fibers in skeletal muscle are
parallel to the muscle
muscle cells are
multinucleate
muscles need ___ to function
oxygen, glucose, and calcium
cells in the same fascicle
don’t need to contract at the same time
levels of organization for muscle
muscle cell is surrounded by endomysium
muscle cells grouped together by parimysium
gouped muscle cells in a fascicle
multiple fascicles are surrounded by epimysium
tendons made of
collagen fibers
sheet like attachment structures
aponeurosis
skeletal muscle function
1) maintain posture
2) produce movement
3) generate heat
4) stabilize joints
I band
actin (thin filament)
A band
both actin and myosin (Thick filament)
plasma membrane of muscle cell
sarcolemma
fibers within a muscle cell
myofibril
one unit of a muscle cell
sarcomere
myosin heads are called _ when they contract
cross bridges
stores and releases Calcium into mucle
sarcoplasmic reticulum
nerve signal for muscle contraction
action potential
where nerve meets muscle
nueromuscular junction
irritability
ability to receive and respond to a stimulus
contractility
ability to shorten when an adequate stimulus is presented
extensibility
ability of muscles to be stretched
elasticity
ability to recoil and resume resting length after stretching
motor unit
one motor neuron and all the muscle cells it stimulates
neuromuscular junction
junction of the axon terminal and the sarcolemma of the muscle
neurotransmitter
chemical released in the neuromuscular joint to stimulate the muscle
neurotransmitter for skeletal muscles
Acetylcholine
gap between nerve and muscle
synaptic cleft
action potential
nerve signal to t muscle
events at the neuromuscular junction
1) calcium enters the axon terminal
2) calcium causes acetycholine to be released
3) Acetylcholine crosses the synaptic cleft and diffuses across the sarcolemma
4) Sarcolemma becomes more permeable and sodium rushes in while potassium rushes out
5) action potential spreads down the cell as sodium rushes in
6) acetylcholinesterase breaks down acetylcholine ending the process
cross bridge cycle
1) Calcium is released from sarcoplasmic reticulum
2) Calcium causes the tropomyosin to change position on the actin revealing places for the mysoin heads to attach
3) a cross bridge is formed as the mysoin heads attach to the actin
4) myosin performs a power stroke pulling the actin
5) cross bridge detaches
6) ATP re-cocks the mysosin
twitch
single-brief contraction
summing of contractions
one contraction is immediately followed by another
unfused tetanus
multiple summing of contractions
fused tetanus
no relaxation between contractions (only one that happens in real life)
three ways to get energy to a muscle cell
1) re phosphorylation of atp with creatine phosphate
2) aerobic respiration
3) anaerobic glycosis and lactic acid formation
creatine
1 atp per molecule
fastest energy source, lasts 15 seconds
anaerobic glycosis
fast reaction, glucose broken down into pyruvic acid to release 2 ATP
lactic acid formation
ubla
aerobic respiration
most efficient produces 32 ATP
causes of muscle fatigue
1) Ionic imbalance
2) lactic acid accumulation
3) energy supply decreases
isotonic
contraction where muscle moves
isometric
contraction where muscle tenses but doesn’t move
weight lifting is an
isometric exercise
5 rules
1) all skeletal muscles cross a joint
2) bulk of the muscle is proximal to the joint crossed
3) muscles have 2 attachments
4) muscles only pull
5) insertion moves towards the origin
attachment to immovable bone
origin
attachment to movable bone
insertion
flexion
decreases angle
increases angle
extension
shaking head no is an example of
rotation
abduction
movement away from midline
movement towards midline
adduction
circumduction
proximal end of bone remains stationary while the distal end moves in circle
lifting foot up
dorsiflexion
pointing foot
plantar flexion
inversion
sole of the foot turned medially
sole of the foot turned laterally
eversion
supination
forearm turns laterally
forearm turns forearm turns medially
pronation
decease in size
atrophy
produces flexion
muscle that crosses over the anterior side
produces adduction
crosses the medial side
produces extension
crosses the posterior side
produces abduction
crosses the lateral side
muscle with the major responsibility for a movement
prime mover
muscle that reverses prime mover
antagonist
muscle that aids the prime mover
synergist
stabilizes the origin of the prime mover
fixator
frontalis
raises eyebrows; face
orbicularis oculi
closes eyes, squints, blinks, winks; face
orbicularis oris
closes mouth and protrudes the lips; face
buccinator
flattens the cheek, chews; face
zygomaticus
raises corners of the mouth; face
masseter
closes jaw and elevates mandible
temporalis
synergist of the masseter, closes jaw; face
platysma
pulls corners of mouth inferiorly; neck
sternoclasomastoid
flexes the neck, rotates the head; neck
trapezious
elevates, depresses, adducts, and stabilizes the scapula; posterior trunk
latissimus dorsi
extends and adducts the humerus; posterior trunk
erector spinae
back extension; posterior trunk
quadratus lumborum
flexes the spine laterally; posterior trunk
deltoid
arm abduction; posterior arm
pectoralis major
adducts and flexes the humerus; anterior trunk
external intercostals
raise rib cage during
inhalation; anterior trunk
internal intercostals
depress the rib cage to move air out of the lungs when you exhale forcibly; anterior trunk
rectus abdominis
flexes vertebral column
and compresses abdominal contents; abdominal girdle
external oblique
flex vertebral column; rotate trunk and bend it laterally; abdominal gridle
internal oblique
flex vertebral column; rotate trunk and bend it laterally
transverse abdominis
compresses abdominal contents
Biceps Brachii
supinates forearm, flexes elbow
brachialis
elbow flexion
brachioradialus
weak muscle; elbow flexion
triceps brachii
elbow extension (antagonist to biceps brachii)
flexor carpi
wrist flexion (forearm)
flexor digitorum
finger flexion
extensor carpi
wrist extension
extensor digitorum
finger extension
gluteous maximous
hip extension
gluteous medius
hip abduction, steadies pelvis when walking
Iliopsoas
hip flexion, keeps the upper body from falling backward when standing erect
adductor muscles
adduct the thighs
Hamstring group
Biceps femoris
Semimembranosus
Semitendinosus
quadriceps
rectus femoris
vastus lateralis
vastus medialis
vastus intermedius
sartorious
flexes thigh
quadricepts group function
extends the knee
hamstring group function
thigh extension and knee flexion
tibialis anterior
dorsiflexion, foot inversion
extensor digitorum longus
toe extension and
dorsiflexion of the foot
fibularis muscles
plantar flexion, foot eversion
soleus
plantar flexion
