Chapter 1 – Why don’t zebras get ulcers?
Ways to get upset:
1. Acute physical crises
2. Chronic physical challenges
3. Psychological and social disruptions
Sustained psychological stress is a recent invention, mostly limited to humans and other social
primates. For the vast majority of beasts on this planet, stress is about a short-term crisis, after which
it’s either over with or you’re over with. When we sit around and worry about stressful things, we turn
on the same physiological system that has evolved for responding to acute physical emergencies, but
we turn it on for months on end, worrying about mortgages, relationships, and promotions.
Begrippen
Homeostasis: all sorts of physiological measures are being kept at the optimal level. Goal: stability
through constancy.
Stressor: anything in the outside world that knocks you out of homeostatic balance. Or the
anticipation of that happening.
Stress-response: what your body does to reestablish homeostasis/allostasis. The secretion of certain
hormones, the inhibition of others etc. regardless of the stressor, you turn on the same stress-response.
Allostasis: efficient regulation requires anticipating needs and preparing to satisfy them before they
arise. Goal: stability through variation.
Hallmarks of the stress-response: Energy is mobilized and delivered to tissues that need them; long-
term building and repair projects are deferred until the disaster has passed. Pain is blunted, cognition
sharpened.
The stress-response can become more damaging than the stressor itself
Chapter 2 – Glands, gooseflesh and hormones
Autonomic Nervous System
One half of the Autonomic Nervous System (ANS) is activated in
response to stress, the other half is suppressed.
The half that is turned on is the Sympathetic Nervous System.
Originating in the brain, sympathetic projections exit your spine and
branch out to nearly every organ, blood vessel and sweat gland in your
body. The SNS kicks into action during emergencies. It helps mediate
vigilance, arousal, activation, mobilization. (fight, flight, fright, sex). The
nerve endings of this system release epinephrine (adrenaline) and the
closely related norepinephrine (noradrenaline). Epinephrine is secreted
as a result of the actions of the sympathetic nerve endings in your adrenal
glands; norepinephrine is secreted by all other sympathetic nerve endings
throughout the body. These are the chemical messengers that kick various
organs into gear.
,The half that is suppressed is the parasympathetic nervous system (PNS). This component mediates
calm, vegetative activities. It promotes growth, energy storage and other optimistic processes. Rest
and digest.
It would be a disaster if both halves are active at the same time, so lots of safety features exist to make
sure that doesn’t happen. For example, the parts of the brain that activate one branch, typically inhibit
the other.
Neurotransmitters vs. hormones
If a neuron secretes a chemical messenger that travels and causes the next cell in line to do something
different, that messenger is called a neurotransmitter.
If a neuron secretes a messenger that percolates into the bloodstream and affects events far and wide,
the messenger is a hormone.
The peripheral hormone-secreting glands are not autonomous, but are under control of something else:
the pituitary gland. The pituitary contains a whole array of hormones that run the show throughout the
rest of the body. The brain controls certain pituitary hormones by stimulating or inhibiting their
release. In fact it is the hypothalamus, which contains a huge array of those releasing and inhibiting
hormones, which instruct the pituitary, which in turn regulates the secretions of the peripheral glands.
Hormones of the stress-response
Two hormones vital to the stress-response are epinephrine and norepinephrine, released by the
sympathetic nervous system. Another important class of hormones are glucocorticoids. These are
steroid hormones, secreted by the adrenal gland and they often act in ways similar to epinephrine. But
epinephrine acts within seconds; glucocorticoids over the course of minutes or
hours.
Glucocorticoid secretion
1. Stressor is sensed or anticipated in the brain
2. Release of CRH by hypothalamus is triggered
3. Hormones enter private circulatory system linking hypothalamus and
anterior pituitary
4. Release of ACTH by anterior pituitary
5. ACTH enters general circulation
6. Release of glucocorticoids by adrenal gland
Other hormones
In addition, in times of stress your pancreas is stimulated to release glucagon.
Glucocorticoids, glucagon and the SNS raise circulating levels of glucose. These
are essential for mobilizing energy during stress.
Prolactin is secreted by the pituitary and plays a role in suppressing
reproduction during stress.
Endorphins and enkephalins (morphine-like) are secreted by the brain and
pituitary, which help blunt pain perception.
Vasopressin (ADH) is secreted by the pituitary and plays a role in the
cardiovascular stress-response.
The secretion of various reproductive hormones is inhibited. As well as growth hormones and insulin.
, It turns out that not all stressors produce the exact same stress-response. The SNS and glucocorticoids
play a role in the response to virtually all stressors. But the speed and magnitudes of the sympathetic
and glucocorticoid branches can vary depending on the stressor. And not all of the other endocrine
components of the stress-response are activated for all stressors. The orchestration and patterning of
hormone release tend to vary at least somewhat from stressor to stressor.
Chapter 3 – Stroke, heart attacks, and voodoo death
Cardiovascular stress-response
First, your heart is beating faster. Which is accomplished by turning down parasympathetic tone end
activating sympathetic part. Glucocorticoids add to this as well: activating neurons in brainstem that
stimulate sympathetic arousal and enhancing the effects of epinephrine and norepinephrine on heart
muscle.
To increase the force, SNS causes the veins that return blood to your heart to constrict. BP goes up.
Arteries are relaxed and dilated: for more bloodflow. But a decrease in blood flow to nonessential
parts. This also includes the flow to your kidneys. In addition, Vasopressin causes the kidneys to
reabsorb the water into the circulatory system.
Chronic stress and cardiovascular disease
First step is developing hypertension. Now your little blood vessels have to work harder to regulate
blood flow. This causes them to build a thicker muscle layer around them, to better control the
increased force of blood flow. Which causes them to become more rigid, more resistant to the force of
blood flow. Which tends to increase the blood pressure etc. etc. hypertension will lead to left
ventricular hypertrophy: the wall thickens with more muscle. Because your heart is now
overdeveloped in one quadrant, it increases the risk of an irregular heartbeat. But the thickened walls
may now require more blood than the coronary arteries can supply
Another place for issues is at the bifurcations, which are vulnerable to injury. With increased BP,
turbulence increases and the walls at the bifurcations are more likely to get damaged. The damage
leads to an inflammatory response atherosclerotic plaques. Form enough of them to obstruct flow to
the lower half of your body and you get claudication, which means your legs and chest hurt for lack of
oxygen and glucose whenever you walk. Or you can get a thrombus: loose plaque.
To measure the amount of inflammatory damage, you can measure the marker CRP. Which is made in
the liver and secreted in response to a signal indicating an injury. It migrates to the damaged vessel,
where it helps amplify the cascade of inflammation. It helps trap bad cholesterol in the inflamed
aggregate. CRP is a better predictor of CVD than cholesterol
Sudden cardiac death
Sudden cardiac death is an extreme version of acute stress causing venrictular arrhythmia of
ventricular fibrillation plus ischemia in the heart. It involves the SNS and is more likely to happen in
damaged heart tissue. People can suffer sudden cardiac death without a history of heart disease.
Diametrically opposite emotions can have similar physiological underpinnings.
Estrogen protects against the formation of atherosclerosis, it doesn’t reverse it. Stress causes estrogen
levels to decline.
Ways to get upset:
1. Acute physical crises
2. Chronic physical challenges
3. Psychological and social disruptions
Sustained psychological stress is a recent invention, mostly limited to humans and other social
primates. For the vast majority of beasts on this planet, stress is about a short-term crisis, after which
it’s either over with or you’re over with. When we sit around and worry about stressful things, we turn
on the same physiological system that has evolved for responding to acute physical emergencies, but
we turn it on for months on end, worrying about mortgages, relationships, and promotions.
Begrippen
Homeostasis: all sorts of physiological measures are being kept at the optimal level. Goal: stability
through constancy.
Stressor: anything in the outside world that knocks you out of homeostatic balance. Or the
anticipation of that happening.
Stress-response: what your body does to reestablish homeostasis/allostasis. The secretion of certain
hormones, the inhibition of others etc. regardless of the stressor, you turn on the same stress-response.
Allostasis: efficient regulation requires anticipating needs and preparing to satisfy them before they
arise. Goal: stability through variation.
Hallmarks of the stress-response: Energy is mobilized and delivered to tissues that need them; long-
term building and repair projects are deferred until the disaster has passed. Pain is blunted, cognition
sharpened.
The stress-response can become more damaging than the stressor itself
Chapter 2 – Glands, gooseflesh and hormones
Autonomic Nervous System
One half of the Autonomic Nervous System (ANS) is activated in
response to stress, the other half is suppressed.
The half that is turned on is the Sympathetic Nervous System.
Originating in the brain, sympathetic projections exit your spine and
branch out to nearly every organ, blood vessel and sweat gland in your
body. The SNS kicks into action during emergencies. It helps mediate
vigilance, arousal, activation, mobilization. (fight, flight, fright, sex). The
nerve endings of this system release epinephrine (adrenaline) and the
closely related norepinephrine (noradrenaline). Epinephrine is secreted
as a result of the actions of the sympathetic nerve endings in your adrenal
glands; norepinephrine is secreted by all other sympathetic nerve endings
throughout the body. These are the chemical messengers that kick various
organs into gear.
,The half that is suppressed is the parasympathetic nervous system (PNS). This component mediates
calm, vegetative activities. It promotes growth, energy storage and other optimistic processes. Rest
and digest.
It would be a disaster if both halves are active at the same time, so lots of safety features exist to make
sure that doesn’t happen. For example, the parts of the brain that activate one branch, typically inhibit
the other.
Neurotransmitters vs. hormones
If a neuron secretes a chemical messenger that travels and causes the next cell in line to do something
different, that messenger is called a neurotransmitter.
If a neuron secretes a messenger that percolates into the bloodstream and affects events far and wide,
the messenger is a hormone.
The peripheral hormone-secreting glands are not autonomous, but are under control of something else:
the pituitary gland. The pituitary contains a whole array of hormones that run the show throughout the
rest of the body. The brain controls certain pituitary hormones by stimulating or inhibiting their
release. In fact it is the hypothalamus, which contains a huge array of those releasing and inhibiting
hormones, which instruct the pituitary, which in turn regulates the secretions of the peripheral glands.
Hormones of the stress-response
Two hormones vital to the stress-response are epinephrine and norepinephrine, released by the
sympathetic nervous system. Another important class of hormones are glucocorticoids. These are
steroid hormones, secreted by the adrenal gland and they often act in ways similar to epinephrine. But
epinephrine acts within seconds; glucocorticoids over the course of minutes or
hours.
Glucocorticoid secretion
1. Stressor is sensed or anticipated in the brain
2. Release of CRH by hypothalamus is triggered
3. Hormones enter private circulatory system linking hypothalamus and
anterior pituitary
4. Release of ACTH by anterior pituitary
5. ACTH enters general circulation
6. Release of glucocorticoids by adrenal gland
Other hormones
In addition, in times of stress your pancreas is stimulated to release glucagon.
Glucocorticoids, glucagon and the SNS raise circulating levels of glucose. These
are essential for mobilizing energy during stress.
Prolactin is secreted by the pituitary and plays a role in suppressing
reproduction during stress.
Endorphins and enkephalins (morphine-like) are secreted by the brain and
pituitary, which help blunt pain perception.
Vasopressin (ADH) is secreted by the pituitary and plays a role in the
cardiovascular stress-response.
The secretion of various reproductive hormones is inhibited. As well as growth hormones and insulin.
, It turns out that not all stressors produce the exact same stress-response. The SNS and glucocorticoids
play a role in the response to virtually all stressors. But the speed and magnitudes of the sympathetic
and glucocorticoid branches can vary depending on the stressor. And not all of the other endocrine
components of the stress-response are activated for all stressors. The orchestration and patterning of
hormone release tend to vary at least somewhat from stressor to stressor.
Chapter 3 – Stroke, heart attacks, and voodoo death
Cardiovascular stress-response
First, your heart is beating faster. Which is accomplished by turning down parasympathetic tone end
activating sympathetic part. Glucocorticoids add to this as well: activating neurons in brainstem that
stimulate sympathetic arousal and enhancing the effects of epinephrine and norepinephrine on heart
muscle.
To increase the force, SNS causes the veins that return blood to your heart to constrict. BP goes up.
Arteries are relaxed and dilated: for more bloodflow. But a decrease in blood flow to nonessential
parts. This also includes the flow to your kidneys. In addition, Vasopressin causes the kidneys to
reabsorb the water into the circulatory system.
Chronic stress and cardiovascular disease
First step is developing hypertension. Now your little blood vessels have to work harder to regulate
blood flow. This causes them to build a thicker muscle layer around them, to better control the
increased force of blood flow. Which causes them to become more rigid, more resistant to the force of
blood flow. Which tends to increase the blood pressure etc. etc. hypertension will lead to left
ventricular hypertrophy: the wall thickens with more muscle. Because your heart is now
overdeveloped in one quadrant, it increases the risk of an irregular heartbeat. But the thickened walls
may now require more blood than the coronary arteries can supply
Another place for issues is at the bifurcations, which are vulnerable to injury. With increased BP,
turbulence increases and the walls at the bifurcations are more likely to get damaged. The damage
leads to an inflammatory response atherosclerotic plaques. Form enough of them to obstruct flow to
the lower half of your body and you get claudication, which means your legs and chest hurt for lack of
oxygen and glucose whenever you walk. Or you can get a thrombus: loose plaque.
To measure the amount of inflammatory damage, you can measure the marker CRP. Which is made in
the liver and secreted in response to a signal indicating an injury. It migrates to the damaged vessel,
where it helps amplify the cascade of inflammation. It helps trap bad cholesterol in the inflamed
aggregate. CRP is a better predictor of CVD than cholesterol
Sudden cardiac death
Sudden cardiac death is an extreme version of acute stress causing venrictular arrhythmia of
ventricular fibrillation plus ischemia in the heart. It involves the SNS and is more likely to happen in
damaged heart tissue. People can suffer sudden cardiac death without a history of heart disease.
Diametrically opposite emotions can have similar physiological underpinnings.
Estrogen protects against the formation of atherosclerosis, it doesn’t reverse it. Stress causes estrogen
levels to decline.
