Define stress and provide references.

Stress is a physiological response to a perceived threat or challenge that triggers the body's "fight or flight" response. It can be caused by various factors such as work pressure, financial problems, relationship issues, or traumatic events. Chronic stress can have negative effects on both physical and mental health, leading to conditions such as anxiety, depression, high blood pressure, and heart disease.

References:
1. American Psychological Association. (n.d.). Stress effects on the body. Retrieved from https://www.apa.org/topics/stress/body
2. Mayo Clinic. (2020). Stress symptoms: Effects on your body and behavior. Retrieved from https://www.mayoclinic.org/healthy-lifestyle/stress-management/in-depth/stress-symptoms/art-20050987

Definition of Stress

Stress is a psychological and physiological response to perceived threats or demands. It is the body's way of adapting to the challenges and pressures of life.

Physiological Response to Stress

When a stressor is encountered, the body activates the "fight or flight" response, which triggers the release of hormones such as cortisol and adrenaline. These hormones cause:

- Increased heart rate and blood pressure
- Dilated pupils
- Increased respiration
- Tensing of muscles
- Increased release of glucose into the bloodstream

Psychological Response to Stress

Stress can also lead to psychological reactions, such as:

- Anxiety
- Panic
- Irritability
- Difficulty concentrating
- Sleep problems
- Cognitive impairment

Chronic Stress

When stress becomes chronic, it can have a significant impact on physical and mental health. Chronic stress has been linked to:

- Cardiovascular disease
- Stroke
- Diabetes
- Obesity
- Depression
- Anxiety disorders
- Sleep disorders
- Cognitive decline

References

- American Psychological Association. (2017). Stress in America: Coping with stress. Retrieved from: https://www.apa.org/topics/stress/coping-stress
- National Institute of Mental Health. (2018). What is stress? Retrieved from: https://www.nimh.nih.gov/health/topics/stress/index.shtml
- McEwen, B. S., & Gianaros, P. J. (2011). Stress- and allostasis-induced brain plasticity. Annual Review of Medicine, 62, 431-445.
- Segerstrom, S. C., & Miller, G. E. (2004). Psychological stress and the human immune system: A meta-analytic study of 30 years of inquiry. Psychological Bulletin, 130(4), 601-630.