CV Physiology and Exercise Flashcards
At rest, the heart spends […] as much time in diastole than in systole.
Twice
During exercise, what changes occur with regards to:
- HR
- Cardiac cycle
- Length of diastole and systole
- Increases
- Shortens
- Both shorten in duration, but diastole shortens more than systole
All of these changes occur to increase cardiac output
- What is the driving force behind the changes that occur in the heart to increase cardiac output?
- How is this altered in individuals who receive transplanted hearts?
- Increased sympathetic NS activity
- Transplanted hearts do not receive the same innervation as a person’s native heart. As such, their baseline HR at rest will be higher because they experience less PSNS tone. Additionally, they will be less able to increase their HR as much when they exercise due to decreased activity of SNS.
What changes to heart rate occur with aging?
How would you advise a patient on where they should be targeting their HR for exercise?
Decrease in maximum HR
Depends on the person / goals. See chart. For most people, moderate intensity is recommended.
Cardiac output is directly proportional to […]
Demand
During exercise, do SV and HR increase at the same rate or does one increase faster than the other?
SV increases faster than HR due to increasing venous return. Venous return is increased due to increasing muscular contraction which pushes blood through the venous system faster.
Why is there increased venous return during exercise? (i.e. what causes this to happen)
Increased venous return = increased cardiac output
Stroke volume can only increase to a certain point during exercise and then it plateaus. What factors cause stroke volume to be limited?
Frank-Starling mechanism refers to fact that there is an optimal amount of passive tension that leads to optimal active tension. Any more or less results in less active tension.
The figures below show how the venous return and cardiac output increase with exercise. If you are treating a patient who has heart failure and asking them to exercise, what are some symptoms they would display if the exercise is too intense?
Put another way, if CO cannot keep up with VR, then there will be a back up of blood in the heart that is not getting pumped out to the body. What symptoms would a person have in this case?
Edema (within 24 hours)
Sweating (diaphoresis)
Increased JVP
Dyspnea
Decreased BP
Crackles
With prolonged exercise, stroke volume decreases. Why?
Why can a trained athlete produce the same cardiac output at a lower HR compared to an untrained person of the same gender?
The trained athlete has conditioned their heart to have a larger stroke volume due to hypertrophy. Increased SV * lower HR = same CO
With increasing HR, the heart consumes more oxygen. However, increasing HR [does or does not] require more oxygen per beat.
Does not - increasing HR increases the amount of oxygen needed per minute not per beat.
What happens to the following values with exercise and why:
- SBP
- DBP
- SBP is the highest BP of the aorta. It increases b/c CO and SV are increasing.
- DBP is the lowest BP of the aorta. It does not really change much because the amount of relaxation (lusitropy) is not changing appreciably.
During exercise, CO increases ~ 3x as much. However, MAP only increases by ~30%. Why?
There is a decrease in TPR, leading to less drastic increase in MAP.
Given an individual with the following measurements for an individual at rest, calculate TPR.
MAP = DBP + (SBP - DBP / 3) **Divided by 3 b/c of the ratio of time spent in diastole to systole –> spend 3x more time in diastole)
TPR = MAP / CO
Given an individual with the following measurements for an individual while exercising, calculate TPR.
MAP = DBP / ((SBP - DBP ) / 2) **Divided by 2 because during exercise there is about equal amount of time spend in systole as diastole**
TPR = MAP / CO
What changes in distribution of blood flow occur with exercise?
What is the valsalva maneuver? What type of exercise is it seen in? Would this be safe for patients with cardiac conditions?
Valsalva maneuver is holding your breath while exercising
Seen in heavy weight lifting
No
In a patient that has reduced oxygen transport, why does strength training their muscles improve their condition?
Increased muscle use leads to increased mitochondrial density (mitochondrial mitogenesis) which generates more resting and active metabolic demand from the muscles thereby promoting increases in cardiac output and ventilation in order to meet that demand. All the systems are working in connection with one another.
What does the term “VO2” mean?
It’s synonomous with the aerobic capacity of an individual. It can be used to determine the fitness of a person’s aerobic system.
What is a MET? How is it used clinically?
See image for what a MET is.
It is used to prescribe exercise. Want to match the MET level with the person’s VO2max. Would measure VO2max first and then use MET levels to determine what types of exercise they can sustain based on VO2 max.
VO2 max is a strong predictor of […]
Cardiac mortality
What leads to an increase in capillary density with exercise?
Need to stress body into anaerobic exercise (happens at about 55% of VO2max) –> need to make oxygen demand larger than oxygen supply to trigger body to realize that it needs to provide more blood supply to meet future demands
