Problem 8
Pinel + Carlson
When the body is exposed to harm or threat, the result is a cluster of physiological
changes generally referred as the stress response or just stress.
All stressors (experiences that induce stress responses) produce the same core
pattern of physiological changes – whether psychological or physical. Hans Selye first
described the stress response.
In short term it produces adaptive changes that help the animal respond to the
stressor but in long term it produces changes that are maladaptive.
Selye attributed stress response to the activation of the anterior-pituitary adrenal
cortex system. The neurons of the paraventricular nucleus of the hypothalamus
(PVN) secrete a peptide called corticotrophin-releasing hormone (CRH) which
stimulates the release of adrenocorticotropic hormone (ACTH) from the anterior
pituitary. Then, ACTH triggers the release of glucocorticoids from the adrenal cortex
and then the glucocorticoids produce many of the component of the stress response.
The level of circulating glucocorticoids is the most commonly employed physiological
measure of stress.
A stress related glucocorticoid is cortisol, it has profound effects in glucose
metabolism. Glucocorticoids help to break down protein and convert it to glucose,
help make fats available for energy, increase blood flow, stimulate behavioral
responsiveness.
Stressors also activate the sympathetic nervous system and increase the amount of
epinephrine and norepinephrine released from the adrenal medulla.
Epinephrine affects glucose metabolism, causing nutrients stored in muscles to
become available to provide energy.
The stress-induced release of norepinephrine in the brain is controlled by a pathway
from the central nucleus to the locus coeruleus (the nucleus of the brain stem that
contains norepinephrine secreting neurons). Norepinephrine is also secreted in the
brain as a neurotransmitter.
Both epinephrine and norepinephrine increase blood pressure and in the long term
contribute to cardiovascular diseases.
There is good evidence that all kinds of common psychological stressors act like
physical stressors. But stress responses are complex and depend on the stressor,
timing, the nature of the person, how the person reacts etc.
Stressors produce an increase in blood levels of cytokines (a peptide hormone group
that participate in immunological and inflammatory responses). The cytokines are
now classified with adrenal hormones as major stress hormones.
Animals
Problems with animal experiments of stress: 1) ethical issues 2) extreme, unnatural
variations in the stress response, difficult to relate to common human stressors
Better animal models of stress are studies with social threat from conspecifics
(members of the same species). When conspecific stress becomes an enduring
feature of daily life (especially for males), the result is subordination stress. This
forms dominance hierarchies. Subordinate male rodents who are continually
attacked are more likely to attack juveniles, have smaller testes, shorter life spans,
lower testosterone etc. – they’re almost bullied.
Pinel + Carlson
When the body is exposed to harm or threat, the result is a cluster of physiological
changes generally referred as the stress response or just stress.
All stressors (experiences that induce stress responses) produce the same core
pattern of physiological changes – whether psychological or physical. Hans Selye first
described the stress response.
In short term it produces adaptive changes that help the animal respond to the
stressor but in long term it produces changes that are maladaptive.
Selye attributed stress response to the activation of the anterior-pituitary adrenal
cortex system. The neurons of the paraventricular nucleus of the hypothalamus
(PVN) secrete a peptide called corticotrophin-releasing hormone (CRH) which
stimulates the release of adrenocorticotropic hormone (ACTH) from the anterior
pituitary. Then, ACTH triggers the release of glucocorticoids from the adrenal cortex
and then the glucocorticoids produce many of the component of the stress response.
The level of circulating glucocorticoids is the most commonly employed physiological
measure of stress.
A stress related glucocorticoid is cortisol, it has profound effects in glucose
metabolism. Glucocorticoids help to break down protein and convert it to glucose,
help make fats available for energy, increase blood flow, stimulate behavioral
responsiveness.
Stressors also activate the sympathetic nervous system and increase the amount of
epinephrine and norepinephrine released from the adrenal medulla.
Epinephrine affects glucose metabolism, causing nutrients stored in muscles to
become available to provide energy.
The stress-induced release of norepinephrine in the brain is controlled by a pathway
from the central nucleus to the locus coeruleus (the nucleus of the brain stem that
contains norepinephrine secreting neurons). Norepinephrine is also secreted in the
brain as a neurotransmitter.
Both epinephrine and norepinephrine increase blood pressure and in the long term
contribute to cardiovascular diseases.
There is good evidence that all kinds of common psychological stressors act like
physical stressors. But stress responses are complex and depend on the stressor,
timing, the nature of the person, how the person reacts etc.
Stressors produce an increase in blood levels of cytokines (a peptide hormone group
that participate in immunological and inflammatory responses). The cytokines are
now classified with adrenal hormones as major stress hormones.
Animals
Problems with animal experiments of stress: 1) ethical issues 2) extreme, unnatural
variations in the stress response, difficult to relate to common human stressors
Better animal models of stress are studies with social threat from conspecifics
(members of the same species). When conspecific stress becomes an enduring
feature of daily life (especially for males), the result is subordination stress. This
forms dominance hierarchies. Subordinate male rodents who are continually
attacked are more likely to attack juveniles, have smaller testes, shorter life spans,
lower testosterone etc. – they’re almost bullied.
