Answer:
When you sit on a plane for 6 hours without moving, blood accumulates in your veins, and the moment you get up, gravitational forces affect venous return, cardiac output, blood pressure, and venous pressure. That way, when you're sitting on a plane, the gravitational force is the same at the upper and lower extremities, such as the chest, abdomen, and legs, causing venous blood pressure and volume to be evenly distributed throughout the body. However, when one gets up, one becomes dizzy because of abnormal regulation of blood pressure. This is because gravity causes blood to accumulate in the lower extremities (veins of the legs and trunk). This lowers the blood pressure and the blood that the heart pumps. By causing blood to accumulate in the lower extremities, and as venous compliance increases, the veins expand with blood that causes the volume of blood to shift in the veins. This increases the volume and venous pressure in the lower extremities when standing. And the volume of thoracic venous blood is less and less central venous pressure. This leads to a decline in stroke volume. Cardiac output and mean arterial pressure also decrease as left ventricular stroke volume decreases, reducing pulmonary venous return. Decreased standing blood pressure, referred to as orthostatic or postural hypotension. Thus, lowering blood pressure decreases cerebral blood flow, which means less range of blood in the brain causing dizziness.
Explanation:
False. The subunits are dependent on the cell itself, and they cannot survive on their own.
Answer:
Hotspot
Explanation:
Volcanoes can form in three different places: a convergent boundary, a divergent boundary, or a hot spot.
-At a convergent plate boundary, two plates collide and form a subduction zone. In the subduction zone, the denser, heavier plate goes below the more buoyant plate. The plate that goes under is subjected to immense heat and pressure and melts to form magma. This magma is less dense than the surrounding solid rock and rises to the surface through cracks in the plates to form a volcano.
- Volcanoes will form along divergent plate boundaries. A divergent boundary is when the plates move apart from each other. When the plates part, magma from under either plate rises and forms a volcano.
-A hotspot is the third place a volcano can form. This particular type is the least common. Hot spots are when thermal plumes from deep in the Earth rises. This heat, combined with the lower pressure at the bottom of the lithosphere, causes magma to form. The magma, as we discussed, is less dense than the surrounding solid crust and rises to the surface through cracks and channels and then erupts at the surface to form a volcano.
