The effects of anoxia upon animal cells and tissues

Anoxia is a general term denotingoxygen lack regardlessof how orwhere in the body it is produced. There are fourgeneral types of anoxia: anoxic anoxia (anoxemia) , anemicanoxia, stagnant anoxia and histological anoxia.In normal oxygenation oftissues, oxygen is given up to thetissuesbecause of a difference in oxygen tension in the capil-laries and the tissue fluid, the greater tension being in thecapillary. Oxygen canbe carried into thecells only by theenzyme, oxidase. With the aid ofvarious enzymes, oxygen isbrought to the metabolite in the cell which is oxidized. In-jury toany of the respiratory enzymes of thecell causes anoxiadue to the inability of the cell to take upavailable oxygen.Nervous tissue is extremely sensitive tothe effects ofoxygen lack. However, a constant supply of oxygen rather thana rich one is necessary for its functioning. Anoxia decreasessomatic excitability and increases autonomic excitability, sug-gesting that somatic centers are more sensitive to oxygen lackthan the autonomic centers. The nerve endings in the bowel are,in general, resistant to anoxia. The eye, on the other hand isextremely sensitive and is believed to be a good indicator ofthe early effects oflack of oxygenupon the central nervoussystem ofmammals. Anoxia causes an increase in respiration,rise in blood pressure and cardioinhibi tion due to stimulationof the chemoreceptors of the carotid and aortic bodies. The