Body Design Principle
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38 Terms
Why does the circulatory system exist?
It exists to overcome diffusion limits by transporting oxygen, nutrients, and waste in large organisms.
What is the main function of the cardiovascular system?
To deliver oxygen, nutrients, and signals and remove carbon dioxide, heat, and waste.
What is homeostasis?
The process of maintaining a stable internal environment.
Who introduced the concept of homeostasis?
Walter Cannon.
Where do cells live in the body?
In interstitial fluid.
What are the three components of homeostasis?
Receptor, control center, effector.
What does a receptor do?
Detects changes from a set point.
What does the control center do?
Processes information and decides a response.
What does the effector do?
Carries out the response.
What is negative feedback?
A response that reverses a change to return to normal.
What is positive feedback?
A response that amplifies a change.
Give an example of negative feedback.
Insulin lowering blood glucose.
Give an example of positive feedback.
Labor contractions or blood clotting.
What is the surface area to volume relationship?
Surface area increases as x² and volume increases as x³.
What happens to SA:V ratio as size increases?
It decreases.
Why is SA:V ratio important?
It determines how efficiently materials can be exchanged.
How do organisms increase surface area?
By folding or branching structures.
Examples of high surface area structures?
Alveoli, villi, capillaries.
What is diffusion?
Movement of molecules from high to low concentration.
What equation describes diffusion distance?
x = √(D × t)
How does diffusion time relate to distance?
Time increases with the square of distance.
How long does diffusion take over 100 µm?
About 1 second.
How long does diffusion take over 1 cm?
About 3 hours.
How long does diffusion take over 1 meter?
About 3 years.
Why is diffusion alone not enough?
It is too slow over long distances.
What is bulk flow?
The rapid movement of fluids driven by pressure.
What does the circulatory system use for long distances?
Bulk flow.
What does the body use diffusion for?
Short-distance exchange at capillaries.
How close are capillaries to cells?
About 100 micrometers.
Why are lungs thin?
To allow fast diffusion of oxygen.
What is the main limitation of diffusion?
It becomes very slow over long distances.
Why do large organisms need circulatory systems?
Because diffusion cannot supply cells efficiently.
What is the main role of capillaries?
To allow exchange between blood and tissues.
What powers the circulatory system?
The heart.
What regulates the circulatory system?
Homeostatic mechanisms.
What happens as organism size increases?
They need transport systems due to lower SA:V ratio.
What is the key idea of circulatory systems?
Bring exchange surfaces close to every cell.
What is the core argument for circulation?
Diffusion is fast for short distances but too slow for large bodies, so bulk transport is required.