Circulation Plants and Animals

All organisms need a transport system to transport essential nutrients, water and gases around the body as well as waste products out – both plants and animals This also involves transporting blood around animals. The systems used by different organisms are a reflection of their requirements and structure – the more complex the organism the more complex the system. - intracellular fluid: the fluid in the cells - extracellular fluid: all other fluid in an organism blood contains both intra and extra cellular fluid - Interstitial fluid: the fluid outside the cells but in the tissues

Some organisms have open circulatory systems others have closed. - no blood as such, fluid just circulates throughout the body - tubular heart with open ended vessels - low pressure - long time for the complete circuit - poor pumps, meaning the fluid does not return directly to the heart

Closed: - system of vessels, including arteries and veins/Xylem and phloem in plants - muscular heart - blood is returned rapidly to the heart - higher pressure - blood is seperated from the interstitial fluid - allows the special functions of blood to be possible - not totally closed, some molecules do diffuse through the walls of the vessels (especially the capillaries or small vessels that are only one cell thick) - diffuse from a region of high concentration to low concentration (remember the concentration gradient)

Our Circulation System - Mammals Take your own notes from page 152 onwards to include: - The way blood flows through the heart - The importance/difference between veins and arteries - Value of valves (will need to jump to pg 155-157 too) - Deoxygenated vs oxygenated blood

Blood pressure Pressure is caused by the contraction of the ventricles The right ventricle is thinner than the left and contracts with less force Blood pressure in the right ventricle is less than the left… Why? - blood pressure fluctuates in the arteries with each heart beat - you can feel this when you take your pulse Systolic pressure: the ventricle contracting Diastolic pressure: the relaxation of the ventricles This is the two numbers you are given when you have you blood pressure taken (eg 130/70)

Lymphatic system This system returns the interstitial fluid that leaks out of the capillaries back into the circulation system Once in this system fluid is called lymph Follows a similar route to the circulatory system, but is an open system If you have ever noticed swelling of your ankles if you stand in one spot for a long time, this is the lymph system, causing a problem – the lymph is returned around the body by muscular contractions pressing on the lymphatic vessels. Inactivity means it can’t move it pools. Read about heart attacks on page 159 and complete questions on page 160