ch15.1 - neurobiology of stress (background)

something to cheer you up if you’re stressed today:)

who popularized the use of the term “stress”

Hans Selye

Selye’s stress definition

the rate of all wear and tear caused by life (negative emotions)

connection made by Selye between stress and disease

general adaptation syndrome

phases of general adaptation syndrome

1. alarm reaction

2. adaptation stage (appropriate responses and homeostatic balance)

3. exhaustion stage (occurs when there’s prolonged stress → ⬆susceptibility to disease)

better definition of stress

body’s multisystem response to a challenge that overwhelms response mechanisms

stress activates two physiological systems in the body:

1. sympathetic NS

2. hypothalamo-pituitary-adrenal (HPA) axis

sympathetic NS is the ____ that prepares us for emergencies.

fight or flight response

HPA

produces endocrine changes to help us adapt (releases hormones and stuff). predominates if stress is prolonged

when is HPA activated

when info is conveyed into PVH

PVH activates

HPA axis

CRF (corticotropin releasing factor)

peptide synthesized by neurons in PVH

ACTH (adrenocorticotropic hormone)

secreted into bloodstream by cells in anterior pituitary

click to reveal PVH and its peptides/hormones

ACTH role

tells adrenal gland to release cortisol (glucocorticoid hormone)

two types of stress that lead to different PVH pathways

1. physiological stress

2. psychological stress

physiological stress (blood loss, low O2, etc)

brain stem projects to PVH from nucleus of solitary tract/ ventrolateral medulla

psychological stress (predator exposure. public speaking)

pathways more sensory (relayed to limbic regions like hippoc/ prefrontal cortex by avBST). indirect to PVH.

in psychological stress, inputs over PVH are _____ and release “ _____”, to prevent over activation (but HPA⬆)

inhibitory/ breaks

physiological/ psychological stress diagram

cortisol is

primary stress hormone

4 things cortisol does in response to threats from environment

1. ⬆blood sugar (activates glucose metabolism)

2. breaks down fats and proteins (for energy)

3. inhibits immune function (like inflammation)

4. does cognitive adjustments

what does cortisol do when stressor subsides (i.e: you escape a bear)?

cortisol feeds back ontem brain and shuts OFF HPA axis response

steps of how glucocorticoid receptors work (4)

1. CORT diffuses and enters cell through plasma membrane

2. binds to glucocorticoid receptor (GR), CORT-GR forms dimer

3. activated dimer translocates to nucleus

4. binds to DNA to alter gene expression

click to reveal glucocorticoid diagram