Structure And Function Of Heart

Question 1

What is the first two steps of the heart beat

Answer 1

1- deoxygenated blood enters RA from the superior vena carva and inferior (low pressure)
2- as blood flows in, slight pressure builds up until AVN opens.

Question 2

What happens after the AVN opens in RA

Answer 2

• allows blood to flow into the right ventricle
  When both RA and RV are full with blood, the RA contracts and all the blood is forced into the RV, stretching the walls.
  -RV contracts and this closes AVN preventing backflow

Question 3

What happens after the RV contracts and the AVN opens?

Answer 3

1- the RV contracts fully and pumps deoxygenated blood through semilunar into pulmonary artery
2- transport it to capillary bed of lungs

Question 4

What happens at the same time as the deoxygenated blood enters the ra

Answer 4

1) oxygenated blood from lungs enter LA from pulmonary vein
2) when the pressure builds up in LA, bicuspid valve opens and lets blood flow into LV

Question 5

What happens when the Bicuspid valve opens to let blood into LV

Answer 5

1- LV fills with oxygenated blood and when both LA and LV are full, the LA contracts fully forcing all of the blood into LV
2- when LV is full, it contracts and pumps oxygenated blood into aorta around body

Question 6

Which side is thicker and why

Answer 6

The left side much thicker with more muscle walls to provide more force to overcome resistance of aorta

Question 7

What happens in diastole

Answer 7

Heart is relaxed
All valves closed
Atria fills then ventricles
Volume and pressure in heart build slowly as heart fills

Question 8

What happens in atrial systole

Answer 8

Atria contracts
Atrial volume decreases
Atrial pressure increases more than ventricle causin av valves to open
Ventricles start filling ( ventricular diastole)

Question 9

What happens in ventricular systole

Answer 9

Ventricles contract
Ventricle volume decreases
Ventricle pressure increases more than atria so av valves close
Pressure very high causes semilunar valves to open and blood flows into arteries

Question 10

Steps of the heart rhythm

Answer 10

1-a wave of excitation in SAN causes atria to contract- initiates heartbeat. Layer of non conducting tissue causes hesitation
2- electrical activity picked up by AVN and causes slight delay before stimulating bundle of his (made of Purkinje fibres) which penetrate through septum between ventricles
3-bundle of his splits into 2 branches and conducts wave of excitation to apex
4- at apex, purkynge fibres spread out through walls on both sides, contraction allows more efficient emptying of ventricles