What are the 3 stages of the cardiac cycle?
Diastole
Atrial systole
Ventricular systole
What is diastole?
Relaxation phase lasts 0.5 seconds
Both atria fill with blood. AV valves closed
Atrial pressure rises above ventricular pressure
Rising blood pressure forces AV valves open and blood passively passes into both ventricles.
Semi lunar valves closed
What is atrial systole?
Lasts 0.3 seconds
Contraction of left and eight atria
Rising atrial pressure forces remaining blood into the left and right ventricles
Semi lunar valves remain closed
What is the ventricular systole?
Contraction of both left and right ventricles
Increases ventricle pressure reforming blood out of left and right ventricles
Aortic and pulmonary valves forced open
AV valves closed
Blood forced out into:
Aorta to body tissues
Pulmonary arteries to lungs
40/50% blood ejected at rest during ventricular systole
What does the conduction system do?
Controls the cardiac cycle
How does the conduction system control the cardiac cycle?
Control is regulated via an electrical impulse called the cardiac impulse
What does myogenic mean?
Generates its own cardiac impulse
What is the heart rate?
Number of heart beats per minute
What is stroke volume?
The volume of blood ejected from the heart ventricles in 1 beat
What is the average resting heart beat?
70-72 beats per minute
What is cardiac output?
The volume of blood ejected by the heart per minute
What may indicate high aerobic fitness?
A low rating hr and rapid hr recovery after exercise
What hr is bradycardia?
Below 60 bpm
What affects the resting heart rate?
Hyper trophy: increase in sv due to an increase in size and strength of the heart muscle wall
Affected by environmental conditions such as articulate and temperature- low= decrease
What is maximum heart rate?
The highest heart rate value in can achieve in all out effort to the point of exhaustion
Estimated 220- age in years
Indications of a steady state/ sub maximal hr
Heart rate plateau reached during constant rate of sub maximal work
Aerobic work where O2 supply= muscular demand
It is the optimal heart rate for meeting circulatory demands at that rate of work
The lower the steady star heart rate, the more efficient the heart
What is sv?
Difference in volume of blood in the ventricles before and after ventricular contraction
What is edv?
End diastolic volume: volume blood left in the ventricles at the end of the diastole
What is esv?
End systolic volume: volume blood left in the ventricles at the end of the systole
How can sv be calculated?
Edv - esv
How to calculate cardiac output
Stroke volume ( millimetres per min) x heart rate (bpm)= cardiac output (litres per minute)
How many litres of blood is pumped out of the heart every minute?
5 litres
Where is the greatest percentage of cardiac output distributed during resting conditions?
Organs
Only 20% to the muscles
In relation of their overall mass compared to the percentage of cardiac output distributed to the kidneys and that distributed to the muscles
Percentage distr used to the kidneys is the same as the muscles yet kidneys are very small compared to muscle mass
Why is the distribution of cardiac output muscles so low during resting conditions despite the larger surface area of muscle!
During rest muscles are mostly inactive and do not require a large percentage of cardiac output to supply the oxygen for their energy supply
What are the events of a heart beat?
Consists of 2 phases lasting 0.8 seconds
1. Diastole relaxation phase during which the chambers fill with blood
Systole contraction phase when Attica and ventricles chambers contract to expel blood
Resting values exercise
SV: 60/80 ml untrained
80/100 ml trained
HR: 70/72 untrained
60 or below trained
Q 5 L/ min
Sub maximal values exercise
SV: 80/100ml untrained
160/200 ml trained
HR: 100/130 bpm untrained
Up to 160 bpm trained
Q: 10 to 20 L/min
Maximal values exercise
SV: 100/120 ml untrained
160/ 200 ml trained
HR: 220- age. Trained= closer U= below
Q: 20/40 L/ min untrained
25 L/ min trained
Heart rates at rest
Untrained: 70 bpm
Trained: 50 bpm, also known as an athletes pulse
Stroke volume at rest
Untrained: 71 ml
Trained: 100 ml
Cardiac output at rest
Untrained: 4970 ml
Trained: 5000ml
Convert in to Litres!!!!!!!
Systolic blood pressure resting value
100-130 mmHg
Diastolic blood pressure resting value
70-90 mmHg
How does an increase in blood increase cardiac output?
More blood returning to the heart
Increased stretch of the atrial wall
Increased EDV
Causing greater force of contraction during ventricular systole
As stroke volume increases more blood is pumped out of the heart per beat
Q= HR X SV, therefore Q increases
More blood returning to the right atrium, stimulated the SA node which increases HR
More or faster blood pumped to working muscles
How does an increase in blood flow increase performance?
Increased time or intensity for exercise
Delays fatigue or OBlA
Starlings law
Venous return increases during exercise resulting in more blood returning to the heart
A greater EDV stretches and enlarges the ventricles
Greater stretch and recoil increases the force of ventricular contraction
This increases ventricular contractility almost completely emptying the EDV and increasing SV
Heart rate response to exercise
HR increases above resting values prior to exercise starring- anticipatory rise
Due to a release in adrenalin
Adrenalin in blood stimulates the SA node to increase HR
HR increases/ in line with exercise intensity- linear relationship
May plateau during sub-maximal work representing a steady state optimal HR to meet the demand for oxygen
HR slow down just prior to maximal HR values
Heart rate after exercise
HR decreases rapidly after exercise stops
Due to decreased muscular demand for oxygen
More gradual and slower decrease in HR towards resting HR values
Elevated HR during recovery is termed the oxygen debt
More intense the exercise the greater the oxygen debt and therefore the longer the HR recovery
Hearts response to an BAHL
Hypertrophic: increase resting HR by increasing SV to maintain the same Q at rest and increase potential Q to supply oxygen during exercise
More efficient and healthy heart, bradycardia is under less strain at rest and over period of ones lifetime slows down the hearts deterioration in efficiency due to natural ageing process
May improve the length of an individual’s QoL in relation to sustaining a more active and healthy lifestyle
Increased potential intensity of physical activity
Consequences of bradycardia and excessive training
HR lower than 40bpm- may not pump enough blood, fainting and develop longer ventricular pauses
Increased risk of developing heart block which sometimes require pace makers to be implanted