The
Muscular
System
QUICK FACTS
Muscle is 30-40 % of body mass
More than 600 muscles in the human body
All muscles work in agonist-antagonist pairs
Functions of Muscle
1. Movement
• Allows us to interact with our environment and perform athletic
activities
2. Support
• Maintains stability and balance
3. Heat production
• Rapid contraction of muscles (ie. shivering)
4. Life sustaining activities
• Heart beating and blood pressure control
• Digestive movement
The Muscular System
Muscle is a type of connective tissue which has the
ability to contract (shorten) and relax (lengthen).
Powerful movements are created by the
contractions of the muscle tissue
The Three Types of Muscle Fibres
There are three main types of muscles:
a) smooth muscle
b) cardiac muscle
c) skeletal muscle
Smooth Muscle Tissue
walls of visceral (internal) organs
stomach, intestines, bladder, tubes in lungs, walls
of arteries
involuntary (not under conscious control)
no striations
perform slow, sustained contractions
Cardiac Muscle Tissue
only in heart
Striated (striped appearance)
involuntary
Skeletal Muscle Tissue
attached to and covers bony skeleton
typically longest of muscle cell types
striations
voluntary (conscious control)
tire easily and must rest after short
periods of activity
Basic properties of
musculotendinous unit (EEICC)
extensibility:
elasticity:
ability to be stretched
ability to return to
normal length
irritability:
ability to respond to
stimulus (response to
neural stimulation)
contractibility:
ability to actively
shorten
ability to transmit
nerve impulses
conductivity:
How Muscles Are Named
Naming Principle
Action/Function
Direction of Fibres
Example
Flexion/Extension
Rectus/Transversus
Location
Anterior/Posterior
Number of Divisions/Heads
Number of heads
Shape
Deltoid/Trapezius
Points of Attachment
Sternum/Clavicle/Mastoid process
Muscles Working Together
Control of Body Movements
Muscle groups occur in pairs which
work both against and with each other
These opposing groups are located on
opposite side of a joint and perform
opposite actions on it
Agonist
groups work together for fine control
and balance of a movement
Agonist: Primary joint mover
Antagonist: acts against the agonist to
return the joint to original position or
counterbalance the activity
Example:
Antagonist
Biceps (agonist) vs Triceps (antagonist)
Origin, Insertion, and Function
• Origin:
• Proximal attachment
• Where muscle attaches to the
areas closest to the bones of the
axial skeleton (least moving bone)
• Insertion:
• Distal attachment
• Where muscle attaches to the area
furthest from the axial skeleton
(bone that moves the most)
• Function:
• Action/motion
• What the muscle does when
activated in a certain position
Types of Muscle Contractions
• Concentric:
• Muscle fibres shorten while performing a movement
• Eccentric:
• Muscle fibres lengthen while performing a movement (ie. slow down a
movement
Isometric:
•
• Muscle fibres do not change in length
• Hold a movement steady
Exercises Based on Contractions
• Isotonic exercise
Insertion
• Controlled shortening and lengthening of the muscle (Same Tone)
• Isometric exercise
• No motion – muscle fibres maintain a constant length throughout contraction (Same
Length)
Origin
• Isokinetic exercise
• Use machines to control speed of contractions
• Combines best features
of both isotonic and isometric training (Same Speed)
Name that Contraction Type
Examples
Step Down
Contraction Type
(Concentric, Eccentric, or
Isometric)
Antagonistic Pairs
Examples
Elbow flexion
Shoulder abduction
Flexed Arm Hang
Medial shoulder
rotation
Reverse Fly
Knee extension
Wrist flexion
Football Catch (Decelerating)
Biceps Curl
Dorsi flexion
Trunk flexion
Hip flexion
Agonist
(Prime Mover)
Antagonist
(Counteracts)