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.
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.
the heart beats, it pumps blood to the arteries and creates pressure
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 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.
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.
Nervous System (SNS) is a branch of the autonomic nervous system along
with the enteric nervous system and parasympathetic nervous system.
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.
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.
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.
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.
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.