THE MUSCULAR SYSTEM 






There are over 600 muscles in the human body.   These comprise between 40 and 50 percent of
your body weight.





Structure and types:


1. ____________________ (skeletal or voluntary muscle)


2. ____________________ muscle (branching muscle)


3. ____________________ muscle (visceral or smooth, involuntary muscle)





Function: ____________________


All muscles work by contraction.





SKELETAL MUSCLES


Structure -


1. Composed of __________ muscle cells and connective tissue.


2. Connect from one bone across a movable  joint to another bone


3. Parts of a skeletal muscle:


    
  
  • ____________________ - attachment to a __________  bone
    • 
  
  • ____________________ - attachment to __________  bone
    • 
  
  • ____________________ - main part of muscle
    • 




4. ____________________ attach muscles to bones


    
  
  • Strong cords of fibrous connective tissue, some enclosed by synovial-lined tubes that  secrete
synovial fluid for lubrication.
    • 
  
  • ____________________ - inflammation of tendon sheaths (tendonitis)
    • 




5. ____________________ - small synovial-lined sacs containing fluid; located between tendons 


    and bone


6. ____________________ - inflammation of the bursae





Microscopic Structure:


Muscle cells (muscle fibers) are long and cylindrical.  Some may reach 12 inches.


Each is ____________________.  Muscle fibers are broken down into hundreds of smaller fibers
called __________ .


____________________ consist of thick and thin myofilaments.


____________________ - the thick myofilaments


____________________ - the thin myofilaments


Myofilaments are arranged within the fiber in small units called ____________________.





____________________ - the basic contractile unit .  Each sarcomere consists of  the:


    
  
  • ____________________ - the total length of the thick myofilaments
    • 
  
  • ____________________ - the band of thin myofilaments
    • 
  
  • ____________________ -  anchoring point of the thin actin
    • 
  
  • ____________________ - the midportion of the A band where only the myosin can be seen
    • 










Muscle Stimulus:     "All or None Phenomenon"


1. ____________________ - won't cause contraction at all


2. ____________________ - will cause contraction of the individual sarcomere


3. ____________________ - all muscle fibers in the muscle will contract


4. ____________________ - no additional effect





Sliding Filament (or Ratchet) Theory:     


During muscle contraction  the ____________________ and ____________________ to slide
toward each other and overlap.  This shortens the ____________________ and the entire muscle. 
Muscle cells are "shocked" by nerve impulses from ____________________.  The point of
attachment to the muscle is called a ____________________ junction.   A motor neuron and its
muscle cells are referred to as a ____________________ .    The nerve impulse is carried from the neuron across
the gap to the membrane (sarcolemma) of the muscle cell by a chemical called ____________________.  After
the impulse is passed an enzyme called ____________________   "de-activates" the acetylcholine, readying the
muscle for the next nerve impulse.  Stimulation of the muscle cell causes Ca++ ions to be released
into the cell.  This calcium binds with the actin filaments causing them to expose active sites to the
____________________ cross bridges.  Myosin cross bridges bind to the active sites, forming a new
molecular structure which causes the cross bridge to bend toward the center, pulling the actin
filament with it.  Energy from ____________________ is used to break the bond,  straighten the
cross bridge, and allow the cross bridge to form a new bond with another active site further down the
actin filament.  This cycle continues until the muscle contraction is complete.  Then ATP is used to
cause active transport to move the calcium ions out of the muscle fiber causing relaxation of the
muscle.





____________________:  shortage of oxygen to the muscle cells during strenuous exercise causes
a buildup of lactic acid which causes muscle soreness.





Functions:     Muscle function depends on normal function of other systems such as bones, nerves.





1. Muscles produce movement:   Groups of muscles work together to produce movement.


____________________ - the main muscle for a movement


____________________ -      muscles that help the prime mover





Types of movements


    
  
  • ____________________ - makes angle at joint smaller
    • 
  
  • ____________________ - makes angle at joint larger
    • 
  
  • ____________________ - moves away from midline
    • 
  
  • ____________________ - moves toward midline
    • 
  
  • ____________________ contractions produce muscle tension without movement.
    • 
  
  • ____________________ contractions produce movements
    • 
  
  • ____________________ contractions - no movement but increase muscle firmness
    • 
  
  • ____________________ contraction - jerky contraction to single stimulus, consists of a latent
period, contraction period,  and relaxation period.
    • 
  
  • ____________________ contraction - sustained contraction
    • 







2.  Heat Production:


    
  
  • Body maintains approx. 98.6 degrees
    • 
  
  • Muscle cells produce ____________________ by oxidizing food as they shorten.
    • 
  
  • Because muscle cells are highly active and numerous, they produce most of our body heat.
    • 







Muscle Disorders:


1. ____________________ - wasting away of muscles


2. ____________________ - loss of ability to move voluntarily


3. ____________________ - decrease in muscle size


4. ____________________ - increase in muscle size


5. ____________________ - progressive muscular weakness