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Muscular Unit Giselle Gonzalez P.3 - Coggle Diagram
Muscular Unit Giselle Gonzalez P.3
Major Functions of the Muscular System
Movement
– body motion, organ movement
Posture
– maintains body position
Stabilization
– stabilizes joints
Heat production
– generates body heat during contraction
Protection
– shields internal organs
3 Types of Muscles & Functions
Skeletal Muscle
voluntary, sitrated, moves bones and facial features
Cardiac Muscle
:
involunatry, sitrated, found only in the walls of the heart and pumps blood.
Smooth Muscle
involuntary, non-sitrated, found in walls of organs (bladder, digestive tract)
Sarcomere: Functional unit of a muscle fiber
(between two Z-lines)
Actin (thin filament)
Myosin (thick filament)
Z-line, M-line, A-band, I-band, H-zone
Function: Shortens during contraction (sliding filament process
Action Potential in a Muscle Fiber
Resting state:
Negative inside, positive outside
Depolarization:
Na⁺ ions enter → inside becomes positive
Repolarization:
K⁺ ions leave → restores resting potential
Result:
Triggers Ca²⁺ release → contraction begins
Sliding Filament Theory (How muscles contract)
Process: Myosin heads attach to actin forming cross-bridges
Myosin pulls actin filaments inward → sarcomere shortens ATP breaks cross-bridge to reset myosin
Repeated cycles = muscle contraction
Neuromuscular Junction (Connection between motor neuron and muscle fiber)
Nerve impulse reaches axon terminal
Acetylcholine (ACh) released into synaptic cleft ACh binds to receptors on muscle fiber
Muscle fiber depolarizes → action potential generated
Disorders Associated with the Muscular System
Muscular dystrophy
: Genetic disorder causing muscle weakness
Myasthenia gravis:
Autoimmune disorder blocking ACh receptors
Tendinitis:
Inflammation of tendons
Muscle strain:
Overstretching or tearing muscle fibers
Fibromyalgia:
Chronic muscle pain and fatigue
Names of Skeletal Muscles
Head/Face:
Frontalis, Orbicularis oculi, Zygomaticus, Masseter, Temporalis
Neck:
Sternocleidomastoid, Trapezius
Torso:
Pectoralis major, Rectus abdominis, External obliques, Latissimus dorsi, extended spine
Upper Limb:
Deltoid, Biceps brachii, Triceps brachii, Brachioradialis, wrist flexors
Lower Limb
: Gluteus maximus, Quadriceps group, Hamstrings group, Gastrocnemius, Soleus
Muscle Coverings (Connective Tissue Layers)
Epimysium:
Surrounds entire muscle
Perimysium:
Surrounds muscle fascicles (bundles)
Endomysium
: Surrounds individual muscle fibers
Function:
Support, protection, and transmit force