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Gravity In Cardiovascular System

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Gravity is a constant force that influences nearly every aspect of biological activity, to some extent. The gravitational force on organisms follows physical laws that are well-known; thus, the gravity can have predictable effects. There are gravitational forces acting on physiological systems such as the cardiovascular and circulatory systems. Any fluid columns, like blood vessels, are subjected to large pressure gradients when subjected to sudden changes in body posture, especially in humans which are designed for upright posture. There are physiological adaptations in the human cardiovascular system designed to counteract the effects of gravity on the circulatory system under postural changes such as when in a standing, sitting, or lying …show more content…

Therefore, when lying down your blood pressure is similar along your entire body and blood return to the heart is less influenced by the pull of gravity. When you stand for a long period of time without moving, or when you have lain down for a long time and stand up suddenly, you might experience a feeling of faintness or dizziness that
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passes quickly. This slight dizziness is due to the effects of gravity on the cardiovascular system. This sudden posture change from a supine to an upright posture creates a strong vertical gradient of gravitational pull on the fluid (blood) in our circulatory column. The heart is now below the head and neck, and the heart is approximately 2-4 ft above the legs.
Blood pressure decreases briefly in the head and neck while pressure increases in the legs. Furthermore, the increased blood pressure in our lower limbs causes blood to pool in our venous system because the vessels are elastic and stretchy, unlike the rigid-walled arterial vessels. The venous system stores about 80% of your total blood volume while the arterial system stores about 10% at any one time. Thus, the venous system is a blood reservoir.
There are several things that occur in your body when you change from a supine to a standing position quickly: …show more content…

These changes are sometimes accompanied by feelings of dizziness or lightheadedness, and might even lead to fainting (syncope).
When you change quickly from a supine to an upright posture there are several things that your body will do immediately to counteract the change in blood pressure and pooling of blood in the veins. (1) Your heart rate increases and pumps a greater volume of blood. This will increase blood pressure (BP) so that you avoid fainting. (2) The valves in your veins maintain a one-way flow of blood to the heart which aids venous return of blood to the heart. (3) Your skeletal muscles contract and help compress the veins providing resistance to pooling of blood. These muscle twitches act much like a flight suit of jet pilots which squeeze the body and provide resistance to the elastic-walled veins. (4) The nervous system elicits several compensatory and autonomic responses to restore normal blood volume and pressure.
Your medulla oblongata has two autonomic centers: the cardiac and vasomotor center. The cardiac center responds

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