1. Neuromusculoskeletal System
VCE PE Units 1 & 2
Neuromusculoskeletal System
Muscle formation, recruitment and contraction

2. KEY KNOWLEDGE KEY SKILLS Key Knowledge and skills
The way the neuromuscular and musculoskeletal systems work together to bring about movements including major bones, muscles, joints and joint action
The various characteristics of the different muscle types – fibre and arrangement
Isotonic, isokinetic and isometric muscle contractions
The agonist and antagonist relationship as related to reciprocal inhibition and the associated use of stabilisers
The nervous control of muscles including recruitment of motor units, fibres and types of contraction
Correct use of anatomical terms related to major bones, muscles, common joints and their actions that bring about movements.
Participate in and analyse a broad range of movements used in sporting activities and be able to identify key bones, muscles and joint movements associated with those movements.
Explain and discuss how reciprocal inhibition works
Identify the different types of muscle fibres and contractions responsible for a wide range of physical activities performed at varied intensities

3. Learning Intentions Strengthen your understanding of the
musculoskeletal system
To learn the characteristics of a motor unit
including how it is controlled

4. Muscle fibre arrangement
Fusiform- Run longitudinally with the tendon.
E.g. Biceps in the arm
Produce low force but can shorten over a long range
Penniform- run at angles to tendon.
Can produce greater force with a higher number of fibers
Divided into 3 groups:
Unipennate (fibers branch out to one side of the tendon)
E.g. Gastrocnemius
Bipennate (Fibers branch out to both sides of the central tendon)
E.g. Quadriceps
Multipennate (fibers branch out repeatedly from a number of tendons)
E.g. Deltoid

5. Muscle fibre arrangement
Using what you have learnt, label the following muscle fibre types

6. ANSWERS….

7. Complete text book ‘Thinking Things Through’
Page 16
Questions 1-4

8. The microscopic structure of muscles

9. Neuromuscular Junction
A single muscle contraction is initiated by an electrical signal in
the CNS (Central Nervous System) that is transmitted along a
threadlike axon of a motor unit to a group of skeletal muscle fibres.
when the signal reaches the end of a motor unit, it must cross a ‘gap’
before it can stimulate the skeletal muscle fibre to contract.
This “gap” is called the neuromuscular junction (NMJ).
A chemical know as the neurotransmitter assists in carrying the
Electrical signal across to the adjacent muscle fibre.
A momentary change in cell voltage then results in action
potentials spreading across the skeletal muscle fibre which results
in contraction and force production.
A stronger stimulus will produce a greater number of action
potentials per second and a stronger contraction.

11. Microscopic Structure of a Skeletal Muscle worksheet

12. Nervous control of muscular contractions
Motor neurons convey nerve impulses form the brain to muscles
A motor neuron and the fibres it controls/stimulates are known as the motor unit
Sensory neurons convey nerve impulses from muscles, organs and cells to the brain

13. The all or nothing principles states:
It is not until an electrical threshold is surpassed that all of the fibres linked to a motor unit will fire together and maximally.
Gross movements requiring major muscle involvement require more motor units than precise/ fine movements
Fibres will be recruited according to the activity demand and this is known as preferential recruitment

14. Sliding Filament Theory
*How muscles contract
*Myofilaments sliding across each other
Steps:
Electrical impulse sent from brain to the synapse of individual myofibrils
[neuromuscular junction]
Acetylcholine activates the release of calcium ions
This stimulates oar-like projections call ‘Cross-bridges’ to reach out and attach
to the actin filaments
Cross bridges shorten and pull actin filaments towards the center
The muscle contracts
(SFT song)

15. The effect of muscle contraction on structures of the sarcomere
Sarcomere region
Muscle shortening
Muscle lengthening
A band
Unchanged
I band
Shortens
Lengthens
H zone
Shortens and disappears
Reappears and lengthens
Z line

16. How muscles contract
Insert 1.23

17. Thinking Things Through
Pg. 22
Questions: 1,2,3,4,5

18. Types of Contraction
There are basically three types of muscular contraction, classified by the movement they cause. These are listed below in order of occurrence in everyday activity, from most common to least common:
• isotonic (concentric and eccentric)
• isometric
• isokinetic
lsotonic contraction
Occurs whenever the muscle length changes through a range of motion or action. When a constant load (weight) is being moved, differences exist in the amount of force applied at various joint angles.
Isometric contraction
Occur when tension is developed but no change results in the length of the muscle. Isometric contractions hence involve little, if any, change in muscle length while tension is developed.
lsokinetic contraction
Tension developed is maximal throughout the entire range of motion and is common on hydraulic fitness equipment. The amount of force applied by the machine always equals the amount of force applied by the muscle.

19. Fast & Slow Twitch Fibres
Muscles are made up of two different types of fibres:
• Red, type I, slow-twitch fibres (ST), best suited to aerobic, endurance work such as triathlons.
• White, type II, fast-twitch fibres (FT), best suited to short-duration, high intensity anaerobic work, for example the bursts of power and speed required to sprint.

20. Thinking Things Through
Pg. 26
Questions:1-4

21. Fibre Recruitment Theory
Recruitment: The progressive activation of a muscle by consecutive
activation of motor units
i.e. When the muscle is first activated, the earliest motor units to
fire will be small in size with progressively larger units recruited as
the strength of muscle contraction is increased.
To measure the neural activity of muscle you use an
Electromyography (EMG). An EMG records both the quality and
quantity of electrical activity within a muscle.

22. Factors Affecting Muscle Strength
Fibre arrangement
Muscle fibre recruitment
Muscle fibre type
Speed of contraction
Gender
Age

23. Lab
Muscle cross-sectional area V.s strength
Pg. 27

24. SAC revision
Practical- complete the worksheet