Biology of Stress Flashcards
Definition of stress
A biological response to +ve/-ve triggers which leads to SNS and hypothalamic pituitary adrenal axis activation
What is stress
What are the 2 most potent stressors
What 2 systems does it activate
P+ve/-ve triggers => physiological mechanism
Potent stressors
- emotions (joy, anger, fear)
- expectations
Activates SNS and hypothalamic pituitary adrenal (HPA) axis
What 5 brain areas are involved in HPA
Amygdala Hypothalamus Pituitary gland Prefrontal cortex Hippocampus
What is the function of the amygdala
How many can be found in the brain
Receives threat and danger info and conveys emotional info => other brain regions via corticotrophin releasing factor
1 found in each side
What is the function of the hypothalamus and pituitary
Helps control emotional reactions, feeding, drinking
Emotional responses organised here trigger hormonal secretion in the pituitary
What is the function of the hippocampus
How many can be found in the brain
Organises memory storage and memory retrieval in cortex
1 found in each side
What is the function of the prefrontal cortex
Frontal most region of frontal cortex
Planning and organisation of behaviour based on use of working memory
What is the function of the adrenal glands
What do they release and where from
ACTH released by pituitary acts on adrenal glands
Cortisol released from zona fasciculata into the blood
Where are the cortisol binding sites found
Glucocorticoid receptors on
- hypothalamus
- hippocampus
- pituitary
- pre frontal cortex
Describe the pathway in the HPA
What type of feedback loop is this
Amygdala receives threatening stimuli => CRF onto hypothalamus
Hypothalamus involved in emotional reaction => CRF onto pituitary
Pituitary => ACTH into bloodstream
Adrenal cortex => cortisol into bloodstream
Cortisol acts on glucocorticoid receptors and stimulates
- prefrontal cortex
- hippocampus
Cortisol acts on glucocorticoid receptors and inhibits
- pituitary
- hypothalamus
Hippocampus and prefrontal cortex fire AP on and inhibit hypothalamus
NEGATIVE FEEDBACK
Compare the normal HPA function vs abnormal function in chronic stress
Baseline levels of cortisol always secreted but broken down by bloodstream enzymes
Constant barrage of glucocorticoids => death of receptors and cells
–ve feedback system fails => +ve feedback
Describe the fight or flight response invovled in the stress response
Hypothalamus stimulates SNS
Adrenal medulla releases adrenaline
Peripheral SNS releases NA
Both lead to
- increased HR, BP
- iris contracts => larger pupil
- decreased gut motility
PNS calms body down
