Neurotransmitter and Maximal Contractile Response

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Department of Physiology

PHY2021
Body Systems Physiology

Activity of Gastrointestinal
Smooth Muscle Worksheet

Due by:

Noon (12 pm) Friday April 12

Pre-prac Reading: Vander, 12th Edition:
Section 6D.4 (pp 175-180), Section 15.2 (pp 521-522), Section 15.4 (pp 528-529, 536-538 & 542-543).

INTRODUCTION
Give a brief description in your own words of the objectives and aims of this practical.

The aim of this practical was to discover the effects that numerous hormones and drugs have on the sample ileum’s nerves and relate this to the human autonomic nervous system. The objectives include observing the change in contractions during different levels of stimulation and inhibition, such as that from different voltages and alpha/beta blockers.

A. RESPONSES TO NERVE STIMULATION

Figure 1.0
Spontaneous contractions of rabbit ileum at 20Hz.

Figure 1,1
Contractions of rabbit ileum at 20Hz, with a stimulation of 2V applied to produce a moderate reaction.

Figure 1.2
Contractions of rabbit ileum at 20Hz, with a stimulation of 3V applied to produce a maximal contractile response.

1)Briefly describe the response of the ileum when it is unstimulated and during stimulation of the nerves.

When unstimulated, the contractions of the rabbit ileum occur at a constant slow rate. When the ileum becomes stimulated, however, the amplitude of these contractions drop. This is due to the higher voltage, which inhibits the contractions.

2) What is the frequency of the regular spontaneous contractions of the ileum? What causes these spontaneous contractions?

The frequency of the contractions was approximately 14 per minute. Spontaneous contractions occur due to the presence of pacemaker cells, which spontaneously produce action potentials.

 Attach a copy of your experimental recordings showing the response to...
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