Download The Muscular System - Chaparral Middle School

The Muscular System
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Chapter 19, section 3
Parts of the Muscular System
 Muscle cells working
together (muscle tissue)
 Connective tissue that
attaches the muscle to
the bone (tendons)
 What system controls
your muscles?
 When a muscle fiber is
electrically excited what
happens?
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3 types of muscle tissue
 Smooth:
Allows hollow organs to contract
(“contractility”)
Involuntary (with few exceptions)
 Digestive tract, blood vessels
 One nucleus/cell
 Slower to contract,
but does not tire easily

Cardiac muscle
 Cardiac muscle: in the heart only
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Uninucleated, striated, and branched
Have intercalated disks: locks fibers together
so heart may contract quickly
Relax completely between contractions, which
prevents fatigue
Involuntary.
Skeletal muscle
 Skeletal muscle:
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Attach to the bones for movement, help
protect internal organs
Under voluntary control
Multinucleated
Have “striations”
 Which type of muscle is slow to contract?
 Which type of muscle is found only in the
heart?
 Which type of muscle is usually voluntary
(controlled by your conscious mind)?
Connecting muscles to bones
 Connective tissue attaches muscles to bones
 “tendons”
Contraction occurs in pairs:
 http://biology.clc.uc.edu/courses/bio105/muscles.htm
 Flexor: muscle which bends a part of the body
 Extensor: muscle which straightens a part of the body
 Example:
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Exercise Types
 Resistance:
 Most effective in
developing size and
strength of skeletal
muscles
 Overcome resistance
(weight) of another
object
 Aerobic:
 Steady, moderate
intensity activity
 Strengthens the skeletal
muscles somewhat, but
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most effective in
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developing the heart
movie
 Which type of muscle has different columns
of molecules lined up in it’s cells so that there
are alternating colored bands or striations?
 Which kind of exercise would you want to do
to strengthen the heart?
Levers
click on the word “levers” to go to a website clip
 A bar that moves around a fixed point
(“fulcrum”)
 Three types of levers: 1st, 2nd and 3rd class
First Class Levers (head)
Fulcrum is between the effort
and the load.
Which way will the load move?
Second Class Levers (on toes)
This time the load is between
The fulcrum and the effort.
Which way will the load
move?
Third Class Levers (your arm)
Now the effort is between the
fulcrum and the load.
Which way will the load
move?
Mechanical Advantage
 Mechanical advantage is how much the lever
magnifies the force
MA (mechanical advantage) =
load/effort
According to the
formula what is
the mechanical
advantage of the
lever if the load is
10 N and the force
is only 5 N to
move the load?
Pushing
down with
10 N of
force.
Pushing
down with
only 5 N of
force.
Did the lever help
do some work?