The four most abundant elements needed by the human body are carbon, hydrogen, oxygen, and nitrogen because these are needed in large amounts to support our cells, these are referred to as bulk elements.
Oxygen is the most essential element required by our body. The body requires oxygen in the form of gas which is inhaled by the air around us. All the cells in a human body require oxygen which is transported by the blood inside.
Cell is the most basic and fundamental unit of life. It can be of two types: prokaryotic and eukaryotic. Prokaryotic cell is the primitive one with no true nucleus and eukaryotic cell has a true nucleus and all the cell organelles. Generally eukaryotic cells require abundant amount of oxygen.
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A trilobite. Trilobites became extinct about 250 million years ago while a ammonite became extinct around the same time as dinosaurs(65 million years ago). You wouldn't find a human skull or a dinosaur footprint
The correct answer is HPA axis.
The Hypothalamic-Pituitary-Adrenal (HPA) axis is one of the most important neuroendocrine systems, which regulates the stress response and other functions such as the digestion, mood, emotions and the immune system.
The hypothalamus, when triggered by a possible stressor, releases two hormones; the vasopressin and the corticotropin-releasing hormone (CRH). CRH, in turn, triggers the release of the adrenocorticotropin hormone (ACTH) from the pituitary gland. As a result of the secretion of ACTH, cortisol is secreted by the adrenal cortex.
Cortisol is a steroid hormone, considered to be our body's stress hormone.