Download Chapter 10 The Muscular System

Chapter 10 Muscular System
Muscle tissue
 It is contractile tissue.
 It is responsible for movement in the organism.
Muscle tissue is grouped in two ways:
1)Structure of the cells
2)Whether it is under the control of our conscious or
unconscious mind.
Three Types of Muscle Tissue
1. Skeletal (Striated) Muscle
2. Cardiac (Striated) Muscle
3. Smooth Muscle
1. Skeletal Muscle—is attached to the organism’s
skeleton.
 Moves the organism.
 Antagonistic pairs are muscles paired up in
such a way as their movements oppose each
other.
Skeletal muscles contract actively, while the
same muscle
will relax passively. If a limb is moved in one
direction
actively, it cannot get back to its original place
by just
relaxing. Another muscle must contract to pull it
back to its
original place. For example: the elbow joint is
moved by
alternate contraction and relaxation of the biceps
and
triceps muscles.
2. Cardiac Muscle—only found in the heart.
 It is striated. Muscles cells are branched, and
the junctions between the cells contain
intercalated discs that electrically connects all
heart muscle cells, allowing coordinated action.
 Generates own action potential
3. Smooth Muscle—lack striations
 Contractions are slow but there is a greater
range of control.
 Calcium must enter the cell through the plasma
membrane during an action potential.
 Found in the walls of blood vessels and the
digestive organs.
Muscle Mechanics
Lever Systems: Bone-Muscle Relationships
The operation of most skeletal muscles involve the
use of leverage or lever systems.
 Lever—rigid bar that moves on a fixed point,
or fulcrum, when a force is applied to it.
 Effort—(applied force) used to move the
resistance, or load.
Joints—act as fulcrums
Bones—act as levers
Muscle contractions—provides effort
Load—is the bone itself…and anything else you are
trying to move
Types of Levers
1st Class Levers—the effort is applied at one end of
the lever & the load is at the other…the fulcrum is
somewhere in between them…examples are
scissors, seesaws, use of crowbar, etc…
2nd Class Levers—the effort is applied at one end of
the lever & the fulcrum is located at the other…with
the load somewhere in between them…examples
wheelbarrow…standing on your toes.
3rd Class Levers—the effort applied at the point
between the load & the fulcrum…operate at great
speed…mechanical disadvantage.
Example…tweezers, most skeletal muscles
The Muscular System Continued…
 The muscles of your body produce movement by
pulling, not pushing.
 If all your muscles pulled in one direction, your
body could lift almost 25 tons.
“Skeletal muscles”
The voluntary, striated muscles attached to bones.
There are more than 600 muscles in your body; here
are the locations of each of the following skeletal
muscles:
The Arms
 Deltoid
o abducts arm
 Biceps brachii
o flexes forearm
o supinates forearm from neutral
 Triceps brachii
o extends forearm
The Legs
 Sartorius
o flexes hip and knee
 Rectus femoris (Quadraceps femoris)
o extends knee
 Gluteus maximus
o extensor of hip
o rotates thigh
 Biceps femoris
o flexes knee
 Gastrocnemius
o flexes ankle
o stabilizes ankle and knee when standing




The Trunk
Pectoralis major
o adducts humerus
Rectus Abdominus
o produces trunk motions
Trapezius
o elevates and rotates scapula
Latissimus dorsi
o rotates humerus
Naming Skeletal Muscles
1. Location
2. Shape
3. Size
4. Direction of the Fibers
5. Number of Origins
6. Location of the Muscle’s Origin and/or Insertion
7. Action of the Muscle
Muscle attachment:
Origin - point of attachment on the stationary bone.
Insertion - point of attachment on the moving bone.
Muscle movement:
Most skeletal muscles work in groups:
 Agonists - muscles primarily responsible for
an action due to their contraction.
 Antagonists - muscles that relax to smooth
the action of the agonists