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