Question

Explain two different ways that the body can respond to low blood oxygen content. Describe the entire feedback loop, including where problem is sensed, what signals are sent by the sensing organ, and how the eventual changes in the body change the oxygen content of the blood.

Answer 1

Hypoxemia occurs when levels of oxygen in the blood are lower than normal. If blood oxygen levels are too low, your body may not work properly.
Blood carries oxygen to the cells throughout your body to keep them healthy. Hypoxemia can cause mild problems such as headaches and shortness of breath. In severe cases, it can interfere with heart and brain function. Hypoxemia that causes low oxygen levels in your body’s tissues is called hypoxia. Sometimes people use the two terms interchangeably, but they are not the same thing.
A variety of conditions and circumstances can interfere with the body’s ability to deliver normal levels of oxygen to the blood. Some of the most common causes of hypoxemia include:
Heart conditions, including heart defects
Lung conditions such as asthma, emphysema, and bronchitis
Locations of high altitudes, where oxygen in the air is lower
Strong pain medications or other problems that slow breathing
Sleep apnea (impaired breathing during sleep)
Inflammation or scarring of the lung tissue (as in pulmonary fibrosis)
Hypoxia can also result from lung damage due to trauma.
Other things can cause hypoxia include:
Lung diseases such as chronic obstructive pulmonary disease (COPD), emphysema, bronchitis, pneumonia, and pulmonary edema (fluid in the lungs)
Strong pain medicines and other drugs that hold back breathing
Heart problems
Anemia (a low number of red blood cells, which carry oxygen)
Cyanide poisoning (Cyanide is a chemical used to make plastics and other products.)

Symptoms:
Symptoms of hypoxemia vary depending on the severity of the condition. They include:
Headache
Shortness of breath
Fast heartbeat
Coughing
Wheezing
Confusion
Bluish color in skin, fingernails, and lips
1.
If oxygen delivery to cells is insufficient for the demand (hypoxia), electrons will be shifted to pyruvic acid in the process of lactic acid fermentation. This temporary measure (anaerobic metabolism) allows small amounts of energy to be released. Lactic acid build up (in tissues and blood) is a sign of inadequate mitochondrial oxygenation, which may be due to hypoxemia, poor blood flow (e.g., shock) or a combination of both.[36] If severe or prolonged it could lead to cell death.[citation needed]
In humans, hypoxia is detected by the peripheral chemoreceptors in the carotid body and aortic body, with the carotid body chemoreceptors being the major mediators of reflex responses to hypoxia. This response does not control ventilation rate at normal pO2 but below normal the activity of neurons innervating these receptors increases dramatically, so much so to override the signals from central chemoreceptors in the hypothalamus, increasing pO2 despite a falling pCO2 it is seen in a few humans (encountered with hypoxia), there is word loss in their speech due to their state of confusion and cell damage in the brain. in most tissues of the body, the response to hypoxia is vasodilation. By widening the blood vessels, the tissue allows greater perfusion. By contrast, in the lungs, the response to hypoxia is vasoconstriction. This is known as hypoxic pulmonary vasoconstriction, or "HPV".
2.
If tissue is not being perfused properly, it may feel cold and appear pale; if severe, hypoxia can result in cyanosis, a blue discoloration of the skin. If hypoxia is very severe, a tissue may eventually become gangrenous. Extreme pain may also be felt at or around the site.[citation needed]
Tissue hypoxia from low oxygen delivery may be due to low haemoglobin concentration (anaemic hypoxia), low cardiac output (stagnant hypoxia) or low haemoglobin saturation (hypoxic hypoxia).The consequence of oxygen deprivation in tissues is a switch to anaerobic metabolism at the cellular level. As such, reduced systemic blood flow may result in increased serum lactate. Serum lactate levels have been correlated with illness severity and mortality in critically ill adults and in ventilated neonates with respiratory distress.