Transport in mammals and the heart

Learning objectives

• Trace pressure-driven circulation.
• Explain haemoglobin oxygen transport.
• Interpret cardiac output.

The big idea

The cardiac cycle coordinates atrial and ventricular contraction with pressure-sensitive valves. Electrical excitation begins in pacemaker tissue and spreads through a conduction system; valves open because of pressure differences rather than active pulling.

Haemoglobin’s cooperative oxygen binding supports loading at high oxygen partial pressure and unloading in respiring tissues. Carbon dioxide is transported mainly after conversion to hydrogencarbonate, with additional dissolved and haemoglobin-associated forms. Vessel structure matches pressure, return and exchange roles.

Investigate and explain

Using the worked example as supplied data, predict the effect of changing one condition. Draw a labelled model, record your reasoning and identify a variable that would need controlling. No human, animal or microbial experiment is required.

No exact PhET model is claimed for this topic. Use diagrams and supplied-data reasoning instead.

Open the interactive investigation

Check your understanding