Types of Muscles
Skeletal Muscles: Found on bones, characterized by a striated appearance, voluntary control, and multinucleation. Named based on location, size, direction, number of origins, and actions (e.g., flexor and extensor).
Cardiac Muscles: Found only in the heart, striated and branched, involuntary. Cells are fused, enabling synchronized contractions to create the heartbeat.
Smooth Muscles: Found in organs and blood vessels, also known as visceral muscles, and are involuntary.
Sphincter Muscles: Special circular muscles that open and close to allow passage of substances. Found in the digestive and urinary systems.
Structures of the Muscular System
Connective Tissue: Includes tendons (connect muscles to bones) and fascia (fibrous sheets wrapping around muscle bundles).
Characteristics of Muscles
Extensibility: Ability to stretch or extend.
Contractibility: Ability to shorten or pull.
Elasticity: Ability to return to the original state.
Excitability: Ability to respond to stimuli.
Muscle Tone: Tension in muscles.
Atrophy: Decrease in muscle size due to disuse.
Hypertrophy: Increase in muscle size due to strength training.
Muscle Fatigue: Decrease in maximal force or power production.
Muscles of the Body
Head and Neck: Includes muscles like frontalis (moves eyebrows), masseter (chewing), orbicular oculi (closes eyelids), and sternocleidomastoid (rotates head).
Torso/Trunk: Includes external intercostals (assist lungs), diaphragm (aids in breathing), rectus abdominus (abs), and latissimus dorsi (lower back).
Upper Extremities: Includes trapezius (supports arm), deltoid (lifts upper arm), pectoralis major (chest), biceps brachii (lifts forearm), and triceps brachii (straightens arm).
Lower Extremities: Includes gluteus medius/maximus (hip movement), vastus lateralis (extends knee), gastrocnemius (calf muscle), and tibialis anterior (dorsiflexes foot).
Functions of the Muscular System
Movement: Result of muscle contraction and relaxation.
Posture: Maintained by musculoskeletal system.
Body Heat: Generated by muscle contractions.
Movement Types
Includes rotation, extension, circumduction, supination, pronation, flexion, abduction, and adduction.
Disorders of the Muscular System
Fibromyalgia: Causes muscle pain, fatigue, sleep disorders; mostly affects women.
Hernia: Organ pushes through a muscle opening; often occurs in the abdomen or groin.
Muscle Spasms: Sudden involuntary contractions; caused by overuse or dehydration.
Strain: Muscle tear or tendon damage; treated with RICE and NSAIDs.
Tendonitis: Inflammation of tendons; common in shoulders and elbows.
Muscular Dystrophy: Group of diseases causing progressive muscle weakness; mostly affects boys.
Tetanus: Serious illness caused by Clostridium bacteria; prevented by vaccine.