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Muscular System

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I. Introduction to the

Muscular System

A.      Functions of Muscular System

1. Skeletal muscle tissue forms skeletal
muscles, organs that also contain
connective tissue, nerves and blood
vessels.

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2. The muscular system includes
approximately 700 skeletal muscles.

3. There are few functions of the
muscular system they are:

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a.     Produce movement

b.     Maintain posture and body position
 
c.      Support soft tissue

e. Maintain body temperature

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B. Anatomy of Skeletal

Muscles

    There are three types of muscles in the

body: smooth, cardiac and skeletal, all
differ in structure and function. All
muscle tissues posses some basic
characteristics and properties.

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Smooth Muscle

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Skeletal muscle

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Cardiac Muscle

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Comparison of Types of

Muscle

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Has no striations
Spindle-shaped cells
Single Nucleus
Involuntary—no
conscious control
Found mainly in the
walls of hollow organs

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Has striations
Usually has a single nucleus
Joined to another cardiac
muscle cell
Involuntary
Found only in the heart

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

Functions of Skeletal Muscle

–

Produce Movement

–

Maintain posture

–

Stabilize joints

–

Generate Heat

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Sites of Muscle Attachment

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Bones

–

Cartilage

–

Connective tissue coverings

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C. Development of Skeletal

Muscles

1.      The formation of the muscular

system begins about 4 weeks of

embryonic development. The beginning

cells are called myobasts.

2. It is not certain when skeletal muscles

are able to move but by the 17

th

week

the fetal movements- quickening are

strong enough for the mother to feel.

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Antagonistic muscles perform
opposite functions and are generally
located on the opposite sides of the
limb.

Example-Biceps contract together
(flex) and the triceps extend (relaxes)

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III. The Energetics of

Muscular Activity

A. Muscle contraction requires large

amounts of energy. Example- an active
skeletal muscle fiber may require 600
TRILLION ATP molecules EACH second!

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B. Muscle Fatigue

1.     A skeletal muscle fiber is said to be

fatigued when it can no longer contract
despite continued neural stimulation.

 

2. Muscle fatigue is caused by the
exhaustion of energy reserves or builds
up of lactic acid.

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Boston Marathon

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3. If muscle contraction uses ATP at or
below the maximum rate of
mitochondria ATP generation, the
muscle fiber can function aerobically.

4. Fatigue will NOT occur until
glycogen and other reserves such as
lipids and amino acids are depleted.

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Joke Time

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5. This type of fatigue affects the
muscles of long-distance athletes, such
as marathon runners, after hours of
exertion.

6. When a muscle produces a sudden,
intense burst of activity, the ATP is
provided by glycolysis.

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7. After a relatively short time (seconds

to minutes) the rising lactic acids levels

lower the tissue pH and the muscle can

no longer function normally.

8. Athletes running sprints have this

type of fatigue

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8. Liver cells consume most of the extra

oxygen, as they produce ATP for the

conversion of lactic acid back to glucose,

and by muscle cells as they restore their

reserves of ATP.

 

9. While the oxygen debt is being repaid,

breathing rate and depth are increased. This

is why you continue to breath heavy after

exercising.

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Joke time

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IV. Cardiac and Smooth

muscle tissues

A.

Cardiac muscle tissue

 

1.     Cardiac muscle cells are relatively small

and usually have a single, centrally placed

nucleus. Cardiac muscle tissue is found only

in the heart.

 

2. Cardiac muscle tissue contrast WITHOUT

stimulation-automatic. Pacemaker cells

normally determine the timing of contractions.

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3. Cardiac muscle cell contractions last
roughly 10 times as long as those of
skeletal muscle fibers.

4. Cardiac muscle cells rely on aerobic
metabolism for the energy needed to
continue to contract.

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B. Smooth Muscle tissue

1. Smooth muscle tissue is found
within almost every organ.

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V. Anatomy of the Muscular

System

A.

The muscular system includes all of
the skeletal muscles that can be
controlled voluntarily.

B. Each muscle begins at an origin, ends

at an insertion, and contract to
produce a specific action.

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1.     The human body has approximately

700 muscles, which all have names.

 

2. The names of muscles give clues to the

locations of the muscles.

 

3. The first part of man names indicates

the origin and the second part the

insertion of the muscle.

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B. Integration with other

systems.

 
1. To operate at maximum efficiency,
the muscular system must be
supported by many other systems.
Such as the cardiac system, respiratory,
Integumentary, nervous and endocrine
system.

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Clinical considerations

A.

Problems with the muscular system.

 1. Muscular Dystrophy is an inherited
disease, which cause progressive
muscular weakness and deterioration.

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Umbilical hernia

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Epigastric hernia