Transcript Document
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
Cardiac muscle
Smooth muscle
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)
Components of skeletal muscle
a) Muscle
b) muscle fibre bundle
c) muscle fibre
d) myofibril
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
The Muscle Biopsy
Used to determine muscle fibre type
1. Injection of local anesthetic into the muscle being sampled
2. Incision of approximately 5-7mm is made in the skin and
fascia of the muscle
3. The piece of tissue (250-300mg) removed via the biopsy
needle is imbedded in OCT compound
4. The sample is frozen in isopentane cooled to –180C
Muscle Biopsy
Glycogen
fibres
Large diameter
Capillary blood
vessels
Oxidative fibres
Small diameter
The Histochemistry
The biopsy samples are first sectioned (8-10 μm
thickness)
Sections are processed for myosin ATPase:
Fast twitch fibres – rich in myosin ATPase (alkaline
labile)
Slow twitch fibres – low in myosin ATPase (acid labile)
Sections are processed for other metabolic characteristics
Nerve-Muscle Interaction
Skeletal muscle activation is initiated through neural activation
NS can be divided into central (CNS) and peripheral (PNS)
The NS can be divided in terms of function: motor and sensory activity
Sensory: collects info from the various sensors located throughout the
body and transmits the info to the brain
Motor: conducts signals to activate muscle contraction
Activation of motor unit and its innervation systems
1. Spinal cord 2. Cytosome
3. Spinal nerve
4. Motor nerve 5. Sensory nerve 6. Muscle with muscle fibres
Motor Unit
Motor nerves extend from the spinal cord to the muscle fibres
Each fibre is activated through impulses delivered via motor end plate
Motor unit: a group of fibres activated via the same nerve
All muscle fibres of one particular motor unit are always of the same fibre
type
Muscles needed to perform precise movements generally consist of a large
number of motor units and few muscle fibres
Less precise movements are carried out by muscles composed of fewer
motor units with many fibres per unit
All-or-none Principle
Whether or not a motor unit activates upon the
arrival of an impulse depends upon the so called
all-or-none principle
An impulse of a certain magnitude (or strength) is
required to cause the innervated fibres to contract
Every motor unit has a specific threshold that
must be reached for such activation to occur
Intra-muscle Coordination
The capacity to apply motor units simultaneously is
known as intra-muscle coordination
Many highly trained power athletes, such as
weightlifters, wrestlers, and shot putters, are able to
activate up to 85% of their available muscle fibres
simultaneously (untrained: 60%)
Force deficit: the difference between assisted and
voluntarily generated maximal force (trained: 10%,
untrained: 20-35%)
Intra-muscle Coordination cont.
Trained athletes have not only a larger muscle mass than
untrained individuals, but can also exploit a larger number
of muscle fibres
Athletes are more restricted in further developing strength
by improving intra-muscular coordination
Trained individuals can further increase strength only by
increasing muscle diameter
Inter-muscle Coordination
The interplay between muscles that generate movement
through contraction (agonists) and muscles responsible for
opposing movement (antagonists) is called inter-muscle
coordination
The greater the participation of muscles and muscle groups,
the higher the importance of inter-muscle coordination
To benefit from strength training the individual muscle
groups can be trained in relative isolation
Difficulties may occur if the athlete fails to develop all the
relevant muscles in a balanced manner
Inter-muscle Coordination cont.
High-level inter-muscle coordination greatly improves
strength performance and also enhances the flow, rhythm, and
precision of movement
Trained athlete is able to translate strength potential to
enhance inter-muscle coordination
Muscle’s Adaptation to Strength Training
Individual’s performance improvements occur through a
process of biological adaptation, which is reflected in the
body’s increased strength
Adaptation process proceeds at different time rates for
different functional systems and physiological processes
Adaptation depends on intensity levels used in training and
on athlete’s unique biological make-up
Enzymes adapt within hours, cardiovascular adaptation
within 10 to 14 days
Discussion Questions
1) What are the 3 types of muscle found in the human body?
2) Skeletal muscle is made up of bundles of ________, each of which are
made up of a number of ________.
3) What are the 3 types of muscle fibres? Give two characteristics of each
type of fibre.
4) What are the main types of fibre contraction? Give real life examples of
each.
6) Discuss the differences between inter- and intra-muscle coordination
Make a Table with muscles from pg.
44-45 in text
Muscle Name
Function
Describe
movements
Origin
Bicep
Brachii
Prime mover
Flexes lower arms Coracoid
Process
Head of
Humerus
Insertion
Radius
There will be some information that is not in your text. Do your best for now.
Key Terms
Skeletal muscle
Smooth muscle
Cardiac muscle
Biomechanics
Muscle fibres
Myofilaments
Motor unit
Sarcomeres
Cross bridge formation
Slow twitch fibres
Fast twitch fibres
Muscle biopsy
Isometric contraction
Isotonic contraction
Isokinetic contraction
Concentric contraction
Eccentric contraction
Plyocentric contraction