Page 1

Introduction to Muscular Tissue

• Chapter 11: Muscular Tissue from "Anatomy & Physiology: The Unity of Form and Function" (Tenth Edition) by Kenneth S. Saladin.

• Importance of muscular tissue discussed in the context of anatomy and physiology.

Page 2

Types and Characteristics of Muscular Tissue

• Expected Learning Outcomes:

  • Understand physiological properties shared by all muscle types.

  • Identify skeletal muscle characteristics.

  • Discuss connective tissue functions in muscles.

Page 3

Universal Characteristics of Muscle

• All muscle cells possess the following characteristics:

  • Excitability: Responsiveness to stimuli such as chemical signals, stretch, and electrical changes.

  • Conductivity: Local electrical excitation leads to a traveling wave of excitation.

  • Contractility: Ability to shorten when stimulated.

  • Extensibility: Capability of being stretched between contractions.

  • Elasticity: Returns to its original length after being stretched.

Page 4

Skeletal Muscle Overview

• Skeletal Muscle Characteristics:

  • Voluntary and striated muscle, usually attached to bones.

  • Striations: Alternating light and dark transverse bands due to internal protein arrangement.

  • Typically under conscious control, unlike cardiac and smooth muscle.

  • Cell type known as muscle fibers or myofibers.

Page 5

Skeletal Muscle Fibers

• Visual representation of skeletal muscle fibers.

Page 6

Structure of Skeletal Muscle

• Contains fibrous connective tissues:

  • Endomysium: Surrounds each muscle fiber.

  • Perimysium: Bundles fibers into fascicles.

  • Epimysium: Surrounds the entire muscle.

Page 7

Connective Tissues in Muscles

• Skeletal muscles composed of muscular tissue, connective tissue, nerves, and blood vessels:

  • Endomysium: Thin sleeve around each muscle fiber for nourishment and chemical environment.

  • Perimysium: Thicker layer that wraps fascicles and contains blood vessels and stretch receptors.

  • Epimysium: Fibrous sheath surrounding the entire muscle, blending with outer fascia.

Page 8

Connective Tissues of a Muscle

• Visual representation of muscle connective tissues.

Page 9

Continued Visualization of Connective Tissues

• Additional visual detail on muscle connective tissues.

Page 10

Skeletal Muscle Cells

• Expected Learning Outcomes:

  • Describe structural components of muscle fibers.

  • Identify major proteins in muscle fibers.

  • Relate striations to protein filament arrangement.

Page 11

Components of a Muscle Fiber

• Components include:

  • Sarcolemma: Plasma membrane.

  • Sarcoplasm: Cytoplasm.

  • Myofibrils: Long protein cords.

  • Glycogen: Energy source for exercise.

  • Myoglobin: Oxygen-binding protein.

  • Mitochondria: Multiple mitochondria present for energy.

  • Nuclei: Muscle fibers are multi-nucleated.

Page 12

Continued Components of a Muscle Fiber

• Sarcoplasmic Reticulum (SR): Smooth ER forming a network around myofibrils.

  • Terminal Cisterns: Dilated ends of SR serving as calcium reservoirs.

  • Transverse (T) Tubules: Invaginations of sarcolemma facilitating signal transmission.

Page 13

Structure of a Skeletal Muscle Fiber

• Visual aid illustrating muscle fiber structure.

Page 14

Myofilaments - Overview

• Myofibrils made of three types of myofilaments:

  • Thick filaments made from myosin protein.

  • Structure: Golf club-like shape aiding in muscle contraction.

  • Arrangement creates a distinct helix and bare zone.

Page 15

Molecular Structure of Thick and Thin Filaments

• Visual illustration of thick and thin filament molecular structure.

Page 16

Myofilaments - Thin Filaments

• Thin filaments consist of three proteins:

  • Fibrous (F) Actin: Twisted strands with active sites for myosin.

  • Tropomyosin: Covers active sites on actin.

  • Troponin: Calcium-binding protein regulating contraction.

Page 17

Continued Molecular Structure of Filaments

• Visual of overlapping thick and thin filaments.

Page 18

Continued Visualization of Filament Structure

• More detailed structural illustration of filaments.

Page 19

Myofilaments - Elastic Filaments

• Elastic filaments:

  • Made of titin, anchoring thick filaments to Z discs.

  • Stabilizes positions, prevents overstretching, allows recoil.

Page 20

Contractile Proteins

• Contractile Proteins: Myosin and Actin

  • Tropomyosin and troponin serve as regulatory proteins.

  • Activation Mechanism: Calcium binds to troponin, enabling contraction.

Page 21

Striations and Sarcomeres

• Myosin and actin organized in an array forming striations.

  • A Bands: Dark bands (thick filament overlap).

  • I Bands: Light bands (thin filaments).

  • H Band: Area where thick filaments do not overlap.

  • Z Disc: Protein complex anchoring thin filaments.

Page 22

Visualization of Striations

• Illustration showing muscle striations and their structural basis.

Page 23

Sarcomere Function

• Sarcomere: Functional unit of muscle, from Z-disc to Z-disc.

  • Muscle contraction occurs through shortening of sarcomeres.

  • Thick and thin filaments slide past each other.

Page 24

The Nerve-Muscle Relationship

• Expected Learning Outcomes:

  • Understand motor unit dynamics in muscle contraction.

  • Explain nerve to muscle fiber junction structure.

  • Discuss electrical charge differences across membranes.

Page 25

Motor Neurons and Motor Units

• Skeletal muscle requires nerve stimulation to contract.

  • Somatic Motor Neurons: Specialize in muscle serving.

  • Motor neuron branches reach muscle fibers.

Page 26

Motor Unit Definition

• Motor Unit: One neuron and all muscle fibers it innervates.

  • Functions as an unit; effective contractions require multiple motor units.

Page 27

Motor Unit Size and Control

• Average motor unit contains about 200 muscle fibers.

  • Small motor units provide fine control (3-5 fibers).

  • Large motor units deliver powerful contractions (1000+ fibers).

Page 28

Motor Unit Visuals

• Illustrations comparing large and small motor units.

Page 29

Neuromuscular Junction (NMJ)

• Synapse: Junction where nerve fibers meet muscle fibers.

  • Axon Terminal: Releases neurotransmitter ACh into synaptic cleft.

Page 30

Diagram of NMJ

• Structural illustration of neuromuscular junction components.

Page 31

NMJ Structure and Function

• ACh receptors on the muscle cell's sarcolemma increase responsiveness.

  • Basal lamina encloses entire NMJ, facilitating function.

Page 32

Electrically Excitable Cells

• Muscle and nerve cells exhibit voltage changes upon stimulation.

  • Differences in ion concentrations contribute to excitability.

Page 33

Action Potentials in Muscle Fibers

• Resting cell: Negative resting membrane potential.

  • Stimulated cell: Ion channels open, allowing sodium influx, leading to depolarization and generation of action potentials.

Page 34

Behavior of Skeletal Muscle Fibers

• Expected Learning Outcomes:

  • Explain stimulation mechanisms activating muscle contraction.

  • Outline contraction and relaxation phases.

Page 35

Phases of Contraction and Relaxation

• Four phases:

  • Excitation: Action potentials lead to muscle action.

  • Excitation-contraction coupling: Links electrical signals to myofilament contraction.

  • Contraction: Muscle develops tension, may shorten.

  • Relaxation: Muscle returns to resting length after stimulation ends.

Page 36

Excitation of a Muscle Fiber

• Visual illustrations explaining excitation phase processes.

Page 37

Continuing Excitation Observations

• Further detailed diagrams demonstrating excitation steps.

Page 38

Continuation of Excitation Process

• Additional visuals depicting the excitation pathway.

Page 39

Excitation-Contraction Coupling

• Action potentials propagate through T-tubules; calcium released from SR for muscle contraction.

Page 40

Role of Calcium

• Calcium binding to troponin triggers contraction initiation by exposing active sites on actin.

Page 41

Contractile Mechanisms

• Hydrolysis of ATP activates myosin; myosin heads prepare for cross-bridge formation.

Page 42

Forming Cross Bridges

• Myosin-actin cross-bridge formation occurs during contraction.

Page 43

Power Stroke Mechanism

• Sliding of thin filaments over thick filaments, drawing them closer together during muscle contraction.

Page 44

ATP Role in Detachment

• New ATP binding causes myosin head release from actin to allow for another contraction cycle.

Page 45

Repeating Contraction Cycle

• Illustration showcases cyclical nature of contraction involving myosin, actin, and ATP.

Page 46

Muscle Relaxation Process

• Cessation of stimulation leads to ACh breakdown and muscle relaxation.

Page 47

Calcium Reabsorption

• SR reabsorbs calcium ions from cytosol, leading to decreased contraction signaling.

Page 48

Returning to Blocked State

• Tropomyosin returns to block actin active sites post-contraction.

Page 49

Length-Tension Relationship

• Muscle tension set by pre-contraction muscle length; importance of optimal rest length.

Page 50

Curve Analysis of Tension

• Graphical representation detailing tension generated relative to sarcomere length.

Page 51

Rigor Mortis Explained

• Rigor Mortis: Muscle stiffening postmortem due to sustained myosin-actin binding in the absence of ATP.

Page 52

Behavior of Whole Muscles

• Expected Learning Outcomes:

  • Describe muscle twitch stages.

  • Explain twitch strength variations.

  • Differentiate contraction types.

Page 53

Stages of Muscle Twitches

• Muscle twitch involves latent, contraction, and relaxation phases.

Page 54

Visualization of Muscle Twitches

• Representation showing idealized myogram pattern of muscle twitch activity.

Page 55

Stimulus Intensity and Contraction Strength

• Key Concept: Minimum voltage necessary to initiate a muscle twitch.

Page 56

Strength Variation with Stimuli

• Higher stimulus yields stronger contractions through motor unit recruitment.

Page 57

Interaction of Intensity and Tension

• Graph representing muscle responses linked to stimulus intensity.

Page 58

Effects of Stimulation Frequency

• Temporal Summation: Higher frequency stimuli lead to increased muscle tension due to partial relaxation.

Page 59

Frequency and Muscle Tension Visualization

• Graphical illustrations comparing effects of different stimulation frequencies on contraction.

Page 60

Isometric vs Isotonic Contractions

• Isometric Contraction: Muscle tension without length change.

• Isotonic Contraction: Muscle changes length while maintaining constant tension.

Page 61

Isotonic Contraction Types

• Distinct forms of isotonic contraction include concentric (shortening) and eccentric (lengthening).

Page 62

Isometric and Isotonic Visual Aids

• Visual representation displaying phases of muscle contraction and corresponding muscle behavior.

Page 63

Phases of Contractions Illustrated

• Graph showing two distinct phases: isometric (constant tension) and isotonic (length change).

Page 64

Muscle Metabolism Overview

• Expected Learning Outcomes:

  • Muscle energy demands during rest vs exercise.

  • Understand muscle fatigue and oxygen debt.

Page 65

ATP Sources for Muscle Contraction

• ATP Role: Primary energy source for muscle activity, reliant on oxygen and substrates.

Page 66

ATP Synthesis Pathways

• Anaerobic Fermentation: Short-term ATP production without oxygen.

• Aerobic Respiration: Efficient ATP production utilizing oxygen.

Page 67

Immediate Energy Sources

• Short, intense exercise: Myoglobin stores oxygen briefly while ATP demand is met via phosphate borrowing.

Page 68

The Phosphagen System

• Illustration depicting ATP synthesis from the phosphagen system (creatine phosphate and ADP).

Page 69

Short-Term Energy Production

• Muscles switch to anaerobic fermentation for ATP needs post phosphagen depletion.

Page 70

Long-Term Energy Support

• After 40 seconds, aerobic respiration becomes primary source for ATP production during prolonged exercise.

Page 71

Muscle Fatigue Mechanisms

• Muscle Fatigue Factors:

  • High-intensity: ion imbalance and metabolic byproducts.

  • Low-intensity: fuel depletion and electrolyte loss.

Page 72

Skeletal Muscle Fiber Classes

• Classification into slow (SO) and fast (FG) fibers based on endurance and contraction types.

Page 73

Fast-Twitch vs Slow-Twitch Fibers

• Distinctions between fast glycolytic fibers and slow oxidative fibers concerning function and appearance.

Page 74

Overview of Fiber Types

• Visual representation highlighting skeletal muscle fiber types among others.

Page 75

Cardiac and Smooth Muscle

• Expected Learning Outcomes:

  • Differences between cardiac and skeletal muscle structures and functions.

Page 76

Introduction to Cardiac and Smooth Muscle

• Both muscle types share some characteristics with muscular tissue but differ in structure and control mechanisms.

Page 77

Cardiac Muscle Structure

• Cardiac Muscle Characteristics:

  • Striated, shorter than skeletal muscle with intercalated discs for cellular junctions.

Page 78

Cardiac Muscle Function

• Can contract autonomously via built-in pacemakers, rhythmically stimulating contractions without nerve impulses.

Page 79

Smooth Muscle Overview

• Smooth Muscle Features:

  • Lack of striations, capable of mitosis and injury regeneration.

Page 80

Varicosities in Smooth Muscle

• Structures allowing neurotransmitter release across unitary smooth muscle fibers.

Page 81

Function of Smooth Muscle

• Smooth muscles facilitate organ content propulsion and modify organ blood flow and pressure.

Page 82

Cross-Section of Esophagus Muscle Layers

• Illustration of visceral muscle layers within the esophagus.

Page 83

Smooth Muscle Cell Structure

• Myocyte features including fusiform shape, density of proteins, and absence of organized striations.

Page 84

Multiunit vs Unitary Smooth Muscle

• Comparison between different functional smooth muscle types based on connectivity and structural organization.

Page 85

Smooth Muscle Contraction Dynamics

• Illustrations showing relaxed and contracted states highlighting structural changes.

Page 86

Conclusion of Chapter

• Recap emphasizing the significance of muscular tissue across physiological processes.

Page 87

Accessibility Content

• Availability of text alternatives for images to enhance understanding.

Page 88

Text Alternative Description

• Description of similarities in muscle fiber structures focusing on connective tissues like endomysium.

Page 89

Structural Description of a Skeletal Muscle Fiber

• Overview of muscle cell structure including detailed organelle layout (myofibrils, SR, etc.).

Page 90

Myosin Molecular Structure

• Detailed depiction of myosin and thick filament alignment in muscle fibers.

Page 91

Thin Filament Composition

• Description of the thin filament structure emphasizing actin and regulatory proteins.

Page 92

Filament Overlap Dynamics

• Representation of how the arrangement of thick and thin filaments contributes to muscle function.

Page 93

Dystrophin's Role

• Exploration of dystrophin's connection to structural integrity in muscle fibers.

Page 94

Muscle Striations Mechanism

• Visual representation of molecular structures accounting for muscle striations during contraction.

Page 95

Motor Units Visual Depiction

• Diagrams showcasing motor units in muscles with varying fiber types.

Page 96

Innervation of Skeletal Muscle

• Describing motor nerve collaboration with muscle fibers in muscular activation.

Page 97

Initial Steps in Excitation

• Observation of nerve signal transitions and resultant actions within muscle fibers.

Page 98

Binding Process in Excitation

• Detailed steps tracing ACh release and receptor interactions at the neuromuscular junction.

Page 99

Voltage-Dependent Changes During Excitation

• Explanation of action potentials created by sodium and potassium dynamics.

Page 100

T-Tubules in Contraction

• Tracking action potentials deep into muscle fibers via T-tubule mechanisms.

Page 101

Calcium Interaction and Contraction

• Binding of Ca2+ to troponin illustrated with active sites exposure details.

Page 102

Myosin Activation Steps

• Consequence of ATP hydrolysis leading to myosin head readiness for contraction.

Page 103

Cross-Bridge Formation

• Detailed explanation and visuals on cross-bridge establishment between actin and myosin.

Page 104

Sliding Mechanism of Contraction

• Visuals showing the actions leading to muscle fiber shortening through filament sliding.

Page 105

ATP's Role in Muscle Cycle

• Depiction of ATP binding leading to cross-bridge disconnection and continuation of contraction cycles.

Page 106

Ongoing Contraction Illustration

• Reiteration of contraction steps demonstrating ATP's cyclic role.

Page 107

Relaxation After Contraction

• Detailing cessation of stimulation processes affecting muscle relaxation.

Page 108

Overview of Calcium Management

• Calcium ion reassessment by sarcoplasmic reticulum for returning muscle to resting state.

Page 109

Blocking Active Sites Post-Relaxation

• Tropomyosin's role in muscle fiber transition back to resting potential explained.

Page 110

Length-Tension Graph Analysis

• Examination of how sarcomere length influences muscle tension development during stimulation.

Page 111

Muscle Twitch Myogram Interpretation

• Graphical analysis of muscle twitch phases clarifying contraction dynamics.

Page 112

Response Intensity and Muscle Function

• Key visualizations connecting stimulus intensity with muscular tension outcomes.

Page 113

Phases of Contraction Illustrated

• Illustrative breakdown of isometric vs isotonic contraction phases based on real-world applications.

Page 114

Isometric and Isotonic Contraction Dynamics

• Exploration of contraction function illustrated via graphical representation of simultaneous tension and length.

Page 115

ATP Synthesis Modes During Activity

• Breakdown of energy pathways during distinct exercise duration phases.

Page 116

The Phosphagen System Breakdown

• Diagrams explaining mechanisms behind ATP re-synthesis within muscles under varying conditions.

Page 117

Types of Skeletal Muscle Fibers

• Description of fiber types based on physiological and functional properties.

Page 118

Unitary Smooth Muscle Structure

• Visual illustration and description elucidating smooth muscle characteristics and functions.

Page 119

Esophagus Muscle Layering

• Cross-sectional view detailing muscle organization within the esophageal structure.

Page 120

Smooth Tissue Contrasts

• Description of structural variations between multiunit and unitary smooth muscles illustrated.

Page 121

Dynamics of Smooth Muscle Contraction

• Comparative analysis of relaxed and contracted states in smooth muscle cells.

Page 122

Testing Myasthenia Gravis Effects

• Illustrative representation showcasing physiological effects of testing on muscular control and response.