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Physical Education - What controls the heart rate?
What controls the heart rate?
Unlike skeletal muscle, which is under voluntary control, the heart is an
involuntary muscle. Most of us cannot just tell our heart to slow down or
speed up (biofeedback training not withstanding). The beating frequency
(heart rate) is controlled by the balance of stimulation coming from the
_sympathetic_ and _parasympathetic_ branches of the _autonomic nervous
system_. Both nervous inputs to the heart converge on a small area of
tissue on the right atrium called the _sinoatrial node_.
Parasympathetic (rest and recover) stimulation tends to slow down the
rate, while sympathetic (fight or flight) input increases the rate (and the
force of contraction). Normally, there is a balance between the two inputs,
leaning toward the parasympathetic side. However, even without any nervous
input, the heart will beat automatically, due to some unique features of
its membrane [1] physiology. This intrinsic rate is quite slow, however
(about 20 bpm). A purely parasympathetic stimulation will result in a heart
rate of about 30.
Elite endurance athletes may have resting heart rates of 35 to 40.
So the average untrained person has a resting heart rate of about 70 as a
result of some constant sympathetic stimulation. With training, the heart
receives less sympathetic stimulation at rest, resulting in a slower
resting heart rate. Elite endurance athletes may have resting heart rates
of 35 to 40. Values of 28 have been reported!
Heart rate is usually in direct ratio to body size. An elephant has a very
low HR of 10-15 bpm at rest, whereas a budgerigar may have a resting HR as
high as 1,000 bpm. Imagine the size of the stroke volume [2] of the
elephant!
The initiation of activity results first in a withdrawal of the
parasympathetic stimulation (up to a heart rate of about 100), followed by
an increase in sympathetic stimulation with more intense activity up to the
maximum heart rate.
maximal heart rate [3]
No, the maximum heart rate is not increased by training [4]! (As we get
older, our maximum heart rate decreases). The major difference in the
endurance-trained heart is a bigger stroke volume [5]. The trained heart
gets bigger and pumps more blood each beat.
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If we do more training, we can get bigger heart with bigger stroke volume.
What controls heart rate?
What controls the heart rate? Unlike skeletal muscle, which is under voluntary control, the heart is an involuntary muscle. Most of us cannot just tell our heart to slow down or speed up Both nervous inputs to the heart converge on a small area of tissue on the right atrium called the sinoatrial node. Normally, there is a balance between the two inputs, leaning toward the parasympathetic side. However, even without any nervous input, the heart will beat automatically, due to some unique features of its membrane physiology. So the average untrained person has a resting heart rate of about 70 as a result of some constant sympathetic stimulation. With training, the heart receives less sympathetic stimulation at rest, resulting in a slower resting heart rate. Elite endurance athletes may have resting heart rates of 35 to 40. Values of 28 have been reported! Heart rate is usually in direct ratio to body size. An elephant has a very low HR of 10-15 bpm at rest, whereas a budgerigar may have a resting HR as high as 1,000 bpm. Imagine the size of the stroke volume of the elephant! The initiation of activity results first in a withdrawal of the parasympathetic stimulation (up to a heart rate of about 100), followed by an increase in sympathetic stimulation with more intense activity up to the maximum heart rate. Will training make maximal heart rate increase?
Which things control the heart rate?