Question

A chemical signal that has both endocrine and neural roles is
A. Epinephrine
B. Cortisol
C. Melatonin
D. Calcitonin

Answer 1

Hint: The nervous system uses two types of intercellular communication – one is electrical and the other is chemical that signals the action of chemical neurotransmitters such as serotonin or norepinephrine. Neurotransmitters act locally and rapidly.

Complete answer: When an electrical signal reaches the synaptic terminal, it diffuses across the synaptic cleft. Once the neurotransmitters bind with receptors on the postsynaptic cell, it will transform into an electrical signal. The target cell responds within milliseconds of receiving the chemical. This response then ceases very quickly once the neural signaling ends. In this way, neural communication occurs. These signals are sent by the endocrine organs. The hormone which acts as both an endocrine hormone, as well as a neurotransmitter, is epinephrine. It is secreted from the adrenal medulla, as a hormone, it increases metabolic rate and as a neurotransmitter, it transmits impulses at the synaptic cleft.
-Cortisol is a steroid hormone, in the glucocorticoid class of hormones. When used as a medication, it is known as hydrocortisone. It is produced in many animals, mainly by the zona fasciculata of the adrenal cortex in the adrenal gland. It is produced in other tissues in lower quantities.
-Melatonin is a hormone primarily released by the pineal gland that regulates the sleep-wake cycle. As a dietary supplement, it is often used for the short-term treatment of insomnia, such as from jet lag or shift work, and is typically taken by mouth.
-Calcitonin is a hormone that is produced in humans by the parafollicular cells (commonly known as C-cells) of the thyroid gland. Calcitonin is involved in helping to regulate levels of calcium and phosphate in the blood, opposing the action of the parathyroid hormone.
Therefore it plays both roles hence the correct answer is option A.

Note: The endocrine signaling is typically less specific than neural signaling. The same hormone may play a role in a variety of different physiological processes depending on the target cells involved.