Chapter 43 - Guyton

Question 1

Decrease in _________ _________ is the basic cause of all the hypoxia problems in high-altitude physiology.

Answer 1

barometric pressure

Question 2

Sea Level PCO2 = __ mm Hg

Answer 2

40

Question 3

Acute effects of hypoxia.

Answer 3

drowsiness, lassitude, mental and muscle fatigue, headache, nausea, and sometimes euphoria

Question 4

Acclimatization

Answer 4

(1) great increase in pulmonary ventilation due to decreased PO2 - increase slowed by decreased PCO2
(2) increased number of red blood cells (hematocrit content)
(3) increased diffusing capacity of lungs
(4) increased vascularity of peripheral tissues (increased capillarity)
(5) increased ability of the tissue cells to use oxygen despite low PO2

Question 5

Increased Pulmonary ventilation - Role of arterial chemoreceptors

Answer 5

• Immediate exposure to low PO2 stimulates arterial chemoreceptors, which increase alveolar ventilation to 1.65x normal
• Remaining at altitude for several days can increase ventilation by 5x normal
• Increase in pulmonary ventilation reduces PCO2 and increases pH of body fluids

Question 6

Acute cerebral edema

Answer 6

• results from local vasodilation of cerebral blood vessels caused by hypoxia
• can lead to severe disorientation and other effects of cerebral dysfunction

Question 7

Acute pulmonary edema

Answer 7

• local edema can result from constriction of pulmonary arterioles and increased capillary pressure in these areas
• typically breathing pure oxygen can reverse this process in hours

Question 8

Effects of a prolonged stay in space:

Answer 8

(1) decrease in blood volume
(2) decrease in RBC mass
(3) decrease in muscle strength and work capacity
(4) decrease in maximum cardiac output
(5) loss of calcium and phosphate from bones