Читать книгу Understanding Anatomy and Physiology in Nursing - John Knight - Страница 101

By the age of 50 around 50–75 per cent of the pacemaker cells of the heart’s natural pacemaker SAN have been lost, while the cardiac muscle fibres of the atrioventricular bundle (bundle of His) undergo varying degrees of fibrosis. These changes may reduce the efficiency of cardiac conduction and contribute to the increased risk of ectopic beats (palpitations) seen in older people.