SB8 Flashcards
How do humans move the majority of substances into the body?
Diffusuon
How are the diffusion surfaces adapted for quick diffusion?
Thin
Large surface area
Large surface area to volume ratio
Allows for diffusion to happen faster because there’s more surface area for particles to diffuse through
Thin capillaries
The walls of the capillaries are very thin so the substances don’t have very far to diffuse which makes it faster
What do lungs have that make the surface area bigger
Alveoli
1 dm3
1000 cm3
How does concentration gradient affect the diffusion rate
The bigger the difference in concentration, the steeper the concentration gradient, and the faster the rate of diffusion the rate of diffusion is directly proportion to the conc difference
Concentration gradient in lungs maintained
A good blood supply moves oxygen quickly out of the lungs so the concentration gradient is maintain as steep
Surface area
Small particles can pass through membranes in diffusion so when the surface area is increased that means there’s more space for particle particles to fuse. The overall rate of diffusion increases but the rate at which particles pass through each unit area is unchanged so the rate of diffusion is directly proportional to surface area increase
Distance in terms of diffusion
Increasing the thickness of a membrane decreases the rate of diffusion because there is more distance for the particles to defuse. Therefore the rate of diffusion is inversely proportional to the thickness of the membrane. If you double the thickness of the membrane the rate of diffusion would half
What is Ficks law
The rate of diffusion is determined by surface area X concentration
/thickness of membrane
Circulatory system
The blood flows away from heart into arteries which then divide into capillaries that deliver the blood to the tissues and then the deoxygenated blood returns back to the heart from veins
Pulse
When your heart beat it squirts blood into the arteries under a high-pressure. The walls of arteries are thick to withstand this pressure but they stretch. This wave of stretching is felt as a pulse
Veins adaptations
When blood flows towards the heart in veins they flow under low pressure so the walls are thin. Muscles helped to push blood along the veins and to stop the blood backflowing they have valves
Veins have a wide tube and thin walls
Artery adaptations
They have a narrow tube and a thick layer of elastic or fibres in the walls because of the pressure