CHAPTER 2: GLANDS, GOOSEFLESH, AND HORMONES
The second chapter covers the building blocks of the stress response system.
First, the autonomic nervous system. This is split into the sympathetic and parasympathetic nervous systems.
The sympathetic activates in times of stress. It'll dilate your pupils, accelerate your heartbeat, stimulate secretion of adrenaline (aka epinephrine), and much more.
Remember in chapter one Sapolsky covers the early history of stress research, introducing us to Walter Cannon and Hans Selye. As a reminder, Cannon introduced the physics term "stress" and coined the "fight or flight" phrase to describe the body's response. Selye formalized these concepts, highlighting two key ideas:
1. "The body has a surprisingly similar set of responses (which he called the general adaptation syndrome, but which we now call the stress response) to a broad array of stressors." (pg. 8)
2. "If stressors go on for too long, they can make you sick." (pg. 8)
Psychologist Shelley Taylor of UCLA suggested expansion of the fight or flight model of stress. She suggests that females experience and respond to stress differently than males (in some contexts - a hungry lion chasing prey is a hungry lion; male or female, same biochemistry). She suggests and "tend and befriend" model in which social affiliation is a strong response to stress. The "tend and befriend" model of stress response expands the simplistic "fight or flight" model that itself only covers a portion of the reasonable response range.
(Michael Crichton's Prey provides the best description I've read of the adaptive advantage of freezing. The ostensibly bizarre response of being unable to respond, frozen from fear, is actually protective when it occurs in the context of predation, especially if the predator is skilled at or dependent on motion for tracking. Thus the instinctive response to stand still can provide an adaptive, evolutionary advantage within environments where predators lose track without motion. In modern society this adaptation is less valuable, as comedian Jerry Seinfeld points out in regard to public speaking: "According to most studies, people's number one fear is public speaking. Number two is death. Death is number two. Does that sound right? This means to the average person, if you go to a funeral, you're better off in the casket than doing the eulogy.")
In terms of the "fight or flight" approach, there are two key hormones to introduce now.
Adrenaline (Epinephrine): Stress hormone released by adrenal glands.
Noradrenaline (Norepinephrine): Stress hormone released by all of the other sympathetic nerve endings.
The parasympathetic nervous system works in the opposite direction, helping to calm the body. It "mediates calm, vegetative activities....promotes growth, energy storage, and other optimistic processes." (pp.22-23)
The brain is ultimately in control of all this coordinated activity.
Neurotransmitters are chemical messengers secreted by neurons which impact the next cell in line. They travel across small spaces (synapses).
Hormones are chemical messengers secreted by neurons that travel to the bloodstream.
During the 20th century, research demonstrated that the brain, by way of the hypothalamus, regulates these systems. Early in the 20th century, the line of reasoning was that the organs themselves ran their own programs, secreting the hormones associated with them (for example testosterone would be secreted by the testes, with them knowing how and when and how much on their own.) That theory gave way to the idea that the program was controlled by the brain with the focus centering on the pituitary gland. However, research on this idea suggested that the pituitary did not run the show since the pituitary gland when removed and prompted by hormones in a Petri dish, would respond erratically, producing hormones but not in the expected volume or controlled manner. It seemed that the pituitary needed instructions rather than just stimulation by hormones. In 1944 physiologist Geoffrey Harris proposed that the brain itself was the one regulating this activity. His idea was later proved by competing scientists, Roger Guillemin and Andrew Schally.
There was fierce competition between Roger Guillemin and Andrew Schally to isolate and identify the releasing and inhibiting hormones that would guide the pituitary. They conducted their research by collecting brain materials from slaughterhouses and then pulling the back of the brains out, mixing them up in a brain stew and then injecting the formula into rats' pituitaries. By so doing they were able to trigger the rats' pituitaries to respond in predictable ways. Those extracts were then purified and identified, with Guillemin being the first to publish what the hypothalamic hormone would have to be to stimulate the rat's pituitary in a certain defined way and Schally being the first to actually find and prove the existence of a hormone matching that description and function. Guillemin and Schally shared the Nobel Prize in 1976, though Sapolsky notes that they didn't like each other and were certainly not collegial.
Having established that the brain runs the show by way of the hypothalamus, Sapolsky introduces some stress hormones that we'll encounter frequently throughout the text.
Hormones of the stress response
Adrenaline/Noradrenaline, (aka Epinephrine/Norepinephrine) - A hormone secreted by the adrenal glands, especially in conditions of stress, increasing rates of blood circulation, breathing, and carbohydrate metabolism and preparing muscles for exertion.
Glucocorticoids - steroid hormones. These are produced in the adrenal glands (atop the kidneys).
CRH - Corticotropin releasing hormone.
ACTH - hormone corticotropin.
Glucagon - hormone released by pancreas during stress. Raises circulating levels of glucose in the bloodstream.
Endorphins - Any of a group of hormones secreted within the brain and nervous system and having a number of physiological functions. They are peptides which activate the body's opiate receptors, causing an analgesic effect.
Enkephalins - Either of two pentapeptides with opiate and analgesic activity that occur naturally especially in the brain and have a marked affinity for opiate receptors
Vasopressin - Hormone secreted by the posterior lobe of the pituitary gland or obtained synthetically that increases blood pressure and decreases urine flow
Oxytocin - A hormone and a neurotransmitter that is involved in childbirth and breast-feeding. It is also associated with empathy, trust, sexual activity,
Stimulatory pathway is: Hypothalamus->CRH Released->Pituitary->ACTH Released->Adrenal Gland Stimulated->Glucocorticoids.
The second chapter covers the building blocks of the stress response system.
First, the autonomic nervous system. This is split into the sympathetic and parasympathetic nervous systems.
The sympathetic activates in times of stress. It'll dilate your pupils, accelerate your heartbeat, stimulate secretion of adrenaline (aka epinephrine), and much more.
Remember in chapter one Sapolsky covers the early history of stress research, introducing us to Walter Cannon and Hans Selye. As a reminder, Cannon introduced the physics term "stress" and coined the "fight or flight" phrase to describe the body's response. Selye formalized these concepts, highlighting two key ideas:
1. "The body has a surprisingly similar set of responses (which he called the general adaptation syndrome, but which we now call the stress response) to a broad array of stressors." (pg. 8)
2. "If stressors go on for too long, they can make you sick." (pg. 8)
Psychologist Shelley Taylor of UCLA suggested expansion of the fight or flight model of stress. She suggests that females experience and respond to stress differently than males (in some contexts - a hungry lion chasing prey is a hungry lion; male or female, same biochemistry). She suggests and "tend and befriend" model in which social affiliation is a strong response to stress. The "tend and befriend" model of stress response expands the simplistic "fight or flight" model that itself only covers a portion of the reasonable response range.
(Michael Crichton's Prey provides the best description I've read of the adaptive advantage of freezing. The ostensibly bizarre response of being unable to respond, frozen from fear, is actually protective when it occurs in the context of predation, especially if the predator is skilled at or dependent on motion for tracking. Thus the instinctive response to stand still can provide an adaptive, evolutionary advantage within environments where predators lose track without motion. In modern society this adaptation is less valuable, as comedian Jerry Seinfeld points out in regard to public speaking: "According to most studies, people's number one fear is public speaking. Number two is death. Death is number two. Does that sound right? This means to the average person, if you go to a funeral, you're better off in the casket than doing the eulogy.")
In terms of the "fight or flight" approach, there are two key hormones to introduce now.
Adrenaline (Epinephrine): Stress hormone released by adrenal glands.
Noradrenaline (Norepinephrine): Stress hormone released by all of the other sympathetic nerve endings.
The parasympathetic nervous system works in the opposite direction, helping to calm the body. It "mediates calm, vegetative activities....promotes growth, energy storage, and other optimistic processes." (pp.22-23)
The brain is ultimately in control of all this coordinated activity.
Neurotransmitters are chemical messengers secreted by neurons which impact the next cell in line. They travel across small spaces (synapses).
Hormones are chemical messengers secreted by neurons that travel to the bloodstream.
During the 20th century, research demonstrated that the brain, by way of the hypothalamus, regulates these systems. Early in the 20th century, the line of reasoning was that the organs themselves ran their own programs, secreting the hormones associated with them (for example testosterone would be secreted by the testes, with them knowing how and when and how much on their own.) That theory gave way to the idea that the program was controlled by the brain with the focus centering on the pituitary gland. However, research on this idea suggested that the pituitary did not run the show since the pituitary gland when removed and prompted by hormones in a Petri dish, would respond erratically, producing hormones but not in the expected volume or controlled manner. It seemed that the pituitary needed instructions rather than just stimulation by hormones. In 1944 physiologist Geoffrey Harris proposed that the brain itself was the one regulating this activity. His idea was later proved by competing scientists, Roger Guillemin and Andrew Schally.
There was fierce competition between Roger Guillemin and Andrew Schally to isolate and identify the releasing and inhibiting hormones that would guide the pituitary. They conducted their research by collecting brain materials from slaughterhouses and then pulling the back of the brains out, mixing them up in a brain stew and then injecting the formula into rats' pituitaries. By so doing they were able to trigger the rats' pituitaries to respond in predictable ways. Those extracts were then purified and identified, with Guillemin being the first to publish what the hypothalamic hormone would have to be to stimulate the rat's pituitary in a certain defined way and Schally being the first to actually find and prove the existence of a hormone matching that description and function. Guillemin and Schally shared the Nobel Prize in 1976, though Sapolsky notes that they didn't like each other and were certainly not collegial.
Having established that the brain runs the show by way of the hypothalamus, Sapolsky introduces some stress hormones that we'll encounter frequently throughout the text.
Hormones of the stress response
Adrenaline/Noradrenaline, (aka Epinephrine/Norepinephrine) - A hormone secreted by the adrenal glands, especially in conditions of stress, increasing rates of blood circulation, breathing, and carbohydrate metabolism and preparing muscles for exertion.
Glucocorticoids - steroid hormones. These are produced in the adrenal glands (atop the kidneys).
CRH - Corticotropin releasing hormone.
ACTH - hormone corticotropin.
Glucagon - hormone released by pancreas during stress. Raises circulating levels of glucose in the bloodstream.
Endorphins - Any of a group of hormones secreted within the brain and nervous system and having a number of physiological functions. They are peptides which activate the body's opiate receptors, causing an analgesic effect.
Enkephalins - Either of two pentapeptides with opiate and analgesic activity that occur naturally especially in the brain and have a marked affinity for opiate receptors
Vasopressin - Hormone secreted by the posterior lobe of the pituitary gland or obtained synthetically that increases blood pressure and decreases urine flow
Oxytocin - A hormone and a neurotransmitter that is involved in childbirth and breast-feeding. It is also associated with empathy, trust, sexual activity,
Stimulatory pathway is: Hypothalamus->CRH Released->Pituitary->ACTH Released->Adrenal Gland Stimulated->Glucocorticoids.
As we move along in the book we'll learn more about the roles of the sympathetic nervous system, adrenaline and glucocorticoids. As a primer, "sympathetic arousal is a relative marker of anxiety and vigilance, while heavy secretion of glucocorticoids is more a marker of depression."(35). In other words - short term bursts will give you the stimulus you need to respond to stress (system acting as designed). Long term bursts will wear you out and give you ulcers.
