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Summary Alevel AQA biology unit 6 - control of heart rate
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Summary notes for the control of heart rate.
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3.6.1.3 Control of heart rateThe heart is made up of a tissue known as the myogenic tissue, this means it can initiate its own
contraction without help from the nervous system.
There are 4 phases of the cardiac cycle:
1. Atrial systole – atria contracts and pumps blood into ventricles. Aortic and semilunar valves
are closed
2. Ventricular systole – ventricles contract and pump blood into the aortic and pulmonary
trunks. Aortic and mitral valves are opened at beginning and closed after ventricular
contraction. Atrioventricular valves are closed
3. Atrial diastole – atria relax and blood flows in via systematic and pulmonary veins
4. Ventricular diastole – atrioventricular valves open and ventricular cardiac muscles relax and
blood flows in passively.
Heart rate process
The right atrium walls is where the sinoatrial node is, this node is what starts the wave of electrical
stimulation
1. The sinoatrial node produces a wave of electrical stimulation – SAN sends a wave of
electricity to the atrial walls which causes the atria to contract at approximately the same
time
2. The signal passes down the atrial septum – atrioventricular septum prevents wave of
electricity form reaching ventricles. SAN passes wave of excitation passes to AVN
3. The atrioventricular node (AVN) conducts an electrical wave to ventricles - AVN passes wave
of electricity between ventricles along muscle fibres called Purkyne tissue, this makes up
structure called bundle of His.
4. Bundle of His transmits the wave to the base of heart – it goes through atrioventricular
septum to base of ventricles where bundle breaks up into Purkyne tissue
5. Electricity passes up the Purkyne fibres – this allows ventricles to contract form base up,
which allows ventricles to fully empty, pushing blood into aorta and pulmonary artery
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