1. The Muscular System More than 600 muscles in the human body
attached to bones by tendons
Exert force by converting chemical energy (food) into mechanical energy (muscle contraction)

2. Types of Muscles Skeletal Voluntary striated Most in human body
e.g biceps
Cardiac
Involuntary
e.g. heart only
Smooth
Involuntary/not striated
Surrounds internal organs
Contracts slowly but can sustain a contraction for a long period of time
e.g. intestine lining

3. Properties of Muscle Fibres
Irritability: muscle responds to stimulus
Contractibility: shorten in length
Elasticity: Ability to stretch and return to its normal position
Extensibility: ability to extend in length
Conductivity: can transmit nerve impulses

4. Skeletal Muscles Functions
Movement
Locomotion or movement of parts
Heat Production
Responsible for a major share of total body heat and maintaining homeostasis of temperature
3. Posture
Partial contractions of man skeletal muscles

7. Muscle Structure Macroscopic Level: Muscles are surrounded by fascia
Fascia is a thin, tight sheath of connective tissue
Protects muscles, and
prevent
friction between
muscles

10. Microscopic Level:
Epimysium: large, strong sheath that envelopes entire muscle and becomes tendon (deep fascia)
Perimysium: connective tissue that binds groups of fasciles
Fasicles: bundles of individual muscles fibres
Endomysium: sheath of connective tissue that surrounds individual muscle fibres

12. Sarcolemma: beneath endomysium/acts as a plasma membrane
Sarcoplasm: muscle
cell cytoplasm- inside
sarcolemma (contains
proteins, stores gylcogen
and myoglobin)

13. Sarcomere: site of muscular contraction and house for myosin and actin
Myofibril: thread like structure inside muscle fibre/house myosin and actin
Sarcomere: site of muscular contraction and house for myosin and actin
Myosin
Cellular protein
has a head and tail
Head is attachment site for actin
Actin
Binding site for myosin
2 proteins
Troponin – binding site for calcium
Tropomyosin – covers the binding site on actin

15. The Neuromuscular System
The NMS is linkage
Muscular System
Nervous System (nervous impulses originating in the CNS and sent through PNS)
Use and practice improve the coordination between the two systems

16. Motor Unit
Includes a neuron/nerve called the ‘motor neuron’, the axon and the muscle fibers it stimulates
Where the motor
neuron and muscle
fiber meet is called the
neuromuscular junction

18. How the Motor Unit Works
Electrical impulse travels along nerve pathway
Once at neuromuscular junction, a chemical neurotransmitter is then released (acetylcholine)
ACh is detected by receptors on the surface of the muscle fiber resulting in muscle contraction
SO…..
Electrical energy-chemical energy-mechanical work

19. ‘The All or None Principle’
When a motor unit is stimulated to contract, it does to its full potential
Motor units can be small or large
small: produce fine motor movements (threading a needle)
large: produce big motor movements (kicking a ball)

20. Naming Muscles Action of the Muscle: flexion, extension
e.g. flexor carpi ulnaris
Direction of Fibres: rectus, transversus
e.g. rectus abdominus
Location of the Muscle: anterior, posterior
e.g. tibialis anterior
Number of Divisions: 2 or 3 heads
e.g. biceps brachii
Shape of Muscles: deltoid, trapezius
e.g. trapezius looks like a trapezoid
Point of Attachment: sternum, clavicle, mastoid
e.g. sternocleidomastoid

21. How Muscles Attach to Bone
Indirectly: epimysium extends as a tendon and then connects with periosteum
Directly: epimysium adheres to and fuses with periosteum

22. Origin: point where muscle attaches to more stationary bones of the axial skeleton
Insertion: point where muscle attaches to bone that is moved most

23. Agonistic pairs: skeletal muscles arranged in opposing pairs (e. g
Agonistic pairs: skeletal muscles arranged in opposing pairs (e.g. flexors and extensors)
Agonist: prime mover
Synergists: assist the agonist, but not primarily responsible
Antagonist: muscle that counteracts the agonist; lengthen when agonist contracts
Fixators: Stabilize the joint
See Table 3.3 in text

24. Types of Contractions Concentric- muscle fibres shorten
Bicep shortens when lifting an object
Eccentric- muscle fibres lengthen
Bicep places weight on the grounds
Isometric- muscle fibres stay the same
Trying to lift something too heavy

25. Contraction during Exercise
Isotonic Exercise:
Shortening and lengthening contraction
Isometric Exercise:
Muscles maintain length
Good for developing specific muscle groups (rehab)
Isokinetic Exercise:
Isometric and Isotonic exercise combined
E.g. advanced high performance machines

27. How do our skeletal muscles contract?

28. The Sliding Filament Theory
Diagram of a Sarcomere

29. The Process Begins…..
Message sent by brain (raise your hand)
CNS
PNS
Neuromuscular junction (motor unit)
ACh released (acetylcholine)
Action potential generated opening up sarcolemma (membrane)
Calcium ions is released into sarcoplasm due to ATP……

30. What is ATP:
An energy carrying molecule that results from food metabolism
Energy source behind the release of calcium
Release of calcium is what triggers contraction
Also detaches myosin from actin
As you work, more and more ATP is used, and you must replace through food and metabolism

31. At Rest
Calcium ion within sarcoplasmic reticulum
ATP bound to myosin (thick filaments)
Actin intact
Contraction
Calcium binds to troponin
Tropomysoin swivels
Binding sites are exposed
Crossbridges from myosin
bind to new sites on actin
ATP breakdown = energy as
heat and moves crossbridges
causing sliding action
Actin is drawn to center
of sarcomere
Crossbridge cycle repeats
Z line is drawn together
Sarcomere shortens

32. Back to Resting State…
A Ch release halted and remaining is inactive
Calcium ions back to sarcoplasmic reticulum by active transport
Shape of actin is restored – no binding site available as they are covered by tropomyosin
Crossbridges breakway

33. Visuals http://www.youtube.com/watch?v=EdHzKYDxrKc