Stress and Health Flashcards
stress
When the body is exposed to harm or threat –> cluster of physiological changes: stress response—or just stress.
stressors
Are experiences that veroorzaken the stress response.
Produce the same core pattern of physiological changes, whether psychological or physical
Hans Selye’s description of stress in 1950
In the short term, it produces adaptive changes that help the animal respond to the stressor (e.g., mobilization of energy resources); in the long term, however, it produces changes that are maladaptive (e.g., enlarged adrenal glands).
anterior-pituitary adrenal-cortex system
- Stressors acting on neural circuits stimulate the release of adrenocorticotropic hormone (ACTh) from the anterior pituitary
- This triggers the release of glucocorticoids from the adrenal cortex
- > Glucocorticoids(cortisol) produce many of the components of the stress response.
- > The level of circulating glucocorticoids is the most commonly employed physiological measure of stress.
sympathetic-nervous-system adrenal-medulla system
Stressors activate the sympathetic nervous system, thereby increasing the amounts of epinephrine and nor-epinephrine released from the adrenal medulla.
Selye’s –> only one stress response = simplification
Stress responses are complex and varied, with the exact response depending on
- the stressor
- its timing
- the nature of the stressed person
- and how the stressed person reacts to the stressor
cytokines
- Peptide hormones released by many cells.
- Participate in a variety of physiological and immunological responses, causing inflammation and fever.
- Classified with the adrenal hormones as major stress hormones.
1990s –> important advances in understanding stress response
- Stressors produce physiological reactions that participate in the body’s inflammatory responses.
- Stressors produce an increase in blood levels of cytokines.
2 problems of animal research for stress
- ethics, creating stressful situations which are over the top
- studies that use extreme, unnatural forms of stress are often of questionable scientific value.
subordination stress
- When threats from conspecifics (members of the same species) becomes an enduring feature of daily life, the result is subordination stress.
- Most easily studied in social species that form dominance hierarchy.
psychosomatic disorders
medical disorders in which psychological factors play a causal role
gastric ulcers
- Painful lesions at the lining of stomach and duodenum -> can be life-threatening.
- Bacteria Helicobacter pylori infection alone is insufficient to produce the disorder in most people.
- Gastric ulcers occur more commonly in people living in stressful situations, and stressors can produce gastric ulcers in laboratory animals.
bullying
the chronic social threat that veroorzaakt subordination stress in the members of many species
psychoneuroimmunology
The study of interactions among psychological factors, the nervous system, and the immune system.
Body’s 4 lines of defense to keep it from being overwhelmed by microorganisms
- Behavioral immune systems: Humans avoid contact with individuals who are ill. Bodies respond more aggressively to infection when they perceive signs of infection in others.
- Variety of surface barriers. Major one is skin, but other mechanisms include coughing, sneezing, tears, mucous(slijm), and numerous chemical barriers.
- If microorganisms do manage to breach the surface –> the innate immune system
- and the adaptive immune system. Together, called the immune system
Innate immune system
- Reacts quickly and generally near points of entry of pathogens to the body.
- Is triggered when toll-like receptors bind to molecules on the surface of the pathogens or when injured cells send out alarm signals.
- Complex, but general(all pathogens same reaction) reaction
Pathogens
disease-causing agents
Inflammation
- One of the first reactions of the innate immune system to the invasion of pathogens
- Is triggered by the release of chemicals from damaged cells –> Particularly influential are cytokines, they attract leukocytes and other phagocytes into the infected area.
- Cytokines promote healing of the damaged tissue once pathogens are destroyed.
Leukocytes
White blood cells
Phagocytes
Cells that engulf(opslokken) and destroy pathogens
Microglia
Phagocytes that are specific to the central nervous system
Phagocytosis
- Destruction of pathogens by phagocytes
- Thought to be one of the first immune reactions to have evolved.
- Phagocytes have been identified in alle gewervelde en niet gewervelde dieren that have been examined.
Adaptive immune system
- evolved more recently, first appearing in early gewervelde dieren.
- is slower; its immune reaction to pathogens takes longer to be fully manifested.
- is specific –> reacts against specific antigens.
- has a memory; second time meeting a pathogen –> reacts more effectively
Lymphocytes
- Are produced in bone marrow and the thymus gland, stored in the lymphatic system until activated.
- 2 major classes of lymphocytes:
- -> Cell-mediated immunity is directed by T cells (T lymphocytes);
- -> Antibody-mediated immunity is directed by B cells (B lymphocytes).
Cell-mediated immunity –> T cells
Reaction begins when phagocyte ingests foreign microorganism.
–> The phagocyte displays microorganism’s antigens on the surface of its cell membrane –> this attracts T cells.
T cell has 2 kinds of receptors on its surface,
- for molecules normally found on surface of phagocytes and other body cells
- for a specific foreign antigen.
There are millions of different receptors for foreign antigens on T cells, but there is only one kind on each T cell, and there are only a few T cells with each kind of receptor.
Once a T cell with receptor for foreign antigen binds to surface of an infected macrophage, a series of reactions is initiated.
- Multiplication of the bound T cell to destroy all invaders that contain the target antigens and all body cells that have been infected by the invaders.
Antigens
Molecules, usually proteins, that can trigger an immune response
Antibody-mediated immune reaction
Begins when B cell binds to foreign antigen for which it contains an appropriate receptor. –> B cell multiplies and makes a deadly form of its receptor molecules (antibodies). –> released into intracellular fluid, where they bind to foreign antigens and destroy or deactivate the microorganisms that possess them.
Memory B cells for the specific antigen produced during the process; accelerate(versnellen) antibody-mediated immunity in same situation
Vaccination
Involves administering a weakened form of a virus so that if the virus later invades, the adaptive immune system is prepared to act against it.
Immunization
The process of creating immunity through vaccination
Name the 2 events that helped clarify relation between
stress and immune function.
- Meta-analysis of Segerstrom and Miller (2004)
2. Discovery of the bidirectional role played by the cytokines in the innate immune system.
Distress
Stress that disrupts health or other aspects of functioning
Eustress
stress that improves health or other aspects of functioning
Meta-analysis of Segerstrom and Miller (2004)
Effects of stress on immune function depend on the kind of stress:
- Brief stressors (lasting less than 100 minutes) –> improvements in innate immune function.
- Chronic (long-lasting stress: taking care of sick relative) –> adversely affected the adaptive immune system.
Discovery of bidirectional role played by cytokines in innate immune system.
- Short-term cytokine-induced inflammatory responses help the body combat infection
- Long-term cytokine release associated with a variety of adverse health consequences
Stress produces widespread changes in the body through its effects on the…
- Anterior-pituitary adrenal-cortex system
- Sympathetic-nervous-system adrenal-medulla system
- Innumerable mechanisms by which those systems can influence immune function.
Name the behavioral routes by which stress can affect immune function
- People under severe stress often change their diet, exercise, sleep, and drug use, any of which could influence immune function.
- Behavior of a stressed or ill person can produce stress and illness in others. —–> Wolf and colleagues (2007) found that stress in mothers aggravates asthmatic symptoms in their children; conversely, asthma in the children increases measures of stress in their mothers.
3 reasons why stress-produced decreases in immune function may not be reflected in an increased susceptibility to infectious disease.
- The immune system has redundant(overvloedige)components –> disruption of 1 has little or no effect on vulnerability to infection.
- Stress-produced changes in immune function may be too short-lived to have substantial effects on the probability of infection.
- Declines in some aspects of immune function may induce compensatory increases in others.
Direct causal link between stress and susceptibility to infectious disease –>
3 basic types of evidence are persuasive(overtuigend):
- Correlational studies in humans have found correlations between stress levels and numerous measures of health.
- Controlled experiments conducted with laboratory animals show that stress can increase susceptibility to infectious disease in these species.
- A few partially controlled studies of humans have added greatly to the weight of evidence.
One of the first partially controlled studies demonstrating stress-induced increases in the susceptibility of humans to infectious disease
- Conducted by Cohen and colleagues (1991).
- Using questionnaires, they assessed psychological stress levels in 394 healthy participants. Then, each participant randomly received zoutoplossing nasal drops that contained a ademhaling virus or only zoutoplossing. Then, all of the participants were quarantined until the end of the study. A higher proportion of those participants who scored highly on the stress scales developed colds.
Research on the role of early experience in the development of the stress response –> rats
- Handling of rat pups by researchers for a few minutes per day during the first few weeks of the rats’ lives thought to have variety of salutary (health-promoting) effects
- Liu and colleagues (1997) –> handled rat pups are groomed (licked) more by their mothers: the salutary effects resulted from the extra grooming, rather than from the handling itself. Unhandled rat pups that received a lot of grooming from their mothers developed the same profile of less glucocorticoid release that was observed in handled pups.
Stress has been shown to…(hippocampus)
- Reduce dendritic branching in the hippocampus
- Reduce adult neurogenesis in the hippocampus
- Modify the structure of some hippocampal synapses
- Disrupt the performance of hippocampus-dependent tasks
Why is hippocampus particularly susceptible to stress-induced effects?
Dense population of glucocorticoid receptors in the hippocampus.
- > Induced by corticosterone(a major glucocorticoid)
- > Blocked by adrenalectomy (surgical removal of the adrenal glands).
