Types of Muscle 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
Smooth muscle
Cardiac muscle
Characteristics of a Muscle Irritability
Muscles have ability to receive and respond to stimuli (force and electrical)
Contractility Muscle has the ability to shorten
Extendibility Muscle has the ability to lengthen
Elasticity Muscle has the ability to return to normal length
A. Skeletal (Striated) Muscle 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 Located in the blood vessels, the respiratory
tract, the iris of the eye, the gastro-intestinal tract
The contractions are slow and uniform Functions to alter the activity of various body
parts to meet the needs of the body at that time
Is fatigue resistant Activation is involuntary
C. Cardiac Muscle Has characteristics of both skeletal and
smooth muscle Functions to provide the contractile
activity of the heart Contractile activity can be gradated (like
skeletal muscle) Is very fatigue resistant Activation of cardiac muscle is
involuntary (like smooth muscle)
a) Muscle b) muscle fibre bundle c) muscle fibre d) myofibril
Components of skeletal muscle
Muscle Fibres Cylinder-shaped cells that make up skeletal muscle Each fibre is made up of a number of myofilaments Diameter of fibre (0.05-0.10 mm) Length of fibre (appr. 15 cm) Surrounded by a connective tissue sheath called Sarcolemma Many fibres are enclosed by connective tissue sheath Perimycium to
form bundle of fibres Each fibre contains contractile machinery and cell organelles Activated through impulses via motor end plate Group of fibres activated via same nerve: motor unit Each fibre has capillaries that supply nutrients and eliminate waste
Muscle Teamwork Agonist (prime mover): - the muscle or group of muscles producing a desired effect
Antagonist: - the muscle or group of muscles opposing the action
Synergist: - the muscles surrounding the joint being moved
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
In order for muscles to contract, they must be attached to the bones to create movement
Tendons: strong fibrous tissues at the ends of each muscle that attach muscle to bone
Origin: the end of the muscle attached to the bone that does not move
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 Suited for repeated contractions during activities requiring a
force output of < 20-25% of max force output
Examples: lower power activities, endurance events
B) Fast Twitch Fibres Significantly greater force and speed generating capability than
slow twitch fibres
Well suited for activities involving high power
Examples: sprinting, jumping, throwing
Glycogen fibresLarge diameter
Oxidative fibresSmall diameter
Capillary blood vessels
Muscle Biopsy