beginning of muscle tissues

Unit 3 Lecture Overview

• Focus: Muscular System
  - Topics: Physiology and Cellular Anatomy
  - Overview of major themes and detours through related topics (cellular respiration and impulse transmission)
  

Muscle Tissues

• Muscle tissue types: 3 main types, each with distinct characteristics
  - Cells referred to asfibers
  - Fibers have the ability tocontract, generating force
  - Important to distinguish muscle tissues by:

  • Location

  • Fiber shape

  • Number of nuclei per cell

  • Striations (presence or absence of stripes)

  • Contraction control(voluntary vs involuntary)
    

1. Skeletal Muscle Tissue

• Structure:

  • Shape: Cylinder, often long

  • Nuclei: Multinucleate (multiple nuclei per fiber)

  • Striations: Present, giving a striped appearance

  • Control: Voluntary (conscious control of contraction)

• Location: Attached to bones, forming skeletal muscles (e.g., biceps brachii)
  

2. Smooth Muscle Tissue

• Structure:

  • Shape: Spindle-shaped (thicker in the middle, tapering at ends)

  • Nuclei: Single nucleus per fiber

  • Striations: Absent, providing a smooth appearance

  • Control: Involuntary (no conscious control)

• Location: Walls of hollow internal organs (e.g., stomach, intestine)
  

3. Cardiac Muscle Tissue

• Structure:

  • Shape: Branched cylinder

  • Nuclei: Typically one nucleus per fiber

  • Striations: Present, similar to skeletal muscle

  • Intercalated discs: Connect fibers end-to-end, allowing coordinated contractions
    - Control: Involuntary (cannot consciously control heart beating
    

Functions of Skeletal Muscle Tissue

• Movement of skeleton

• Maintenance of posture and body position

• Support for soft tissues

• Guarding entrances and exits

• Maintaining body temperature (e.g., shivering)

• Storage of nutrients (e.g., glycogen
  

Muscle Anatomy

• Muscles are organs made up of various tissue types (muscle, connective, nervous)
  -Connective Tissue Layers:

  • Fascia: Covers entire muscle

  • Epimysium: Surrounds the entire muscle

  • Perimysium: Surrounds each fascicle (bundle of fibers)

  • Endomysium: Surrounds individual muscle fibers
    

Muscle Contraction Mechanics

• Origin: Muscle attachment point that does not move during contraction

• Insertion: Muscle attachment point that moves during contraction

• Action: Specific movement produced (e.g., flexion at elbow)

• Agonist (Prime Mover): Primary muscle responsible for an action (e.g., biceps during flexion)

• Antagonist: Muscle that produces the opposite action (e.g., triceps during extension)

• Synergist: Assists the agonist in movement
  

Skeletal Muscle Fiber Structure

• Sarcolemma: Plasma membrane of muscle fiber

• Sarcoplasm: Cytoplasm of muscle fiber

• Mitochondria: Sites of ATP production for muscle contraction
  -Myofibrils: Structures that contract to allow muscle shortening

  • Comprised of myofilaments:

    • Thick filaments: Containing myosin

    • Thin filaments: Containing actin

Sarcoplasmic Reticulum and T-Tubules

• Sarcoplasmic Reticulum (SR): Stores calcium for contraction

  • Cisternae: Enlarged areas of the SR

  • Transverse Tubules (T Tubules): Extensions of the sarcolemma that penetrate into the cell, facilitating the spread of the action potential
    

Summary

• In-depth exploration of muscle tissue types, anatomy, functions, and mechanics of contraction
  - Importance of understanding muscle structure for future study of muscle physiology and activities
  

Note: Refer to the detailed diagrams and slides provided in the course for a visual understanding of these concepts.