Explain the difference between open and closed circulatory systems + single/double.

open system: blood is not confined to blood vessels and comes into direct contact with tissues and cells closed system: blood confined within blood vessels - single: blood passes through the heart once during each circulation - double: blood passes through the heart twice during each circulation

Name the different types of blood vessels and their adaptations and function.

arteries: - carry oxygenated blood away from the heart - thick muscular wall allows it to withstand high pressure - elastic tissue stretches and recoils to smoothen pressure fluctuations arterioles: - link the arteries and the capillaries - controls blood flow to tissues by using its smooth muscle in its walls to do vasodilation/constriction capillaries: - link the arterioles to the venules - oxygen leaves blood through capillary walls - one cell thick endothelium for hort diffusion distance - very narrow lumen which slows blood flow venules: - link the capillaries with the veins - thin walls for short diffusion distance veins: - carry deoxygenated blood to the heart (except pulmonary vein) - thin walls - valves prevent backflow of blood

Explain the process of tissue fluid formation.

- blood enters capillary from arterioles at high pressure - this increases hydrostatic pressure in capillary walls - the pressure forces water and small solutes out of the capillary walls, forming tissue fluid - solutes in the blood increase oncotic pressure in the blood, causing some of the water to move back into the blood via osmosis - hydrostatic pressure is lower at venule end - this causes water to move back into the capillaries through osmosis due to the oncotic pressure in the blood - extra tissue fluid drains into the lymphatic system

Describe the lymphatic system.

- tissue fluid drains into lymphatic system through lymph capillaries, now called lymph - lymph passes through lymph nodes, which can activate lymphocytes in the lymph and produce the immune response

Describe cooperative binding of oxygen to haemoglobin.

- haemoglobin is highly folded, making it hard for the first oxygen molecule to bind - the first oxygen molecule binding causes the haemoglobin to change shape, which exposes other haem groups, increasing the affinity for oxygen, causing binding to speed up rapidly - it becomes harder for the final oxygen molecule to bind because most of the binding sites have been taken up

Describe the Bohr effect.

- active, respiring tissues produce high levels of carbon dioxide, lowering blood pH - this alters the tertiary structure of the haemoglobin, reducing affinity for oxygen and making unloading more efficient

Explain the difference in affinity of oxygen in fetal haemoglobin compared to adult.

- fetal haemoglobin has a higher affinity for oxygen because oxygen saturation in the blood is much lower by the time it reaches the placenta and the fetus relies on its mothers blood for oxygen

Describe the electrical coordination of the heart.

- SAN generates electrical impulse - this causes the atria to contract - impulse reaches AVN - AVN introduces a delay so that the atria can finish contracting - impulse travels down Bundle of His which conducts the impulse to the apex of the heart - impulse reaches Purkyne fibres - ventricles contract from the apex of the heart upwards

Describe the cardiac cycle.

diastole: - blood enters heart through the vena cava and pulmonary veins - blood flows passively into ventricles because of their low pressure atrial systole: - atria contract, causing their pressure to become higher than the pressure in the ventricles - this forces the remaining blood into the ventricles ventricular systole: - ventricles contract, causing their pressure to become high than the pressure in the atria - the pressure increase also causes the atrioventricular (AV) valves to close, preventing backflow of blood - pressure keeps rising until it exceeds the pressure in the arteries - this causes the semilunar valves to open and blood to be forced into the aorta and pulmonary artery