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
Capillaries adaptations
They’re only one cell thick so this allows faster diffusion because there’s less distance for it to the fuse out of. And it has a very narrow tube
Valves and how they work
When your muscles contract the valves in the direction that the blood is moving towards the heart open so the blood can be pushed through it by the muscles and the valves that it has just passed through closes to stop the blood flowing back down due to gravity. When your muscles are relaxed your valves are closed
What do we find in blood
Red blood cells are called erythrocytes
White blood cells
Platelets
And all of these are suspended in plasma which also carries dissolved substances like glucose co2 and urea
Red blood cells and adaptations
Red blood cells have lots of haemoglobin in them which binds to oxygen in the lungs and releases it again in the tissues. The more oxygen that is bound to haemoglobin the brighter red the cells are.
Red blood cells have no nucleus so there is more space for the haemoglobin. They have a biconcave shape that allows for a large surface area to volume ratio which increases the rate of diffusion
White blood cells and adaptations
There are different types of white blood blood cells.
Phagocytes surround foreign cells and digest them
Lymphocytes remove foreign cells and produce antibodies that help fight illness.
Platelets
Platelets are fragments of cells and they have no nucleus. They produce substances to clot the blood when you are injured
4 chambers of the heart
 Right atrium left atrium and right ventricle left ventricle
Hearts structure and works
Blood from the body enters the right atrium through the vena cava. Blood that comes from the lungs enters the left atrium through the pulmonary vein. When both these chambers are full the muscles contract to push the blood into the ventricles. The muscles in the ventricle walls contract which forces the blood out of the heart. This keeps repeating and the muscles in the atrium walls relax and they refill with blood continuing the cycle. There are valves in the heart that stop blood flow in the wrong way.
Cardiac output (litres per min)
Stroke volume X heart rate
Effects of regular excercise on heart
Muscle under ventricle size get bigger so people who are fitter often have a bigger stroke volume and the heart can beat slower to still achieve the same cardiac output the heart isn’t having to work harder
Cellular respiration
A series of chemical reactions that release energy from glucose
Respiration is
Exothermic because energy is transferred out of the cells by heating to keep the animals warm
What happens in terms of respiration during excercise
Your muscles need more energy so the rate of aerobic respiration increases because your muscle cells are taking more oxygen and glucose from your blood. Your heart beats faster to get more blood to your muscles, you breathe faster to increase the amount of oxygen that’s coming into your lungs and therefore going into your bloods, and the fast action of breathing also allows your lungs to get rid of more carbon dioxide
Benefits/ disadvantages of anaerobic respiration
B: releases burst of energy without needing a sudden increase in oxygen supply, this is important if you need to run away from a predator
It releases less energy and it can cause muscles to tire quickly and you need extra oxygen afterwards to get rid of the lactic acid
