The Cardiovascular System on Stress || Health : Fitness || LoveLife4you

The Cardiovascular System on Stress.

To keep the body alive, each of its cells must receive a continuous supply of nutrients and oxygen.

At the same time, carbon dioxide and other metabolic wastes produced by the cells must be collected and

disposed of. This dual function is provided by the circulatory system.

Organization of the circulatory system

The circulatory system includes a set of pipes in which the blood circulates. It is organized so that the circuit forms

a loop. The blood always follows the same path: it starts from the heart through the arteries, passes into

the capillaries and returns to the heart through the veins. There are two circuits:

Small circulation (pulmonary circulation)

The blood flows from the right heart through the pulmonary artery to regenerate in the lungs and returns to the

left heart through the four pulmonary veins.

The large circulation (systemic circulation)

The blood flows from the left heart through the aorta, assures its functions in the whole body and returns to the right heart through the inferior and superior cellar veins. In the great traffic we note three important derivations:

  • one who goes to the digestive system then comes back to the heart: nutrition function
  • the other which irrigates the kidneys then returns to the heart: function of excretion
  • the last one that feeds the trunk and legs

Heart: Anatomy

The heart is a hollow muscle, located in the middle of the chest and lodged between the two lungs. It has the shape of a pear measuring about 13 centimeters long and 8 wide.

Its weight in an average adult is about 500 grams. It is covered with a fibrous sac: the pericardium. Its walls consist of muscle fibers and form the myocardium.

In humans, the heart consists of two parts that do not communicate with each other: the right heart and the left heart.

Each heart consists of an upper cavity: the atrium, and a lower cavity: the ventricle. The atrium and the ventricle are separated by a valve.

In the right atrium, the inferior and superior cellar veins abut. In the left atrium, pulmonary veins.

From the right ventricle leaves the pulmonary artery, from the left ventricle the aorta. The myocardium has its own circulatory system: arteries and coronary veins.

Heart mechanics.

Heart revolution

The heart is the seat of periodic changes of form. There is a contraction of the atria followed by that of the ventricles and finally a general rest of the heart. The contraction of the atria or ventricles is named: systole, rest: diastole.These phases are as follows:

  • The two right and left cavities contract at the same time.
  • The phases follow each other in the direction: atrial systole, ventricular systole, diastole.

This cycle repeats itself continuously.

Duration and frequency of cardiac revolution

In men, it is about 120/130 pulsations per minute at the age of 1 year, and is fixed around 75 to 20 years (much less in an athlete).

Intracardiac hemodynamics

The heart, by its contractions, creates pressures in its cavities, so that blood always follows the same path

The filling of cavities

It is fulfilled during the diastole. That of the atrium begins at the beginning of the ventricular systole. That of the ventricle is effected at the opening of the atrioventricular valves. The ventricle receives blood throughout the diastole and not only at the time of systole.

Cardiac output

The flow rate of the heart is equal to the volume of blood expelled. In men and at rest, the volume of systolic ejection is on average 70 milliliters. At a heart rate of 70/80 pulsations, the flow rate is then 5 to 6 liters per minute.

Flow variations

Cardiac output has physiological variations

  • Standing up lowers it, gravity reduces the return of blood to the right heart.
  • ingestion of liquid and digestion increase it.
  • the heat acts in the same way, because of the cutaneous vasodilatation.
  • physical exercise changes the cardiac output considerably.

The cardiovascular system with the effort

Endurance is a basic physical skill. It consists in making the cardiovascular system undergo a prolonged effort with a heart rate at around 150 beats per minute.

Long acquisition, it is maintained for a long time and allows the athlete to develop other physical abilities. The cardiovascular system adapts to this type of work which is a dynamic effort. It is characterized by muscular contractions and relaxations as well as a high respiratory rate.

Consequence of endurance on the cardiovascular system

Heart rate

At the beginning of the effort, the rhythm of the heart accelerates quickly. The most important acceleration is done in less than a minute. Then, during work, the heart rate stabilizes. If the exercise is intense, a second acceleration can take place. The maximum heart rate is 220 beats per minute.

Venous and pulmonary circulation

During the effort, the venous flow increases (effect due to the vasoconstriction of the veins). In the lungs, all the pulmonary alveoli in the upper part (which are not ventilated at rest) are put to work, so that the blood undergoes hematosis (oxygenation of the blood).

Adaptation of the cardiovascular system to the effort

At the beginning of the exercise

There is a lifting of the vagal brake (decrease of the parasympathetic system and increase of the sympathetic system) the heart will beat faster. The nerve impulses come from the psychomotor centers before reaching the heart. This phase is called ‘cardiac catch’.

In the early stages of the exercise

At the active muscle level, the increase in metabolism will dilate the arterioles and cause an opening of all blood capillaries. At resting muscles, arterioles will enter into vasoconstriction. During the effort, the skin layer goes into vasodilatation, in order to increase the blood flow, which facilitates the evacuation of the heat produced by the muscular contraction.

The maintenance phase

The heart rate remains stable. Tachycardia is due to the action of metabolites on the chemoreceptor centers. The heat acts directly as a cardio-accelerator and locally as a vasodilator.

The return to calm

At the end of the exercise, the heart resumes its normal rhythm in two stages:

  • An initial drop in heart rate in less than 2 minutes
  • A secondary fall that brings the pulse back to normal with fluctuating phases.

During this phase, a persistence of tachycardia is observed which is essential. It represents the payment of the oxygen debt. The duration of the return to calm will depend on the following parameters:

  • intensity of exercise
  • fitness of the practitioner
  • ambient heat
  • sportsman stress
  • adaptation of the subject to the effort

Variation of blood pressure during exercise

During the effort, a tension regime is established, a compromise between the hypertension of the territory in vasoconstriction and the braking and hypotensive jolts of the cardio-moderator system.

Warm up

The increase in blood pressure coincides with the increase in heart rate and pulmonary ventilation. The blood pressure reaches 21/10 to 21/12 cm of mercury in 4 minutes.

The second wind

After 10 minutes, the blood pressure stabilizes around 18/11 cm of mercury.

The return to calm

A well-trained athlete returns to normal tension in 45 minutes for a 5000-meter run. If the test was difficult, the maximum voltage drops slightly and returns to normal between 2 and 4 days.

Effects of long-term endurance on the heart

Increased heart volume

The heart like any other muscle is likely to grow with the effort. The athlete’s heart is globular and shows good adaptation to the effort. It is often found that the left heart is hypertrophic with respect to the right heart, with a tendency to lie on the diaphragm. This hypertrophy is due to a greater development of its musculature and the increase of its cavities. At the end of training, it will resume its initial size.

The strength of contractions

In athletes, the quality of the myocardium gives powerful contractions that allow a better volume of systolic ejection.


This is the most important parameter when acquiring endurance. It causes a reduction in the resting heart rate, while keeping the maximum heart rate. The difference between the maximum and minimum frequency allows a wider range of use. This difference is due to an increase in vagal tone.

Pulse taking

This is the only practical sign on the ground that defines the physical fitness in which the effort was made. Reliable pulse is taken by the radial pulse, because that of the carotid pulse can be distorted by the crushing of the jugular vein. To take the most with greater precision, the use of a heart rate monitor is recommended (see heart rate monitor).

Adaptation of the circulatory system to the static effort

During this type of effort, the ribcage is fixed on lungs filled with air, the glottis being closed. The rib cage then becomes a fulcrum.

Changes in the peripheral circulation

At the static contraction of the muscles, the speed of the blood is slowed down. The arterial blood is repressed and the venous return diminished. The heart receiving little blood increases its frequency. At the end of the exercise, a circulatory jolt occurs.

A lot of blood comes to the heart, it increases its frequency and the pressure drops. Then, everything is regularized, the pressure goes up to go down slowly when returning to calm.

This water hammer is detrimental to some shocking territories such as the brain. During the effort, the pulmonary circulatory speed is slowed because of the important intra-thoracic pressure. The right heart is fighting against this increased pressure, which is detrimental to it.

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