Cardiac cycle

Question 1

What is convection?

Answer 1

It is the mass movement of fluid caused by pressure difference

Question 2

What is a sinoatrial node?

Answer 2

It is a group of cells located in the wall of the right atrium

Question 3

What does the SA produce?

Answer 3

The SA spontaneously produces action potentials that travel through the heart via electrical conduction system

Question 4

What is the SA also known as?

Answer 4

Also known as the hearts natural pacemaker

Question 5

What is the heart rate influenced by?

Answer 5

Heart rate influenced by nerves that supply the SA node

Question 6

What does the AVN coordinate?

Answer 6

Coordinates top of the heart

Question 7

What does the AVN connect and do?

Answer 7

Eletrically connects the right atrium and right ventricle, delaying impulses so that the atria have time to eject blood into ventricles before ventricular contraction

Question 8

What is If?

Answer 8

It is hyperpolarisation activated Na+ channels causing Na+ influx

Question 9

Phase 0(Rapid depolarisation) in atrioventricular action potentials?

Answer 9

Voltage gated Na+ channels open, Na+ influx

Voltage gated Ca2+ channels open slowly

Question 10

Phase 1 in atrioventricular action potentials?

Answer 10

Na+ channels close

Question 11

Phase 2 in atrioventricular action potentials?

Answer 11

VGCC’s fully open-Ca2+ influx(CICR)

K+ channels open slowly

Question 12

Phase 3(Rapid repolarisation) in atrioventricular action potentials?

Answer 12

VGCC’s close

K+ channels fully open

Question 13

Phase 4(Resting phase) in atrioventricular action potentials?

Answer 13

Na+/K+ pump(3 Na+ out, 2K+ in)

Question 14

Electrical conduction through the heart

Answer 14

1. Electrical activity generated in SA node and spreads out via gap junctions into atria
2. At AVN, conduction delayed to allow correct filling ventricles
3. Conduction occurs rapidly through bundle of His into ventricles
4. Conduction through purkinje fibres spreads quickly throughout the ventricles
   - Ventricular contraction begins from apex

Question 15

What is the P wave in an ECG?

Answer 15

Atrial depolarisation

Question 16

What is the QRS complex in an ECG?

Answer 16

Ventricular depolarisation

Question 17

What is the PR segment in an ECG?

Answer 17

AVN delay

Question 18

What is the ST segment in an ECG?

Answer 18

Time during which ventricles are contracting and emptying

Question 19

What is the T wave in an ECG?

Answer 19

Ventricular repolarisation

Question 20

What is the TP interval in an ECG?

Answer 20

Time during which ventricles are relaxing filling

Question 21

Cardiac cycle outline

Answer 21

Diastole:
     Ventricular filling
     Atrial contraction
Systole:
     Ventricular contraction
     Atrial relaxation
Cardiac diastole
     Both atria and ventricles relaxed

Question 22

Chamber and volume change in (ventricular filling/aorta contraction)

Answer 22

Pressure in atria>ventricles

Mitral/tricuspid valve open aided by atria contraction

Question 23

Chamber and volume change in (Isovolumetric contraction)

Answer 23

Pressure in ventricles>atria
Mitral/tricuspid valve close
Pressure rises

Question 24

Chamber and volume change (Ejection)

Answer 24

Pressure in ventricles>Aorta/Pulmonary artery
Valves open, ejection of blood
Atria start to refill

Question 25

Chamber and volume change in (Isovolumetric relaxation)

Answer 25

Pressure in aorta/pulmonary artery>Ventricles | Aortic/pulmonary valves close

Question 26

Equation for stroke volume

Answer 26

EDV-ESV=stroke volume

Question 27

Ventricular pressure-volume loop

Answer 27

Work=change in ventricles x change in volume | Stroke work done= Area inside loop

Question 28

Heart sound (S1)

Answer 28

Lub | Close of tricuspid/mitral valves at beginning

Question 29

Heart sound (S2)

Answer 29

Dub | Closure of aortic/pulmonary valves at the end of ventricular systole

Question 30

Heart sound (S3)

Answer 30

Occasional | Turbulent flow into ventricles, detected end of 1/3 diastole

Question 31

Heart sound (S4)

Answer 31

Forceful atrial contraction against a stiff ventricle | Less in young people