The Muscular System - Anatomy Coloring Sheet Page 5
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22LWBK244-4102G-C04_48-69.qxd 12/11/08 6:11 PM Page 52 LWBK160-3985G-C95_1329-135#C1BC
Coloring Exercise 4-3
Muscle Contraction
The Sliding Filament Mechanism
COLORING INSTRUCTIONS
• Remember that each muscle fiber is organized in sarcomeres
A
Color each structure and its
name at the same time, us-
• Each sarcomere contains overlapping filaments of
ing the same color. On the
Myosin
: long filamentous protein with globular head
B
•
top figure:
Actin
C
: globular protein linked together in long strands; each actin has a
•
1. Use the same colors for
binding site
D
for myosin
structures
to
as
A
C
• During muscle contraction, sarcomeres SHORTEN
you used in the previous
The length of myosin and actin filaments does not change
•
Coloring Exercise.
The overlap between thick and thin filaments increases; filaments “slide
•
2. Color the bracket repre-
over” each other
senting the sarcomere
As sarcomeres shorten, the muscle shortens
•
.
A
• Sliding filament mechanism includes three stages
3. For the top diagram,
Attachment
: myosin
binds specific binding sites
on the actin
E
B
D
•
color the bracket repre-
, forming a cross-bridge
C
senting the name of the
Power Stroke
: Myosin pulls on actin, shortening the sarcomere (and
F
•
stage
.
E
thus the muscle)
4. Lightly color the myosin
Release/Reattachment
: Myosin head detaches (step requires fresh ATP
G
•
and actin
B
C
molecule), binds further along the actin molecule
molecules. Color the
Cycle repeats
actin binding sites
•
D
using a dark color.
5. Repeat steps 3 and 4 for
Calcium and Muscle Contraction
the other two diagrams,
• The sliding filament mechanism only occurs if calcium
is present
representing stages
H
F
and
.
G
• Calcium is present in the muscle cell following an action potential in the
6. After coloring all three
motor end plate
diagrams, note that the
• If calcium is absent;
overlap between thick
Tropomyosin
covers the binding sites
I
D
•
and thin filaments
The three-part troponin complex
keeps tropomyosin in place
J
•
increases. This results in
shortening of both the
• If calcium is present:
sarcomere and the
Calcium binds troponin
•
muscle.
Troponin lets tropomyosin move away from binding sites on actin
•
7 . Note that the myosin
Myosin heads can bind actin
•
heads reattach to a dif-
Muscle contraction occurs
•
ferent site on the actin
molecules.
COLORING INSTRUCTIONS
On the bottom figure:
1. Color all of the compo-
nents in the top
diagram, when calcium
is not present.
2. Color all of the compo-
nents in the bottom dia-
gram, when calcium is
present.
52
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