Muscular_System

Muscular System Overview

Learning Objectives

  • Compare the types of muscle.

  • List the functions of the muscular system.

  • Explain the functional properties of muscle tissue.

  • Describe a neuromuscular junction.

Functions of the Muscular System

  • Production of Body Heat: Muscles generate heat through contractions which helps maintain body temperature.

  • Maintenance of Posture: Continuous muscle contractions help to stabilize the body and maintain posture.

  • Movement of the Body: Muscles enable physical movement by contracting and working with bones.

  • Constriction of Organs and Vessels: Muscles regulate the movement of substances through organs internally and control blood vessels' diameter.

  • Respiration: Muscles involved in breathing (such as the diaphragm) enable respiration.

  • Communication: Facial muscles allow for expression, contributing to communication.

  • Contraction of the Heart: Cardiac muscles are responsible for pumping blood throughout the body.

Functional Characteristics of Muscle Tissue

  • Contractility: Ability to shorten actively and exert force.

  • Excitability: Ability to receive and respond to stimuli.

  • Extensibility: Ability to be stretched without damage.

  • Elasticity: Ability to return to its original shape after being stretched.

Types of Muscles

  • The muscular system comprises three main types of muscle tissue:

    • Skeletal Muscles: Voluntary muscles attached to the skeleton, responsible for body movement.

    • Cardiac Muscles: Involuntary muscles found in the heart, responsible for pumping blood.

    • Smooth Muscles: Involuntary muscles found in walls of organs, helping to move substances through the body.

Skeletal Muscles

  • Structure: Elongated, cylindrical fibers with striations; multinucleated and attached to bones via tendons.

  • Control: Voluntary control, movements regulated by the nervous system.

  • Function: Facilitate movement, maintain posture, and heat production.

  • Examples: Biceps brachii, quadriceps, pectoralis major.

Cardiac Muscle

  • Structure: Striated, branched fibers interconnected by intercalated discs; usually mononucleated.

  • Control: Involuntary, regulated by the autonomic nervous system and hormones.

  • Function: Pumps blood throughout the body.

  • Location: Exclusively in the heart.

Smooth Muscles

  • Structure: Non-striated, spindle-shaped fibers with a single nucleus.

  • Control: Involuntary, regulated by autonomic nervous system and local factors.

  • Function: Moves substances through internal passageways and regulates organ contractions.

  • Examples: Digestive tract walls, blood vessels, urinary bladder.

Anatomy of Skeletal Muscle

  • Muscle Structure: Composed of fascicles separated by perimysium, each fascicle contains muscle fibers surrounded by endomysium, and the entire muscle is wrapped in epimysium.

  • Muscle Fiber: The basic unit of muscle containing multiple nuclei.

  • Functional Components: Each muscle fiber contains myofibrils, sarcomeres, actin, and myosin filaments, critical for contraction.

Neuromuscular Junction

  • The interface where a motor neuron communicates with a muscle fiber.

  • Important Components: Motor neuron, synaptic cleft, and muscle fiber.

  • Synaptic Transmission: Involves neurotransmitter molecules released into the synapse to stimulate muscle contraction.

Muscle Contraction

  • Myosin and Actin: Interaction of these proteins facilitates muscle contraction.

  • Role of ATP: Energy from ATP is required for muscle contractions.

  • Types of Contractions:

    • Isotonic Contractions: Varied lengths (concentric: muscle shortens; eccentric: muscle lengthens).

    • Isometric Contracts: Muscle length remains the same, but tension increases.

Key Terms Related to Muscle Features

  • Location: Anatomical region (e.g., rectus abdominis).

  • Origin and Insertion: Points of attachment; origin is stationary, insertion moves.

  • Agonist/Prime Mover: The contracting muscle;

  • Antagonist: The relaxing muscle working opposite to the agonist.

Understanding Muscle Names from Latin

  • Abductor: A muscle that moves away from the midline.

  • Adductor: A muscle that moves towards the midline.

Muscle Groups and Their Functions

  • Major Skeletal Muscles: Include deltoid (abduction), pectoralis major (adduction), latissimus dorsi (shoulder adduction), and quadriceps (knee extension).

  • Functional Roles: Diverse functions in movement, stability, and locomotive abilities.

Study References

  • Resource: Cinnamon VanPutte, J. R. (2019). Seely's Essentials of Anatomy & Physiology Tenth Edition, New York: McGraw Hill Education.