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Muscular System Jessica Velazquez Period 3 - Coggle Diagram
Muscular System Jessica Velazquez Period 3
Major functions of the muscular system
Movement
Skeletal muscles pull on bones for voluntary movement.
Smooth muscles move food, blood, and other substances.
Cardiac muscle pumps blood throughout the body.
Posture & Stability
Continuous muscle tension maintains body posture and joint stability.
Heat Production
Muscle contractions release heat to help maintain body temperature.
Support & Protection
Muscles protect organs and support soft tissues.
3 types of muscles & their functions
Skeletal
Location: Attached to bones
Appearance: Striated
Control: Voluntary
Function: Moves the skeleton; posture; heat production
Cardiac
Location: Heart walls
Appearance: Striated; branched; intercalated discs
Control: Involuntary
Function: Pumps blood through heart and vessels
Smooth
Location: Walls of organs (stomach, intestines, vessels)
Apperance: Non-striated
Control: Involuntary
Function: Moves substances through organs; controls vessel diameter
Names of all the skeletal muscles
Facial Muscles
Frontalis (Epicranius frontal belly) – raises eyebrows
Occipitalis (Epicranius occipital belly) – moves scalp backward
Temporalis – elevates mandible (chewing)
Zygomaticus – raises corners of mouth (smiling)
Orbicularis oculi – closes eyes
Orbicularis oris – closes and puckers lips
Masseter – elevates mandible for chewing
Neck Muscles
Sternocleidomastoid – flexes and rotates head
Sternohyoid – depresses hyoid bone (swallowing)
Shoulder & Arm Muscles
Deltoid – abducts arm
Bicep brachii – flexes elbow, supinates forearm
Brachialis – flexes elbow
Brachioradialis – aids in elbow flexion
Tricep brachii – extends elbow
Forearm & Hand Muscles
Pronator teres – pronates forearm
Palmaris longus – flexes wrist
Flexor carpi radialis – flexes and abducts wrist
Flexor carpi ulnaris – flexes and adducts wrist
Extensor carpi radialis – extends and abducts wrist
Extensor carpi ulnaris – extends and adducts wrist
Torso Muscles
Pectoralis major – flexes and adducts arm
Serratus anterior – pulls scapula forward (“boxer’s muscle”)
Rectus abdominis – flexes spine (“abs”)
External obliques – rotates and compresses abdomen
Trapezius – elevates, rotates, and retracts scapula
Latissimus dorsi – extends and adducts arm
Rhomboid major – retracts scapula
Infraspinatus – rotates arm laterally
Teres major – extends and rotates arm
Hip & Thigh Muscles
Iliopsoas – flexes thigh at hip
Pectineus – adducts and flexes thigh
Tensor fasciae latae – stabilizes and abducts thigh
Adductor longus – adducts thigh
Adductor magnus – adducts and extends thigh
Gracilis – adducts thigh, flexes knee
Sartorius – flexes and rotates thigh
Gluteus maximus – extends and laterally rotates thigh
Gluteus medius – abducts and stabilizes thigh
Leg & Lower Limb Muscles
Rectus femoris – extends knee, flexes hip
Vastus lateralis – extends knee
Vastus medialis – extends knee
Bicep femoris – flexes knee, extends thigh
Semitendinosus – flexes knee, extends thigh
Semimembranosus – flexes knee, extends thigh
Iliotibial tract – stabilizes lateral thigh
Lower leg & Foot muscles
Tibialis anterior – dorsiflexes foot
Extensor digitorum longus – extends toes
Fibularis (Peroneus) longus – everts and plantar flexes foot
Soleus – plantar flexes foot
Gastrocnemius – plantar flexes foot and flexes knee
Calcaneal (Achilles) tendon – attaches calf muscles to heel
Sarcomere
Structure: From Z disc to Z disc; made of actin and myosin filaments.
Thick filament: Myosin – has heads that bind to actin.
Thin filament: Actin – interacts with myosin.
Bands
A band = thick + thin overlap
I band = thin only
H zone = myosin only
Regulatory proteins: Troponin & tropomyosin control binding sites.
Neuromuscular junction
Nerve impulse reaches axon terminal.
Calcium enters, causing ACh release
ACh crosses synaptic cleft → binds to receptors on sarcolemma.
Depolarization triggers muscle action potential.
ACh broken down by AChE → ends signal.
Structures: Axon terminal, synaptic cleft, ACh vesicles, receptors, motor end plate.
Sliding filament theory of muscle contraction
Calcium binds to troponin, moving tropomyosin.
Myosin heads attach to actin → cross-bridges form.
Power stroke: myosin pulls actin toward center (ADP + Pi released).
ATP binds → myosin detaches.
ATP hydrolyzed → myosin re-cocks.
Cycle repeats → sarcomere shortens, muscle contracts.
Action potential in a muscle fiber
ACh opens Na⁺ channels → depolarization.
Voltage-gated Na⁺ channels spread action potential.
K⁺ exits → repolarization.
Na⁺/K⁺ pump restores resting potential.
Signal travels through T-tubules → triggers Ca²⁺ release.
Muscle coverings
Epimysium: wraps entire muscle.
Perimysium: wraps bundles (fascicles).
Endomysium: surrounds each fiber.
Fascia: separates muscles.
Tendon: connects muscle to bone.
Function: protection, organization, and transmission of force.
Disorders associated with the Muscular system
Muscular Dystrophy: genetic, muscle fibers degenerate.
Myasthenia Gravis: autoimmune; ACh receptors destroyed.
Rigor Mortis: ATP loss → myosin can’t detach → stiffness.
Muscle Fatigue: low ATP, ion imbalance, or lactic acid buildup.
Strain/Sprain: overstretched or torn fibers/tendons.