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Is there a relationship between heart rate and blood pressure?



Dear Adam,

It is a dynamic relationship. For example, the heart rate and blood pressure tend to both increase during exercise, and decrease during sleep. On the flip side, if a person receives a medication that raises blood pressure, such as phenylephrine, the heart rate can decrease.

The pulse rate is the count of heart beat and normal range is 60 to 100. Blood pressure is the pressure generated by the heart (systolic) and the resistance offered by the circulation (diastolic). The two are independent of each other.

When the heart beats, it pumps blood to the arteries and creates pressure in them.
This pressure (blood pressure) results from two forces. The first force is created as blood pumps into the arteries and through the circulatory system. The second is created as the arteries resist the blood flow.

Your blood pressure can change from minute to minute, with changes in posture, exercise or sleeping, but it should normally be less than 120/80 mm Hg (millimeters of mercury) for an adult.

Heart rate variability depends on both vagal and sympathetic influences. However, only the former component affects BP variability. The vagus nerve is responsible for such varied tasks as heart rate.

The Sympathetic Nervous System (SNS) is a branch of the autonomic nervous system along with the enteric nervous system and parasympathetic nervous system.

It is always active at a basal level (called sympathetic tone) and becomes more active during times of stress. Its actions during the stress response comprise the fight-or-flight response.

Roger Bannister (the man who ran the first "4-minute Mile") had a resting pulse rate of about 55 bpm. His CO was normal, -just over 5 liters/minute-, and his stroke volume (SV, the volume of blood pumped from one ventricle of the heart with each beat), therefore was just over 90 ccs. He most certainly wasn't hypertensive. When tested at rest (after the race, and he had relaxed to normal pulse rate again) his BP was recorded as 135/ 75 mms/Hg, giving a Mean of 95.

Blood pressure increases will increase heart rate in intact chick embryos, prior to the development of neural control. Similarly, in surgically isolated hearts, increases in intraventricular fluid pressure will increase the rate of beat. However, fluid pressure applied equally to both interior and exterior surfaces of the isolated heart does not result in increased heart rate.

The increased pressure stretches the heart muscle and that this stretch stimulates the increased heart rate.
While heart rate is clearly influenced by blood pressure, the reverse is not true. Propranolol reduces the heart rate to about half normal in intact embryos but does not significantly alter the blood pressure.

It should be healthy to have a low heart rate. No one knows for sure, but in the animal kingdom it is observed that animals that have lower heart rates frequently live longer.

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