The Structure of

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					The Structure
      of



SKELETAL
 MUSCLE
Function of Muscle
    • Movement
      • Support
 • Heat production
              Types of Muscles
Skeletal – voluntary (conscious control), striated
Cardiac – pumps blood from
     heart to rest of body
 Smooth – surround body’s
internal organs, ie. digestive
  tract, blood vessels, etc.
     Properties of Muscle Cells
1. Irritability – ability of muscle to respond to
   a stimulus
2. Contractibility – ability of muscle to shorten
   in length
3. Elasticity – ability of muscle to stretch and
   return to normal length
4. Extensibility – ability of muscle to extend in
   length
5. Conductivity – ability of muscle of transmit
   nerve impulses
   Neuromuscular System
 Ability of the brain and muscles to work
                   together
  This ability can be improved with
                 practice

Some coaches believe that it takes 10,000
       repetitions to learn a skill!
MOTOR UNIT – text page 34-35
•    After reading pages 34 and 35,
     complete the following:
1.   What comprises a motor unit?
2.   Describe the All-or-None Principle.
3.   Briefly describe what happens when
     you want to kick a soccer ball.
4.   Workbook page 46 label
     neuromuscular diagram only
Motor Unit
 The motor neuron, its axon
 (pathway) and muscle fibres
 that it stimulates
All or None Principle
• When a motor unit is stimulated to
  contract, it will do so to its fullest
  potential
• Either ALL fibres in the motor unit will
  contract or NONE will
• Message sent from brain to
  neuromuscular junction – travels along
  the nerve pathway (axon)
• Chemical reaction with receptors on
  muscle fibres causes contraction –
  Calcium ions
   STRUCTURE OF MUSCLE CELL
• Muscle Belly –
• EPIMYSIUM - tissue that surrounds
  the bundles of fibres
• PERIMYSIUM – tissue that surrounds
  the individual bundles of fibres
• ENDOMYSIUM - thin sheath of tissue
  surrounding each muscle fibre
Microstructure of Skeletal Muscle Cell
• Muscle Fibre –
  – Sarcolemma – plasma membrane which
    contains the sarcoplasm
  – Sarcoplasm – same role as cytoplasm
  Myofibrils – thread-like structures which run
    along the length of the muscle
        Myofibril Structures

• Myosin – THICK filaments
• Actin – THIN filaments
• Myosin and Actin are found within
  SACROMERES
• Myosin – consists of a head and tail
  – Has an attachment site for actin
• Actin – has a binding site for the myosin
  head
• Contains two proteins – troponin and
  tropomyosin
       Sliding Filament Theory
• http://3dotstudio.com/zz.html
The Sliding Filament Theory
• The theory of muscle contraction is
  based on Huxley’s sliding filament
  theory of muscle contraction.
• In relaxed muscle all the bands are
  visible, whereas in contracted muscle
  the light I band narrows and then
  disappears, since the thin actin
  filaments are being drawn further in
  between the thick myosin filaments.
• The key to the process of muscle
  contraction lies in the overlapping of
  the thick myosin and thin actin
  filaments.
• The thin actin filaments are made up
  of two chains of globular proteins,
  called tropomyosin and troponin.
• Tropomyosin strands are wound
  about the thin actin filaments and
  troponin is attached to the
  tropomyosin at regular intervals.
• At rest troponin holds the
  tropomyosin in position to block the
  myosin binding sites on actin filaments.
Sliding Filament Theory con’t
• neural action potential is converted to a
  muscle action potential.
• As the nervous impulse reaches the
  muscle cell it initiates the release of
  calcium ions (Ca++) from special
  storage ‘T’ vesicles in the
  sarcoplasmic reticulum.
• Troponin has a high affinity for
  calcium ions and, as the Ca++ bind to
  the troponin, the shape of the
  troponin—tropomyosin complex
  changes to expose the active sites on
  the actin filaments. The calcium ions
  stimulate the contraction of the muscle
  by exposing the active sites on the actin
  filaments.
• At the same time the heads of the
  myosin filaments become activated by
  ATP which, when broken down into ADP
  and free phosphate releases large
  amounts of energy
• The myosin heads attach themselves to
  selected sites on nearby actin filaments
  to form actin—myosin bonds, usually
  called cross-bridges.
• This is immediately followed by the
  detachment of cross-bridges and the
  reattachment of the myosin heads to
  the next actin sites and so on.
• With many thousands of
  thin filaments pulling past
  thick filaments within a
  single cell and many
  thousands of muscle cells
  contracting in this way,
  skeletal muscle can
  quickly respond to the
  demands of activity, such
  as in a flat-out 100m swim
  or sprint.
Homework
• Text – page 40-43 read for further
  information
• Diagram page 45 handbook
• Fill in the blank handout
• Colouring book page 14
 Naming Muscles
• Page 37 text
• Create a table that explains the 6 ways
  muscles are named. Include one
  example of each type of muscle
Antagonistic Pairs
 •Page 38 text, Colouring book page
 45
 •Define: agonist muscle
 •Define: antagonist muscle
Types of Muscle Contractions
• Page 39 text
• There are three types of contractions.
  Name each and give an example of an
  exercise/action for each.
• Describe the three types of exercises
  and give an example of each.
• What are the benefits of each type of
  training?
ACTION of muscle       Flexion, extension      Flexor carpi ulnaris
                                               Extensor carpi ulnaris
DIRECTION of fibers    Rectus, Transversus     Rectus Abdominus
                                               Trasversus Abdominus
LOCATION of muscle     Anterior, posterior     Tibilais anterior, tibialis
                                               posterior
NUMBER of              Two or Three            Biceps brachii, triceps
heads/divisions        Bi or Tri               brachii
SHAPE of the muscle    Geometric shape         Deltoid, trapezius

POINTS of attachment   Bones, processes, etc   Sternocleidomastoid
                                               Sternum, clavicle, mastoid
                                               process
• AGONIST: muscle primarily responsible
  for movement of a body part
• ANTAGONIST: the muscle that
  counteracts the agonist (lengthens
  when the agonist contracts)
Origins, Insertions, and Function
1. Origin – least movable part of muscle,
   proximal attachment
2. Insertion – most movable part, distal
   attachment
3. Function (action/motion) – what
   action the muscle does when activated
• Concentric: muscle fibres shorten, ie
  lifting an object
• Eccentric: muscle fibres lengthen, ie
  putting object back down
• Isometric: muscle fibres do NOT
  change in length, ie. Wall sit
• ISOTONIC: controlled shortening and
  lengthening of a muscle, ie. Dumbbells, body
  weight. Moves through a range of motion.
  Curls, pushups
• ISOMETRIC: retain constant length and no
  motion, ie. Pushing against an immovable
  object
• ISOKINETIC: use machines to control speed
  of contraction within the muscle’s range of
  motion.
 ASSIGNED WORK – CHECK LIST

 Be sure all work is complete and all notes
 are up to date

Text pg. 33 – 43
Colouring Book – pg. 44, 45 and 14
Workbook – page 45, 46
 Questions from powerpoint