VCE PE Units 1 & 2
Neuromusculoskeletal System
Muscle formation, recruitment and contraction
Key Knowledge and skills
KEY KNOWLEDGE
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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
KEY SKILLS
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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
Learning Intentions
• Strengthen your understanding of the
musculoskeletal system
• To learn the characteristics of a motor unit
including how it is controlled
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
Muscle fibre arrangement
Using what you have learnt, label the following muscle fibre types
ANSWERS….
Complete text book ‘Thinking Things Through’
Page 16
Questions 1-4
The microscopic structure of muscles
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.
Microscopic Structure of a Skeletal Muscle worksheet
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
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
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
http://youtu.be/xhgDbjrrmFg (SFT song)
http://youtu.be/0kFmbrRJq4w
The effect of muscle contraction on structures of the sarcomere
Sarcomere
region
Muscle
shortening
Muscle
lengthening
A band
Unchanged
Unchanged
I band
Shortens
Lengthens
H zone
Shortens and
disappears
Reappears and
lengthens
Z line
Unchanged
Unchanged
How muscles contract
Insert 1.23
Thinking Things Through
Pg. 22
Questions: 1,2,3,4,5
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:
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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.
http://youtu.be/4qCaiaFwtL0
http://youtu.be/T3OiOJ6-x34
Fast & Slow Twitch Fibres
http://youtu.be/0XhSlRkytkE
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.
Thinking Things Through
Pg. 26
Questions:1-4
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.
Factors Affecting Muscle Strength
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Fibre arrangement
Muscle fibre recruitment
Muscle fibre type
Speed of contraction
Gender
Age
Lab
Muscle cross-sectional area V.s strength
Pg. 27
SAC revision
Practical- complete the worksheet