Stress Flashcards
What are the stress responses?
- Saliva production decreases
- Surface blood vessels constrict, draining blood from skin
- Heart rate increase
- Stomach enzymes decrease
- Muscles become tense
- Pupils of eyes dilate
- Breath becomes fast
- Peristalsis slows down and can stop
- Deep blood vessels dilate to allow more blood flow to muscle
How does long-term stress affect your immune system?
- The immune system protects the body from infection ○ Invading bacteria ○ Viruses ○ Foreign bodies - Derives from white blood cells ○ Bone marrow – B lymphocytes ○ Thymus gland – T lymphocytes - Stress – via cortisol – can directly suppress the activity of the DEimmune system
What are the effects of chronic stress?
- Muscles of body – constant state of guardedness
- Tension-type headache/ migraines
- Long-term heart/ blood problems
- Hypertension
- Heart attack
What is the effect of chronic stress on healing?
Kiecolt-Glaser et al., 1995
- Wounds of people under stress take longer to heal.
What happens when you encounter a threat?
When you encounter a threat structures in the brain trigger a stress response.
A slow response occurs through the HPA axis and a fast change through the ANS.
What are the 3 components of the HPA axis?
- Hypothalamus, located in central brain, releases hormone called Corticotrophin Releasing Hormone into bloodstream.
- Receptors in pituitary gland, detect circulating CRH, causing the release of Adrenocorticotropic Releasing Hormone or ACTH into bloodstream.
- Adrenal gland located on top of kidneys detects the circulating ACTH and as a result, release hormone cortisol into bloodstream.
Role of cortisol in the body in response to stress.
○ Cortisol is anti-inflammatory. If cut local inflammatory processes provide an immediate reaction: WBCs heal wound.
○ Cortisol levels peak ~10-30 minutes after start of stressor, allowing initial inflammation processes to occur before cortisol promotes resolution.
○ Cortisol can help regulate blood pressure and blood sugar.
○ Cortisol is involved in managing use of carbohydrates, fats and proteins.
○ Cortisol acts on the hypothalamus to downregulate the release of CRH and ACTH preventing cycle of CRH - ACTH - Cortisol from continuing endlessly.
What is the role of the adrenal glands?
- Sit on top of your kidneys
- Release a set of hormones involved in stress:
○ Cortisol is released in response to ACTH - Metabolism (increases blood glucose)
- Immune system suppression (anti-inflammatory effect)
- Reduces release of CRH and ACTH from hypothalamus and pituitary gland, respectively.
- Epinephrine
Chronic exposure to stressors leads to a sequence of 3 stages. What are they?
Alarm
Resistance
Exhaustion
Describe the Alarm stage in the Chronic exposure to stressors.
- Arousal of the Autonomic Nervous System
- Primarily during first encounter with stressor
○ Resistance to stressor drops below normal with potential for shock - At this point, hormones like epinephrine & cortisol are released into the bloodstream
- Sympathetic nervous system activated.
Describe the Resistance stage in the Chronic exposure to stressors.
- Continued exposure to stressor
○ Resistance – Parasympathetic system returns physiological functions to normal levels
○ Blood glucose, epinephrine & cortisol all remain high
○ Heart rate, blood pressure, breathing all increased - Over time, resistance to stressor increases, levels out at normal levels.
- Resistance = adaptation to environmental stressors
Describe the Exhaustion stage in the Chronic exposure to stressors.
- If stressor continues beyond body’s capacity, stressor depletes available resources.
- Loss of ability to adapt to situations
- Susceptible to illness, and even death
Effects of prenatal stress on metabolism.
- Pregnancy during famine
○ Foetus ‘learns’ that food is scarce
○ Metabolism of foetus has permanent shift
→ “Metabolic imprinting”
○ Afterwards, foetus becomes good at storing consumed food, retaining salt from diet.
○ Developed ‘thrifty’ metabolism
Effects of postnatal stress
Plotsky & Meaney, 1993
○ maternal separation of rats
○ As adults, rats showed increased glucocorticoid response to stress.
§ Greater fearfulness
Stress in infancy can reduce growth hormones – lower adult height
Romanian orphanages Gunnar et al., 2001 - Compared daytime cortisol measures in children from: ○ Romanian orphanages for >8 months ○ Romanian orphanages for <= 4 months ○ Canadian children Studied at 7-8 years old
Effect of chronic stress on brain structure in rats.
If there is chronic stress in rats there is a loss in structure if the limbic regions of the brain.
