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Anat and phys muscular system
The muscular system allows movement of the skeleton
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The types are:
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Skeletal or Striated (Voluntary)
Smooth (Involuntary)
Cardiac

What is skeletal muscle?
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Skeletal muscle is the most abundant tissue in the vertebrate body
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White muscle:
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Limited blood supply
Fewer mitochondria
Low myoglobin content
Anaerobic breakdown of glycogen
Fast contractions
Develops great tension for a short period
Fatigues rapidly

Other info:
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Oxidises - To combine with oxygen; make into an oxide
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It functions as an oxygen-storage unit,
providing oxygen to the working muscles
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Structure of skeletal muscle:

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Skeletal muscles attached to bone are formed from parallel muscle fibres
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The cells are roughly cylindrical shape
Each cell is known as a fibre
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Each fibre is composed of bundles myofibrils
These are made of two contractile proteins:
Actin - thin filaments
Myosin - thick filaments
Each muscle is surrounded by three layers of connective tissue:
Epimysium - outer layer
Perimysium - middle layer
Endomysium - inner layer
The whole muscle is surrounded by a muscle sheath which is continuous with the tendons that
connect the muscle to a bone
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Composed of numerous muscle fibres bound together by connective tissue
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Entire structure is known as the sarcomere
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Entire structure is known as the sarcomere
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Contraction takes place when the stimulus is of threshold intensity and rate
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A group of muscle fibres supplied by one nerve fibre is called a motor unit
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In order for contraction to occur energy is required
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These are broken down to form Adenosine triphosphate (ATP)
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The energy from the ATP is released as it undergoes changes
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ATP alone won't do the trick
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ATP causes the myosin to detach from the actin; it will automatically attach further
down
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If the action is repeated then the greater the contraction
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Action of Muscles:
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Muscles always have a point of origin and a point of insertion
As the origin maintains its position, the attachment at the point of insertion is drawn towards it
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Muscle Tone:
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Muscles are always in a slight state of tension, known as muscle tone
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The nervous system adjusts this, and the number of motor units stimulated will increase when
the animal is in an anxious state i
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the muscles become ‘twitchy’
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Controlled by the autonomic nervous system
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g
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One nucleus in its centre
Arranged in sheets or bundles

Cardiac Muscle:
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Found in the walls of the heart
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Each muscle fibre has a nucleus and one or more branches
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Microscopically these joints, known as intercalated discs, can be seen as thicker and darker lines
than the ordinary cross stripes

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