The heart

Question 1

what are the 2 atrioventricular valves? where are they?

Answer 1

Mitral and tricuspid
They are between ventricles and atria

Question 2

what are the 2 semilunar valves? where are they?

Answer 2

Aortic and pulmonary
They separate ventricles from the arteries

aortic- aorta
pulmonary- pulmonary artery

Question 3

How are valves connected to the cardiac wall?

Answer 3

tendinous cords and papillary muscles

Question 4

Why is the left side of the heart under more pressure?

Answer 4

pumps blood all around the body

Question 5

what is the cardiac cycle?

Answer 5

flow of blood through the heart to meet the needs of the body

Question 6

what is the function of valves?

Answer 6

they control unidirectional blood flow in the cardiac cycle

BLOOD FLOWS IN 1 DIRECTION ONLY

Question 7

what is the largest vein and artery?

Answer 7

vein- vena cava
artery- aorta

Question 8

what are the 3 layers of the heart wall?
*all cells are electrically active

Answer 8

Epicardium- outside layer
Myocardium- heart muscle
Endocardium- inner lining

Question 9

what are the 2 types of cells within the myocardium?

Answer 9

conducting cells- rapidly spread action potentials
contractile cells- action potentials lead to contraction–>generation of force/pressure

Question 10

where is the SAN located?

Answer 10

top of the right atrium

Question 11

what is the link between the electrical signals and contraction of the myocytes?

Answer 11

extracellular calcium

Question 12

myocardium are extensively branched muscle fibre cells, what are they connected by?

Answer 12

Intercalated discs (ID)

Question 13

What structure are intercalated discs a part of?

Answer 13

Sarcolemma

Question 14

We now know that myocardium are connected by ID. What else is found within these ID?

Answer 14

Gap junctions- channels between cells that allow depolarising current to flow from cell to cell

Question 15

What does syncytium mean in myocardial cell structure?

Answer 15

When cells act together in a wave like formation

Question 16

What gives the myocardium structural integrity?

Answer 16

Desmosomes- anchor fibres together

Question 17

What are the 2 main phases of the cardiac cycle?

Answer 17

Diastole- relaxation
Systole- contraction

Question 18

Explain the cardiac cycle- depolarisation sequence

Answer 18

Electrical signal starts from SAN (primary pacemaker) where cells depolarise spontaneously

Action potentials can EITHER move from cell to cell via gap junctions from right to left atria
OR
through conducting pathways

It takes 0.1s to reach the AVN (because there is a non conducting layer of tissue between atria and ventricles). This allows optimal atrial emptying

Action potential has reached AVN (secondary pacemaker) which is linked to His purkinje fibre system

Action potential is then carried to the ventricular muscles via left+right branches of conducting cells

Action potential propagates cells to cell allowing SYNCHRONISED ventricular contraction

Optimal ejection of blood

Question 19

What are the 3 pacemakers? Outline the differences

Answer 19

1- SAN (60-100bpm)
2- AVN (40bpm)
3- Purkinje fibres (20bpm)

Question 20

Explain the first part of the cardiac cycle sequence(wiggers diagram)

Answer 20

1- Atria depolarise due to SAN stimulation
2- Due to atria contracting, ATRIAL PRESSURE INCREASES
Ventricles are relaxed + mitral/tricuspid valves open (ventricles further fill with blood)
3- Ventricles contract leading to INCREASED VENTRICULAR PRESSURE
4- However, ventricular volume stays the same
5- Mitral + tricuspid valves close

Question 21

Explain the second part of the cardiac cycle sequence(wiggers diagram)

Answer 21

1- Semilunar valves open- rapid blood ejection so DECREASED VENTRICULAR VOLUME
2- As the ventricular volume decreases, blood moves through to the aorta so ARTERIAL PRESSURE INCREASES
3-Ventricles are repolarising so pressure decreases as ventricles are no longer contacting
4- Arterial volume decreases due to elastic recoil

Question 22

Explain the last part of the cardiac cycle sequence(wiggers diagram)

Answer 22

Isovolumetric ventricular relaxation:
1- Happens after ventricles fully repolarise
2- ventricles relaxed so pressure decreases
3- SLV close - ventricular pressure is below arterial pressure (S2)
4 - All valves closed + ventricular volume is constant

Question 23

What causes heart sounds?

Answer 23

S1- mistrial and tricuspid valve closure
S2- aortic and pulmonary valve closure
S3- ventricles filling from atria

Question 24

What Varys in myocytes?

Answer 24

They vary anatomy and channels. They have time dependent + voltage gated currents during cardiac cycle

Question 25

Describe what the waves of an ECG show

Answer 25

P wave- depolarisation of atria

PR interval- time between atrial depolarisation and ventricular depolarisation

QRS complex- depolarisation of ventricles

ST segment- region between en of V depolarisation and V repolarisation

T wave- repolarisation of ventricles