BRAINCAKECirculatory Systems
Revision notes for Circulatory Systems in Edexcel Biology (8BI0). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- The Need for Transport SystemsEvery cell needs a supply of substances such as oxygen and glucose, and must get rid of wastes such as carbon dioxide and urea.
- Features of a Mass Transport SystemA mass transport system moves substances in bulk from one part of an organism to another by mass flow: a whole body of fluid moves, carrying…
- Circulation SystemsAnimals with a circulatory system use one of two basic designs: an open or a closed circulation.
- Single Circulation SystemIn a single circulation system, blood passes through the heart once for each complete circuit of the body.
- Double Circulation SystemIn a double circulation system, blood passes through the heart twice for each complete circuit of the body.
- Cardiovascular SystemThe cardiovascular system of a mammal is made up of the heart, the blood vessels and the blood.
- Components of BloodBlood is a tissue made of cells suspended in a liquid.
- PlasmaPlasma is the pale yellow liquid part of the blood, making up about 55% of its volume.
- ErythrocytesErythrocytes (red blood cells) are the most numerous cells in the blood, about 5 million per mm3.
- LeucocytesLeucocytes (white blood cells) defend the body against infection by pathogens and help to remove damaged cells and debris.
- GranulocytesGranulocytes are leucocytes with a granular cytoplasm and a lobed nucleus.
- AgranulocytesAgranulocytes are leucocytes with no visible granules in their cytoplasm and a nucleus that is not lobed.
- PlateletsPlatelets (thrombocytes) are small fragments of cells, about 2 to 3 µm across.
- Haemoglobin and Oxygen TransportMost oxygen is carried in the blood bound to haemoglobin (Hb) in erythrocytes.
- Oxygen Dissociation Curve for HaemoglobinAn oxygen dissociation curve shows the percentage saturation of haemoglobin with oxygen (y-axis) at different partial pressures of oxygen, pO2…
- The Bohr EffectThe Bohr effect (Bohr shift) is the decrease in the affinity of haemoglobin for oxygen when the partial pressure of carbon dioxide (pCO2) is high.
- Fetal HaemoglobinA fetus gets its oxygen from its mother's blood at the placenta.
- MyoglobinMyoglobin is an oxygen-binding protein found in muscle cells, particularly in skeletal and heart muscle.
- Transport of Carbon DioxideCarbon dioxide produced by respiring cells diffuses into the blood and is carried to the lungs in three ways: • about 5% is dissolved in the plasma…
- Blood ClottingWhen a blood vessel is damaged, blood clotting (coagulation) quickly seals the break.
- The Blood Clotting CascadeThe clot that seals a wound is made in a cascade: a series of reactions in which each step produces an enzyme that catalyses the next step.
- Blood VesselsBlood is carried around the body in a closed system of vessels.
- ArteriesArteries carry blood away from the heart.
- ArteriolesArterioles are small blood vessels that branch off arteries and carry blood into the capillary beds of organs and tissues.
- CapillariesCapillaries are the smallest blood vessels.
- Veins and venulesVenules collect blood from the capillary beds.
- Tissue FluidEvery cell in the body is surrounded and bathed by a liquid called tissue fluid.
- Oncotic PressureBlood plasma contains large dissolved proteins, the most abundant of which is albumin.
- Hydrostatic PressureHydrostatic pressure is the pressure a fluid exerts on the walls of its container.
- Arterial End of CapillariesWhether fluid leaves a capillary depends on the balance between two opposing pressures: hydrostatic pressure, which pushes fluid out, and oncotic…
- Venous End of CapillariesAs blood flows along a capillary, it loses fluid and meets resistance, so its hydrostatic pressure falls.
- Formation of LymphMore tissue fluid leaves the capillaries at the arterial end than returns at the venous end.
- Lymph NodesAlong the lymph vessels are small swellings called lymph nodes.