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Muscular System Sarah Hernandez P.6 - Coggle Diagram
Muscular System
Sarah Hernandez
P.6
major functions of muscular system
major functions: muscles are organs that generate force, causing all movement types throughout the body
skeletal muscles allows movement at joints and maintains postures
smooth muscles allow viscera movements
cardiac muscles functions for pumping actions of the heart
Skeletal Muscles and Facial Muscles
Facial Muscles
temporalis: closes jaw and retract mandible
zygomatics: raises lateral corners of mouth
orbicularis oris: closes lips
frontalis: raises eyebrows and forehead horizontally
orbicularis oculi: closes eyes, blinking
masseter: prime mover of jaw closure
platysma: tenses skin of the neck
Skeletal muscles
upper half:
trapezius
sternocleidomastoid
deltoid
pectoralis major
serratus anterior
bicep branchii
tricep branchii
brachioradialis
flexor carpi radialus
rectus abdominis
external oblique
teres major
-infraspinatus
latissimus dorsi
extensor carpi radialus
flexor carpi ulnaris
extensor digitorum
rhomboid major
Skeletal muscles
Lower half:
illiopsoas
-adductor longus
satorius
gradlius
rectus femors
vastus lateralis
vastus medialis
bicep femoris
semitendinosus
semimembranous
tribialis anterior
-extensor digitorum longus
fibularis longus
gastronemius
soleus
gluteus maximus
-calcaneal tendon (achilles)
3 types of muscles and their functions
skeletal muscles:
striations, many nuclei, well-dev transverse tubules, voluntary
function: movement of bones at joints, maintains posture
smooth muscles: no striations, single nucleus, lacks transverse tubules, involuntary
functions: viscera movement, peristalsis+ vasoconstriction
cardiac muscles: striations, single nucleus, well-dev transverse tubules- intercalated discs, involuntary
functions: pumping action of the heart
Sliding filament theory of muscle contraction
Step 1: Signals sent to motor neuron. Motor neurons are included in a vesicle containing acetylcholine. Ach reaches receptors on muscle sarcolemma and creates an impulse
Step 2: Impulse travels down membranes into transverse tubules and calcium is realeased from scaroplasmic reticulum
Step 3:
Calcium binds to actin and actin changes shape
Step 4:
Actin shape change causes myosin heads to form cross bridges between actin and myosin
Step 5: ATP is used to create a "power stroke between the filaments. The filaments slides inwards and shortens, or contracts the muscle.
Sarcomere
sarcomeres extend inbetween z lines
consist of striations; light/dark bands
I bands: light bands/ actin filaments anchored to z lines
A bands: dark bands/ made of thick/thin filaments; centers of Abands= H zone- myosin filaments only; M line= center of H zone, proteins that hold myosin in place
Neuromuscular junctions
skeletal muscle fibers= only stimulated by motor neuron
muscle fibers= functionally connected to motor neuron, creates synapse
neurotransmitters are released by synapse
neuromuscular junction= synapse between motor neuron and muscle fiber that regulates it
motor end plate= specific receptors for neurotransmitter
synaptic cleft: gap between membrane of neuron and muscle fiber> neurotransmitters diffuse across cleft> binds to motor end plate> stimulate contraction
Muscle coverings
connective tissue coverings
fascia- layers of dense connective tissue, surrounds/separates muscle
aponeurosis- muscles connected by broad sheets of connective tissue
epimysium- layer of connective tissue around skeletal muscle
perimysium- surrounds bundles of skeletal muscle fibers; fascicles
each muscle fiber is covered by endomysium connective tissue layer
Action potential of muscle fiber
Muscle contractions
Impulse travels down a motor neuron axon
The motor neuron releases ACh
ACh binds to ACh receptors in muscle fiber membranes
Sarcolemma is stimulated. An impulse travels deep through transverse tubules.
Impulse reaches sarcoplasmic reticulum, calcium channels open
Calcium ions diffuse from sarcoplasmic reticulum into cytosol and binds to troponin muscle
Tropomyosin molecules move/expose actin sites where myosin binds
Cross- bridges form, links thin/thick filaments
Thin filaments are pulled center by cross-bridges
Contraction occurs
Muscle Relaxation
Acetylcholinesterase decomposes ACh and simulation ends
Calcium ions are actively transported into sarcoplasmic reticulum
ATP breaks cross-bridges
ATP breakdown raises myosin heads
Troponin/ tropomyosin molecules block filament interaction
Muscle fibers remain relaxed until stimulated again