Week 8 - Muscular Tissue
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.