The Cardiac Cycle

Question 1

what is the cardiac cycle?

Answer 1

series of events that occur when the heart beats, circulates blood through pulmonary & systemic circuits that make up double circulatory system.

Question 2

why is the double circulatory system more efficient?

Answer 2

keeps the oxygenated & deoxygenated blood separate.

Question 3

where does the pulmonary circuit carry the blood?

Answer 3

to the lungs to be oxygenated & back to the heart.

Question 4

what happens in the lungs?

Answer 4

CO2 is removed from the blood & O2 taken up by haemoglobin in RBC

Question 5

where does the systemic circuit carry the blood?

Answer 5

around the body to deliver O2 & returns deoxygenated blood to the heart

Question 6

what is the cardiac cycle broken down into?

Answer 6

the sequence of mechanical & electrical events that are repeated every heartbeat. 2 phases - diastole, systole.

Question 7

whats diastole?

Answer 7

relaxation phase, during this stage blood pressure is at lowest.

Question 8

whats systole?

Answer 8

contraction phase, this is when the blood pressure rises.

Question 9

how do we monitor the frequency of the cardiac cycle?

Answer 9

heart rate - number of beats per minute.

Question 10

how does the cardiac cycle start in the left side of the heart? CC in LSoH

Answer 10

blood drains into the left atrium from the lungs along the pulmonary vein.

Question 11

what happens after the blood enters the left atrium? CC in LSoH

Answer 11

raise of BP in left atrium forces the left bicuspid valve open.

Question 12

what happens when the left bicuspid valve is forced open? CC in LSoH

Answer 12

contraction of the left atrial muscle forces more blood through the valve.

Question 13

what happens after the left atrial muscle is done contracting? CC in LSoH

Answer 13

the left ventricular muscles start to contract.

Question 14

what happens after left ventricular systole is done?

Answer 14

forces the left bicuspid valve to close & opens the aortic valve causing blood to leave left ventricle via aorta.

Question 15

whats cardiac diastole?

Answer 15

when heart refills with blood

Question 16

whats ventricular diastole?

Answer 16

when the ventricles are refilling & relaxed

Question 17

what does the heart need to beat?

Answer 17

electrical signals to trigger the muscles to contract & relax.

Question 18

what are the components of the specific pathway for the heartbeat?

Answer 18

sinoatrial node, atrioventricular node, bundle of his, purkinje fibres.

Question 19

describe the sinoatrial node.

Answer 19

known as natural pacemaker - causes impulse to travel through the atria causing them to contract & forces blood into ventricles. It also sets hearts rhythm & rate.

Question 20

describe the atrioventricular node.

Answer 20

detects impulse travelling through the atria & redirects it to bundle of his - causes a delay , slowing the spread of electrical impulse across the heart & allowing atria to contract before ventricles.

Question 21

describe the bundle of his (atrioventricular bundle)

Answer 21

group of fibres in the septum which the impulse travels through to base of ventricles

Question 22

describe the purkinje fibres.

Answer 22

act as neurons & are found in the walls of the ventricles. the impulse from bundle of his reach here which cause ventricles to contract.

Question 23

what are baroreceptors?

Answer 23

the detect changes in pressure of blood filling the atria, they send signals to the CNS which triggers vasodilation which reduces pressure in the blood.