Applying ACh to the small intestine will cause a smooth muscle , which is through activation of receptors.

The correct answer is -  Excitation; and Gi receptors.

Explanation:

ACh or acetylcholine is a secondary messenger that cause excitation by propagate the signal to the muscles from neurons. It is helps in transport the signal from the motor neurons to the muscles.

ACh release from the parasympathetic neurons and can directly excitation to the smooth muscle by binding to the Gi receptors or muscarinic receptors and activate them for excitation and contraction.

Thus, the correct answer is - Excitation; and Gi receptors.

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