Acclimatization 2

Question 1

What is an advantage at high altitude with total hypoxic vasoconstriction?

Answer 1

V/Q is more matched -> vessels at apex dilate

Question 2

What are 2 mechanisms that PAP and vascular reistance is increased due to?

Answer 2

Diffuse hypoxic vasoconstriction
Pulmonary arteriolar remodelling

Question 3

What happens to vascular remodelling in 1-5% of the population?

Answer 3

Endothelium hypertrophies and encroaches into lumen increasing vascular resistance and right ventricle begins to fail

Question 4

What did Wagner prove in 1987?

Answer 4

V-Q mismatch increases during acclimatisation

Question 5

What inhibitors can reduce pulmonary vascular resistance?

Answer 5

IV rhi kinase inhibitor

Question 6

What type of response is the increase in PVR in response to high altitude?

Answer 6

maladaptive response

Question 7

What causes an increased in RBC at high altitude?

Answer 7

Low PaO2 triggers kidneys to make more erythropoietin to increase O2 carrying capacity

Question 8

What does increased RBC content cause?

Answer 8

increased viscosity -> increased resistance

Question 9

What is haematocrit?

Answer 9

Proportion of blood that is occupied by RBCs

Question 10

What causes an increase in haematocrit?

Answer 10

Reduction in plasma volume
increase in RBC

Question 11

What are 2 disadvantages of increasing haematocrit

Answer 11

Reduced blood volume - affects CO
Increased viscosity

Question 12

What is the optimum Hb level?

Answer 12

around 60/70

Question 13

What way does the Hb O2 dissociation curve shift to at respiratory alkalosis at high altitudes?

Answer 13

Left ward shift -> more O2 loaded by Hb

Question 14

What receptors are involved in the integrated response to hypoxia?

Answer 14

Chemoreceptor
Pulmonary stretch

Question 15

What 3 things happen in the CVS in response to hypoxia?

Answer 15

Tachycardia
Increased CO
Reduced total PVR

Question 16

How is blood pressure maintained at normoxic values?

Answer 16

Direct vasodilator action on systemic blood vessels
Partially antagonized by increased SNS activity
directs blood flow to active tissues

Question 17

What receptors drive SNS activity?

Answer 17

Peripheral chemoreceptors
pulmonary arterial baroreceptors

Question 18

What do the arterial baroreceptors do to high SNS?

Answer 18

Seek to maintain systemic pressue by reducing SNS

Question 19

What happens to CO after acclimatization?

Answer 19

Returns to sea level values
HR increased & SV reduced

Question 20

What happens to the systemic capillaries at high altitude?

Answer 20

Increased capillary density in brain, retina, liver, skeletal muscle

Question 21

What is the increase of capillary density achieved by?

Answer 21

Angiogensis

Question 22

What are 3 advantages of capillary angiogenesis?

Answer 22

Increased SA
Reduced diffusing distance - speeds up O2 transfer
Slowed blood velocity at constant total flow rate

Question 23

What happens in muscle at high altitude?

Answer 23

Muscle atrophies -> muscle fibres shrink -> capillaries are closer together

Question 24

What are 2 other adaptations?

Answer 24

Optimise ATP production
Reduce O2 requirement

Question 25

What are tissue changes that occur in skeletal muscle?

Answer 25

Increased myoglobin
Increased enzymes of glycolytic pathway, tricarboxylic acid cycle and electron transport chain
increased mitochondrial density

Question 26

What is myoglobin’s role in hypoxia?

Answer 26

Increase O2 solubility in cytosol of cell -> diffuse into mitochondria

Question 27

What are 3 ways oxygen requirement is reduced?

Answer 27

Reduce activity
Weight reduction
Reduced workrate

Question 28

What happens to enzymes of tricarboxylic acid cycle and electron transport chain at extreme altitudes?

Answer 28

No increase