The Muscular System
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Unit 3 Objectives:
Be able to explain the differences between the 3
types of muscles in the human body
Be able to describe common muscle actions and
how muscle contractions are initiated
Be able to name the major skeletal muscles of
the body (human and cat) as well as their
origin/insertion points
Group 1 Muscles
Warm- Up 10/6/11:
Identify the 8 muscles above.
The Muscular System
• Muscles are responsible for all types of body movement
• Muscle Functions:
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Movement
Maintain posture
Stabilize joints
Heat
• Three basic muscle types found in the body:
– Smooth muscle
– Cardiac muscle
– Skeletal muscle
Characteristics of Muscles
• Muscle cells are elongated
• Contraction of muscles is
due to the movement of
microfilaments – many
cells contracting at the
same time
• All muscles share some
terminology
– Prefix myo refers to muscle
Smooth Muscle Characteristics:
How blood and food move
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•
•
•
No striations
Spindle-shaped cells
Single nucleus
Involuntary – no
conscious control
• Found mainly in the
walls of hollow organs
(blood vessels,
intestines)
Figure 6.2a
Cardiac Muscle Characteristics:
What makes your heart beat?
• Striations
• Usually only one
nucleus
• Cells joined to each
other at an
intercalated disc
• Involuntary
• Found only in the
heart
Figure 6.2b
Skeletal Muscle Characteristics:
Moving your bones!
• Most are attached by tendons to bones
– Remember “tendons tug”
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•
•
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Cells have more than one nucleus
Striated – have visible banding
Voluntary – subject to conscious control
Cells are surrounded and bundled by connective
tissue
Connective Tissue Wrappings of
Skeletal Muscle
• Endomysium – around
single muscle fiber
• Perimysium – around a
bundle of fibers
• Epimysium – covers
the entire skeletal
muscle
• Fascia – on the outside
of the epimysium
Figure 6.1
Skeletal Muscle Attachments
• Epimysium blends into a connective tissue attachment;
the tendon – a cord-like structure
• Sites of muscle attachment
– Bones
– Cartilages
– Connective tissue coverings
Animation: http://www.wisconline.com/objects/index_tj.asp?objID=AP13904
Contraction of a Skeletal Muscle
• Video
• Muscle fiber contraction is “all or none”
• Within a skeletal muscle, not all fibers may be
stimulated during the same interval
• Different combinations of muscle fiber
contractions may give differing responses
• Graded responses – different degrees of skeletal
muscle shortening
• Must have ATP in order to contract
Muscle Response to Strong
Stimuli
• Muscle force depends upon the number of
fibers stimulated
• More fibers contracting results in greater muscle
tension
• Muscles can continue to contract unless they run
out of energy (ATP)
Energy for Muscle Contraction
• Initially, muscles used stored ATP for energy –
aerobic activities
– Bonds of ATP are broken to release energy
– Only 4-6 seconds worth of ATP is stored by muscles
• After this initial time, other pathways must be
utilized to produce ATP – anaerobic activities
and lactic acid build-up
Muscle Fatigue and Oxygen Debt
• When a muscle is fatigued, it is unable to
contract
• The common reason for muscle fatigue is
oxygen debt
– Oxygen must be returned to tissue to remove
oxygen debt
– Oxygen is required to get rid of accumulated lactic
acid
• Increasing acidity (from lactic acid) and lack of
ATP causes the muscle to contract less
Muscles and Body Movements
• Movement is attained
due to a muscle moving
an attached bone
• Muscles are attached to
at least two points
– Origin – attachment to an
immoveable bone
– Insertion – attachment to
a movable bone
Figure 6.12
Ordinary Body Movements
• Flexion – decreases the angle between two adjacent
body segments
• Extension – increases the angle between two adjacent
body segments
• Rotation – the bone distal to the joint is moved either
toward (medial) or away from (lateral) the midline
• Abduction – movement of a body part away from the
midline
• Adduction – movement of a body part back toward the
midline
• Circumduction – a combination of flexion, abduction,
extension, and adduction
http://www.med.umich.edu/lrc/hypermuscle/hyper.html
Body Movements
Figure 6.13a–c
Body Movements
Body Movements
Figure 6.13d
Naming of Skeletal Muscles
• Direction of muscle fibers
– Example: rectus (straight)
• Relative size of the muscle
– Example: maximus (largest)
• Location of the muscle
– Example: many muscles are named for bones (e.g.,
temporalis)
• Number of origins
– Example: triceps (three heads)
Naming of Skeletal Muscles
• Location of the muscle’s origin and insertion
– Example: sterno (on the sternum)
• Shape of the muscle
– Example: deltoid (triangular)
• Action of the muscle
– Example: flexor and extensor (flexes or extends a
bone)
Head and Neck Muscles
Figure 6.15
Trunk Muscles
Figure 6.16
Deep Trunk and Arm Muscles
Figure 6.17
Muscles of the Pelvis, Hip, and Thigh
Figure 6.19c
Muscles of the Lower Leg
Figure 6.20
Superficial Muscles: Anterior
Figure 6.21
Superficial Muscles: Posterior
Figure 6.22
Movement Worksheet p.1
Standing on your toes as in ballet is
(1) of
the foot. Walking on your heels is
(2) .
Winding up for a pitch (as in baseball) can properly
be called (3) . To keep your seat when riding a
horse, the tendency is to
(4) your thighs.
In running, the action at the hip joint is (5) in
reference to the leg moving forward and
(6)
in reference to the leg in the posterior position.
When kicking a football, the action at the knee is
(7) . In climbing stairs, the hip and knee of
the forward leg are both
(8) .
You have just touched your chin to your chest; this is
(9)
of the neck.
Using a screwdriver with a straight arm requires
(10) of the arm. Consider all the movements of
which the arm is capable. One often used for
strengthening the upper arm and shoulder muscles is
(11) .
Moving the head to signify “no” is
(12) . Action
that moves the distal end of the radius across the ulna
is
(13) . Raising the arms laterally away from the
body is called
(14) of the arms.When you are
cupping your hands in order to hold a bowl of soup,
the position is called __(15)__.