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Title:
Movement of small intestinal smooth muscle in vitro
Objectives:
1. To observe general physiological characteristics of smooth muscle
in digestive trac;
2. To study perfusion method of body-isolated organ in mammal;
3. To observe the effect of several factors on small intestinal smooth
muscle.
Material AND Method:
BL-420 system; tension transducer; syringe; beaker; a set of
homeothermic smooth muscle bath tank ; dropper; Tyrodo’s solution;
atropin; Acetylcholine(ACh); Adrenaline(Adr); calcium chlorine (CaCl2).
1. Preparation of experimental instrument
The bath tank is filled with water, preheating tube and sample tube are
filled with Tyrodo’s solution; open the power, then set the experimental
temperature at about 37°C. Adjust the flow of oxygen.
2. Preparation of rabbit’s small intestine:
i. Beat the head with a mallet to make rabbit coma and rapidly open
the abdomen, find duodenum, then free 10cm in length of small
intestine near to the duodenum from rabbit, immediately place it
into a beaker filled with 37°C Tyrodo’s solution.
ii. Dissect a small intestine about 2cm in length and wash it with
Tyrodo’s solution repeatedly until it becomes clean.
iii. Connect one end of small intestine to transducer, other end to
experimental hook.put intestinal segment into sample tube and fix
it up.
PROCEDURE:
1.Hang the intestinal segment diagonally
2.The thread must be vertical and avoid touching the wall of sample
tube.
3.Oxygen bubble should not be too intense lest it affect recording
results.
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3. Open BL-420 biology experimental system, click “Signal selection”,
select channel and “tension” signal. Click “start ” button to start
experiment.
4. Record the normal curve and after recoding that perform the
experiment with different given chemicals like, Ach effect, Atropine
Effect, Adr effect, CaCl2 effect, high temperature effect, decrease
temperature effect.
Results:
1- By adding 2 drops of Ach there was increase in the amplitude of
curve.
2- By adding Atropin their wasn’t any change in curve amplitude.
3- By adding Adr there was decrease in the amplitude of curve.
4- By adding CaCl2 there was increase in amplitude of curve.
5- By increasing the temperature there was increase in amplitude of
curve.
6- By decreasing temperature there was decrease in amplitude of
curve.
Discussion:
Explain why the amplitude of contractive curve increases when
increasing temperature and adding Ach and CaCl2?
Increasing temperature can affect metabolism of intestinal smooth
muscle. The increase temperature of solution, the elevation of
metabolism, which can lead to the increase in excitability, rate and
amplitude of contraction.
ACh can combine with M cholinergic receptor on intestinal smooth
muscle,
which can activate Ca2+ channel. The activation of Ca2+ channel can
enhance Ca2+ influx ,which can enhance the contraction and the tonus
of intestinal smooth muscle.
Because the force of contraction of smooth muscle is usually
highly
dependent on Ca2+ concentration in extracellular fluid . When Ca2+
concentration rises, The influx of Ca2+ increases and smooth muscle
contraction is enhanced.
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Explain why the amplitude of contractive curve decreases when
decreasing temperature and adding Adr?
Decreasing Curve by adding temperature Mechanism:
The decrease temperature of solution, the fall of metabolism, which
can lead to the decrease in excitability, rate and amplitude of
contraction.
Decreasing Curve by adding Adr Mechanism:
Adr can combine with β2 and α2 adrenergic receptor on intestinal
smooth
muscle, which can activate calcium pump. The activation of calcium
pump can enhance Ca2+ out-flux and lead to the decrease of muscle
activity.
Explain why the amplitude of contractive curve is unchanged
when adding atropin?
Unchanged Curve Adding Atropin Mechanism:
The contractive curve should be unchanged.
Atropin is the blocker of M cholinergic receptor, so it can inhibit the effect
of ACh.
Conclusion:
1- By adding the Ach, CaCl2 and increasing temperature it causes
the contraction of sooth muscles by increasing the amplitude of
wave.
2- By adding the Adr and decreasing the temperature it causes the
relaxation of muscles by decreasing amplitude of wave.
3- There was no effect of Atropin on curve and muscle.

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