Ex3 L11 - Immune System and Stress Flashcards
What is the evolutionary goal of cortisol?
survive a short term stressor
What is cortisol and what are its effects?
- glucocorticoid hormone released by the adrenal glands in response to stressors
- increased sympathetic NS activity (associated changes)
- mobilize energy sources (glycogenolysis by muscle, gluconeogenesis by the liver, lipolysis of fat, and proteolysis by muscle)
- suppresses immune response (anti inflammatory in the short term, impairs wound healing)
Synthetic analogs of cortisol are…
cortisone and prednisone
Describe the HPA axis
hypothalamus releases CRH, stimulates anterior pituitary to release ACTH, stimulates adrenal gland to release cortisol, which has metabolic effects
Cortisol has negative feedback on the anterior pituitary, hypothalamus, and the stressor
In relation to the HPA axis, chronic stress can…
override the negative feedback to the hypothalamus and cortisol remains elevated, causing long term suppression of the immune system
7 effects of cortisol are:
- weakened immune system
- heart disease
- high blood pressure
- high blood sugar
- digestive issues
- nerve problems
- anxiety, depression, and headaches
Chronic stress relates to telomeres because…
chronic stress is correlated with accelerated shortening of telomeres in humans (and therefore accelerated aging)
- perceived stress is strongly correlated, regardless of absolute stress
What stressors have shown to decrease telomerase activity and increase oxidative stress?
loneliness, long term unemployment, untreated depression, chronic phobic anxiety
What effect does reducing stress have?
slows telomere shortening
What is allostasis?
restoring homeostasis in response to stress (maintaining stability through change)
What is the allostatic load?
effort to maintain stability (the wear and tear on your body from responding to stressors)
What effect does aging have on allostatic load?
increases allostatic load
- homeostenosis means that physiological reserves are narrowed, so it causes more wear and tear to maintain stability under stresses)
Allostatic load increases the…
cell’s energy expenditure (and therefore the energy mobilization)
- leads to more ROS and mitochondrial breakdown, which causes inflammation
Increased allostatic load increases age-related disease like:
- cognitive decline
- cardiovascular disease
- insulin resistance and obesity
- late life depression and anxiety
What is innate immunity?
- first line of defense that is non-specific
- physical barriers: epithelial and mucosal linings
- macrophages, natural killer cells, etc.
What is adaptive immunity?
- activated by innate immune response
- react to specific pathogens
- mediate by lymphocytes (T and B)
In terms of immune system, aged individuals have…
- increased risk of infection, cancer, and autoimmune disease
- decreased incidence of organ transplant rejection and wound repair
- chronic low grade inflammation (inflammaging)
What is immunosenescence?
- complex changes the occur with age and reduce immune system function
What are B lymphocytes?
- derived from bone marrow, mature in the spleen
- important for antigen processing and presentation
- differentiation into plasma cells for antibody secretion
How do B lymphocytes change in aged individuals?
- less circulating B cells
- reduced B cell diversity
- lower production of memory B cells
What are T lymphocytes?
- derived from bone marrow, mature in the thymus
- high proliferative potential with long lifespan
- defense against intracellular pathogens
- help B cells generate an antibody response
How do T lymphocytes change in aged individuals?
- hyporesponsive T cells
- reduced T cell diversity
- lower production of new T cells
- accumulation of senescent T cells
- appearance of hybrid T cell/natural killer cells
What is the thymus?
- gland in the mediastinum
- secretes thymosin that plays a role in T cell maturation
- destroys autoreactive lymphocytes using negative selection (central tolerance)
- peripheral tolerance is also involved for regulatory T cells
How does the thymus change with age?
thymic involution -
- begins shortly after birth, not induced by senescence as once was thought
- T cells also decrease, but not to the same level as thymic involution
