W11 - Adaptations (3.7)

Question 1

Describe the 3 energy systems of skeletal muscle.

Graph.

Answer 1

• power events (few seconds):
  immediate E sources = ATP, CrP
• several seconds - minute:
  non-oxidative breakdown of glycogen
• 2 minutes and longer:
  oxidation of fat and glucose derived from circ.

Question 2

How does the oxygen consumption (= V_O2) change w/ increasing intensity of exercise?

Explain.

Graph.

Answer 2

increases to ensure an increased rate of ATP generation

due to incr. tidal volume (1l) and incr. breathing frequency (60/min)

_{0, 50, 100, 150 W}

Question 3

How does the V_O2 of athletes differ from that of untrained people?

Graph.

Answer 3

increased V_O2max
functional capacity of body’s ability to generate aerobic power

→ O₂ uptake by lungs sufficient even during higher intensities, plateaus later

Question 4

Which 3 steps limit the O₂ transport from atmosphere to muscle?

How can they be influenced?

Answer 4

1. O₂ uptake by lungs depends on pulmonary ventilation (↑ alveolar ventilation → ↑ O₂ uptake)
2. O₂ delivery to muscle depends on cardiac output and O₂ content (↑ CO → O₂ delivery)
3. extraction of O₂ from blood by muscle depends on O₂ delivery and P_O2 gradient btw blood and mitochondria (↓ P_O2 in mixed venous blood)

Question 5

Values for

• O₂ content of ambient air
• alveolar air

Answer 5

• ambient air = 21%
• alveolar air = 15%

​NOTE: values don’t change, even during exercise

Question 6

Values for O₂ consumption

• at rest
• of untrained person during exercise
• of trained person during exercise

How does it affect alveolar ventilation?

Answer 6

• at rest = 250ml/min
• untrained person during exercise = 2500 - 3000ml/min
• trained person during exercise = 4000 - 4500ml/min

​→ increases alveolar ventilation in order to meet its demands

Question 7

Why is the alveolar ventilation in trained people increased?

Values.

Answer 7

elevated vital capacity → higher reserves to elevate tidal volue
BUT: same breathing frequency as untrained persons during exercise (60/min)

• resting tidal volume = 500ml
• tidal volume in untrained = 1l
• tidal volume in trained = 1.3l

_{<u>REMEMBER</u>: VA = (TV - VD) * resp. rate}

Question 8

Values for

• CO₂ content of ambient air
• alveolar air

Answer 8

• ambient air = 0%
• alveolar air = 5%

​NOTE: values don’t change, even during exercise

Question 9

How does the production of CO₂ (= V_CO2) change during exercise?

Values

• at rest
• of untrained person during exercise
• of trained person during exercise

Answer 9

increases due to increased E demand in muscle

• at rest = 200ml/min
• untrained person during exercise = 2500ml/min
• trained person during exercise = 3500ml/min

Question 10

Values for O₂ extraction

• at rest
• of a untrained person during exercise
• of a trained person during exercise

Answer 10

O₂ extraction = CO * ΔP_O2,art-ven

• at rest = 250ml/min
• of a untrained person during exercise = 2700ml/min
• of a trained person during exercise = 3750ml/min

​→ during exercise ΔP_O2,art-ven incr. to 150ml/l

Question 11

How much O₂ is normally stored in the body?

Where?

Answer 11

∽ 2l

• 0.5l in the air of the lungs
• 0.25l dissolved in the body uids
• 1l combined with the Hb of the blood
• 0.3l stored in the muscle fibers, combined mainly with myoglobin

Question 12

Define oxygen debt.

Answer 12

in periods of incr. metabolic rate

• O₂ storages are rapidly depleted for aerobic metabolism (2l)
• disturbances in ATP/CrP and lactic acid system (9l)

⇒ incr. O₂ uptake to “repay” about 11.5l of O₂
= O₂ debt

Question 13

Draw and explain the graph how O₂ uptake increases during and after exercise.

Answer 13

incr. O₂ uptake during + even after exercise

• during exercise: reconstituting the ATP/CrP system and repaying the stored O₂
• *= alactic O2 debt ∽ 3.5l**
• after exercise: lowered level to remove lactic acid
• *= lactic acid O2 debt ∽ 8l**

Question 14

Define anaerobic treshold.

Why is it physiologically important?

Graph.

Answer 14

at V_O2 = 1.5l/min. = anarobic threshold​​
V_O2 above which aerobic E production is supplemented by anaerobic mechanisms, causing a sustained incr. in lactic acid

• accumulates in blood → ↓pH (= metabolic acidosis)
• combines w/ HCO₃^-, CO₂ formed → ↑ exhaled CO₂ (= V_CO2)
• ↑ respiratory quotient (= V_CO2/V_O2)
• ↑ ventilation (unproportional incr. to HR)
• cardiac output close to maximum

Question 15

How does the lactate level in the blood change during heavy exercise?

Explain.

Answer 15

1. isovolumetric contr. of skeletal m. compresses vessels → no further blood flow, insufficient O₂ delivery
2. lactic acid generated during anaerobic E production accumulates in blood
3. metabolized in liver (Cori cycle), but reaches maximum capacity at anaerobic threshold

_{<u>NOTE:</u> lactic acid elevates local blood flow}

Question 16

How does the heart rate change w/ increasing intensity of exercise?

Explain.

Graph.

Answer 16

incr. up to 3 times resting heart rate

contraction of sk. m. → ↑ metabolites → local vasodilation → ↓ MAP → arterial baroreceptors → ↑ HR

_{0, 50, 100, 150 W}

Question 17

Values for HR

• of untrained person at rest
• of trained person at rest
• during exercise

Answer 17

• of untrained person at rest = 60 bpm
• of trained person at rest = 50 bpm
  → physiological bradycardia
• during exercise = 180 bpm

Question 18

How does the stroke volume change w/ increasing intensity of exercise?

Explain.

Graph.

Answer 18

incr. up to 1.5 times resting stroke volume

contraction of sk. m → muscle pump → ↑ venous return → ↑ right atrial pressure → ↑ end-diastolic pressure → ↑ EDV → ↑ stroke volume

_{0, 50, 100, 150 W}

Question 19

Values for stroke volume

• at rest
• of untrained person during exercise
• of trained person during exercise

Answer 19

• at rest = 70ml
• of untrained person during exercise = 100ml
• of trained person during exercise = 150ml

Question 20

How does the cardiac output change w/ increasing intensity of exercise?

Explain.

Graph.

Answer 20

incr. up to 4-5 times resting CO

result of incr. HR and stroke volume

_{0, 50, 100, 150 W}

Question 21

Values for stroke volume

• at rest
• of untrained person during exercise
• of trained person during exercise

Answer 21

• at rest = 5l/min
• of untrained person during exercise = 18l/min
• of trained person during exercise = 27l/min

Question 22

How does the pulmonary pressure change during exercise?

Explain.

Answer 22

↑ CO → ↑ pulmonary art. pressure → dilation → ↓ pulmonary resistance

Question 23

How does the arterial pressure change w/ increasing intensity of exercise?

Explain.

Graph.

Answer 23

• strong incr. in systolic pressure due to vasoconstriction in inactive tissues triggered by symp. nervous system
• slight incr. in diastolic pressure
• incr. in MAP

_{<u><strong>BUT:</strong></u> TPR decreases as a result of vasodilation in skin vessels for thermoregulation offsetting incr. in MAP}

_{0, 50, 100, 150 W}

Question 24

How does the TPR change w/ increasing intensity of exercise?

Explain.

Graph.

Answer 24

decreases as a result of

• vasodilation in skin vessels → thermoregulation
• vasodilation of arterioles due to ↑ metabolites
• capillary recruitment

NOTE: offsetting incr. in MAP

_{0, 50, 100, 150 W}

Question 25

How does the AVDO change w/ increasing intensity of exercise? Explain. Graph.

Answer 25

**increases bc mm. are avidly extracting O₂ from blood stream** due to shift in Hb O₂ dissociation curve _{0, 50, 100, 150 W}

Question 26

How is blood redistributed during exercise?

Answer 26

* _away from organs w/ no imm. nec. function_ * _​_**splanchnic** * **kidney** * **skin** * _toward organs w/ imm. nec. function_ * _​_**brain** * **heart** * **working mm.** * **skin in case of core temp. elevation**

Question 27

List some further biochemical adaptations to exercise.

Answer 27

* _​_incr. control of citric acid cycle enzymes * conversion of glycogen phosphorylase b to a * vasoneogenesis * incr. maximal O₂ uptake * hypertrophy of sk. muscle

Question 28

# Define circulatory shock. Different types?

Answer 28

reduced CO and reduced arterial pressure due to pathology emerging in the vascular system * **hypovolemic shock** * **cardiogenic shock** * **distributive shock** * **obstructive shock**

Question 29

What happens in case of a hypovolemic shock? Reason?

Answer 29

↓ **blood volume** → impairs ventr. filling → ↓ CO and ↓ MAP e.g. due to hemorrhage, exsiccocsis _{most common type of circulatory shot}

Question 30

What happens in case of a cardiogenic shock? Reason?

Answer 30

**↓↓ CO** → peripheral alterations e.g. heart infarct affecting large ventricular masses

Question 31

What happens in case of a distributive shock? Reason?

Answer 31

**loss of tone of peripheral vessels** → ↓ MAP e.g. due to bacterial infection, spinal shock

Question 32

What happens in case of a obstructive shock?

Answer 32

**obstruction of sufficient part of circulation**

Question 33

What are symptoms of a hemorrhagic shock? List SOME.

Answer 33

* **signs of blood loss** on scene and on the body of patient * **pulse, heart beats frequent** (sympathetic) * **pulse feeble**, can be easily suppressed (low MAP) * **P_sys \< 70 mmHg** (diastolic can not be measured) * **skin pale, cool** (vasoconstriction, sympathetic, loss of RBCs) * **confusion, blurred conscience, communication difficulties** (cerebral autoregulation fails at 60 mmHg MABP) * **breathing unfrequent, shallow** (brain stem respiratory centers affected, weakness of respiratory muscles) * **anuria** (no filtration at 60 mmHg) * **thirst** (AT II, Vasopressin, low pressure baroreceptors) * **metabolic acidosis**, arterial p_O2 can be normal

Question 34

What are the stages of a hemorrhagic shock? Graph.

Answer 34

1. **progressive stages:** blood loss of 200 - 600ml → can be controlled by BP control mechanisms 2. **irreversible shock:** blood loss of 1200+ ml → results in death in a few hours unless transfusions are applied

Question 35

Which negative feedback mechanism is the most important in order to restore blood pressure in case of a hemorrhagic shock? Effects?

Answer 35

**high pressure baroreceptor reflexes** down to about 60-70 mmHg MAP ⇒ tachycardia, proper redistribution of cardiac output

Question 36

Which negative feedback mechanisms are activated in order to restore blood pressure in case of a hemorrhagic shock?

Answer 36

1. **Low pressure baroreceptor reflexes** (also contributing to volume control) 2. **peripheral and central chemoreflexes,** Cushing reflex (at 20-40 mmHg MAP) 3. **restoration of plasma volume from extracellular space** (Starling forces) 4. **anaeorobic metabolism** in tissues with this ability (metabolic acidosis) 5. **AT II-aldosterone** (vasoconstriction, volume saving, tubulo-glomerular feed-back, thirst) 6. **Vasopressin** 7. **decreased GFR** as a result of reduced MAP, glomerulotubular feedback, anuria below 60 mmHg MAP restoration of urine flow when MAP is restored with limited delay 8. **restoration of RBC mass**, several days after (EPO, reticulocytosis)

Question 37

Which mechanisms prevail in uncompensated shock situations?

Answer 37

_positive feedback mechanisms activated_ * **↓ coronary circulation** due to reduced MAP, ↓ ventricular contractility, it further ↓ MAP * **↓ brain circulation** reduces the activity of brainstem circulatory and breathing centers, loss of peripheral sympathetic tone, vasodilation, hypoxia, further ↓ MAP * **endothelial damage** due to hypoxia and low flow, closure of capillaries * **anaerobic metabolism**, lactic acid dilates vascular smooth muscle, low pH damages

Question 38

What happens in case of acute mountain sickness? At which heights can it usually appear?

Answer 38

_3000+ m_ **↓ P_bar → ↓P_alv → hypoxemia** * stimulation of per. chemoreceptors → **hyperventilation + resp. alkalosis** * stimulation of EPO production **→ ↑Hb → ↑O₂ content** * pulmonary vasoconstriction **→ ↑P_pul → right ventr. hypertrophy, pulm. edema** * **↑** 2,3-BPG **→ unloading of O2 in tissue** **​**

Question 39

What happens in case of adaptation to acute mountain sickness?

Answer 39

* adaptation to resp. alkalosis * breathing driven by p_O2 not by p_CO2 * biochemical adaptation to lower tissue p_O2 * incr. Ht (EPO) _{​(Tibetian pop. has incr. expression of PHD2 gene which induces HIF2α for incr. RBC development)}

Question 40

What is the effect of microgravity on the cardiovascular system? What happens after landing?

Answer 40

_during space flights_ **missing gravitational effects** → art. pressures equilibriate in the body (100 mmHg), venous orthostatic reflexes disappear _BUT:_ after landing rapid regain of venous orth. reflexes → fainting