Back to AI Flashcard MakerBiology /OCR Biology A - 3.1.2 - Transport in Animals Part 4
Atrioventricular valves in diastole
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Key Terms
Term
Definition
Atrioventricular valves in diastole
Open
Semi lunar valves in diastole
Shut
Atrial systole
Atria contract together Ventricles are relaxed Small increase in atrial pressure to push blood to ventricles Ventricles stretch as they fill
Atrioventricular valves in atrial systole
Open due to pressure gradient
Semilunar valves in atrial systole
Shut
Ventricular systole
Atria relax Ventricles contract simultaneously Contraction starts at apex of heart to push blood upwards Huge increase in pressure forcing blood into ...
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| Term | Definition |
|---|---|
Atrioventricular valves in diastole | Open |
Semi lunar valves in diastole | Shut |
Atrial systole | Atria contract together Ventricles are relaxed Small increase in atrial pressure to push blood to ventricles Ventricles stretch as they fill |
Atrioventricular valves in atrial systole | Open due to pressure gradient |
Semilunar valves in atrial systole | Shut |
Ventricular systole | Atria relax Ventricles contract simultaneously Contraction starts at apex of heart to push blood upwards Huge increase in pressure forcing blood into aorta and pulmonary artery |
Atrioventricular valves in ventricular systole | Shut |
Semilunar valves in ventricular systole | Open |
When do the atrioventricular valves open | Diastole - pressure in ventricles drop below pressure in atria Blood flowing from atria to ventricles force valves open |
When do the atrioventricular valves close | Ventricular systole - pressure in the ventricles rises above pressure in atria due to contraction |
When do the semilunar valves open | Ventricular systole - when ventricular pressure rises above atrial pressure |
When do the semilunar valves close | Diastole - ventricular pressure drops below the pressure in the major arteries |
Where is the pressure highest in the blood vessels | Aorta Artery Arteriole Capillary Venule Vein |
Why does blood pressure fluctuate in the aorta | Due to rhythmical contractions of cardiac muscle in the left ventricle The troughs are caused by relaxation |
Why does pressure drop the further from the heart | The total cross-sectional area of the blood vessels further away from the heart gets larger as does the volume Resistance to flow |
Why is heart muscle myogenic | It can initiate its own contraction |
What happens when the contractions of the chambers are not synchronised | This could cause inefficient pumping (fibrillation) so the heart needs a mechanism that coordinates heart contraction |
Initiation and control of the heartbeat | SAN (found at the top of the right atrium) - initiates a wave of excitation Wave of excitation quickly spreads over walls of both atria (travels quicker on left, atria contract simultaneously - atrial systole) Wave of excitation passes through AVN, delays impulse Carried away from the AVN, down the bundle of His and down the purkyne fibres Spreads out over walls of ventricles to apex |
Why does the AVN delay the wave of excitation | Allow the atria to finish contacting so the blood can fill the ventricles before they begin to contract Maximising amount of blood pumped out |
Why do the ventricles contract from the base upwards | So the blood can be pushed up towards the major arteries |
ECG | Electrocardiograms - monitor the electrical activity of the heart |
What can ECG traces indicate | When part of the heart muscle is not healthy and therefore can be used to be diagnosed to diagnose heart problems |
How do ECG’s work | Attaching a number of sensors to the skin. The sensors picks up electrical excitation created by the heart and convert this into a trace |
Parts of ECG traces | P wave QRS complex T wave |
What do the P waves show | Atrial stimulation |