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Gravity: The effects of gravity on venous return seem paradoxical because when a person stands up, hydrostatic forces cause the right atrial pressure to decrease and the venous pressure in the dependent limbs to increase. This increases the pressure gradient for venous return from the dependent limbs to the right atrium; however, venous return ...
When the astronauts return to Earth, low blood volume can cause orthostatic intolerance or dizziness when standing. [82] Under the influence of the earth's gravity, when a person is standing, blood and other body fluids are pulled towards the lower body, increasing pressure at the feet. When gravity is removed, hydrostatic pressures throughout ...
Additional factors associated with the return to Earth's gravity may also be implicated. This, the observed diminished stroke volume (cardiac output) is certainly contributory and, in turn, is a reflection of diminished venous return and contracted effective circulating blood volume induced by spaceflight factors. [9]
As blood is pumped through the body, the valves within the veins prevent the blood from flowing backwards. After extensive, prolonged standing, these valves can become weak and eventually fail. When this happens, blood is no longer being prevented from flowing backward. Gravity will pull the blood back into an individual's legs, ankles and feet.
Mean blood pressure drops over the whole circulation, although most of the fall occurs along the small arteries and arterioles. [35] Gravity affects blood pressure via hydrostatic forces (e.g., during standing), and valves in veins, breathing, and pumping from contraction of skeletal muscles also influence blood pressure in veins. [32]
The venous hypertension also contributes to the head swelling seen in photos of astronauts and the nasal and sinus congestion along with headache noted by many. There is also subsequent venous hypertension in the venous system of the eye which may contribute to the findings noted on ophthalmic exam and contributing to the visual disturbances noted.
"ESPN Return Man has already proven itself as an incredibly fun hit for millions wanna-be return men on ESPN Arcade, so it only made sense to bring it to the growing audience of Facebook gamers ...
Gravitational biology is the study of the effects gravity has on living organisms. Throughout the history of the Earth life has evolved to survive changing conditions, such as changes in the climate and habitat. However, one constant factor in evolution since life first began on Earth is the force of gravity.