Cardio-Vascular system Flashcards
Why is it called a double circulatory system?
There’s a systemic circulatory system (to the body)
And a pulmonary one (to the lungs)
Why is the cardiac impulse of the heart described as myogenic?
The muscle generates its own electrical signal, causes its own contraction.
Where is the cardiac impulse generated?
In the SA node in the right atrium
How does the cardiac impulse travel from the SA node to the AV node?
Passes through the right and left atria walls causing both atria to contract
What is it called when both atria contract?
Atrial systole
What does the AV node do?
Conducts the impulse down through the Bundle of His and down left and right branches via the septum to the apex of the heart.
What happens to the cardiac signal at the apex of the heart?
Impulse travels up and around the ventricle walls via the purkinje fibres
What is the effect of the cardiac signal travelling up and around the ventricle walls?
Both ventricles contract from the bottom (ventricular systole) forcing blood up and out of the heart
After the ventricles contract what happens?
The heart relaxes (diastole) allowing the atria to fill before the next cardiac impulse is generated.
What is the cardiac cycle?
The events of one heart beat
What are the 2 phases of the cardiac cycle?
Diastole
Systole (atrial and ventricular)
How long does the cardiac cycle last?
0.8 seconds
How long is diastole?
0.5 seconds
How long is systole?
0.3 seconds
Describe what happens in diastole
Relaxation phase of the cardiac cycle
0.5 seconds
Both atria fill with blood, increasing atrial pressure.
70% of blood is forced past AV valves into ventricles
What are the 2 AV valves?
Bicuspid (left)
Tricuspid (right)
Describe atrial systole
Aortic and pulmonary valves are closed.
Both atria contract forcing remaining blood past AV valves into ventricles
AV valves then close.
Describe ventricular systole
Both ventricles contract forcing blood up past the aortic and pulmonary valves.
Aortic and pulmonary valves then close again as diastole starts the cycle again.
What is the definition of stroke volume?
Volume of blood ejected from the heart ventricles per beat
What is the definition of heart rate?
Number of heartbeats per minute
What is the definition of cardiac output?
Volume of blood ejected from the heart ventricles per minute
What is the normal resting value for stroke volume?
70ml
What is the trained value for stroke volume?
85ml
What is the normal resting value for heart rate?
70bpm
What is the trained value for heart rate?
Less than 60 bpm (bradycardia)
What is the cardiac output for both untrained and trained people?
5 Lmin (litres per minute)
What 2 things indicate high aerobic fitness based on heart rate
A low resting heart rate
Quick heart rate recovery after exercise
What causes bradycardia?
Hypertrophy of the heart muscle walls increases stroke volume as there are stronger contractions
What is stroke volume dependent on?
Venous return (mainly) High altitude (increases SV) High temperature (Increases SV) Gravity can also affect it
What is the definition of maximum heart rate?
The highest heart rate value one can achieve in an all-out effort to the point of exhaustion.
When will heart rate plateau?
During constant rate of sub-maximal work.
Aerobic work where oxygen supply = muscular demand
What is it called where the heart rate plateaus?
Steady state heart rate
What is the steady state heart rate?
The optimal heart rate for meeting the circulatory needs at that rate of work
How do you use steady state heart rate to know if a heart is efficient?
The lower the steady state heart rate the more efficient the heart