By Jonny Lupsha, Wondrium Staff Writer
A new study supports the theory that stress comes from the hippocampus, Science Alert reported. The hippocampus is a region of the brain that deals with many aspects of a normal day, from memory to navigation. Hormones and glands help complete the stress response.
As the relationship between the hippocampus and stress has been studied in the past, the Science Alert article stated the role of the hippocampus has gained more traction with a new study that has found that there are specific areas of the brain—the hippocampus to the hypothalamus, parahippocampal cortex (PHC), and inferior temporal gyrus (ITG)—where activity corresponds to stress level felt by an individual.
“Researchers recruited 60 healthy adults and showed them a series of highly aversive and threatening images designed to produce a form of stress response (such as anger, disgust, fear, and sadness), alternated with various neutral scenes to help them relax,” the article said. “During the experiment, participants had their brain activity measured by functional magnetic resonance imaging (fMRI), and also ranked how stressed and aroused they felt from each set of confronting images.”
The results showed that higher activity linking the hippocampus to the hypothalamus and other areas corresponded with higher reported levels of stress. However, the whole stress response doesn’t just take place in the hippocampus.
The Hormonal Stress Response
One seemingly simple effect of the stress response being activated is the release of certain hormones, but which ones?
“The sympathetic nervous system is turned on, and the main hormone that it regulates is adrenaline—in the United States [it’s] typically known as epinephrine; in England and commonwealth countries, adrenaline,” said Dr. Robert Sapolsky, the John A. and Cynthia Fry Gunn Professor of Biological Sciences at Stanford University and Professor of Neurology and Neurosurgery in Stanford’s School of Medicine. “It comes out of the adrenal glands. The sympathetic nervous system sends a message to the adrenals, out comes adrenaline or epinephrine.”
While adrenaline is released, some hormones from the nervous system’s other half—the parasympathetic nervous system—are actually inhibited from secreting. Dr. Sapolsky said these include growth hormone, insulin, and the reproductive hormones. So our bodies slow those down while increasing the flow of adrenaline. However, adrenaline isn’t the only hormone that’s given a boost.
“The next major player is a class of steroid hormones that come out of the adrenal glands as well, called glucocorticoids,” Dr. Sapolsky said. “Other players that get increased secretory rates during stress [include] prolactin, glucagon, and beta-endorphin.”
Hormones and Glands: The Big Picture
Hormones and glands play major roles in the stress response, but what are each of those? Hormones need the most explanation.
“You’ve got a brain cell, a neuron which dribbles out some chemical messenger, and it goes one-thousandth of an inch until it hits the next neuron, and it changes something or other in that neuron’s function,” Dr. Sapolsky said. “What you’ve got is a neurotransmitter. Instead, now, [suppose] you have that neuron that secretes this same exact chemical messenger, except this time instead of going a tiny distance to the next neuron, it gets in the bloodstream where it can circulate throughout the body and affect something going on in your ankles.
“What we’ve just defined is a hormone,” he added.
Of course, the ankles are just one example; hormones can ride your bloodstream to anywhere and send a chemical signal for change. Where do they come from? Glands, which are basically homes for hormones.
“That’s kind of a definition of a gland,” Dr. Sapolsky said. “A gland secretes hormones, chemical messengers that get blood borne. A gland secretes hormones—glands like ovaries, testes, adrenals, and thyroids, that kind of thing.”
So stress may originate from the hippocampus, but the stress response involves hormones, which are released from glands and then travel the bloodstream affecting chemical change in your body.
Dr. Robert Sapolsky contributed to this article. Dr. Sapolsky is John A. and Cynthia Fry Gunn Professor of Biological Sciences at Stanford University and Professor of Neurology and Neurosurgery in Stanford’s School of Medicine. Professor Sapolsky earned his A.B. summa cum laude in Biological Anthropology from Harvard University and his Ph.D. in Neuroendocrinology from The Rockefeller University in New York.