Download Muscle Structure and Function - CCVI

Types of Muscle
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The human body is comprised of 324 muscles
Muscle makes up 30-35% (in women) and 42-47% (in men) of body
mass.
Three types of muscle:
Skeletal muscle
Cardiac muscle
Smooth muscle
Characteristics of a Muscle
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Irritability
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Contractility
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Muscle has the ability to shorten
Extendibility
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Muscles have ability to receive and respond to
stimuli (force and electrical)
Muscle has the ability to lengthen
Elasticity
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Muscle has the ability to return to normal length
A. Skeletal (Striated) Muscle
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Connects the various parts of the skeleton
through one or more connective tissue tendons
During muscle contraction, skeletal muscle
shortens and moves various parts of the
skeleton
Through graded activation of the muscles, the
speed and smoothness of the movement can be
gradated
Activated through signals carried to the
muscles via nerves (voluntary control)
Repeated activation of a skeletal muscle can
lead to fatigue
Biomechanics: assessment of movement and
the sequential pattern of muscle activation that
move body segments
B. Smooth Muscle
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Located in the blood vessels, the respiratory
tract, the iris of the eye, the gastro-intestinal
tract
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The contractions are slow and uniform
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Functions to alter the activity of various body
parts to meet the needs of the body at that
time
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Is fatigue resistant
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Activation is involuntary
C. Cardiac Muscle
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Has characteristics of both skeletal and
smooth muscle
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Functions to provide the contractile
activity of the heart
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Contractile activity can be gradated (like
skeletal muscle)
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Is very fatigue resistant
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Activation of cardiac muscle is
involuntary (like smooth muscle)
Components of skeletal muscle
a) Muscle
b) muscle fibre bundle
c) muscle fibre
d) myofibril
Muscle Fibres
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Cylinder-shaped cells that make up skeletal muscle
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Each fibre is made up of a number of myofilaments
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Diameter of fibre (0.05-0.10 mm)
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Length of fibre (appr. 15 cm)
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Surrounded by a connective tissue sheath called Sarcolemma
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Many fibres are enclosed by connective tissue sheath Perimycium to
form bundle of fibres
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Each fibre contains contractile machinery and cell organelles
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Activated through impulses via motor end plate
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Group of fibres activated via same nerve: motor unit
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Each fibre has capillaries that supply nutrients and eliminate waste
Muscle Teamwork
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Agonist (prime mover):
- the muscle or group of muscles producing a desired effect
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Antagonist:
- the muscle or group of muscles opposing the action
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Synergist:
- the muscles surrounding the joint being moved
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Fixators:
- the muscle or group of muscles that steady joints closer to the body axis so
that the desired action can occur
Bending or straightening of elbow requires the coordinated
interplay of the biceps and triceps muscles
Contractile Machinery:
Tendons, origin, insertion
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In order for muscles to contract, they must be
attached to the bones to create movement
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Tendons: strong fibrous tissues at the ends of
each muscle that attach muscle to bone
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Origin:
the end of the muscle attached to the
bone that does not move
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Insertion: the point of attachment of the muscle
on the bone that moves
Muscle Fibre Types
Slow twitch fibres:
Slow Oxidative (Type I)
Fast twitch fibres:
Fast Glycolytic (Type IIb)
Fast Oxidative Glyc. (Type IIb)
A. Slow Twitch Fibres
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Suited for repeated contractions during activities requiring a
force output of < 20-25% of max force output
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Examples: lower power activities, endurance events
B) Fast Twitch Fibres
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Significantly greater force and speed generating capability than
slow twitch fibres
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Well suited for activities involving high power
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Examples: sprinting, jumping, throwing
Muscle Biopsy
Glycogen
fibres
Large diameter
Capillary blood
vessels
Oxidative fibres
Small diameter