Shanvi wants to be a cardiologist when she grows up. And she has started preparing for the same from now! Every day Shanvi takes up a new topic related to the heart and aims to learn all about it. Today, she wants to learn about the heart rate and its different ranges.
We know that you are also looking for different ways to enhance your knowledge. This is why today we are going to help both you and Shanvi learn about the heart rate or human heartbeat per minute.
Human Heart Beat Per Minute
In the simplest terms, the heart rate can be defined as the speed of the heartbeat that is measured by the number of contractions or human heartbeat per minute. The heart rate of an individual can vary according to the physical needs of the body.
Some factors that affect the human heartbeat per minute include:
- The need to absorb oxygen
- Excrete carbon dioxide
- Physical fitness
- Genetics
- Psychological status
- Diet
- Drugs
- Environment
- Hormonal status
- Drugs
- Disease
- Illness
- Stress
According to the American Heart Association, the human heartbeat per minute is usually equal or close to the pulse that is measured at any peripheral point. The normal resting adult human heartbeat per minute is between 60 to 100 bpm.
There are also some conditions that are related to the human heartbeat per minute. For example, if an individual has a low heart rate, then he or she is suffering from bradycardia. If one has an irregularly beating heart rate, then that is known as arrhythmia. These abnormalities are often indicative of other underlying diseases.
Factors Influencing Human Heart Beat Per Minute
We have mentioned some factors in the section above that influence the human heartbeat per minute rate. In this section, we’ll take a closer look at those factors.
- Epinephrine and Norepinephrine
The catecholamines like epinephrine and norepinephrine are secreted by the adrenal medulla to form one component of the extended fight or flight response. The other component involved in this mechanism is sympathetic stimulation.
Epinephrine and norepinephrine have similar effects as they bind to the beta-1 adrenergic receptors and open sodium and calcium ion chemical or ligand-gated channels. The rate of depolarization is increased by the enhanced influx of positively charged ions. This means that the threshold is reached more quickly and the period of repolarization is shortened.
However, if the massive release of these hormones is coupled with sympathetic stimulation, then that may lead to arrhythmias. In this case, there is no parasympathetic stimulation to the adrenal medulla.
- Thyroid Hormones
Usually, increased levels of the thyroid hormones, which are thyroxine (T4) and triiodothyronine (T3), increase the heart rate. Excessive levels of the same hormone can trigger tachycardia.
The impact of the thyroid hormones is usually not of a larger duration than the effect of catecholamines. However, the effect of thyroid hormones also impacts the beta-adrenergic response similar to epinephrine and norepinephrine.
- Calcium
The calcium ions have a large impact on the heart rate and contractility. The increased calcium levels cause an increase in both human heartbeats per minute and contractility of the heart.
High levels of calcium ions have also been known to result in hypercalcemia and further excess levels can induce cardiac arrest. Certain medications are known as calcium channel blockers slow HR by binding to these channels and blocking or slowing the inward movement of the calcium ions.
- Caffeine and Nicotine
It is a widely known fact that caffeine and nicotine are both stimulants of the nervous system. However, what most people don’t know is that caffeine and nicotine also act as a stimulant of the cardiac centers and increases the human heartbeat per minute.
Caffeine works by increasing the rates of depolarization at the SA node. On the other hand, nicotine stimulates the activity of the sympathetic neurons that deliver the impulses to the heart. Both the stimulants are legal and not regulated. Nicotine is very addictive.
Resting Heart Rate
Earlier it was mentioned that the normal human heartbeat per minute is between 60 and 100 beats per minute. But now let’s take a closer look at the normal pulse rates of children and adults. All this is depicted in the table given below.
|
Newborn (0 – 1 Months Old) |
Infants (1 – 11 Months) | Children (1 – 2 Years Old) | Children (3 – 4 Years) | Children (5 – 6 Years) | Children (7 – 9 Years) | Children Over the Age of 10 Years + Adults and Senior Citizens | Well Trained Adult Athletes |
| 70 – 190 | 80 – 160 | 80 – 130 | 80 – 120 | 75 – 115 | 70 – 110 | 60 – 100 |
40 – 60 |
The Physiology
There are a lot of physiological mechanisms involved in regards to the human heartbeat per minute. The heart rhythm is regulated entirely by the sinoatrial node under normal conditions. The heart rate is regulated by sympathetic and parasympathetic input to the sinoatrial node.
The accelerans nerve provides sympathetic input to the heart. This is done by releasing norepinephrine onto the cells of the sinoatrial node (SA node) and the vagus nerve provides parasympathetic input to the input to the heart by releasing acetylcholine onto sinoatrial node cells.
Hence, the stimulation of the accelerans nerve increases heart rate while stimulation of the vagus nerve decreases it. The central nervous system stimulants such as substituted amphetamines increase heart rate.
There are a lot of mechanisms involved in the human heartbeat per minute. However, that is not the concern at the moment. Shanvi has learned a lot today and she wants to continue learning about the heart some other day now. Do you think that your day has been as productive as Shanvi’s day?
