Biomedical Engineering Reference
In-Depth Information
while in the
y
-direction:
c
0
(
−
u
x
+
u
y
)
=
0.
This gives two equations from which the two unknowns (
u
x
and
u
y
) can be solved.
F
y
−
Exercises
4.1
The length change of a muscle, with respect to the length
0
in the relaxed
state, can be written as
δ
=
−
0
.
(a) Give an expression for the force
F
in the activated muscle as a
function of
c
,
c
.
(b) What is the magnitude of the force
F
when
δ
,
0
and
δ
=
0?
4.2
Give a sketch of the force as a function of the active muscle length in the
diagram below
F
c
2
2
c
0
c
0
4.3
In reality the force length equation for an activated muscle in Eq. (
4.9
)is
only valid in a very limited range of extension ratios. The force that a sar-
comere (and thus a skeletal muscle) can exert has a maximum, as depicted
in the figure below. Sarcomere lengths at several interesting points in the
graph are depicted by
L
i
, with
i
=
1,
...
,5.
L2
100
80
Maximum
tension
(%)
L3
60
L1
L2
L3 L4
L5
40
L4
20
0
Actin
Myosin
l5
0.5 1.0
1.5 2.0 2.5
Sarcomere length [
3.0
3.5
4.0
µ
m]
Z disk
