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Amanda Montanez Period 5 Muscular System - Coggle Diagram
Amanda Montanez Period 5
Muscular System
major functions
produce movement
skeletal: pull on bones allowing all locomotion & manipulation; cardiac: pumps blood; smooth: propels substances through organs, along tract
maintain posture and body position
counteract downward pull of gravity
strengthen and
stabilize joints
generate heat
muscles generate heat as they contract (maintain body temp)
action potential (AP) in a muscle fiber
electrical signal / nerve impulse
muscle twitch
muscle fiber's response to single AP from motor neuron; contracts quickly, then relaxes
neuromuscular junction / motor end plate
2. muscle fiber excitation
EPP triggers AP in adjacent sarcolemma
3. excitation-contraction coupling
AP in sarcolemma travels down T tubules
sarcoplasmic reticulum releases Ca2+
Ca2+ binds to troponin (thin filament) which shifts trypomyosin to uncover myosin binding sites on actin. myosin heads bind actin
1. events at neuromuscular junction
motor neuron fires AP (nerve impulse) down axon
1) AP arrives at axon terminal
2)
voltage gated
Ca2+ channels open. Ca2+ enters axon terminal
motor neuron releases ACh into synaptic cleft
3) Ca2+ entry causes release of ACh neurotransmitter into synaptic cleft
ACh binds receptors on junctional folds of sarcolemma
4) ACh diffuses across synaptic cleft to ACh receptors on sarcolemma
ACh binding causes local depolarization called
end plate potential
(EPP)
5) ACh binding opens
chemically gated
ion channels allow passage of Na+ & K+ out of muscle fiber. Na+ entry > K+ ions exiting = EPP
6) acetylcholinesterase degrades ACh in synaptic cleft
4. cross bridge cycling
muscle contracts as a result of a repeating cycle
ion channels
chemically gated
voltage-gated
anatomy
axon terminal
- end of axon
synaptic cleft
- space separating axon and sarcolemma of muscle fiber
synaptic vesicles
- small membranous sacs containing ACh
junctional folds
- folds in sarcolemma of muscle fiber that contain ACh receptors
region where a motor neuron comes into close contact with a skeletal muscle cell
disorders associated
fibromyalgia
muscle pain; more common in women
cerebral palsy
spastic paralysis causing muscle weakness as a result of abnormal brain development / damage
muscular dystrophy
muscle weakness & atrophy; inherited
myasthenia gravis
neuromuscular disorder that blocks neurotransmitters; autoimmune disease, involves shortage of ACh receptors
myositis
inflammation of the muscle; autoimmune
sliding filament theory of muscle contraction
thin filaments slide past thick filaments, causing myosin and actin to overlap more; neither change length during contraction
nervous system stimulates muscle fibers, myosin heads (thick filaments) latch onto myosin-binding sites on actin (thin filaments) & sliding begins
cross bridge attachments form + break several times, generate tension & propel thin filaments toward center
shortening of muscle fiber
I bands shorten
Z discs pulled toward M line, approach thick filament & thin filaments overlap
H zones disappear
A bands move closer tg (length doesn't change)
sarcomere
segment of
myofibril
smallest contractile unit of muscle fiber, composed of myofilaments (
thick & thin
) made up of contractile proteins (
myosin & actin
)
arrangements
thick filament extends length of
A band
H zone
of A band,
M line
in center
thin filament extends across
I band
, partway into A band
Z disc
align myofilaments and anchor sarcolemma
3 types of muscles & their functions
characteristics
excitability
(responsiveness) ability to receive & respond to stimuli
contractility
ability to shorten forcibly when stimulated
extensibility
ability to be stretched
elasticity
ability to recoil to resting length
skeletal
attached to bones or (some facial muscles) to skin
striated, voluntary control
cardiac
walls of the heart
striated, involuntary
smooth
in walls of hollow visceral organs
nonstriated, involuntary
muscle coverings (CT)
perimysium
dense irregular CT surrounding each
fascicle
(muscle fiber groups)
endomysium
fine areolar CT that surrounds each muscle fiber
muscle fibers make up skeletal & smooth muscle
epimysium
dense irregular CT that surrounds entire muscle; may blend w/ fascia
anterior skeletal muscles
head
frontalis
orbicularis oculi
zygomaticus - raises corners of mouth
orbicularis oris
temporalis - closes jaw
masseter - closes jaw
buccinator - cheek
neck
platysma
sternohyoid
sternocleidomastoid
upper body
trapezius
deltoids
pectoralis major
serratus anterior
external obliques
rectus abdominus
arms
biceps brachii
brachioridalis
brachialis
wrist flexors
lower body
tensor fascia lata
sartorius
adductors
vastus lateralis
rectus femorus
vastus medialis
gracilis
tibialis anterior
extensor digitorum longus
posterior skeletal muscles
upper body
deltoids
trapezius
latissimus dorsi
arms
triceps brachii
brachioridalis
wrist extensors
lower body
gluteus maximus
iliotibial tract (ITB)
biceps femoris
gastrocnemius
soleus
fibularis longus