Human Transport System Flashcards Preview

Biology > Human Transport System > Flashcards

Flashcards in Human Transport System Deck (26):

Why do multi-cellular organisms require a transport system?

They are much bigger than unicellular organisms. The latter’s small size means that there is a very short diffusion distance from the outside of the organism to the centre of the organism. They also have a much larger surface area to volume ration. Diffusion is therefore sufficient to supple the cell with essential materials for metabolism (a transport system is not needed).
Multi-cellular organisms being much bigger, diffusion is insufficient to provide all the cells with the required materials. They therefore need to have transport systems to diffuse materials close to the cells that are in need and diffusion can then take over from there.


What does plasma transport and what colour is it?

It is straw-coloured.
It transports:
Digested food
Heat energy
Carbon dioxide


What is the role of platelets?

They are small fragments of cells
When you have a cut, your blood comes into contact with air, stimulating the platelets to release chemicals which trigger the conversion of fibrinogen into fibrin. These fibrin molecules form a network over the cut, sealing it and preventing further blood loss and the potential entrance of pathogens. This seal is a blood clot, and it consists of fibrin molecules and trapped blood cells and platelets.


What is the main role of red blood cells?

To transport oxygen throughout the body.


What are the features of red blood cells?

Bi-conceive shape provides a large surface area to volume ratio for an increased rate of diffusion.
Presence of haemoglobin, a protein that is able to bind to oxygen.
Absence of nucleus provides extra space so the cell can carry more haemoglobin (and therefore more oxygen).


What is the composition of blood?

Red blood cells, platelets and white blood cells hung in suspension in the plasma.


What is the main role of white blood cells?

To provide protection against pathogens.


What are the two types of white blood cell?

Phagocytes and lymphocytes


What are phagocytes?

They can pass easily through blood vessel walls into the surrounding tissue. They ingest pathogens by changing shape, producing pseudopodia (like arms) which engulf the pathogens. Then the cell releases enzymes to digest the pathogen.


What are lymphocytes?

Lymphocytes carry and produce a specific type of antibody (a protein) which fits a specific antigen on a pathogen. These antibodies are ‘custom-made’ to each antigen, allowing them to recognise and bind to a single one. When a lymphocyte with the appropriate antibody meets the antigen, the lymphocyte reproduces quickly to make many copies of the antibody. Attachment of antibodies to the antigen triggers destruction of the pathogen.


How does vaccination work?

A dead or inactive version of the pathogen is injected into the body.
This is harmless, but causes the formation of memory cells (lymphocytes that are now able to recognise a specific pathogen that has previously infected the patient) which stay in the bloodstream. These are able to recognise when the patient is infected with the harmful pathogen again in the future. If this happens, the memory cells multiply and the production of antibodies occurs sooner, faster and in greater quantity so that the pathogen is dealt with immediately. The patient becomes immune.
However, vaccination doesn’t work for every pathogen due to the fact that some change the shape of their antigens each time.


How is immunity against pathogens achieved?

Even after the patient has recovered, a large number of antibodies will remain in the bloodstream. Additionally, some of the lymphocytes become memory cells which are able to recognise a specific pathogen that has previously infected the patient. The remaining antibodies and these memory cells mean that if the patient is ever infected again with this pathogen, it will be dealt with very quickly. The patient is now immune to the disease.


What do veins do?

They carry blood back to the heart.


What do arteries do?

They carry blood away from the heart.


What do valves do?

They prevent blood from flowing backwards.


Describe the journey of blood through the heart.

1. Deoxygenated blood returns to the right atrium from the rest of the body via the vena cava. Oxygenated blood returns to the left atrium from the lungs via the pulmonary vein.

2. The two atria contract.

3. The right atrium forces blood through the tricuspid valve into the right ventricle. The left atrium forces blood through the bicuspid valve into the left ventricle.

4. The two ventricles contract.

5. The right ventricle forces blood out of the heart, through a semi-lunar valve, into the pulmonary artery. The pulmonary artery carries this deoxygenated blood to the lungs to be oxygenated. The left ventricle forces blood out of the heart, through a semi-lunar valve, and into the aorta. The aorta carries this oxygenated blood to the rest of the body to drop off its oxygen.


How does heart rate change during exercise and under the influence of adrenaline?

- Respiring cells (eg. Muscle cells) using up lots of oxygen and nutrients, so a higher rate of blood flow is needed to supply these cells with oxygen/nutrients.
- Heart rate therefore increases during exercise.
- Increase is caused by nervous system and the hormone adrenaline.
- After exercise, the heart rate returns to normal (this occurs faster for physically fit people).


How does the structure of arteries relate to their function?

Function: carry blood away from the heart at high speed under high pressure.
- Branch into arterioles which branch into capillaries.
- Have thick muscle walls. The diameter of the lumen can change to adjust pressure or redistribute blood as the muscle contracts/relaxes.
- Don’t need valves to prevent back-flow of blood as the blood is under such high speed and pressure that it is sure not to move backwards.


How does the structure of veins relate to their function?

Function: carry blood back into the heart at low speed under low pressure.
- Have thinner walls due to less muscle fibres.
- Capillaries (in tissues/organs) converge into venules which converge into veins.
- Have vales to prevent back-flow of blood (which is possible due to the low speed and pressure).


How does the structure of capillaries relate to their function?

Function: carry blood so that every cell in the body has access to the blood flow.
- Walls are only one-cell thick to facilitate diffusion.
- Found in tissues/organs. Every cell in the body is close to one capillary.


What is coronary heart disease?

Coronary heart disease involves the coronary arteries (that supply the heart muscle with the blood) becoming narrow or blocked, resulting in a lack of oxygen delivery to the heart muscle cells.


What are the factors linked to coronary heart disease?

- Obesity
- High blood pressure
- Smoking
- Excess cholesterol


How does obesity increase the risk of developing coronary heart disease?

- Increased weight put strain on the heart.
- This is also linked to diabetes, which can also damage blood vessels.


How does high blood pressure increase the risk of developing coronary heart disease?

- High blood pressure increases the heart's workload, causing the heart muscle to thicken and become stiffer. This stiffening of the heart muscle is not normal, and causes the heart not to work properly.
- This can be reduced by decreasing salt intake and exercising.


How does smoking increase the risk of developing coronary heart disease?

- Chemical substances in the smoke increase the fatty deposits in your artery walls, leading to high blood pressure and increased risk of clotting.
- Carbon monoxide gas in the smoke also reduces the ability of your red blood cells to carry oxygen.


How does excess cholesterol increase the risk of developing coronary heart disease?

- This substance forms part of the plaques that cause the coronary arteries to narrow so that they are more likely to be blocked by a clot.