Download The Sliding Filament Theory

Sliding Filament Theory
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Muscle Striations
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Components of skeletal muscle
d) myofibril
c) muscle fibre b) muscle fibre bundle a) Muscle belly
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How do muscles contract?
How do muscles contract?
 The muscular system and the nervous
system work together to signal and receive
signals from the brain to allow for muscular
contraction.
 The link = neuromuscular junction
How do muscles contract?
 A muscle contraction results from a signal
from a nerve impulse.
 The electrical impulse travels down the
neuron and body of the nerve to the
neuromuscular junction.
 (Where the nervous system and the muscle
meet)
Neuromuscular Junction
Axon
Neurotransmitter
acetylcholine (Ach)
Sarcolemma
Axon Terminal
Synaptic Cleft
Receptor
©Thompson Educational Publishing, Inc. 2003. All material is copyright protected. It is illegal to copy any of this material.
This material may be used only in a course of study in which Exercise Science: An Introduction to Health and Physical Education (Temertzoglou/Challen) is the required textbook.
How do muscles contract?
 Acetylcholine is released and receptors on
the muscle fibers detect the chemicals
presence and muscle contracts.
 Within a motor unit (bundle of muscle fibers),
all fibers contract at the same time or all
fibers are relaxed = all or none principle
Neuromuscular Junction
Axon
Neurotransmitter
acetylcholine (Ach)
Sarcolemma
Axon Terminal
Synaptic Cleft
Receptor
©Thompson Educational Publishing, Inc. 2003. All material is copyright protected. It is illegal to copy any of this material.
This material may be used only in a course of study in which Exercise Science: An Introduction to Health and Physical Education (Temertzoglou/Challen) is the required textbook.
The Motor Unit
Dendrites
Neuron cell body
Axon hillock
Motor neuron
Direction of action
potential
Myelin sheath
Neurolemma
Neuromuscular junction
Terminal branches
Motor end plate
Muscle
fibres
©Thompson Educational Publishing, Inc. 2003. All material is copyright protected. It is illegal to copy any of this material.
This material may be used only in a course of study in which Exercise Science: An Introduction to Health and Physical Education (Temertzoglou/Challen) is the required textbook.
How our muscle contracts once the
message has been recieved
Sliding Filament Theory
Muscle Structure
 A muscle is a collection of many microscopic
fibers.
 Each muscle fiber consists of many small
fibrils which are composed of even smaller
protein filaments. (actin and myosin)
 Myosin = thicker
Actin = thinner
 When a muscle contracts/shortens the
finer/thinner actin filaments slide toward
eachother and pass over the myosin
filaments.
Longitudinal section of myofibril
(a) At rest
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Sliding Filament Theory
 When a nerve impulse is received at the
muscle (neuromuscular junction) it enters the
interior of the fiber via a tuble.
 The impulse causes the release of calcium
ions (Ca++).
 As a result, the myosin cross-bridges form a
type of bond with selected sites on the actin
filaments.
The Sliding Filament Theory
 ATP is split and the energy released allows
the acting filaments to slide toward each
other. Consequently the muscle fiber
shortens by about one third of its resting
length.
The Sliding Filament Theory
©Thompson Educational Publishing, Inc. 2003. All material is copyright protected. It is illegal to copy any of this material.
This material may be used only in a course of study in which Exercise Science: An Introduction to Health and Physical Education (Temertzoglou/Challen) is the required textbook.
The Sliding Filament Theory
©Thompson Educational Publishing, Inc. 2003. All material is copyright protected. It is illegal to copy any of this material.
This material may be used only in a course of study in which Exercise Science: An Introduction to Health and Physical Education (Temertzoglou/Challen) is the required textbook.
The Sliding Filament Theory

Myosin crossbridges
 Results in the sliding or overlap of the actin and myosin filaments
 Causes sarcomere to contract (muscle contraction)
©Thompson Educational Publishing, Inc. 2003. All material is copyright protected. It is illegal to copy any of this material.
This material may be used only in a course of study in which Exercise Science: An Introduction to Health and Physical Education (Temertzoglou/Challen) is the required textbook.
Sliding Filament Theory
 In relaxation phase, the effect of the nerve
impulse subsides, calcium ions are removed
and the bond between myosin crossbrides
and the actin filaments is broken.
Video
 Contraction and Relaxation of muscle
 Beef Muscle Contraction
Contractile Machinery:
Tendons, origin, insertion
 In order for muscles to contract, they must be attached to
the bones to create movement
 Tendons: strong fibrous tissues at the ends of each muscle
that attach muscle to bone
 Origin: the point of attachment of the muscle to the bone
that does not move
 Insertion: the point of attachment of the muscle on the
bone that moves
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Muscle Fibre Types
Fast twitch fibres:
Slow twitch fibres:
Fast Glycolytic (Type IIa)
Fast Oxidative Glyc. (Type IIb)
Slow Oxidative (Type I)
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A. Slow Twitch Fibres
 Suited for repeated contractions during activities requiring a force
output of less than 20 to 25 percent of max force output
 Examples: lower power activities, endurance events
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B) Fast Twitch Fibres
 Significantly greater force and speed generating capability than slow
twitch fibres
 Well suited for activities involving high power
 Examples: sprinting, jumping, throwing
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Relative involvement of muscle fibre
types in sport events.
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Muscle Biopsy
Fast Twitch
(Type II Fibres)
Capillary Blood
Slow Twitch
(Type I Fibres)
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Vessels
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Muscle Teamwork
 Agonist (prime mover):
- Muscle or group of muscles producing a desired effect
 Antagonist:
- Muscle or group of muscles opposing the action
 Synergist:
- Muscles surrounding the joint being moved
 Fixators:
- Muscle or group of muscles that steady joints closer to the body axis
so the desired action can occur
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Bending or straightening of the elbow requires the
coordinated interplay of the biceps and triceps muscles.
The triceps
contracts
and the
biceps
relaxes
The triceps
relaxes and
the biceps
contracts
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Agonist and Antagonist Pairs