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Yuridia Sigala Period 3 A&P: Muscular System - Coggle Diagram
Yuridia Sigala Period 3 A&P: Muscular System
Major Functions of the Muscular System
Movement: Muscles contract to produce voluntary and involuntary motion.
Posture & Stability: Continuous muscle tone maintains posture and stabilizes joints.
Heat Production: Muscle contraction generates about 85% of body heat (through ATP use).
Support of Soft Tissues: Abdominal and pelvic muscles support internal organs.
Guarding Openings: Circular muscles (sphincters) control openings in the body (mouth, digestive, urinary).
Three Types of Muscle Tissue & Their Functions
Skeletal Muscle
Voluntary and striated.
Attached to bones with tendons.
Responsible for movement and posture.
Cardiac Muscle
Involuntary and striated with intercalated discs.
Found only in the heart.
Pumps blood rhythmically
Smooth Muscle
Involuntary and non-striated.
Found in walls of hollow organs (stomach, intestines, blood vessels).
Moves substances through the body (peristalsis).
Skeletal Muscles
Anterior Muscles
Head & Neck: Frontalis, Temporalis, Masseter, Orbicularis oculi, Orbicularis oris, Zygomaticus, Sternocleidomastoid, Sternohyoid
Torso: Pectoralis major, Serratus anterior, External obliques, Rectus abdominis, Tensor fasciae latae
Arm: Deltoid, Biceps brachii, Brachialis, Brachioradialis, Pronator teres, Flexor carpi radialis, Flexor carpi ulnaris, Palmaris longus
Leg: Iliopsoas, Pectineus, Adductor longus, Sartorius, Rectus femoris, Vastus lateralis, Vastus medialis, Tibialis anterior, Fibularis longus, Extensor digitorum longus, Soleus, Gastrocnemius
Posterior Muscles
Head & Neck: Occipitalis, Sternocleidomastoid, Trapezius
Upper Back: Deltoid, Infraspinatus, Rhomboid major, Teres major, Latissimus dorsi, Triceps brachii, Brachioradialis, Extensor carpi radialis, Extensor carpi ulnaris, Flexor carpi ulnaris
Lower Body: Gluteus maximus, Gluteus medius, Adductor magnus, Biceps femoris, Semitendinosus, Semimembranosus, Gracilis, Gastrocnemius, Soleus, Fibularis longus, Calcaneal (Achilles) tendon
Sarcomere
Structure
Z-line to Z-line marks one sarcomere.
Actin (thin filaments) and myosin (thick filaments) overlap.
A-band: dark region with myosin.
I-band: light region with actin only.
H-zone: center region of myosin only.
Function: Shortens as actin and myosin slide past each other during contraction
Definition: Smallest functional unit of a muscle fiber; found within myofibrils
Neuromuscular Junction
Process
Action potential reaches neuron terminal.
Acetylcholine (ACh) is released into the synaptic cleft.
ACh binds to receptors on the sarcolemma.
Sodium (Na⁺) enters → depolarization → muscle action potential.
ACh broken down by acetylcholinesterase → ends stimulation
Definition: Synapse between a motor neuron and a muscle fiber
Sliding Filament Theory (explains why the mucsle contracts)
Myosin heads attach to actin (forming cross-bridges).
ATP powers myosin to pull actin toward the center (power stroke).
Calcium ions (Ca²⁺) from the sarcoplasmic reticulum bind to troponin, exposing binding sites.
Sarcomeres shorten → entire muscle fiber contracts.
Relaxation occurs when Ca²⁺ is reabsorbed and ATP detaches myosin.
Action Potential in a Muscle Fiber
Step 1: Nerve impulse triggers depolarization of sarcolemma.
Step 2: Action potential travels through T-tubules.
Step 3: Ca²⁺ released from sarcoplasmic reticulum.
Step 4: Ca²⁺ binds to troponin → tropomyosin shifts → myosin binds to actin.
Step 5: Cross-bridge cycle occurs → contraction.
Step 6: Ca²⁺ returns to SR → muscle relaxes.
Muscle Coverings (Connective Tissue Layers)
Epimysium: Surrounds the entire muscle.
Perimysium: Surrounds fascicles (bundles of fibers).
Endomysium: Surrounds individual muscle fibers.
Tendon: Connects muscle to bone.
Aponeurosis: Broad sheet connecting muscles to each other.
Disorders of the Muscular System
Muscular Dystrophy: Genetic disorder → progressive weakening of muscles
Fibromyalgia: Chronic muscle pain and fatigue
Myasthenia Gravis: Autoimmune, muscle weakness, no cure, mediciation
Cerebral Palsy: spastic paralysis causing muscle weakness, head injury, bleeding in brain or premature birth. no cure , shortness of breathe
Myositis: Inflmattion in the muscle, infection, muscle trauma, auto immune, swelling rash, fatigue, medication