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CA (630,000)
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BIOB32H3 (100)
Lecture

BIOB32H3 Lecture Notes - Electron Microscope, Myocyte, Sarcomere


Department
Biological Sciences
Course Code
BIOB32H3
Professor
Kenneth Lam

Page:
of 2
12-04-22 1:01 PMBackground: Muscle Length-Tension Relationship
Page 1 of 2http://ab.mec.edu/abrhs/science/AnatPhys_Labs/backgroundlengthtension.html
Background: Muscle Length-Tension
Relationship
The muscle length-tension relationship is the relationship between
the length of the fiber and the force that the fiber produces at that
length. This length is referring to the length of an isolated fiber and
is dependent upon the position of the actin and myosin filaments in
the sarcomeres. The sarcomere is the contractile unit of a muscle
fiber, and a muscle fiber is composed of thousands of sarcomeres.
The actin and myosin filaments are proteins that create cross bridges
and are responsible for the contractions, or shortening, of a fiber (see
figures).
When an isolated muscle fiber is stretched to the point of minimal
overlap of actin and myosin and then stimulated by an electrode to
contract , the force of contraction measured is minimal. When an
isolated muscle fiber is stimulated to contract when there is optimal
overlap of actin and myosin the force produced is maximal. When
an isolated muscle fiber is stimulated to contract when there is
maximal overlap of actin and myosin the force produced is minimal
(see figure). The result is a graph that has a parabolic shape (see
figure).
The question you will be asking in this lab is can this situation be
applied to whole muscle physiology. Does whole muscle have
optimal lengths which produce optimal force of contraction as well
as positions of stretch and too much overlap as it operates in the
body as a system. You will examine this question by using a bicycle
ergometer that measures watts and then calculating force produced.
You will perform the exercise at different seat heights which puts
the knee at different angles simulating the different lengths of
muscle.
12-04-22 1:01 PMBackground: Muscle Length-Tension Relationship
Page 2 of 2http://ab.mec.edu/abrhs/science/AnatPhys_Labs/backgroundlengthtension.html
Figure shows an electron microscope image of a sarcomere (top), and a schematic diagram of a sarcomere
with structures identified.
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