Animal transport 1.2.2

Single circulatory system = blood passes through heart once per circuit of body; double = twice. Double sytem advantage = pressure is maintained so will flow quickly meaning oxygen and glucose get delivered to tissues quickly. Closed circulatory system = blood in vessels. Maintains presure and increases flow. Insects have a large SA:vol ratio so have an open system
Control of heart beat. SAN = pacemaker - initiates heart beat. Sends wave of excitation over atria walls. AVN delays impulse then sends the impulse down the Purkyne fibres to make sure the venticles contract from the apex upwards. This short delay is vital to allow time for the atria to fully contract and the ventricles to fill - and so the ventricles do not contract too early. By contracting from the apex up it ensures efficient empying of the ventricle.
Blood pressure (hydrostatic pressure - generated in ventricular systole) = highest in arteries since closest to heart. Fluctuations in pressure are a result of ventricular systole and diastole. Pressure = lowest in veins and capillaries since further from heart. No fluctuations in pressure - blood is spread over a much greater cross-sectional area
Heart structure - left ventricle = thickest as it pumps to whole body; right ventricle 2nd thickest = pumps to lungs; atria thinest walls - only pump to ventricles.
1. Know the heart structure and locations of atrioventricular and semilunar valves
2. Valves - ensure one-directional flow. Valves close when pressure builds to stop backflow. e.g. atrioventricular valve stops when ventricular systole startsd so blood moves to aorta and not back into atrium. Semilunar valve shuts when pressure in aorta is greater than ventricel to stop backflow into ventricle.
3. Arteries - folded endothelium so can stretch during ventricular systole; elastic tissue so can recoil during diastole. Smooth muscle so the narrow lumen of artery can be contricted further to maintain pressure. Thick artery walls + collagen for strength.
4. Veins - valves to prevent backflow (pressure is less); large lumen.
Tissue fluid - at arteriole end of capillary, plasma moves out of capillary to form tissue fluid. Fluid moves out due to pressure gradient. Tissue fluid enables glucose and oxygen to reach cells and waste products to travel back to blood.
1. Not all tissue fluid will return directly to the capillary. Some becomes lymph. Lymph contains lymphocytes to filter bacteria and foreign particles - part of the immune system.
2. Blood - high pressure in arteries; lower in veins/capillaries; proteins present; red blood cells present; white blood cells present.
  1. Tissue fluid - low pressure; no red blood cells; some white blood cells; no proteins.
    1. Lymph - like tissue fluid but with lymphocytes =specific white blood cell.
ECG trace = electrocardiogram = shows electrical activity of heart. Heart rate = look at time from start of one peak to the next. Do 60 divided by this time to get heart rate.
Dissociation curves
1. Fetal curve is to the left. Fetal haemoglobin has a higer affinity for oxygen than maternal haeomoglobin. This means it takes up oxygen at a lower partial pressure of oxygen. At lower partial pressures of oxygen, the maternal oxyhaemoglobin will dissociate in the placenta - the fetal haemoglobin will pick this oxygen that has dissociated from the maternal haemoglobin.
2. Actively respiring tissue is to the right (Bohr effect) which means oxyhaemoglobin dissociates more readily. Actively respiring tissue has more need for oxygen so that aerobic respiration can release more energy. Actively respiring tissue also produces more CO2. This CO2 is converted to H+ ions which have a greater affinity for haemoglobin than the oxygen. The H+ causes oxygen to dissociate from the haemoglobin and takes its place forming reduced haemoglobin.

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Animal transport 1.2.2

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