MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

CHAPTER 5. BLOOD AND LYMPH CIRCULATION PROCESSES AND THEIR PATHOLOGY

CARDIAC ACTIVITY

4. HEART RATE

In a healthy adult, The Heart beats an average of 70 times per minute. The heart rate depends on numerous factors. This parameter increases sharply during physical exertion, emotional stress, and elevated body Temperature.

The heart rate increases in young people during inspiration, a phenomenon known as respiratory sinus arrhythmia. Heart rate is also influenced by body position: it is highest in the standing position, lower when sitting, and even slower in the supine position.

Heart rate varies with age. In newborns, it reaches up to 140 beats per minute, in 1-year-old children it is 100-120, at age 10 it is 80, at age 20 it ranges from 60 to 80, and in elderly individuals it increases again to 90-95 beats per minute.

An increase in heart rate is referred to as tachycardia, while a decrease is called bradycardia. Bradycardia is most commonly observed in trained athletes at rest, averaging 40-50 beats per minute (known as the "Napoleon pulse").

Heart rate is regulated by The Nervous system and Hormones. For instance, it increases under the Influence of the sympathetic nerves and the thyroid hormone thyroxine. Conversely, the parasympathetic nerve (the Vagus nerve) slows down Cardiac Activity.

The Cerebral Cortex also influences heart rate. This explains the occurrence of pre-start tachycardia in athletes.