L30 Exercise And High Altitude

Question 1

Cardio respiration and exercise

Answer 1

O2 consumption, CO2 production ventilation rate and CO all increase and are well matched

Question 2

Exercising muscle demands

Answer 2

O2 and steady supply of fuel

Causes disruption homeostasis seen in exercise

Must increase total blood flow
Metabolic vasodilation must occur in muscle
Shunting of blood from gut to working muscle must be achieved

Question 3

Relationship btw work load and arteriovenous (a-v) O2 difference

Answer 3

At rest a-v diff ~ 5.6 vol %

During exercise may rise to 16 vol%

V gets lower, difference gets bigger

(Vol% = [mlO2/100ml blood] x 100)

Question 4

Exercise and TPR

Answer 4

Skeletal muscle vasodilation causes a significant drops in TPR

As metabolic rate increases, TPR decreases

Question 5

Exercise and BP

Answer 5

Diastolic P changes little while systolic and MAP increases

MAP increases w/ decreasing TPR because increased CO (MAP=CO x TPR)

Question 6

Effects of endurance training on HR?

Answer 6

Maximal HR does not change with training
Trained and untrained reach similar max HR

Resting HR is altered with training
Resting HR lower in trained
Greater vagal tone, reduced SNS tone
CO maintained by increased SV

Maximal HR determined by age

Question 7

Effects of endurance training on SV

Answer 7

Increases SV via
Increased heart size / ventricular V
Decreased HR , greater filling
Increased contractility from enhanced release of Ca from SR

Question 8

Effects of endurance training on blood V

Answer 8

Total volume increases with training
Increase in plasma volume
Minor increases in cell volume

Provides cardiovascular stability during exercise
Reduces cardiovascular drift
Fluid volume lost through sweating causes a decrease in venous return which reduces SV ; increases HR ( CV drift to maintain CO)

Question 9

Sedentary versus trained

Answer 9

Differences occur:

At same workload:
CO remains same
But at lower HR and higher SV in the trained

At same VO2:
Trained outworks the sedentary
Uses energy more efficiently

Maximal VO2:
Trained has a great VO2max and CO

Question 10

Adaption got high altitude

Answer 10

Barometric pressure decreases exponentially with altitude

PIO2 at top mt Everest only 43mmHg (normal = 150mmHg)

Question 11

Adaptation to high altitude

Answer 11

Resolute the hypoxia association w high altitude ~15 million people live above 10,000ft and some live about 16k feet (Andes)

Acclimatization to high altitude possible bu combo of respiratory and circulatory changes:
Respiratory: hyperventilation
Circulatory: polycythemia (increase RBCs) and increase conc of 2,3DPG in RBCs

Question 12

2,3DPG levels

Answer 12

Individuals adapted to high altitude (>3000m) showed increased synthesis of 2,3DPG (AKA 2,3BPG) in RBCs

Causes O2 hemoglobin dissociation curve to shift right (oxygen saturation curve = sigmoid)

Decreases affinity of Hb for O2- enhances transferring of O2 to tissues

Mildly impairs loading in the lungs

Question 13

Polycythemia

Answer 13

Increase in RBC conc.

Caused by increase erythropoietin release from kidney

Increased RBC increases O2 carrying compactly (O2 conc) of blood at any given PO2

Blood viscosity also increase w polycythemia. Increases the afterload experiences by the heart

Question 14

Other features of high altitude exposure

Answer 14

Increased capillary density in peripheral tissues

Pulmonary hypertension:
Occurs globally in lung and related to increased pulmonary vascular resistance
Can cause right heart hypertrophy if high altitude exposure is chronic
Due to hypoxia vasoconstriction of pulmonary vasculature

Question 15

Pulmonary vascular resistance:

Hypoxia vasoconstriction

Answer 15

If alveolar PO2 decreases:

Pulmonary vascular smooth muscle
Contracts

Blood is directed away from poorly ventilated alveolar units towards better ventilated unit

Called hypoxic vasoconstriction; mech not clear

Local (not central) control of vascular resistance

Opposite response of systemic circulation to hypoxia