Serotonin (5-hydroxytryptamine, 5-HT) is a neurotransmitter with receptors (5-HT receptors) located in cells throughout the body. a. True
b. False

a. True

Explanation:

Serotonin receptors are G protein-coupled receptors involved in the modulation of both excitatory and inhibitory neurotransmission. Serotonin receptors are divided into seven classes (5-HT1 to 5-HT7) which can be in turn divided into several subclasses (A, B, C, etc.). Most of the serotonin receptors are located in the gut (about 90%), but they are also spread in other parts of the body, including the amygdala, the bed nucleus of the stria terminalis (BNST, also known as the extended amygdala), Merkel cells (skin), taste receptor cells (tongue), Raphe nuclei (brainstem), etc.

the law of original horizontality explains:   why rocks appear in layers. correct answer: b the law suggests that all rock layers are originally laid down (deposited) horizontally and can later be deformed.   the principle is used by geologists to make assumptions about the relative ages of sedimentary rocks.