Lecture 26 Respiratory System Under Stress

Question 1

Hypoxia

Answer 1

deficiency in the amount of oxygen reaching the tissues

Question 2

hyperoxia

Answer 2

excess supply of o2

Question 3

hypocarbia/hypocapnia

Answer 3

reduced carbon dioxide in the blood

Question 4

hypercarbia/hypercapnia

Answer 4

abnormally elevated carbon dioxide levels in the blood

Question 5

What is the control of ventilation for terrestrial animals and birds?

Answer 5

CO2 drive- driven by pH changes in the CSF

Question 6

When does hypoxic drive begin?

Answer 6

when inspired O2 falls below about half normal values

Question 7

The effects of high altitude on the respiratory system

Answer 7

largely relates to triggering hyperventilation through hypoxic drive

Question 8

V/Q matching

Answer 8

reducing perfusion to areas of gas exchange where ventilation is low by arteriolar hypoxic vasoconstriction

Question 9

over perfusion to a well ventilated region of the lung cannot compensate for any fraction of the circulation diverted to poorly ventilated regions, why?

Answer 9

almost all O2 is carried bound to Hb. Loading of O2 into blood crossing an alveolus reaches its maximum rapidly, except in exercising horses
-the high V/Q area, highly oxygenated blood will mix with blood from the low V/Q area, poorly Oxygenated blood. and arterial blood will overall have a lower O2 saturation

Question 10

Why do exercising horses suffer from exercise induced hypoxemia? (3)

Answer 10

diffusion limitation- the time to load O2 into the blood is so short that the process of loading the O2 is incomplete

• exercising horses are also ventilation limited
• this is why they utilize stride frequency

Question 11

Above what height are poorly acclimatized humans at risk of altitude sickness?

Answer 11

3000m

Question 12

Acute altitude sickness

Answer 12

ventilatory control becoming driven by O2 drive in response to hypoxia-> hyperventilation and reduced CO2 levels->decline in CSF bicarbonate and further drives hyperventilation

Question 13

High altitude pulmonary edema and high altitude cerebral edema related to

Answer 13

hypoxic injury and microvascular failure

Question 14

What adaptations do the bar headed geese have to make flight at 10000 m possible?(5)

Answer 14

large wing span
tissue tolerance to hypoxia
muscle capillary density
properties of Hb and myoglobin in O2 transport
higher proportion of mitochodria

Question 15

High mountain disease (brisket disease) in cattle

Answer 15

hypoxic vasoconstriction stimulated by hypobaric hypoxia leads to pulmonary hypertension->vascular remodeling, cor pulmonale, and cardiac failure

Question 16

Reduced O2 dependent strategies

Answer 16

lower metabolic rate and limit blood flow to only essential organs
(turtles, snakes, deep sea diving mammals can remain underwater for at least 2 hours)

Question 17

Caissons disease (the bends) hyperbaric conditions

Answer 17

accumulation of dissolved gases in solution, especially Nitrogen, with deep and long dives. Rapid return to surface leads to gas embolism-> severe pain in joints, muscle spasms, cardiac involvement

Question 18

Adaptations of sperm whales to dive deep (2)

Answer 18

Thorax is highly flexible and collapsible
cartilage in small airway walls (bronchioles) confers rigidity and allows air to be progressively expelled from gas exchange regions,, minimizing the amount of dissolved N that accumulates in the blood during deep dives

Question 19

Breathing of hyperbaric O2 or highly [ ] O2 for long periods leads to

Answer 19

destruction produced by oxygen radical damage to peripheral lung tissue->hyaline membrane disease and pulmonary edema

Question 20

Why do racehorses show hypoxemia during galloping?

Answer 20

massive rise in CO
ventilation rates above 2 breaths per second
insufficient time to load hemoglobin fully as blood is propelled rapidly across the alveolar membrane

Question 21

Detrimental effect of hypoxemia during intense exercise in horses is partially offset by (2)

Answer 21

splenic contraction-> adds RBC mass and enhances O2 carrying capacity
Large lungs with increased gas exchange surface area

Question 22

Short exposures to high g forces (pilots flying high performance aircrafts) causes

Answer 22

blood volume being displaced to the distal extremities and leads to loss of consciousness through an inability to maintain sufficient circulation to thorax and brain.

Question 23

An area of the lungs with no ventilation is termed

Answer 23

a shunt (V/Q of zero)

Question 24

An area of the lungs with no perfusion is termed

Answer 24

dead space (V/Q of infinity)

Question 25

Adaptations to altitude lead to

Answer 25

blunted respiratory drive

Question 26

Dorsal recumbancy effect on V/Q

Answer 26

Gravity= dorsal lung is crushed->poor ventilation

but has good perfusion(gravity) This really becomes an issue after the horse stands upright again