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:
Answer:
less than 1%
Explanation:
The approximate percentage of the geologic time that humans have existed on the Earth since its origin is less than 1%.
The earth is about 4.6 billion years and much of its history has been without the present of human activities.
- Hominis were the first human to appear on the surface of the earth.
- This was in the Miocene epoch which was about 6 million years ago.
- Compared to the age of the earth, this time lapse is very small and not up to 1%.
- Life first appeared on earth about 3.5billion years.
- Since then evolution has taken its due course to give what we have today.
Answer:
Motor neuron
Explanation:
Motor Neurons (effector neurons) relay information from the CNS to other organs terminating at the effectors. It takes the information from the brain to the effector.
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