B3 Muscle Tissue BIOLOGY

Unit Overview

This document covers principles of applied science in biology, focusing on muscle tissue specialization and the sliding filament model.

Cell Specialization

B2: Cell SpecialisationA test on cell specialization will take place next week.

Muscle Tissues & Sliding Filament Model Overview

Resources from The Amoeba Sisters focus on muscle tissues and the sliding filament model, crucial for understanding muscle contraction mechanisms.

Resources for Further Learning

Useful Resources

• Sliding Filament Theory Videos: Link 1, Link 2

B3 Learning Objectives

Objectives

• Understand the microscopic features and functions of skeletal muscular tissue, including:

  • Muscle Fibres Characteristics: Multi-nucleated, striated appearance.

  • Myofibrils and Sarcomeres

  • Sarcolemma and Sarcoplasmic Reticulum

  • Mitochondria, Neuromuscular Junctions, T Tubules

  • Sliding filament theory: Actin, myosin, troponin, tropomyosin, calcium ions, and ATP.

• Recognize the structure of skeletal muscle from diagrams.

Key Terminology

Muscle Structure

• Muscle Cell Terms:

  • Sarco: Greek for muscle.

  • Sarcoplasmic Reticulum: ER found in muscle cells.

  • Sarcolemma: Plasma membrane of a muscle cell.

  • Sarcoplasm: Cytoplasm within a muscle cell.

  • Myo: Latin for muscle.

  • Myocyte: Muscle cell.

  • Myofibril: Components of myocytes.

  • Myofilaments: Proteins for muscle contraction.

Muscle Cells and Filaments

Structure of Muscle Cells

Myocytes contain:

• Myofibrils

• Sarcoplasmic Reticulum

• Nuclei

• Myosin & Actin filaments

• Mitochondrion

• Epimysium

Myofibrils and Myofilaments

• Myofibrils: Contractile threads in striated muscle cells.

• Myofilaments: Thin (Actin) and thick (Myosin) proteins.

Muscle Fiber Characteristics

Muscle fibers are long, multi-nucleated cells, surrounded by the sarcolemma, containing numerous mitochondria and specialized ER.

Sarcomere and Muscle Contraction

Sarcomere StructureDefined by:

• Z-lines: Boundaries of the sarcomere.

• H-zone: Area with no overlap of filaments.

• A-band: Contains both actin and myosin (dark).

• I-band: Light band with only actin.

Sliding Filament Theory

Mechanism of Contraction:

• Rest Position: Actin-myosin binding sites blocked by tropomyosin.

• Activation: Ca2+ binds to troponin, allowing myosin to bind to actin.

• Energy Use: ATP hydrolysis powers contraction via a ratchet mechanism.

• Cycle: Actin-myosin cross-bridge forms, ATP is used to pull actin.

• Relaxation: Stimulation stops, Ca2+ is pumped back into the sarcoplasmic reticulum.

Types of Muscle Fibers

Skeletal Muscle Fibers

• Slow Twitch vs. Fast Twitch:

  • Slow twitch: Efficient for sustained contractions; utilizes oxygen well for ATP.

  • Fast twitch: Can contract quickly but fatigue rapidly; relies on glycogen for anaerobic respiration.

Fast Twitch Fiber Types

• Fast Twitch Oxidative: Quick contractions; resistant to fatigue.

• Fast Twitch Glycolytic: Quick contractions, fatigues quickly due to low myoglobin and mitochondria.