Phys: Test 3: Lecture 9. Reparatory Under Stress

Front 1

How does ventilation change with increased PCO2

Back 1

increases

Front 2

which chemoreceptors are mainly stimulated due to increased PCO2?

Back 2

central

Front 3

how does ventilation change in hypoxia

Back 3

increase

Front 4

which chemoreceptors are mainly stimulated in hypoxia?

Back 4

peripheral

Front 5

Describe and explain the variation of inspired PO2 with altitude.

Back 5

• the barometric pressure drops with altitude
• remember PIO2= (PB-47) x .2093
• thus PIO2 will drop as well sucka!

Front 6

• the barometric pressure drops with altitude
• remember PIO2= (PB-47) x .2093
• thus PIO2 will drop as well sucka!

Back 6

• You have a reduction in inspired PO2, leading to hyperventilation
o This will act to increase the alveolar PO2
 This will get more O2 into the blood
• Hyperventilation decreases alveolar PCO2 (increasing PaO2)

Front 7

. Explain why hyperventilation increases in two phases at altitude

Back 7

• When you start hyperventilating you will make the blood more alkaline
o Thus because of the increased pH you will inhibit ventilation because central chemoreceptors will sense the change
 You will then have arterial and CSF pH correction in the central chemoreceptors, which will inhibit them
• This will cause ventilation to increased

Front 8

List the symptoms associated with acute mountain sickness.

Back 8

due to hypoxemia and alkalosis
headache, insomnia, loss of appetite, dizziness, palpitations, fatigue, nausea

Front 9

Describe and explain the effect of hypoxia on red cell production. Explain why an increase in
hemoglobin content can be useful

Back 9

• Hypoxia will lead to polycythemia (creating more red blood cells)

Good Effect: more red cells increases the total O2

BUT WHAT IT REALLY DOES: makes the O2 graph steeper meaning decrease in PO2 will release more O2 to tissues

Front 10

Describe and explain the effect of hypoxia on red cell production. Explain why an increase in
hemoglobin content can be harmful

Back 10

you get increased viscosity causing increased vascular resistance
-this makes the heart have to work harder, which can be detrimental at high altitudes

Front 11

Describe and explain the effects of moderate and high altitude on the oxygen dissociation
curve.

Back 11

• Moderate altitude
o Shift right due to increased 2,3 BPG
o Hb gives up O2 more readily
• High altitude
o Shift to the left
o Due to alkalosis (increased pH)
o Trying to hold on to the O2 as much as possible

Front 12

What are the systemic circulatory responses to hypoxia, are they helpful?

Back 12

o Increasing mitochondrial enzyme expression
 Enhances/maintains partial pressure gradient (by using up the O2 and depleting it)
o Capillary formation: reduces the diffusion distance for O2, increases the rate of diffusion

Front 13

what are the pulmonary circulatory responses to hypoxia? is it helpful?

Back 13

o Get vasoconstriction all over the lung
o Will get HAPE
 High Altitude Pulmonary Edema
 Right ventricle will have to work harder

Front 14

Explain why pure oxygen can produce absorption atelectasis.

Back 14

• Wash out N2 from air
o The N2 being in equilibrium between alveoli and blood helps keep the alveoli inflated
 When you give pure oxygen you will end up getting rid of the nitrogen in the blood capillary and the alveoli
• Thus you create a huge gradient and the oxygen will get dumped from the alveoli to the blood very easily (occurs if ventilation is blocked)
o This massive dump will cause the alveoli to collapse (you lose splinting)

Front 15

Explain why hyperbaric oxygen therapy is useful in carbon monoxide poisoning.

Back 15

• Increased barometric pressure
o Increased inspired O2
 Increased dissolved O2
• Helping to increase the O2 concentration in the blood

increase PB, and PIO2

Front 16

. Describe the sites of deposition within the lung for small, medium and large air-borne
particles. Explain why inhaled coal dust tends to settle in the respiratory bronchioles.

Back 16

• Large particles
o Stay at nasopharynx
 Are absorped and swallowed
• Medium
o Sedimentation
 Gets stuck in the smaller airways
• Velocity slows as you get deeper, thus the particles get stuck
• Very small
o Stuck in alveoli
o Get cleaned by macrophages

Front 17

Explain why placental gas exchange is less efficient than in the lung. Describe the
circulatory adaptations in the fetus that help with delivery of oxygen.

Back 17

• Placenta is in parallel with other organs
o Meaning some of the oxygenated blood will mix with deoxygenated blood
 You will pump partially deoxy blood to the body

Front 18

Ductus arteriosus?

Back 18

shunts blood away from lungs

Front 19

foramen ovale

Back 19

directs oxygenated blood to heart and brain

Front 20

Describe the respiratory and circulatory changes that mediate the switch from placental to
lung gas exchange at birth

Back 20

• Baby is born
o Gets hypoxic because it doesn’t have the placenta
 So you have sensitization of the chemoreceptors
• Makes inspiratory efforts
o There is fluid in the lung though, so you have to overcome surface tension (although the fluid helps prevent alveolar collapse)
 This makes the pleural pressure very negative in the first few breathes of life
• constrict the ductus arteriosus (due to increase in PO2 and prostaglandin release)
• Pulmonary vascular resistance decreases to help send more blood to the lung
o This will increase pressure to the left atrium, to help shut the foramen ovale