The Muscular System

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The Muscular System
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Overview The Muscular System

• Over 600 muscles in the body

• 30 40 of human body weight

• Enables movement of skeleton (levers)

• Reacts to stimuli (impulses) from nervous system

• Contractions - voluntary/involuntary

• Each muscle contains 1000s of multinucleated
• muscle cells (fibres)

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Types of Muscles
Smooth
Cardiac
Skeletal
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Smooth Muscle

• Involuntary muscle

• One nucleus/cell

• Unstriated

• Line blood vessels
• and hollow organs

(e.g. bladder, uterus, digestive tract)
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Cardiac Muscle

• Involuntary muscle

• Some striations

• Intercalated disks

• Controls heart beat

• found only in heart

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Skeletal Muscle

• Voluntary muscle

• striated/striped

• Attached to bones

• long thread-like, multinucleated cells

(e.g. biceps, deltoids)
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Types of Muscles
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Google (image search skeletal muscle)
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Characteristics of Muscles
Irritability
Ability to respond to various stimuli (e.g.
force, temperature, nerve impulses)
Contractibility
Extensibility
Ability to shorten in response to stimuli
Ability to lengthen in response to stimuli
Elasticity
Conductivity
Ability to stretch and return to its resting
length or shape
Ability to transmit nerve impulses
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Muscle Fibre Arrangement and Direction
Longitudinal
parallel fibres, short tendon
e.g. rectus abdominus
Fusiform
spindle-shaped
e.g. bicep brachii
Radiate
fan-shaped
e.g. pectoralis major
Penniform
fibres arranged at oblique angles
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Penniform Muscles
Penniform muscles come in uni, bi, and multi
types.
Bi - Pennate
Longitudinal
The muscle shown is bi-pennate (fibres run in two
directions obliquely). Pennate muscles are very
powerful due to their greater number of fibres.
(e.g. quads)
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Muscle Function Movement
Different muscles have different functions which
are largely determined by the arrangement and
direction of muscle fibres.
Power
e.g. pennate (quadricep)
Range of Motion
e.g. rectus abdominus, rotator cuff
(longitudinal fibres) (many attachments)
Rapid Movement
e.g. bicep brahcii
Precision
e.g. fingers, hands