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Why can't/don't neurons take up atmospheric oxygen or at-least dissolved oxygen (like amoeba does) to survive and do all life processes outside animal body ???

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    $\begingroup$ Does an amoeba (or other microorganisms) actually take up oxygen directly from the air? My impression is that most if not all actually live in water, so they take up dissolved oxygen (and avoid drying out through loss of their internal water). $\endgroup$ – jamesqf Nov 20 '18 at 18:53
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Short answer
Neurons, and in fact all cells in the body, utilize water-dissolved oxygen to fuel their energy metabolism.

Background
The brain, and tissues in general, obtain their oxygen through passive diffusion (Fig. 1). Water, carbon dioxide, and oxygen are among the few simple molecules that can cross the cell membrane by passive diffusion, or osmosis (source: Estrella Mountain Community College).

The body uses hemoglobin to transport oxygen (Fig. 1), because passive diffusion would take too long, especially in oxygen-hungry warm-blooded animals like humans.

hemoglobin
Gaseous exchange in fluid medium is mediated by hemoglobin. source: Kokyo

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  • $\begingroup$ Thanks but can neurons survive outside body ? by breathing from atmosphere ?? or swim freely in water like amoeba ?? $\endgroup$ – Derek Stone Nov 20 '18 at 10:57
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    $\begingroup$ No. Neurons are incredibly dependent on their micro-environment and require many cells to keep them alive. In many labs, neurons can be cultured outside the body but this requires very specific conditions and they do not live long. $\endgroup$ – S Pr Nov 20 '18 at 11:00
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    $\begingroup$ A brief addendum: not all gas exchange in the body uses haemoglobin/blood. In fact a portion of the oxygen the cells in the cornea of the eye receive is absorbed from the air into the tear film Intro of (Leung, 2011). But note that AliceD's point about dissolved oxygen still applies in that case. Also, (Stuecker, 2004) describes how the skin can take up atmospheric oxygen but that's not to say they haven't got an oxygen supply from vasculature too. $\endgroup$ – Jam Nov 23 '18 at 12:14

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