Activity of Gastrointestinal Smooth Muscle: Worksheet

Referring to Figure 1 and Table 1, briefly describe the response of the spontaneously

contracting ileum to nerve stimulation. Was this response altered by increasing the voltage of nerve

stimulation?

2) What is the frequency of the regular spontaneous contractions of the ileum (measured in

contractions per minute)? What causes or initiates these spontaneous contractions?

[Maximum 100 words]

There is increased contraction amplitude at first but it gradually decreases in the later half as seen

in Fig. 1, whereas an overall decreased contraction amplitude was seen in Table 1. As pacemaker

cells will cause contractions upon nerve stimulation which leads to decreasing contraction

amplitude from the release of neurotransmitters in sympathetic nerve terminal. Yet, increasing

amplitude at the beginning suggested that a larger proportion of parasympathetic nerve fibers is

present in this extrinsic nerve than sympathetic nerves, because of the release of acetylcholine

which caused an excitatory response. And later decrease in amplitude is due to sympathetic nerves

being more active than parasympathetic nerves.

This response was altered by increasing the voltage of nerve stimulation, there was no significant

observation in contraction amplitude upon 4 or 8V. Thus, voltage has been increased to 10V and

the above observation was concluded.

Bench 15.adicht

Ileum Contractility (mV)

-10

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Stimulator On 20Hz, 10V, 1ms

Stimulator Off 20Hz, 10V, 1ms

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11/08/2015