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A level biology cardiac cycle

Would this be a good answer for a 5 marker on the cardiac cycle if it appears in an exam.
Atria contract, decreasing the volume of the chambers and increasing their pressure. The pressure inside the chambers is higher than that of the ventricles so the tri cupid and bicuspid atrioventricular valves open and blood is forced into the ventricle. Atria relax, the ventricles contract decreasing their volume and increasing their pressure, there’s now a higher pressure in the ventricles than in the atria so the tricuspid and bicuspid atrioventricular valves close to prevent backflow. The pressure is also higher than that of the aorta and pulmonary artery so the semi lunar valves open and blood is forced out of the ventricles into the pulmonary artery and aorta. Now there’s a higher pressure in the aorta and pulmonary artery so the semi-lunar valves close. This cycle is repeated again when the blood reaches the pulmonary vain and aorta when there’s higher pressure in the vena cava and pulmonary vein and the tricuspid and bicuspid atrioventricular valves open again.

Reply 1

Hajra Momoniat

Very good answer but you spelt one word wrong. Its vein not vain :smile:

Reply 2

Reality Check

Original post by ben372728

Would this be a good answer for a 5 marker on the cardiac cycle if it appears in an exam.

This is fairly good. I've marked my points below:

Atria contract,where is the blood in the atria coming from? You need to describe the source of this, i.e. from the venæ cavæ and pulmonary vein. decreasing the volume of the chambers and increasing their pressure. The pressure inside the chambers is higher than that of the ventricles so the tri cupid It's "tricuspid', but I suspect this is a typo.and bicuspid atrioventricular valves open and blood is forced into the ventricle. To say the blood is 'forced' by the atria isn't strictly true - it flows due to the pressure difference.
Atria relax, the ventricles contract decreasing their volume and increasing their pressure, there’s now a higher pressure in the ventricles than in the atria so the tricuspid and bicuspid atrioventricular valves close to prevent backflow. The pressure is also higher than that of the aorta and pulmonary artery so the semi lunar valves open and blood is forced out of the ventricles into the pulmonary artery and aorta. Now there’s a higher pressure in the aorta and pulmonary artery than where? so the semi-lunar valves close. This cycle is repeated again when the blood reaches the pulmonary vain and aorta when there’s higher pressure in the vena cava and pulmonary vein and the tricuspid and bicuspid atrioventricular valves open again. It would be even better if you could break these parts down into atrial diastole, atrial systole, ventriclular diastole and ventricular systole.

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(edited 7 years ago)

Reply 3

jemimahiggins13

1. Blood enters atria and ventricles from the pulmonary veins and vena cava
*semi lunar valves close
*left and right atrioventricular valves open
*relaxation of ventricles allows blood to enter from atria
relaxation of heart (diastole)
atria are relaxed and fill with blood
ventricles also relax.

2. *Atria contact to push remaining blood into ventricles
*semi-lunar valves close
*blood pumped from atria to ventricles.
contraction of atria (atria systole)
atria contract, pushing blood into the ventricles.
ventricles remain relaxed

3. Blood pumped into pulmonary arteries and the aorta
*semi-lunar valves open
*left and right atrioventricular valves closed
*ventricles contract and walls thicken
contraction of ventricles (ventricle systole)
atria relax ventricles contract pushing blood away from the heart through pulmonary arteries and the aorta.

Reply 4

macpatgh-Sheldon

@ben372728

Hi, Very good description
ben372728

Ideally you want to segregate the right and left sides of the heart and specify that it is a circuit in series like an "8" shape; so mention that blood flows from the left ventricle into the aorta through the AORTIC valve and from the right ventricle into the pulmonary artery through the PULMONARY valve. The "bicuspid" valve has a more technical name: mitral valve.

Also, atrial contraction is a formality in real life, most of the flow of blood from the right atrium into the right ventricle through the triuspid valve and from the left atrium into the left ventricle through the mitral valve IS OF A PASSIVE NATURE.

DIAGRAM FROM MY BOOK SHOWING "8" shape:

CVS cycle diagram.png