PSY 340 Brain and Behavior
Class 29: Stress and Health [Outline]
I. Stress and the Autonomic Nervous System
- Hans Seyle (1907-1982)
- Stress = the response of the body to any demand put upon it.
- pleasant (e.g., getting married) and unpleasant (e.g., death of a loved one, financial difficulties)
- General Adaptation Syndrome: A generalized response by the body to continued stress which comes in three stages
- Stage 1: Alarm
- Stage 2: Resistance
- Stage 3: Exhaustion
II. Stress, the HPA Axis, & the Immune System
- (1) autonomic nervous system and (2) the HPA Axis (hypothalamus-pituitary gland-adrenal cortex)
- The hypothalamus sends CRF (corticotropin releasing factor) to the pituitary gland which secretes ACTH (adrenocorticotropic hormone) into the bloodstream which, when it reaches the adrenal cortex, stimulates the production of cortisol. When operating normally, elevated levels of cortisol serve in a negative feedback loop to suppress the further production of CRF and ACTH. Thus, cortisol inhibits its own secretion. The hippocampus appears to be a major neural structure to inhibit the HPA axis; hence, damage to the hippocampus would be expected to upset the normal functioning of the axis.
- Cortisol & the Brain: Negative Effects
- Functional: High cortisol and lowered memory
- Structural: Smaller hippocampus among elderly & multiple lowered levels of grey matter among middle-age adults
- Alzheimer's disease: lowered brain volume, lowered brain metabolism, may accelerate disease process, high cortisol as biomarker for decline
Effects of Stress on the Immune System
Cytokines: combat infections and also communicate with the brain
- These prompt the development of a fever
- Increased sleep, decreased muscle activity, and decreased sex drive conserve energy
- Decreased appetite might be helpful by curbing the need to work to provide food
Strong, inescapable, and temporary stresses trigger similar responses to those caused by an illness: fever, sleepiness, decreased appetite & sex drive
Brief stress causes SNS arousal and HPA Axis arousal: in the short run, these strengthen the body.
Long-term or chronic stress, anger, or anxiety leads to harm of the body, e.g.,
- Prolonged cortisol release seems to limit the synthesis of immune system cell proteinss
- Antarctic researchers over 9 months of cold, dark, and isolation show reduced T-cells functions (ca. 50% of normal).
- Individuals with 4 or more weeks of stress are more likely to become sick.
- Severe child maltreatment by their parents by the age of 3 demonstrated significant negative alterations in the overall connectivity patterns in the development of the white matter of their brains
This page was first posted April 7, 2005.