Topic 1- Notes

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What is Cardiovascular Disease?

Cardiovascular diseases (CVDs)- Diseases of the HEART and CIRCULATION

The main forms of CVD are:

- Coronary heart disease (CHD)

- Stroke

Why Have a Heart and Circulatory System?

The heart and circulation- Responsible for moving substances around the body

In small organisms- which have shorter distances- Substances (oxygen, carbon dioxide, digestive products) move around by DIFFUSION.

DIFFUSION: The RANDOM movement of MOLECULES or IONS from and area of HIGH concentration to an area of LOW concentration.

In small organisms- diffusion is fast enough to meet the organisms requirements.

In large, multicellular organisms- Diffusion is not quick enough to support the large organisms requirements. This means they rely on a MAS TRANSPORT SYSTEM to move substances over a larger distance, using MASS FLOW.

The Different Circulatory Systems:

OPEN circulatory system: In INSECTS and other animal groups

- The blood circulates in large open spaces.

- A simple heart pumps blood out and into cavities surrounding the animals organs.

- Substances diffuse between the blood and the cells.

CLOSED circulatory system: Many animals including ALL VERTEBRATES

- The blood is enclosed within tubes (BLOOD VESSELS)

- Blood pressure is higher as it is forced along narrow vessels.

- High blood pressure means that blood travels faster so it is more efficient at delivering substances.

BLOOD FLOW:

- The blood leaves the heart under pressure and flows along the ARTERIES and then the ARTERIOLES to the CAPILLARIES.

- There are lots of capillaries. They surround the cells and organs so substances can be exchanged between the blood and the cells.

- After passing along the capillaries the blood returns to the heart through the VENULES and then the VEINS.

- Valves ensure that blood flows in one direction (Prevents BACKFLOW)

Animals with a closed circulatory system can have wither single or double circulation.

SINGLE circulatory system: FISH

- The blood flows through the heart once for each complete circuit of the body.

BLOOD FLOW:

- The heart pumps DEOXYGENATED blood to the gills.

- Gaseous exchange takes place in the gills- CO2 diffuses from the blood into the water and OXYGEN, from the water, diffuses into the blood.

- The blood in the gills then flows around the rest of the body before returning to the heart.

DOUBLE circulatory system: BIRDS and MAMMALS

BLOOD FLOW:

- The right ventricle pumps deoxygenated blood to the lungs where it receives oxygen.

- The oxygenated blood then returns to the heart o be pumped to the rest of the body by the left ventricle.

Birds and mammals have a high metabolic rate as blood circulates round the body quickly and the oxygen and food substances required for metabolic processes can be delivered rapidly.