Homeostasis and Stress (Learning Objectives)
1. Define homeostasis. Give two examples.
-Homeostasis is when the body strives for constancy despite changes in internal and external
environments.
-Example 1: Blood glucose regulations
-Example 2: Body temperature
(Negative feedback control mechanism and positive feedback control)
2. Define stress and differentiate endogenous and exogenous sources. Name 3 categories of stressors.
-Stress is the body’s response to stimuli that place an intense demand on it, representing a real
or perceived threat to homeostasis.
-Endogenous sources are stressors that originate within the body, often due to genetic,
biological, or internal physiological factors such as illness, hormonal imbalance, chronic pain.
-Exogenous sources arise from outside the body, caused by environmental, social, or physical
factors such as loud noise, relationship conflict, job loss.
3 Categories of stressors:
1. Acute time-limited
2. Chronic intermittent
3. Chronic sustained
3. Describe the 2 components of the generalized neuroendocrine response to stress.
- The body’s response to stress has two main components: the SAM system and the HPA axis.
The SAM system acts quickly, releasing adrenaline and norepinephrine to increase heart rate,
blood pressure, and energy for immediate “fight or flight” action. The HPA axis responds more
slowly, releasing cortisol to raise blood sugar, suppress non-essential functions, and help the body
cope with prolonged stress. Together, they provide both immediate and sustained adaptation to
stress.
4. Define the role of cortisol in the stress response. Contrast the advantages and disadvantages of this
response.
-Cortisol is a glucocorticoid hormone released via the HPA axis (CRF → ACTH → cortisol)
that regulates metabolic, cardiovascular, immune, and behavioral responses during stress.
It maintains blood glucose, enhances catecholamine effects on the cardiovascular system, and
modulates immune activity. Cortisol acts as both a mediator of the stress response and an
inhibitor via negative feedback on the hypothalamus and pituitary.
Advantages:
Sustains energy supply by maintaining blood glucose.
Enhances cardiovascular response to catecholamines.
Helps regulate inflammation and immune activity.
Supports adaptation to prolonged stress.
