IGCSE›Cambridge IGCSE Biology›Mind mapsHeartCambridge IGCSE Biology: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsStructureTwo atria receive bloodTwo ventricles pump blood outSeptum divides left and right sidesCoronary arteries feed the heart muscleValvesAtrioventricular valves: between atria and ventriclesSemilunar valves: at the exits of the ventriclesBoth are one-wayWall thicknessLeft ventricle wall is thickestIt pumps blood round the whole bodyRight ventricle only pumps to the lungsVentricles thicker than atriaHeartstructure and functionCardiac cycleAtria contract – blood into ventriclesVentricles contract – AV valves shut, semilunar openRelax – semilunar valves shut, atria refillHeart rateMeasured by ECG, pulse, or valve soundsExercise increases heart rateMuscles need more oxygenRegular exercise lowers resting rateHeart diseaseCoronary arteries narrowed or blockedRisks: smoking, poor diet, lack of exercise, stressAlso age, sex and geneticsPrevent with healthy diet and exercise