November 22, 2023 Flashcards
Questions at beggining of lecture:
- How old is a person with a maximum HR of 145? (75 years)
- If Q=22 L/min and HR is 120 bpm, what is the SV? (183 ml/beat)
HR Response to Exercise After Heart Transplantations
Heart beats at a higher HR at rest (aka intrinsic HR) (predominantly due to parasympathetic suppression; s)
HR won’t go up as much during exercise as it would in a heart with normal neural control
what is the formula for Q (cardiac output)
Q (cardiac output) = HR x SV
Effect of Prolonged Exercise in the Heat in regards to SV
Prolonged exercise in the heat causes SV to go down
This causes HR to slowly increase to compensate for decrease in SV (cardiac drift)
SV is affected first (loses 10-15%); increase in HR by the same proportion
page 143
Effect of Prolonged Exercise in the Heat in regards to Sweat rate and respiratory water loss
Sweat rate and respiratory water loss is increased;
this causes plasma volume and blood volume to decrease
causes cardiac output to potentially go down
page 143
Effect of Prolonged Exercise in the Heat in regards to MAP
Exercise in heat also increases MAP
which increases capillary pressure,
which causes an increase of movement to the interstitial fluid;
this also reduces plasma and blood volume
page 143
what are the two primary causes of slow decline in SV as a result of Prolonged Exercise in the Heat
- increases MAP
- Sweat rate and respiratory water loss is increased
causes the slow decline in SV (less blood is flowing back to the heart for every beat)
page 143
what reduces the drop in plasma volume, and attenuates cardiac drift
Fluid replacement
reduces the drop in plasma volume, and attenuates cardiac drift
page 143
Effect of Endurance Training on HR
Lower resting HR in trained person compared to untrained (at any workload up until max; workload that was max before now becomes max; can’t change max HR though)
Bradycardia (lower HR): evident at rest and submaximal exercise mainly due to an increase in parasympathetic tone
Benefits of Endurance Training on HR
Better coronary BF and more time for LV filling
Lower energy demand for the heart = less O2 required
Is Q(cardiac output) the same in trained and untrained subjects?
Even though there is a lower HR,
Q is the same in trained and untrained subjects during submaximal exercise because the SV increases to compensate
Better supply:demand ratio
what is the formula for SV
SV = EDV (amount in heart when filled) - ESV (what is left after heart ejects)
SV is higher in trained or untrained individuals
SV is higher in trained individuals (ejects more)
SV plateaus at about what percentage of VO2 max
SV plateaus at about 40% VO2 max
for both trained and untrained
why is SV higher in trained individuals
As training progresses, bradycardia occurs as an early adaptation (increase in parasympathetic drive)
Lower HR leads to:
* ↑ diastolic time →
* ↑ ventricular filling →
* stretches ventricular wall →
* eccentric hypertrophy (adaptation over time/longer cells) →
* ↑ ventricular volume →
* ↑ EDV
As training progresses, bradycardia occurs as an early adaptation. What occurs as a result of the adaptation
After adaptation, you get an increase in EDV and more blood leaving the heart per beat at the same ejection fraction of 50%
because ventricles holds a greater volume than before thus at the same ejection of 50% we have a higher SV
see page 145 image on bottom for clarification
Effect of Endurance Training on myofibrils
Training also increases the sensitivity of the myofibrils to calcium → greater force at a given cytosolic calcium → improved contractility
Ejection fraction =
SV/EDV x 100
or
(EDV-ESV)/EDV x 100
question at bottom of page 146
Effect of Exercise Intensity on SV
Increase in venous return
what is the primary purpose of One way valves in veins
One way valves in veins prevent backflow of blood (more return to the heart).
function of the venous valves and the “muscle pump” during contractions
Increase in sympathetic drive; some veins have smooth muscle which contracts (venoconstriction) via NE acting on a1 adrenergic receptors
Muscle contraction squeezes the veins and increases venous return to the heart
what are Varicose veins and how do they occur
Varicose veins: due to overloaded valves
heredity, sex (females more than males)
due to breakdown in valves (more pressure);
important for people to move so blood does not pool and breakdown valves
how is Exercise is helpful for people with varicose veins
Exercise is helpful for people with varicose veins as it increases muscle tone and prevents blood pooling
