Cardiovascular system: Blood circuits 2/2

Question 1

What is the base of the heart?

Answer 1

The point where all the blood vessels connect into the heart (i.e. the top of the heart)

Question 2

Where is the apex of the heart?

Answer 2

It is at the point of the left ventricle

Question 3

What direction is the apex of the heart pointed?

Answer 3

Inferiorly (i.e. downwards), anteriorly (to the front) and to the left

Question 4

What is the distribution of the mass of the heart inside the chest cavity relative to the midline of the body?

Answer 4

About one third of the mass lies to the right, two thirds to the left

Question 5

What is the pericardium?

Answer 5

A double layer of mesothelial cells that contain the heart

Question 6

What is the structure of pericardium?

Answer 6

A layer of mesothelia cells (simple squamous cells similar to endothelium but not exposed to the enviro FYI) that is folded over itself forming an outer layer (parietal pericardium) and an inner layer connected to the heat (visceral pericardium) and the gap in between (pericardial space) is filled with serous membrane

Question 7

What is the purpose of the serous fluid?

Answer 7

It allows the parietal and viscera surfaces to slide without friction as the heart beats

Question 8

Is the heart inside the pericardial space? Explain

Answer 8

No it is not, it is enclosed in the double layer of mesothelial cells that overlap (i.e. imagine your fist in a balloon, your fist is not in the balloon it is surrounded by the balloon and the air is inside the balloon)

Question 9

What is the name of the mesothelial layer when it is considered connected to the heart vs when it is apart of the pericardium?

Answer 9

When it is apart of the pericardium it is called visceral pericardium (how it is more commonly referenced) and when considered connected to the heart it is called epicardium

Question 10

If the wall of the left ventricle is punctured, where will blood from the ventricle collect? What is this called?

Answer 10

When it is punctured, blood from the ventricle drains into the pericardial space, this is called cardiac tamponade

Question 11

What part of the heart cannot contract as acts as an electric insulator?

Answer 11

The fibrous skeleton of the heart

Question 12

What is the purpose of the fibrous skeleton?

Answer 12

Allt he vales are on a similar plane which makes it a weak plane for the heart so a fibrous skeleton is used to reinforce these points

Question 13

Label the diagram

Answer 13

Question 14

What are the two types of nerves in this diagram? What are the differences?

Answer 14

Myocyte muscle nerve top, Purkinje cells on the bottom

The myocytes nerve is not found in the heart, purkinje cells only found in the heart, Myocytes are more contractile but not as good at conduction compared to purkinje cells

Question 15

What is the pathway of electrical conduction in the heart?

Answer 15

1 - The SA Node depolarises and creates an action potential, propagating through the atriums which cause it to contract

2 - The fibrous skeleton is an electrical insulator so the action potential is re-propogated using the AV Node

3 - The AV node then depolarises the purkinje cells in the ventricles causing them to contract

Question 16

What is the relative speed of action potential propagation in the atrium?

Answer 16

Medium speed

Question 17

What is the relative depolarisation speed of the AV node? What does this allow?

Answer 17

Very slow (100ms contraction delay)

Delay allows the atrium to contract before the ventricles so that there is time for the atrium to fill the ventricle

Question 18

What would happen if there was no delay between atrial and ventricular contraction?

Answer 18

The contractile force of the ventricle would overwhelm the atrial contractile force meaning the atrium would not be very effective at fill the ventricles up

Question 19

What is the relative speed of electrical conduction in the ventricles? Why this speed?

Answer 19

Very fast

This is so that there is even ventricular contraction

Question 20

What side of the heart is this for? What process is happening at each step?

Answer 20

This is for the left side

1 - Ventricular filling

2 - Atrial contraction

3 - Isovolumetric ventricular contraction

4 - Ventricular ejection

5 - Isovolumentric ventricular relaxation

Question 21

What is happening during ventricular filling?

Answer 21

This is when the left atrium and ventricle are filling up PASSIVELY as the heart relaxes after contraction

Question 22

How much of the hearts blood goes into the heart during ventricular filling?

Answer 22

80%

Question 23

What happens during atrial contraction?

Answer 23

This is when the left atrium contracts to further fill the left ventricle with blood

Question 24

Does much more blood comes into the left ventricle during atrial contraction? Why this amount?

Answer 24

It fills the ventricle by about 20%, this is because there are no valves on the atrium so when it contracts it is leaking blood backward and also it is not very strong so it can’t push much more blood into the heart

Question 25

What blood vessel goes into the left atrium?

Answer 25

The pulmonary vein

Question 26

What happens in isovolumetric ventricular contraction?

Answer 26

The left ventricle begins to contract increasing the blood pressure in the ventricle but it is unable to push blood out

Question 27

What makes isovolumetric ventricular contraction isovolumetric (i.e. no change in volume)?

Answer 27

Because the valves into the atrium are closed and the pressure in the aorta is still too high as the ventricle, having only just contracted, has not developed enough pressure to push blood through outlet/semi-lunar valve

Question 28

What happens during ventricular ejection?

Answer 28

The pressure in the ventricle is now large enough to overcome the pressure in the aorta so blood is pumped through the aorta

Question 29

What happens during isovolumetric ventricular relaxation?

Answer 29

The ventricle relaxes after contraction and the pressure is greater is the aorta so outlet valve closes and the pressure in the atrium is lower so the inlet valve is closed therefore pressure inside ventricle drops with no change in volume

Question 30

What processes during the cardiac cycle are the atriums systolic?

Answer 30

Systolic during atrial contraction

Question 31

What processes during the cardiac cycle are the ventricles systolic?

Answer 31

Systolic during isovolumetric ventricular contraction and ventricular ejection

Question 32

What processes are diastolic for both the atrium and ventricle?

Answer 32

Ventricular filling (passive) and isovolumetric ventricular relaxation

Question 33

What is the diastolic and systolic pressure?

Answer 33

Diastolic pressure is the lowest pressure for which the blood can be pumped in the aorta

Systolic is the peak pressure the ventricle produces during contraction

Question 34

What is the normal time of a cardiac cycle?

Answer 34

0.8 - 1 second

Question 35

During exercise, what happens to the phases of the cardiac cycle?

Answer 35

They get shorter

Question 36

What part of the cardiac cycle gets particularly shorter? Why this phase?

Answer 36

Ventricular ejection

The amount of blood pumped out is an inverse relationship (i.e. blood flow rate out of heart decreases over time) so by the end of ventricular ejection not much blood is being pumped out so by shortening it, you are not losing much blood and can get back to the peak pressure again quicker