MUSCLE
Definition: Muscles is a contractile tissue which brings about movements. It can be regarded as motors of the body.
Types of Muscles.
1.
Skeletal
Muscles
2.
Smooth
Muscles
3.
Cardiac
Muscles
1. Skeletal Muscles: Skeletal Muscles are those which attach to bones and have the main function of contracting to facilitate movement of our skeletons.
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They
are also sometime known as striated muscles due to their appearance.
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The
cause of this ‘stripy’ appearance is the bands o actin and myosin which from
the sarcomere, found within the myofibrils.
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Skeletal
muscles are also sometime called voluntary muscles because we have direct
control through nervous impulses from our brains sending messages to the
muscle.
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Contractions
can vary to produce powerful, fast movements or small precision actions.
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Skeletal
muscles also have the ability to stretch or contract and still return to their original
shape.
2.
Smooth
Muscle: Smooth muscle is also sometimes known as involuntary muscle due to our
inability to control its movements, or unstriated as it does not have the
stripy appearance of skeletal muscle.
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Smooth
muscle is found in the walls of hollow organs such as the stomach, oesophagus,
bronchi and in the walls of blood vessels.
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This
muscle type is stimulated by involuntary neurogenic impulses and has slow,
rhythmical contractions used in controlling internal organs.
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For
Example, moving food along the oesophagus or constricting blood vessel during
vasoconstriction.
3. Cardiac Muscle (Heart Muscle): This type of muscle is found solely in the walls of the heart.
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It
has similarities with skeletal muscles in that it is striated and with smooth
muscles in that its contractions are not under conscious control.
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However,
this type of muscle is highly specialized.
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It
is under the control of the autonomic nervous system, however, even without a
nervous input contraction can occur due to cells called pacemaker cells.
- Cardiac muscle is highly resistant to fatigue due to the presence of a large number of mitochondria, myoglobin and a good blood supply allowing continuous aerobic metabolism.