actin)
nerve impulse or action potential travels down sarcolemma & into t-tubules, causing sarcoplasmic reticulum to release Ca++ into sarcoplasm
z lines get closer together as actin and myosin filaments slide past each other, and sarcomeres shorten
Major functions
Posture
maintain body position
Thermogenesis
heat production
Motion/Movement
change in body position
body movement
supination
forearm rotates laterally so palm faces anteriorly
pronation
forearm rotates medially so palm faces posteriorly
eversion
turn sole of foot laterally
inversion
turn sole of foot medially
opposition
movement of thumb to touch tips of other fingers
plantar flexion
pointing toe
dorsiflexion
lifting the superior surface of foot towards shin
circumduction
proximal end of a limb is stationary & the distal end moves in circle
adduction
movement of limb toward the midline
abduction
movement of limb away from midline
rotation
movement of a bone around longitudinal axis
hyperextension
extension beyond 180°
extension
movement that increases angle of joint
flexion
movement that decreases angle of joint
Names of muscles
vastus medialis
deltoid
vastus lateralis
thigh
latissimus dorsi
abdomen
teres major
bicep femoris
hamstrings
infraspinatus
pectoralis major
thorax
sternocleidomastoid
neck
extensor carpi radialis
forearm
trapezius
shoulder
semitendinosus
semimembranosus
flexor carpi ulnaris
serratus anterior
bicep brachii
arm
external oblique
tibialis anterior
leg
iliopsoas
pelvis/thigh
sartorius
structure & organization levels
ligaments
strong cords of fibrous connective tissue that attach bone to bone
body
main part of the muscle
insertion
the end of a muscle attached to the bone that moves when a muscle contracts
epimysium
the layer of connective tissue around each whole muscle
tendons
strong cords of fibrous connective tissue that attach muscles to bone
perimysium
surrounds individual bundles (fascicles) within each muscle
endomysium
covers each muscle cell (muscle fiber)
origin
the end of a muscle that attaches to the bone that does not when contraction of the muscle occurs
myofilaments are actin and myosin
myosin = thick filament actin = thin filament
fascicles
bundle of muscle fibers
myofibrils
consist of sarcomeres
sarcomeres consist of myofilaments
myocyte (muscle fiber)
muscle cell
consist of myofibrils
sarcolemma
cell membrane of muscle cell
sarcoplasm
cytoplasm of muscle cell
a sarcomere extends from one Z line to the next
I bands (light bands) made up of actin filaments are anchored to Z lines
A bands (dark bands) are made up of overlapping thick and thin filaments
sarcoplasmic reticulum
specialized smooth ER functions to store and release calcium when muscle contracts
transverse tubules (T-tubules)
infoldings of sarcolemma that penetrate into muscle fibers
3 types of muscle tissues
cardiac muscle
long, cylindrical, branched, & has single central nucleus
involuntary: cannot consciously control it
forms the heart wall
smooth muscle
spindle-shaped with single central nucleus & has no striations, appears smooth
controls movement inside internal organs
involuntary: cannot consciously control it
skeletal muscle
long, cylindrical, branched, & multinucleated
attached by tendons to bones
voluntary: subject to conscious control