Muscle
Physiology
Functions of Muscular Tissue Producing Body Movements
Stabilizing Joints
Maintaining Posture
Producing heat
Properties of Muscular TissueExcitability
Contractility
Extensibility
Elasticity
Types of Muscle
Types of Muscle
Connective Tissue
Wrappings
Insertion - attachment to a movable bone
Origin - attachment to stationary bone
Attachment - connective tissue layers extend to attach to bone (tendon or aponeurosis)
Muscle Attachments
Anatomy of a Muscle Fiber
Anatomy of a Muscle Fiber
Anatomy of a Muscle Fiber
Sarcomere
Dark(A) & light(I) bands visible with an electron microscope
Sarcomere
Thick and Thin Filaments
Sliding Filament MechanismRelaxed Muscle
Contracted Muscle
The Contraction Cycle
Stimulation and Contraction
Neuromuscular Junction
Summary
Motor Unit: A motor neuron and all the muscle fibers it innervates.
Motor Unit
Muscle Tone
Involuntary contraction of a small number of motor units which leads to partial state of contraction of relaxed muscles
Keeps muscles firm even though relaxed
Essential for maintaining posture
Contraction of a Skeletal MuscleMuscle Twitch: Response of a muscle to a single stimulus
Graded Muscle Responses
1. Frequency of stimulationWave summation and Tetanus
2. Strength of the stimulusMotor Unit Recruitment
Graded - variation in degree of contraction
Contraction of a Skeletal Muscle
More motor units stimulated whichleads to more muscle fibers responding.
Wave Summation and Tetanus
Isotonic and Isometric Contractions
Isotonic - muscle changes length load is moved
Isometric - muscle applies tension but does not move the load
Muscle Metabolism
Types of Skeletal Muscle Fibers
Muscle Fatigue
• Inability to contract after prolonged activity
– central fatigue is feeling of tiredness and a desire to stop (protective mechanism)
– depletion of creatine phosphate
– decline of Ca2+ within the sarcoplasm
• Factors that contribute to muscle fatigue
– insufficient oxygen or glycogen
– buildup of lactic acid and ADP
– insufficient release of acetylcholine from motor neurons