Muscular System Overview

• The document provides an overview of the muscular system, including terminology, muscle fiber types, fascicular arrangements, muscle coordination, nomenclature, and common injuries and conditions.

Definition of Terms

• Insertion is the point where a muscle's tendon attaches to the movable bone, typically distal and moves toward the origin.
• Origin: muscle's tendon attachment to the stationary bone, usually proximal.
• Body/Belly: the fleshy part of the muscle between tendons.
• Actions: main movements occurring when a muscle contracts.
• Reverse Muscle Action (RMA): origin and insertion switch roles during certain movements.
• Most muscles originate in one bone, insert into another, and cross at least one joint.

Effect of Fiber Type on Activity Level

• Isometric contraction: tension increases, but muscle length remains the same.
• Isotonic contraction: tension is constant, but muscle length decreases.
• Muscle tone: continuous small contractions maintaining posture.
• Slow-twitch fibers: better for aerobic respiration.
• Fast-twitch fibers: adapted for anaerobic respiration.

Fascicular Arrangements

• Parallel: fascicles run parallel to the muscle's length and end in flat tendons.
• Fusiform: fascicles nearly parallel to the muscle's length, tapering at the ends with tendons.
• Circular: fascicles arranged in circles, forming sphincter muscles.
• Triangular: fascicles spread over a wide area, converging at a central tendon.
• Pennate: short fascicles attach to a long tendon.
• Unipennate: fascicles on one side of the tendon.
• Bipennate: fascicles on both sides of the tendon.
• Multipennate: fascicles attach obliquely from many directions to several tendons.
• Fascicular arrangement influences a muscle's power and range of motion.

Coordination Among Muscles

• Agonist: muscle responsible for a specific movement.
• Antagonist: muscle that opposes the agonist.
• Synergist: muscles working together to assist the agonist by reducing unnecessary movement.
• Fixators: stabilize the origin of the prime mover to act more efficiently.
• Compartment: group of skeletal muscles, blood vessels, and nerves with common function.

Nomenclature

• Muscle names often reflect features like size, shape, action, origins, and location.
• Sites of origin and insertion are used in naming.
• Location and function are also common naming conventions.

Categories of Skeletal Muscle Actions

• Extensor: increases the angle at a joint.
• Flexor: decreases the angle at a joint.
• Abductor: moves a limb away from the midline.
• Adductor: moves a limb toward the midline.
• Levator: elevates a structure.
• Depressor: lowers a structure.
• Rotator: rotates a bone along its axis.
• Sphincter: constricts an opening.

Clinical Conditions

• Intramuscular Injections: deposit medication directly into the muscle tissue
• Bell’s Palsy: unilateral paralysis of muscles of facial expression due to damage to the facial nerve.
• Strabismus: improper alignment of the eyes due to muscle or nerve problems.
• Dysphagia: difficulty in swallowing.
• Hernia: protrusion of an organ through a containing structure.
• Urinary Stress Incontinence: involuntary leakage of urine when intra-abdominal pressure increases.
• Golfer’s Elbow: strain of flexor muscles due to repetitive movements.
• Carpal Tunnel Syndrome: median nerve compression causing sensory and motor deficits in the hand.
• Groin Pull: rupture or tear in thigh muscles.
• Pulled Hamstrings: strain or tear of hamstring muscles.
• Shin Splint Syndrome: pain along the tibia due to various causes.
• Compartment Syndrome: pressure within a muscle compartment causing ischemia.
• Contracture: permanent muscle shortening due to tissue changes.
• Plantar Fasciitis: inflammation of the plantar fascia causing heel pain.
• Charley Horse: cramp/stiffness due to muscle tearing and bleeding.
• Muscle Strain: tearing of muscle fibers or tendons.
• Paralysis: loss of muscle function due to nerve damage.
• Repetitive Strain Injuries: conditions from overuse and poor mechanics.
• Rhabdomyosarcoma: malignant skeletal muscle tumor.
• Torticollis (Wryneck): contraction of sternocleidomastoid muscle.
• Tic: Involuntary muscle twitching
• Rotator Cuff Injury: strain/tear of rotator cuff muscles

Symptoms of Higher Motor Neuron Damage

• Babinski reflex: abnormal toe extension reflex.
• Hemiplegia: paralysis on one side of the body.
• Paraplegia: paralysis of the lower limbs.
• Quadriplegia: paralysis of all four limbs.
• Chorea: random, uncontrolled muscle contractions.
• Resting Tremor: shaking of limbs at rest.
• Intention Tremor: oscillations during voluntary movements.