Back to AI Flashcard MakerBiology /Biology IB HL - 6.2 The Blood System Part 6
Does ventricular systole occur straight after atrial systole?
NO The electrical signal then reaches a region of non-conducting tissue which prevents it from spreading straight to the ventricles; this causes the signal to pause for around 0.1 s
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Key Terms
Term
Definition
Does ventricular systole occur straight after atrial systole?
NO The electrical signal then reaches a region of non-conducting tissue which prevents it from spreading straight to the ventricles; this causes th...
Why is there a pause after atrial systole?
This delay means that the atria can complete their contraction before the ventricles begin to contract
What is the role of the AVN?
The electrical signal is carried to the ventricles via the atrioventricular node (AVN)
What is the AVN? (structure)
This is a region of conducting tissue between atria and ventricles
How does the signal from the AVN travel further?
The signal then travels to the base of the heart via conductive fibres in the septum known as the bundle of His
What causes ventricular systole once the electrical signal reaches the base of the heart?
The electrical signal is then carried through another set of conductive fibres called Purkyne fibres which spread around the sides of the ventricles, ...
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| Term | Definition |
|---|---|
Does ventricular systole occur straight after atrial systole? | NO The electrical signal then reaches a region of non-conducting tissue which prevents it from spreading straight to the ventricles; this causes the signal to pause for around 0.1 s |
Why is there a pause after atrial systole? | This delay means that the atria can complete their contraction before the ventricles begin to contract |
What is the role of the AVN? | The electrical signal is carried to the ventricles via the atrioventricular node (AVN) |
What is the AVN? (structure) | This is a region of conducting tissue between atria and ventricles |
How does the signal from the AVN travel further? | The signal then travels to the base of the heart via conductive fibres in the septum known as the bundle of His |
What causes ventricular systole once the electrical signal reaches the base of the heart? | The electrical signal is then carried through another set of conductive fibres called Purkyne fibres which spread around the sides of the ventricles, causing contraction of the ventricles from the apex, or base, of the heart upwards |
Where is blood forced after ventricular systole? | This is called ventricular systole | Blood is forced out of the heart into the pulmonary artery and aorta |
State the 5 simple stages of electrical control of the cardiac cycle | sinoatrial node sends out a wave of excitation/depolarisation
atria contract
atrioventricular node sends out a wave of excitaion/depolarisation
Purkinje fibres conducts wave of excitation/depolarisation
ventricles contract |
What is the (v. general) change in pressure of the heart? | Contraction of the heart muscle causes an increase in pressure in the corresponding chamber of the heart, which then decreases again when the muscle relaxes |
What does the change in pressure do to a specific structure of the heart? | Throughout the cardiac cycle, heart valves open and close as a result of pressure changes in different regions of the heart: |
When do valves open? | Valves open when the pressure of blood behind them is greater than the pressure in front of them |
When do valves close? | They close when the pressure of blood in front of them is greater than the pressure behind them |
Why are valves in the heart important? | Valves are an important mechanism to stop blood flowing backwards |
State the stages of the cardiac cycle shown on a graph of pressure | end of diastole; atrial systole; beginning of ventricular systole; ventricular systole; early diastole; diastole; late diastole; COMPARE WITH GRAPH!!!!! |
How is the pressure of the atria affected by diastole? | During diastole, the heart muscle is relaxing
During this period, blood begins to flow into the atria from the veins, increasing the atrial pressure |
Overall, how does diastole affect the pressure of the heart? | Relaxed muscle in the heart walls recoils, increasing the volume of the chambers of the heart:
volume up, pressure down (inverse) |
What valves open during diastole and why? | The atrioventricular valves open as the pressure in the atria is higher than the pressure in the ventricles |
What valves close during diastole and why? | The semilunar valves close as the pressure in the pulmonary artery and aorta is higher than the pressure in the ventricles |
What is the general pressure change during systole? | The contraction of the muscles in the wall of the heart reduces the volume of the heart chambers and increases the pressure within that chamber |
What valves are open during atrial systole and why? | The atrioventricular valves are open as the pressure in the atria exceeds the pressure in the ventricles |
What valves are closed during atrial systole and why? | The semilunar valves are closed as the pressure in the ventricles is less than the pressure in the aorta and pulmonary artery |
What valves are closed during ventricular systole and why? | The atrioventricular valves are closed as the pressure in the ventricles exceeds the pressure in the atria |
What valves are open during ventricular systole and why? | The semilunar valves are open as the pressure in the ventricles exceeds the pressure in the aorta and pulmonary artery |
What happens at the end of diastole? | + pressure | The atrium has filled with blood during the preceding diastole
Pressure is higher in the atrium than in the ventricle, so the AV valve is open |
What happens at atrial systole + pressure? | Left atrium contracts, causing an increase in atrial pressure and forcing blood into the left ventricle; Ventricular pressure increases slightly as it fills with blood; Pressure is higher in the atrium than in the ventricle, so the AV valve is open |