Cardiac cycle

Question 1

Convection

Answer 1

Mass movement of fluid caused by pressure difference

Question 2

Describe the SA node

Answer 2

Group of cells located in the wall of the RIGHT ATRIUM
Can spontaneously produce action potential that travels through the heart
Sets rhythm of the heart - natural pacemaker
Rate of action potential production is influenced by nerves that supply it

Question 3

Describe the AV node

Answer 3

Part of the electrical conduction system of the heart that coordinates the top of the heart
Electrically connects the right atrium and right ventricle - so atria have time to eject their blood into ventricles before ventricular contraction

Question 4

What occurs during Phase 4 in SA pacemaker potentials

Answer 4

Membrane repolarises below the If threshold

At -50mV an Na+ channel opens = Na+ influx = slow depolarisation

Question 5

What occurs during phase 0 in SA pacemaker potentials

Answer 5

Threshold is met for Ca2+ channels to open = Ca2+ influx = RAPID depolarisation

Question 6

What occurs during phase 3 in SA pacemaker potentials

Answer 6

Ca2+ channels switched off

Activation of voltage gated K+ channels = K+efflux

Question 7

What occurs during phase 0 of atrial & ventricular muscle action potentials

Answer 7

RAPID DEPOLARISATION
Recieve depolarisation stimulus from SA node = Na+ channels to open = Na+ influx
Ca2+ start to open slowly

Question 8

What occurs during phase 1 of atrial & ventricular muscle action potentials

Answer 8

EARLY REPOLARISATION

Na+ channels close - cells begin to repolarise

Question 9

What occurs during phase 2 of atrial & ventricular muscle action potentials

Answer 9

PLATEAU PHASE
Ca2+ channels open fully = Ca2+ influx = stops repolarisation
K+ channel open slowly

Question 10

What occurs during phase 3 of atrial & ventricular muscle action potentials

Answer 10

RAPID REPOLARISATION
Ca2+ channels close
K+ channel open fully = K+ efflux

Question 11

What occurs during phase 4 of atrial & ventricular muscle action potentals

Answer 11

RESTING PHASE

Na+/K+ pump

Question 12

Systolic/ diastolic pressure in right atrium

Answer 12

1-5

Question 13

Systolic/ diastolic pressure in right ventricle

Answer 13

25/5

Question 14

Systolic/ diastolic pressure in left atrium

Answer 14

5

Question 15

Systolic/ diastolic pressure in left ventricle

Answer 15

120/80

Question 16

Systolic/ diastolic pressure in aorta

Answer 16

120/80

Question 17

What does the area in a ventricular pressure volume loop show

Answer 17

Stroke volume

Relates to the amount of energy consumption during cardiac cycle

Question 18

Equation for stroke volume

Answer 18

SV = EDV - ESV
EDV = End diastolic volume
ESV = End systole volume

Question 19

Describe the steps of electrical conduction

Answer 19

1) Electrical activity generated in SA node spreads out via gap junctions into atria
2) At AV node, conduction is delayed to allow correct filling of ventricles
3) Conduction occurs rapidly through bundle of His into ventricles
4) Conduction through Purkinje fibres spreads quickly throughout the ventricles