Introduction to the Muscular System

Introduction to the Muscular System

• The skeletal system provides the framework for the body.
• The muscular system enables movement and locomotion.

Role of the Muscular System

• Muscles allow for external motion like moving arms and legs.
• Muscles also facilitate internal motion, such as the movement of the digestive, cardiovascular, and respiratory systems.
• Different types of muscles are responsible for both external and internal movements.
• Voluntary muscles can be consciously controlled.
• Involuntary muscles work automatically and cannot be consciously controlled.
• Muscles fulfill three main functions: movement of body parts, maintenance of posture, and production of body heat.

Types of Muscle Tissue

• "Muscle" is a general term that refers to contractile tissue.
• There are three major types of muscle tissue: skeletal, smooth, and cardiac.

Smooth Muscle

• Smooth muscles (also called visceral muscles) are involuntary and contract more slowly compared to skeletal muscles.
• Smooth muscles lack the striped appearance of skeletal muscles.
• These muscles are located within organs (excluding the heart), blood vessels, and airways, facilitating internal movement.
• Smooth muscle changes the diameter of blood vessels.
• Smooth muscle has a smaller blood supply, which results in slower and poorer tissue repair if injured.

Vasodilation and Vasoconstriction

• Vasodilation refers to the enlarging of the diameter of a blood vessel.
• Vasoconstriction refers to the decreasing of the diameter of a blood vessel.

Smooth Muscle in the Digestive System

• Sphincters are a special type of smooth muscle that is located throughout the digestive system.
• Sphincters are donut-shaped muscles act as doorways to regulate the passage of material.
• Contraction of these muscles closes the opening, while relaxation opens it.

Cardiac Muscle

• Cardiac muscle is a specialized muscle with a striated appearance.
• Cardiac muscle is found exclusively in the heart.
• Cardiac muscle is completely involuntary.
• The contraction of cardiac muscle results in the heartbeat, which is an internal movement.
• Cardiac muscle fibers are shorter and have a greater blood supply compared to other muscles in the body.

Skeletal Muscle

• Skeletal muscles are voluntary and are under conscious control.
• Skeletal muscle fibers appear striped, therefore they are sometimes called striated muscle.
• Skeletal muscles attach to bones and enable body movement.
• Tendons are fibrous tissues that connect skeletal muscles to bones.
• Ligaments connect bone to bone.
• Some muscles attach directly to bone or soft tissue without a tendon.

Skeletal Muscles and Muscle Movement

• Voluntary movement is controlled by skeletal muscles, which are attached to bones.
• Signals from the nervous system (via motor neurons) trigger muscle contraction when movement is initiated.
• Muscle fibers contain actin and myosin filaments that slide past each other during muscle contraction, which shortens the muscle and creates movement.
• An example of muscle pairs is the biceps and triceps; when bending the arm, the biceps contract, and when straightening it, the triceps contract.

Muscle Movements

• Agonist muscles are responsible for creating a specific movement, like the biceps when bending the elbow to lift a book.
• Antagonist muscles control and fine-tune movements initiated by the agonist, an example being the triceps in smoothly bending the elbow.
• Synergist muscles provide additional support and stability, strengthening movements during motion.
• Muscle contraction is essential for any voluntary movement in the body.

Common Disorders

• Myalgia refers to muscle pain or tenderness.
• Fibromyalgia is a common disorder with an unknown cause that can be very painful.
• Sprains involve tears in ligaments.
• Strains involve tears in muscle.
• Tendinitis is inflammation of the tendon.

Major Muscle Groups

• Biceps Brachii are found in the anterior part of the upper arm and flex the elbow, as well as supinate the forearm (rotates the forearm so the palm is facing upward).
• Triceps Brachii is found in the posterior part of the upper arm and extends the elbow (straightens the arm).
• Pectoralis Major is found in the anterior upper chest wall and adducts (moves toward the body) and medially rotates the arm, also helps in flexing the shoulder joint.
• Deltoid covers the shoulder, abducts the arm (raises the arm sideways), also helps in flexing and extending the shoulder.
• Intercostal Muscles are between the ribs. Assist in respiration by elevating or depressing the ribs during breathing.
• Gluteus Maximus, or the "glutes," are the muscles of the buttocks. Extends and laterally rotates the hip, also involved in maintaining an upright posture.
• Quadriceps Group, commonly called quads, are a muscle group composed of three main muscles that surrounds the femur. Extends the knee (straightens the leg) and helps in hip flexion.
• These include the Rectus Femoris, Vastus Lateralis, and Vastus Medialis
• Hamstring Group is located at the posterior aspect of the upper leg and is composed of three muscles. Flexes the knee (bends the leg) and extends the hip.
• Gastrocnemius is the calf muscle on the posterior aspect of the lower leg. Plantar flexes the foot (points the toes downward), also helps flex the knee.

Use It or Lose It

• All body systems are negatively impacted by immobility.
• The skeletal system develops osteoporosis if we do not weight-bear enough.
• The muscular system develops contractures when muscles are not used or stimulated for a long time.
• Contractures are permanent and disfiguring contractions of muscles.
• ROM exercises, both assisted and independent, can help to prevent contractures.