1 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
2 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.
3 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
4 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.
4.1 Know the heart structure and locations
of atrioventricular and semilunar valves
4.2 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
4.3 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
4.4 Veins - valves to prevent backflow (pressure is less); large lumen.
5 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.
5.1 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
5.2 Blood - high pressure in arteries; lower in veins/capillaries;
proteins present; red blood cells present; white blood cells
5.2.1 Tissue fluid - low pressure; no red blood cells; some
white blood cells; no proteins.
220.127.116.11 Lymph - like tissue fluid but with lymphocytes =specific white blood cell.
6 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.
7 Dissociation curves
7.1 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
7.2 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