A 40-year-old man was sleeping in his two-story home when a fire started downsta

Question

A 40-year-old man was sleeping in his two-story home when a fire started downstairs. After being rescued from the burning structure, he had difficulty breathing, severe nausea, displayed confusion, complained of a headache, and his skin had a bluish tint. When the patient was admitted into the hospital, he was placed on oxygen but blood tests revealed that he had still had low arterial oxygen content even though his alveolar oxygen tension was within the normal range. (A) What chemical agent produced in the fire would cause headache, nausea, confusion and low arterial oxygen levels? (B) Explain why tests revealed his alveolar oxygen and arterial PO_2 to be normal but his arterial oxygen content is low. In other words, what does this chemical do physiologically to cause the low arterial oxygen levels? (C) Why haven't either the peripheral or central chemoreceptors induced a respiratory effect in this individual? (D) Would giving this individual 100% oxygen be helpful? Explain. Lucy complained to her doctor that she was feeling cold all the time. The doctor ran blood tests and discovered that Lucy's blood TRH levels were very high, TSH levels were very low, and thyroid hormone levels were very low. (A) Based in these results, what do you think is wrong with Lucy? (B) Would decreasing her TRH to normal levels help? (C) What would be a good treatment for Lucy? A man comes to the doctor with high blood pressure. Tests show that he also has elevated levels of renin in his blood and atherosclerotic plaques that have nearly blocked blood flow through his renal arteries. (A) Describe how atherosclerotic plaques caused the increased renin in his blood. (B) How does an increased level of renin lead to high blood pressure? (C) If this man suddenly hemorrhaged, describe the actions of the cardiovascular system acting to restore homeostasis. Would these actions be different in a normal person?

Explanation / Answer

3.

1) Atherosclerotic plaques are mixtures made up of smooth muscle cells, T lymphocytes, macrophages full of lipids and malfunctioning endothelial cells. These lipid containing macrophages and T lymphocytes form plaque caps by stimulating the adjacent cells to destroy the collagen framework. Renin activates angiotensin, that gets converted to angiotensin II by the pulmonary endothelial angiotensin-converting enzyme. This activation of angiotensin II occurs when there is an increase of the plaque caps. Hence, an increase in plaque caps ( atherosclerosis ) causes an increase in renin in the blood.

2) Increase in the level of renin causes increase in the blood pressure, as increase in renin results in activation of the renin angiotensin system ( RAS ), resulting in the formation of angiotensin II. Angiotensin II when binds to angiotensin II type 1, results in constriction of the vessels, which is calcium dependent. This calcium dependent vasoconstriction results in an increase in blood pressure at both regional and systemic levels.

3) In normal adults, when haemorrhage occurs, to restore homeostasis, there are three steps followed:

- cardiovascular compensation

- isovolemic anaemia, and,

- hematopoiesis

Here, there is a baroreceptor response sensing the drop in pressure. This reflex is known as the baroreceptor reflex. In case of the affected person as well, the mechanisms would be same. These mechanisms only apply up to 20% of damage, and if the damage is above 20%, the mechanisms would be different in both the normal and the affected individual.

2.

1) A low or suppressed TSH level is a marker of hyperthyroidism. But in this case, along with an elevated TSH, there is a low indication of thyroid hormones. Since it is not specified if it is T3 or T4, we can consider any one of those. Considering a low T4, And low TSH, we can conclude that the case is of hypothyroidism with a damaged pituitary gland. If the TSH level was elevated, the damage would have been in the thyroid gland.

2) In order to treat such patients, a shot of TRH is given, so that there is an increase in the level of TSH. If the TRH levels would be reduced, the TSH levels , might decrease even further.

3) Generally, the patient is treated by a thyroid replacement treatment using oral pills. Intravenous treatment is also there for patients who are not able to take oral medications.

1.

1) The chemical that is causing these symptoms is carbon monoxide. The state is called carbon monoxide poisoning.

2) Carbon monoxide combines with hemoglobin and forms carboxyhemoglobin and thus keeps the arterial oxygen lower.

4) Treatment should include 100% oxygen levels along with providing supportive care. This is so because in this case the level of poisoning is higher or more severe and utmost care requires to be taken.

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