11 CV Adaptations Flashcards
• CO def
• CO: amt of blood pumped by the heart in 1 min. Max value for CO reflects the final capacity of CV system to meet physical activity demands
o CO= HR x SV
The Fick Principal:
CO= VO2 x 100 / A-V O2 diff
What differences do you see in CO and SV between gender? from 20-80 y/o?
- Untrained 70 kg male: CO= 5L SV= 70mL
- Untrained 56kg female: CO= 4L SV= 60mL
- SV declines 15% from 20-80yo
What CV adaptations occur at rest?
1) incr vagal tone & decr sympathetic drive→slow HR
2) incr blood volume, myocardial contractility, & compliance of the L ventricle→ improves heart’s SV
Athlete CO adaptations?
• endurance athlete achieves a large max CO through large SV
3 physiologic mechanisms ↑ the heart’s SV during exercise
1) Myocardial factor–enhanced cardiac filling in diastole, followed by a more forceful systolic contraction
2) Neurohormonal factor–normal ventricular filling with a subsequent forceful ejection and emptying during systole
3) Training adaptations–Incr blood volume & reduced resistance to blood flow in peripheral tissue (afterload)
what is cardiovascular drift?
• Gradual time-dependent downward drift is It is characterised by decreases in mean arterial pressure and stroke volume and a parallel increase in heart rate
Why does HR increase after prolonged steady state exercise?
decreased preload results in ↓ SV indicates COMPENSATORY ↑ in HR to maintain CO
o SV decr during prolonged exercise is influenced by incr HR & NOT cutaneous blood flow
During exercise where does blood go? what factors influence this?
Environmental stress, level of fatigue, and exercise mode and intensity affect regional blood flow, but the major portion of the exercise CO diverts to active muscle.
where does majority of blood go at rest?
liver
↑ CO→↑ capacity to circulate O2. Why?
•Even during maximum exercise, hemoglobin saturation with O2 remains nearly complete, so each liter of arterial blood carries about 200 ml of O2.
Therefore, an increase Q produces a proportionate increase in the capacity to circulate O2, largely affecting maximal O2 consumption.
what is the Arteriovenous O2 difference? What increases exercise consumption?
• Hemoglobin releases a considerable quantity of its reserve O2 from blood perfusing active tissues. Exercise O2 consumption increases by 2 mechanisms:
1) AMOUNT Increase in the total quantity of blood pumped by the heart (Q)
2)EFFICIENCY Greater use of the relatively large quantity of O2 already carried by the blood (i.e. expanding the a-v O2 difference)
• Rearranging the Fick equation: VO2=Q x a-v O2 diff
Does upper body or lower body consume more O2 during submaximal exercise?
The higher O2 consumption for upper-body exercise at all submaximal power outputs results from:
1) lower mechanical efficiency in UE exercise from the additional cost of static muscle action that do not contribute to external work
2) recruitment of additional musculature to stabilize the torso during arm exercise.
What adaptations does the ATHLETE’S Heart make to CV exercise? How is it different than pathological?
Enlargement of the heart by:
• Eccentric Hypertrophy: incr size of LV
• Concentric Hypertrophy: modest thickening of the myocardial wall
This is different than hypertrophy induced from disease such as HTN that ↑ afterload
What HR Adaptations to occur with CV exercise training at rest and with exercise?
—Resting & submax bradycardia→incr parasymp activity with a small decr in sympathetic discharge.
—-↑ max SV & Q proportional to the magnitude of training
o ≈10-15 min to return to resting→ need more endurance training
What are 4 SV Adaptations to Ex?
4 factors may increase SV following aerobic training:
- ↑ left ventricular volume and mass.
- ↓ cardiac stiffness
- ↑ diastolic filling time
- ↑ cardiac contractile function
