The heart

Question 1

What is the protective fluid filled sac around the heart ?

Answer 1

The pericardium

Question 2

What does right atria receive?

Answer 2

Deoxygenated systemic venous return

Question 3

Function of right ventricle

Answer 3

Pushes blood to pulmonary circulation for oxygenation

Question 4

What does the left atrium receive?

Answer 4

Oxygenated blood from pulmonary circulation

Question 5

Function of left ventricle

Answer 5

Pumps oxygenated blood under high pressure to brain and body

Question 6

Name what attaches atrioventricular valves to the cardiac wall

Answer 6

Chordae tendinea
Papillary muscles

Question 7

Structure of the heart wall

Answer 7

1. epicardium
2. myocardium
3. endocardium

Question 8

Function of epicardium

Answer 8

Reduces friction with pericardial fluid + coronary blood

Question 9

Specialisation of myocardium

Answer 9

Encased in collagen fibres

Question 10

Specialisation of endocardium

Answer 10

Smooth muscle

Question 11

Function of a conducting cell

Answer 11

Rapidly spread action potentials

Question 12

Name the heart conducting cells

Answer 12

Purkinje system
Sinoatrial node
AV node
Bundle of his
Atrial internodal tracts

Question 13

Function of contractile cells

Answer 13

Ap leads to contraction causing generation of force or pressure

Question 14

What is a myocyte?

Answer 14

Muscle cells in the heart

Question 15

What are the 5 stages of a cardiac action potential?

Answer 15

0 - Upstroke of action potential
1- Rapid depolarisation
2- Plateau phase
3- Repolarisation
4- Electrical diastolic phase

Question 16

What are the 4 time dependent and voltage gated currents?

Answer 16

Na+
Ca+
K+
Pacemaker current

Question 17

Describe the Na+ current

Answer 17

Rapid depolarising phase
Ap in atrial and ventricular muscle and purkinje fibres

Question 18

Which is the largest current in the heart?

Answer 18

Na+ current

Question 19

Describe Ca+ current

Answer 19

Rapid depolarising phase
SAN, AVN
Triggers contraction in all cardiomyocytes

Question 20

Describe K+ current

Answer 20

Repolarises all cardiomyocytes

Question 21

Describe the pacemaker current

Answer 21

Pacemaker activity of SAN, AVN and purkinje fibres

Question 22

How does an action potential propagate in cardiac cells?

Answer 22

Synchronised ventricular contraction
Depolarisation flows from one cell to another (syncytium) via gap junctions

Question 23

What is a myocardium?

Answer 23

A branched muscle fibre cell connected by intercalated discs

Question 24

Describe the cell structure of a myocardium

Answer 24

Intercalated disk is part of the sarcolemma
Gap junctions
Desmosomes anchor fibres together

Question 25

What are t tubules formed from?

Answer 25

Deep invaginations in the sarcolemma

Question 26

Describe the events after T tubule depolarisation

Answer 26

T tubule depolarisation triggers calcium release in the cell core (near z line) Calcium is released from sr Actin and myosin are able to interact and a large instantaneous force occurs

Question 27

What is a dyad?

Answer 27

Sarcoplasmic reticulum and T tubules

Question 28

What is coupled to an L type T tubule Ca2+ channel?

Answer 28

Ca2+ release in cardiomyocytes and VSMC

Question 29

What is a T type Ca2+ channel coupled to ?

Answer 29

Pacemaker and conducting cells

Question 30

What does Cytosolic calcium activate?

Answer 30

Activates a channel on the sarcoplasmic reticulum which causes calcium induced calcium release

Question 31

What is the effect of a global increase in calcium concentration?

Answer 31

Calcium binds troponin C and releases troponin I which inhibits actin

Question 32

What is the cardiac depolarisation sequence?

Answer 32

SAN depolarisation is spontaneous -> AP propagates from left to right side of the heart (rate of 60-100/min) via gap junctions-> Reaches AVN -> Fibrous AVN ring prevents the signals from propagating AVN tissue -> AP is passed to ventricular muscle (via HIS purkinje fibre system)

Question 33

What is the primary pacemaker in the cardiac depolarisation sequence?

Answer 33

SAN

Question 34

What is the secondary pacemaker in the cardiac depolarisation sequence?

Answer 34

AVN

Question 35

Where in the heart is the sinoatrial node?

Answer 35

In the right atrium

Question 36

Where in the heart is the atrioventricular node?

Answer 36

In the right atrium

Question 37

Describe the cardiac cycle

Answer 37

1. Atrial systole 2. Isovolumetric ventricular contraction 3. Rapid ventricular ejection 4. Reduced ventricular ejection 5 . Isovolumetric ventricular relaxation 6. Rapid ventricular filling 7. Reduced ventricular filling

Question 38

What happens in Atrial systole?

Answer 38

Atria are depolarised Mitral and tricuspid valves open Ventricles further fill Contraction causes an increase in p

Question 39

What happens in isovolumetric ventricular contraction?

Answer 39

Ventricular p > atrial p Purkinje fibres electrical activation cause ventricular contraction causing large increase in p Mitral/tricuspid valve closes

Question 40

What happens in rapid ventricular ejection?

Answer 40

Ventricular p > aortic p SLV opens Stroke volume ejection Ventricular volume decreases Atrial p increases

Question 41

What happens in reduced ventricular ejection?

Answer 41

Final blood ejection from ventricles due to contraction Ventricular repolarisation as ventricular p decreases Arterial volume decreases

Question 42

What happens in isovolumetric ventricular relaxation?

Answer 42

Occurs when ventricles are fully repolarised Ventricles relax causing ventricular p decrease Ventricular p > arteriole p All valves are closed Ventricular volume remains constant Atrial p increases Arteriole v decreases

Question 43

What happens in rapid ventricular filling?

Answer 43

Atrial p > ventricular p Mitral and tricuspid valves open Blood enters the ventricles from atria

Question 44

What happens in reduced ventricular filling?

Answer 44

Remaining blood enters the ventricle

Question 45

What does an ECG measure?

Answer 45

The movement of external portion of ions

Question 46

What does the P wave show?

Answer 46

Atrial depolarisation

Question 47

What does the PR interval show?

Answer 47

AVN conduction as it reflects initial depolarisation of atria to ventricles

Question 48

What does QRS show?

Answer 48

Depolarisation of ventricles

Question 49

What does T wave show?

Answer 49

Repolarisation of ventricles

Question 50

What does atrial tachycardia display on ECGs?

Answer 50

P wave masks T wave due to speed

Question 51

What does atrial fibrillation display on ECGs?

Answer 51

P wave isn't presented

Question 52

How does ventricular fibrillation display on ECGs?

Answer 52

No sequenced filling of ventricles so no sequenced pattern