The Cardiac Cycle

Question 1

Describe the events regarding the electrical activity of the heart

Answer 1

• SAN initiates heartbeat
• it is the pacemaker
• it passes electrical impulse over the atria walls to both atria so they can contract
• AVN picks up the electrical impulse and imposes a slight delay
• this is so that the atria can completely contract and empty
• there is also non-conducting tissue between the atria and ventricles so the impulse doesn’t pass
• AVN stimulate the Bundle of His which travel down the septum
• once it reaches the apex, Purkyne fibres stretch out and surround both ventricles eventually causing them to contract from the apex?

Question 2

Why does the atrioventricular node impose a slight delay before stimulating bundle of his?

Answer 2

• so that the atria can finish contracting
• so that the tarok can completely empty
• so the ventricles and atria don’t contract at the same time as this would result in a low blood output

Question 3

Why do ventricles contract from apex?

Answer 3

• complete emptying of ventricles if blood is moved up

Question 4

Why do we use an electrocardiogram?

Answer 4

• to see if there is anything wrong in the electrical activity of the heart
• to diagnose problems

Question 5

What are the components of an electrocardiogram?

Answer 5

• P wave
• QRS wave
• T wave

Question 6

Describe the path deoxygenated blood takes in the heart?

Answer 6

• enters the right atrium via the superior/inferior vena cava
• flows through the bicuspid valves(atrioventricular valve) to the left ventricle
• flows up through semilunar valve and out through the pulmonary artery to the lungs

Question 7

Describe the path oxygenated blood takes in the heart

Answer 7

• enters the left atrium via the pulmonary veins from the lungs
• flows to the left ventricle via tricuspid valve(mitral valve)
• flows up through semi lunar valves and out through the aorta to the rest of the body.

Question 8

What are the three parts of the cardiac cycle?

Answer 8

• atrial systole
• ventricular systole
• diastole

Question 9

Describe atrial systole

Answer 9

• blood flows into the atria
• pressure builds up which pushes open the atrioventricular valve
• blood flows to both atria and ventricles now
• to increase pressure the atria contract, emoting their blood into the ventricles
• to stop back flow of blood down pressure gradient, the atrioventricular valves close

Question 10

Describe ventricular systole?

Answer 10

• the ventricles contract and this increase in pressure forces open the semi lunar valves
• the pressure in the aorta increases as blood flows through it

Question 11

Describe diastole

Answer 11

• both ventricles and atria are relaxing
• semi lunar valves closed to prevent back flow of blood
• atrioventricular valves open

Question 12

What are the different types of diseases that can be seen from an electrocardiograph?

Answer 12

• atrial fibrillation
• ventricular fibrillation
• ectopic heart beat
• tachycardia
• bradycardia

Question 13

What is the lub dub sound caused by?

Answer 13

• closing of the av valve

- closing of the semi lunar valve

Question 14

what Is a double circulatory system?

Answer 14

• blood is pumped through the heart twice for each circuit to the lungs and to the body

Question 15

who do

Answer 15

• metabolic demand of most multicellular organisms are high
• surface area to volume ratio gets smaller
• insufficient oxygen exchange and waste cannot be removed fast enough because diffusion cannot happen fast enough
• diffusion distance is too big