Skeletal Muscle and Movement Overview

Skeletal Muscle and Movement

• Learning Objectives:
  • Identify and describe different muscle types and their properties.
  • Understand the macroscopic arrangement of muscles and its relation to movement.
  • Explain the microscopic function of muscle tissues and its connection to their function.
  • Use levers to predict and interpret movements.
  • Examine bone histology and function.

Muscle Tissue Types

• Smooth Muscle:

  • Involuntary
  • No striations
  • Irregular fibers
  • Mono-nucleated
  • Responds to nerve impulses, hormones, and local stimuli

• Cardiac Muscle:

  • Involuntary
  • Striated
  • Regular fibers
  • 1-2 nuclei
  • Responds to nerve impulses, hormones, and local stimuli

• Skeletal Muscle:

  • Voluntary
  • Striated
  • Regular fibers
  • Multinucleated
  • Responds only to nerve impulses

Skeletal Muscle Functions

• Generates movement
• Maintains posture
• Provides protection
• Produces heat
• Promotes blood flow

Skeletal Muscle Properties

• Excitability: Responds to nerve stimuli
• Conductivity: Stimulus spreads throughout the muscle.
• Contractility: Muscle cells forcefully shorten.
• Elasticity: Ability to return to original length.
• Extensibility: Capable of stretching.

Muscular Connections

• Muscles typically connect bone to bone.
• Some exceptions exist (e.g., facial muscles).
• Muscles attach via tendons.
  • Regular, dense, fibrous connective tissue.
  • Tough and inelastic.

Bone Attachment Points

• Origin: Attachment to the stationary (less movable) bone.
• Insertion: Attachment to the movable bone.

Building a Muscle

• Each muscle tissue layer is surrounded by connective tissue (epimysium).
• Muscle Fascicle: Small packets of muscle cells, surrounded by perimysium.
• Muscle Fiber: Muscle cells (myocytes), multinucleated, surrounded by endomysium.
• Sarcomeres: Smallest functional units in muscle fibers.

Tendons and Ligaments

• Tendons: Tough, inelastic connective tissues connecting muscles to bones.
• Ligaments: Flexible, highly elastic connective tissues connecting bones to bones.

The Skeleton

• Provides framework for the body.
• Composed of approximately 206 bones (in adults).
• Multiple functions: support, movement, protection, and metabolism.

Bone Types

• Compact/Cortical Bone: Rigid, tightly-packed, formed by cylindrical structures (osteons).
• Spongy/Cancellous/Trabecular Bone: Loosely arranged struts.

Bone Composition

• Mixture of organic and inorganic components (primarily hydroxyapatite and collagen).

Bone Histology

• Bone tissue is continually renewed and active.
  • Bone cells (osteocytes, osteoblasts, osteoclasts) are involved.
• Compact and spongy bone structure.
  • Cylindrical structures (osteons) in compact bone.
  • Loosely arranged struts in spongy bone.

Bone Development

• Intramembranous: Bone forms directly in soft tissue.
• Endochondral: Cartilage template forms first, then replaced by bone.
  • Primary ossification centre (in utero).
  • Secondary ossification centres (postnatal).
  • Growth plates separate these areas.

Muscle Shape and Structure

• Muscle shape directly affects its function.
• Mass = magnitude of force.
• Arrangement of fascicles = direction of action.
• Length of fibers = range of motion.
• Arrangement of fascicles varies among the muscles.

Lever Systems

• Muscles, bones, and joints work together as levers.
• Allow movement in a set plane.
  • Lever: Bone
  • Fulcrum/Axis: Joint
  • Applied force: Muscle attachment site

Coordinating Movement

• Muscles don't act in isolation.
• Agonist: Primary muscle producing the movement.
• Synergist: Assists the agonist in movement.
• Antagonist: Opposes the agonist.
• Fixator: Stabilizes the origin of the agonist.

This quiz will explore the different types of muscle tissues including smooth, cardiac, and skeletal muscle. It will cover their properties, functions, and the relationship between muscle structure and movement. You'll also learn about the role of levers in predicting movements and the histology of bones.