Interactive Guide to the Muscular System

Overview

• The muscular system enables body movement.
• Composed of roughly 700 named muscles, weighing about half of the body's weight.
• Consists of skeletal muscle tissue, blood vessels, tendons, and nerves.
• Muscle tissue also present in the heart, digestive organs, and blood vessels.

Anatomy of the Muscular System

Types of Muscle Tissue

1. Visceral Muscle
   • Found in organs like stomach, intestines, blood vessels.
   • Weakest muscle tissue, involuntary control.
   • Known as "smooth muscle" due to uniform appearance.
2. Cardiac Muscle
   • Located only in the heart.
   • Involuntary, striated muscle.
   • Auto-rhythmic with intrinsic control.
   • Structured for endurance and rapid signal transmission.
3. Skeletal Muscle
   • Only voluntary muscle tissue, consciously controlled.
   • Responsible for actions like walking, speaking.
   • Muscles attached to bones, enabling movement across joints.

Gross Anatomy of Skeletal Muscle

• Attached to bones via tendons, which are strong connective tissues.
• Muscle parts: origin (stationary bone), insertion (moving bone), belly (contracting part).

Naming of Skeletal Muscles

• Location: Named after anatomical regions.
• Origin and Insertion: Named based on bone connections.
• Number of Origins: Biceps (two), triceps (three), quadriceps (four).
• Shape, Size, Direction: Distinctive features like deltoid shape, size variations, or fiber directions.
• Function: Named for actions performed, e.g., flexors, supinators.

Group Actions in Skeletal Muscle

• Agonist/Antagonist Pairing: Muscles work in pairs for movement.
• Synergists and Fixators: Assist in stabilizing movements and maintaining posture.

Skeletal Muscle Histology

• Unique organelles: sarcolemma, T-tubules, sarcoplasmic reticulum, mitochondria, myofibrils.
• Sarcomere Structure: Composed of actin, myosin, tropomyosin, troponin.

Physiology of the Muscular System

Functions

• Movement: Primary function of muscles.
• Posture Maintenance: Endurance muscles support body position.
• Substance Movement: Internal transport (blood, food).
• Heat Generation: Muscle contractions produce body heat.

Skeletal Muscles as Levers

• Lever systems in the body: bones, joints, muscles.
• Third class levers: Increase movement distance but require greater force.

Motor Units

• Nerve cells control muscle groups (motor units).
• Size varies by function: precision vs. strength.

Contraction Cycle

• Involves neurotransmitter signals, calcium ion release, actin-myosin interaction.
• Contraction continues until neural stimulus stops.

Types of Muscle Contraction

• Isometric (light tension): No movement.
• Isotonic (movement): Muscle mass development.
• Twitch, Temporal Summation, Tetanus: Varying contraction strength.
• Muscle Tone: Maintains slight tension for posture.

Functional Types of Skeletal Muscle Fibers

1. Type I Fibers
   • Slow, fatigue-resistant, aerobic.
   • Found in stamina/posture muscles.
2. Type II Fibers
   • Type II A: Moderate speed, strength, endurance.
   • Type II B: High speed/strength, low endurance.

Muscle Metabolism and Fatigue

• Aerobic Respiration: Efficient, oxygen-dependent.
• Anaerobic Respiration: Less efficient, quick fatigue.
• Energy reserves: myoglobin, creatine phosphate, glycogen.
• Muscle Fatigue: Caused by energy depletion, requires recovery oxygen uptake (oxygen debt).