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Muscles are effector organs that respond to nervous stimulation by contracting and so bring about
movement.

There are three types of muscle in the body:

Skeletal muscle Always attached to bone
Acts under voluntary control via motor neurones of somatic nervous
system

Cardiac muscle Found exclusively in the heart
Not…

Page 2

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Skeletal muscles are made up of two types of fibres ­ slow twitch and fast twitch.


Slow-twitch fibres Fast-twitch fibres

Contract slowly Contract very quickly

Provide less powerful contractions Provide powerful contractions

Adapted for endurance work Adapted for intense work

Needed to maintain body's upright Needed for fast movement and…

Page 3

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The thick and thin filaments are arranged in a precise lattice to form a sarcomere.
The thick filaments are joined together at the M line, and the thin filaments are joined together at the
Z line, but the two kinds of filaments are not permanently joined to each other.




M…

Page 4

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A neuromuscular junction is the point where a motor neurone meets a skeletal muscle fibre.
There are many junctions along the muscle.
If there were only one junction of this type, it would take time for a wave of contraction to travel across
the muscle, in which case not all…

Page 5

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Myosin filaments have globular heads that are hinged so that they can move back and forth.
Each myosin head has a binding site for actin and a binding site for ATP.
Actin filaments have binding sites for myosin heads, called actin-myosin binding sites.

Two other proteins, tropomyosin and troponin are…

Page 6

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Muscle contraction requires considerable energy.
This is supplied by the hydrolysis of ATP to ADP and inorganic phosphate.




The energy released is needed for:
· The movement of myosin heads
· The reabsorption of calcium ions into the endoplasmic reticulum by active transport


The Aerobic System
Most of the time,…

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