Practise IB Biology HL 3.1.5 through exact HL questions on respiratory muscle coordination, thoracic pressure, spirometry and exercise ventilation.
Explain the mechanism of ventilation of human lungs.
Marking guidance:
Award these points either for inspiration or expiration but not both: ventilation is movement of air into and out of lungs; volume of thorax/lungs/chest increased/decreased; pressure in thorax/lungs/chest decreased/increased; air flows from higher to lower pressure / air flows until the pressures are equal;
During inspiration/inhalation: external intercostal muscles contract so ribcage moved up/out; diaphragm contracts so moves down/becomes flatter; internal intercostal/abdomen (wall) muscles relax;
During expiration/exhalation: external intercostal muscles relax so ribcage moved down/in; diaphragm relaxes; recoil of elastic fibres that stretched during inspiration;
internal intercostal muscles contract (during forced ventilation); abdomen (wall) muscles contract (during forced ventilation);