A detailed mechanism of hypoxia, Physiology

A detailed mechanism of hypoxia

1. Romaisa Roll no 514

2. Hypoxia Respiration adaptation to hypoxia

3. Hypoxia: Hypoxia is  a state in which oxygen is not available in sufficient amounts at the tissue level to maintain adequate homeostasis ; this can result from inadequate oxygen delivery to the tissues either due to low blood supply or low oxygen content in the blood (hypoxemia)

4. Early signs of hypoxia: Restlessness Anxiety Tachycardia Tachypnea Late signs of hypoxia: Bradycardia Extreme restlessness Dyspnea Cyanosis

5. Causes of hypoxia: Inadequate oxygenation of lungs due to lack of oxygen in atmosphere and hypoventilation. Pulmonary diseases Venous to arterial shunt Inadequate transport and delivery of oxygen eg in anemia and tissue edema Inadequate tissue capability of utilizing oxygen eg cyanide poisoning of cytochrome oxidase and vit B deficiency.

6. Classification of hypoxia: Hypoxemic hypoxia Anemic hypoxia/hemic hypoxia Stagnant hypoxia or circulatory hypoxia/ischemic hypoxia Histotoxic hypoxia

7. Hypoxemic hypoxia: the  hypoxemic  type, in which the oxygen  pressure  in the  blood  going to the tissues is too low to saturate the  hemoglobin . Causes of hypoxemic hypoxia: The hypoxemic type of hypoxia is due to one of two mechanisms: (1) a decrease in the amount of breathable oxygen—often encountered in pilots, mountain climbers, and people living at high altitudes. cardiopulmonary failure in which the lungs are unable to efficiently transfer oxygen from the alveoli to the blood. 2. Anemic hypoxia: the anemic type, in which the amount of functional hemoglobin is too small, and hence the capacity of the blood to carry oxygen is too low; 

8. Causes of anemic hypoxia: In the case of anemic hypoxia, either the total amount of hemoglobin is too small to supply the body’s oxygen needs, as in  anemia  or after severe bleeding, or hemoglobin that is present is rendered nonfunctional. Examples of the latter case are  carbon monoxide poisoning  and acquired  methemoglobinemia , in both of which the hemoglobin is so altered by toxic agents that it becomes unavailable for oxygen transport, and thus of no respiratory value. 3. Stagnant hypoxia: the stagnant type, in which the blood is or may be normal but the flow of blood to the tissues is reduced or unevenly distributed.

9. Histotoxic hypoxia: the histotoxic type, in which the  tissue   cells  are poisoned and are therefore unable to make proper use of oxygen.  In histotoxic hypoxia the cells of the body are unable to use the oxygen, although the amount in the blood may be normal and under normal tension. Although characteristically produced by  cyanide poisoning , in which the action of the enzyme  cytochrome oxidase  is completely blocked by the cyanide—to such an extent that the tissues simply cannot use oxygen even when plenty is available.

10. Effects of Hypoxia on the Body Hypoxia, if severe enough, can cause death of cells throughout the body, but in less severe degrees it causes principally (1) depressed mental activity, sometimes culminating in coma, and (2) reduced work capacity of the muscles.

11. Respiration adaptation in hypoxia: Hypoxic pulmonary vasoconstriction: When ventilation is blocked,the lung can protect against the loss of blood oxygenation by activating localized arterial vasoconstriction, reducing blood flow to under ventilated regions, and redirecting flow to better ventilated alveoli. 2. More active capillaries in lungs 3. Increased mitochondria: Increased number of mitochondria help to maintain cellular functions. Also plays an important role in the production of energy in the form of ATP. 4. High concentration of RBCs: Hypoxia induces systemic increase of erythropoietin(EPO) level Which stimulates the production of mature RBCs from the bone marrow.

12. 5.Hypoxia induce factor(HIF): Hypoxia inducible factor(HIF)-1 is a chimeric protein complex that plays an integral role in the body’s response to low oxygen concentrations,or hypoxia. HIF-1 is among the primary Gene’s involved in the homeostatic process, which increase the vascularization in hypoxic areas such as localized ischemia and tumors. HIF-1 further mediates cellular responses to hypoxia by regulating glucose uptake and anaerobic respiration in oxygen depleted environments.

13. 6. Hyperventilation: Increased levels of Carbon Monoxide and exposure to toxic substances are both triggers. Also, when  the level of Oxygen is reduced significantly , this can lead to Hyperventilation. Hypoxia definitely will lead to Hyperventilation. Hyperventilation is rapid or deep breathing.

14. 7. . 2,3 DPG( Diphosphoglycerate): The function of erythrocyte 2,3-DPG is  to bind to deoxyhemoglobin and facilitate oxygen transport . When 2,3-DPG binds to deoxyhemoglobin, the deoxyhemoglobin molecule is stabilized