Muscles

• Functions of Muscles


  Produce Movement,

  Maintain Posture,

  Stabilize Joints,

  Generate Heat

  
• Functional Characteristics of Muscles

  Excitability / Irritability,

  Contractility,

  Extensibility,

  Elasticity
• Irritability/ Excitability


  ability to respond to stimuli

  
• Elasticity


  Characteristic of being able to recover from extension

  
• Muscle Fiber


  Muscle Cell

  
• 3 Types of Muscles

  Skeletal,

  Cardiac,

  Smooth

  
• Special structure of skeletal muscle

  Multinucleated,

  Found attached to bones

  
• Skeletal Muscle Control


  Voluntary/ conscious control by nervous system

  
• Cardiac Muscle & Smooth Muscle Control

  Involuntary / unconscious control by Endocrine System and ANS (autonomic nervous system)

  
• ANS acronym stands for

  Autonomic Nervous System
• Special structure of Cardiac muscle

  Intercalated discs and branching, not called fiber,

  Found in walls of heart

  
• Special structure of Smooth Muscle

  Spindle shaped, no striations,

  Found in walls of hollow organs

  
• Gross anatomy of Skeletal Muscle

  Nerves & blood supply,

  Muscle fibers surrounded by connective tissue sheaths,

  Skeletal muscle attachments

  
• Nerves and Blood Supply

  Each muscle is served by a nerve, artery, and one of more veins that branch profusely through the connective tissue sheaths

  
• Neuromuscular Junction (NMJ)


  Site where motor neuron synapses onto individual skeletal muscle fiber

  
• Each skeletal muscle fiber is supplied with its own

  what?Each skeletal muscle fiber is supplied with its ownnerve ending that controls its activityunlike cardiac and smooth muscle

  
• Why are muscles Highly Vascularized?

  Must have a continuous delivery of oxygen and nutrients (via arteries) to meet extremely high energetic demands

  
• Muscles produce a high amount of


  whatremoved by veins?Produce large amounts ofmetabolic wastesthat must be removed (via veins) in order for contraction to remain efficient
• Why are muscle fibers surrounded by connective tissue sheaths?

  To support each cell and reinforce muscle as a whole

  (even prevent bulging muscles from bursting during exceptionally strong contractions)

  
• Connective Tissue Sheaths


  Surround and Bundle Muscle Fibers.

  Support each cell and reinforce muscle as a whole

  
• Connective Tissue Sheaths from internal to external:

  Endomysium,

  Perimysium,

  Epimysium

  
• Endomysium


  Connective tissue sheatharound a single muscle fiber

  
• Perimysium


  Connective tissue sheatharound a fascicle (bundle) of fibers

  
• Fascicle


  Bundles of Muscle fibers

  
• Epimysium


  Connective tissue sheath thatcovers entire skeletal muscle

  
• Epimysium tissue type:


  Dense irregular connective tissue

  
• Fascia


  On the outside of the epimysium

  
• Epimysium sometimes blends into

  what?Epimysium sometimes blends intodeep fasciathat lies between neighboring muscles orsuperficial fasciadeep to skin

  
• Necrotizing Faciitis


  Flesh eating diseased caused by bacterial infection

  
• All layers of sheaths are continuous with one another and with


  what?All layers of sheaths are continuous with one another and withtendons(epimysium in particular) that join the muscles to bone,

  This transmits the pulling force to the bone when the muscle fibers contract

  
• Skeletal Muscle Attachments


  Direct Attachment,

  Indirect attachment

  
• Direct Attachment


  Epimysium fuses directly to periosteum on bone or perichondrium on cartilage

  
• Indirect Attachment


  Epimysium blends into a CT attachment,

  Ex) Tendon (cord) & Aponeurosis (sheet)

  
• Tendon (cord)

  
• Aponeurosis (sheet)

  
• Two attachment sites


  Origin (O),

  Insertion (I)

  
• Origin


  More Stable,

  More Proximal,

  Less movable

  
• Insertion


  Move movable,

  Distal to origin in limbs

  
• What muscle attachment (origin/ Insertion) moves toward the other?

  Insertion moves towards the origin

  
• 7 Microscopic Anatomy of a Skeletal Muscle Fiber:

  1) Long, Cylindrical cell with multiple nuclei

  2)Huge in size

  3)Sarcolemma

  4)Sarcoplasm

  5)Myofibrils

  6)Sarcomere

  7)Sarcoplasmic Reticulum and T Tubules