Julia Olszewski-Jubelirer
biologybyjulia.wordpress.com
jolszews@live.unc.edu
Extreme Muscles
High School
Standards
OBio.1.1
Bio.4.1.1
Introduction
Muscles contract when a protein
called myosin pulls on a protein
called actin, shortening the
Materials and setting
muscle. Myosin and actin are
Large open space
arranged in units called
Masking tape
sarcomeres. The myosin and actin
Sharpie/marker
are only able to pull on each other
Rope
if they overlap. Otherwise the
Ability to show youtube videos
myosin is unable to reach the actin
Copies of the worksheet
and the muscle cannot shorten.
Scissors
This puts a limit on the muscle’s
Glue or scotch tape
ability to change length. If the
muscle is stretched too far, the
Learning objectives
myosin and actin will no longer
SWBAT name the two major proteins involved overlap, causing the muscle to be
in muscle contraction.
unable to contract. If the muscle is
SWBAT propose limiting factors of muscle
too short, the myosin and actin can
performance based on the arrangement of
become squished, also preventing
muscle proteins.
them from binding. However,
SWBAT diagram one modification to the
some animals have modified
protein structure of chameleon tongue muscles sarcomeres allowing them to
that leads to extreme muscle performance.
contract their muscles at very long
or very short lengths.
Lesson Activity
Engagement
Video of chameleon tongues:
https://www.youtube.com/watch?v=YXbgRU4k3O8
Ask the students to note how far the chameleon is able to extend and retract its
tongue. We do not have any muscles that are capable of such a large length change.
Show the students this diagram of muscle organization. Today we are going to talk
about muscle at the molecular level- the level of the sarcomere.
Julia Olszewski-Jubelirer
biologybyjulia.wordpress.com
jolszews@live.unc.edu
Z-line 1
Z-line 1
Z-line 1
Z-line 1
Z-line 1
Holding hands
Actin 1
Holding hands
Actin 1
Actin 1
Actin 2
Actin 2
Myosin1 Myosin1 Myosin1 Myosin2 Myosin2 Myosin2
Using one hand to hold onto the rope and one hand
to pull on the actin
3) Rules
a. Z-line 1 and Actin 1 must stay in a T orientation.
b. Z-line 2 and Actin 2 must stay in a T orientation.
Actin 2
Z-line 2
Z-line 2
Z-line 2
Z-line 2
Z-line 2
Holding hands
Holding hands
Exploration
This activity will work best for a class of at least 16 students.
1) Split the students into 6 teams. Label each student with a piece of tape or a
nametag.
# of students
Label
At least 2 students Z-line 1
At least 2 students Z-line 2
At least 3 students Actin 1
At least 3 students Actin 2
At least 3 students Myosin 1
At least 3 students Myosin 2
2) Set up
Julia Olszewski-Jubelirer
biologybyjulia.wordpress.com
jolszews@live.unc.edu
c. Myosin 1 and Myosin 2 should hold on to the rope with one hand and
use their other hand to pull on the actin. Myosin 1 can only pull on
actin 1. Myosin 2 can only pull on actin 2.
4) Activity
Start with the orientation shown above. The myosin students should be able
to pull the actin students towards the center of the sarcomere. This should
cause the Z-lines to move closer together. This will cause the muscle to
contract.
Have the students contract until the actin students run into each other.
Then have the students continue to contract (remember myosin 1 can only
pull on actin 1 and myosin 2 can only pull on actin 2), until they run into the
Z-lines.
Ask the students, why can’t the muscle contract any further?
What would allow the muscle to contract further?
Explanation
Students should complete the attached worksheet either in class or at home.
Elaboration
Other extreme muscles:
Super-fast muscles: In most cases, muscles contract when they receive a signal from
a nerve. Dragonflies and other insects are able to flap their wings faster than nerves
are able to signal. Their muscles are set up so that instead of being signaled by a
nerve, they are signaled by the stretching of another muscle.
Super-enduring muscles:
Clams, oysters, and other bivalves are able to contract the muscle that holds their
shells shut indefinitely. Imagine trying to squeeze a clothespin open. Eventually
your fingers would get tired. This is because your muscles have to constantly rebind
the actin and myosin. Bivalves have a special type of myosin that is able to hold on
to the actin until it receives a nerve signal to let go. This means the myosin and actin
only have to bind once and do not continually use energy.
Super-elongating muscles: Earthworms, leeches, and some other invertebrates are
able to contract their muscles even when the sarcomeres are super stretched out. It
is thought that this is because the sarcomeres are arranged with their Z-lines at an
angle. By changing the angle as their muscle lengthens, they are able to increase the
length of the muscle without pulling the actin and myosin too far apart.
Evaluation
1. Muscles contract using which pair of proteins:
A. integrin and selectin
B. myosin and actin
Julia Olszewski-Jubelirer
biologybyjulia.wordpress.com
jolszews@live.unc.edu
C. ferritin and actin
D. integrin and myosin
2. The following is a diagram the sacromere of a typical vertebrate muscle:
A. Chameleons have super-contracting muscle in their tongues. This is due to
differences in their _________________.
B. Draw a diagram of the sarcomeres of a super-contracting chameleon tongue
muscle. Circle the differences between your diagram and the diagram above.
How do your differences allow the muscle to be super-contracting?
Answer key
1. B- myosin and actin
2A. Z-lines
2B.
Holes in the Z-line allow the actin to pass through the Z-line, binding with the
myosin the neighboring sarcomeres.