IB 110 Chap.6 Homeostasis and the Biology of Stress
Homeostasis and the Biology of Stress
Balance inside the body
The second discussion section introduces homeostasis as the body's internal balance, the process of keeping a stable internal environment. The slides break it into three components.
A receptor detects a change in some variable, a control center, such as the brain or spinal cord, receives that information and sends a signal, and an effector produces a change that moves the variable back toward its normal range. Body temperature and blood sugar are familiar examples of variables held in range this way.
Stress as a disruption
The slides define stress as the disruption of homeostasis.
It is a normal human response to an internal or external threat, and it can be prompted by stressors. The response to a stressor, which the slides also call allostasis, is the fight-or-flight reaction: stress hormones such as adrenaline and cortisol are released, the heart beats faster, airways widen and the senses sharpen.
In the short term this helps the body meet a challenge.
What stress does over time
The discussion lists effects of stress on the body: lower immune defences, loss of appetite, headaches, insomnia, anxiety or depression, and stomach and gastrointestinal problems, along with muscle tension, fatigue and chest pain.
These are the costs of a response that is switched on often.
Why stress is unequal
The key step for this course comes next. Stress, and what it does to health, does not land equally on everyone. Genes play a part, but social, economic and environmental conditions weigh heavily on health disparities.
The slides map social determinants of health, including race, education, income, gender, environment and access to food and wellness, onto outcomes such as unsafe housing, low wages, isolation, trauma and psychological stress.
Read with the biology in mind, many of these outcomes are stressors that some people meet every day and others rarely meet at all.
How the chapter links forward
Homeostasis gives the course a biological route from environment to health.
When later units discuss polluted air, heat or contaminated water, the same question applies: what stressor is present, who meets it more often, and what does repeated activation of the stress response do to the body?
What this chapter covers
- 01
Homeostasis defined
- 02
Receptor, control center and effector
- 03
Stress as disrupted balance
- 04
The fight-or-flight response
- 05
Adrenaline and cortisol
- 06
Effects of stress on the body
- 07
Social factors behind unequal stress
Worked example · free
Walk a homeostatic loop step by step
- 1Name the receptor and its role.
- 2Describe the control center and effector response.
- 2Link working conditions to the load on the loop.
Key terms
- Receptor
- The part of a homeostatic loop that detects a change in a variable and reports it to the control center.
- Control Center
- The part of a homeostatic loop, such as the brain, that receives information and signals a response.
- Effector
- The part of a homeostatic loop that produces the change returning a variable to its normal range.
- Stressor
- An internal or external prompt, such as noise or threat, that disrupts homeostasis.
- Cortisol
- A stress hormone released during the stress response, named in the discussion alongside adrenaline.
Homeostasis and the Biology of Stress FAQ
What are the three parts of homeostasis?
A receptor that detects a change, a control center that receives the information and signals, and an effector that produces the change bringing the variable back into range.
Is stress always harmful?
No. The discussion calls it a normal response to a threat, and the short-term fight-or-flight reaction helps the body cope. Harm comes from frequent or continuous activation, which the slides link to weakened immunity, insomnia and anxiety.
How does homeostasis connect to health disparities?
Social, economic and environmental conditions decide how often people meet stressors. Groups exposed more often to unsafe housing, discrimination or insecure work activate the stress response more, which can widen health gaps.
Exam move
Draw the homeostatic loop from memory with its three labelled parts. Then add one environmental stressor from each unit of the course and write how it enters the loop and who meets it most often.
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