Cardiovascular System

Question 1

Why is the heart important?

Answer 1

The heart is the pumping muscle that keeps the blood in motion

Ultimately all of the functions of the body depend on the heart keeping the blood moving

Question 2

Rapid transport

Answer 2

oxygen, glucose, amino acids, fatty acids, vitamins, drugs and water to the tissues

Carbon dioxide, urea and creatinine away from the tissues

Question 3

Control system

Answer 3

Distributing hormones to the tissues and secreting a hormone (atrial natriuretic peptide)

Question 4

how does body temperature regulation work?

Answer 4

Transporting heat from deep organs to the skin surface for dissipation

Question 5

Functions of the CVS

Answer 5

Rapid transport
Control system
Body temperature regulation

Question 6

Important points

Answer 6

Both circuits begin and end at the heart

Blood must travel through them in sequence

Blood is constantly moving in both circuits

Both ventricles eject equal amounts of blood at the same time

One way valves ensure that the blood follows this pattern

The pulmonary circulation is unique in that the arteries carry oxygen poor blood and the veins carry oxygen rich blood

Question 7

Normal values

Answer 7

Stroke volume in a normal adult is typically 70-80ml

Question 8

Cardiac Output

Answer 8

Cardiac output (CO) is the volume of blood ejected by one ventricle in one minute

Question 9

heart rate

Answer 9

The number of times the heart contracts in a minute

Question 10

stroke volume

Answer 10

Each time a ventricle contracts the amount of blood ejected

Question 11

Blood flow

Answer 11

the volume of blood flowing through a vessel in a given period (ml/min)

Question 12

Blood pressure

Answer 12

the force per unit area exerted on a vessel wall by the contained blood, expressed as mmHg. The pressure gradient provides the driving force to keep blood moving

Question 13

Resistance

Answer 13

the opposition to flow and is the amount of resistance blood encounters as it passes through the vessels

Question 14

Darcy’s law of flow

Answer 14

Flow, Q (written with a dot over it) is the volume transferred per unit time (ml/min)

Flow is proportional to the pressure difference between the inlet pressure and outlet pressure in a steady state, along a rigid tube – P1-P2 (mmHg)

Resistance (mmHg/ml/min), R is inversely proportional to conductance the ease of flow

Hence: Q = (P1-P2)/R

Question 15

Resistances in series

Answer 15

Resistances in wide vessels is low, in narrow vessels is high

When vessels are connected in series their resistances are added

the resistance of the large aorta is low as it is connected in series to narrow arterioles and capillaries the overall resistance of the systemic circulation is high

Systemic circulation resistance is 0.02mmHg per ml/min

Pulmonary circulation resistance is much lower at 0.003mmHg per ml/min

Question 16

Changes in local blood flow

Answer 16

The law of flow allows us to understand how flow to an organ is regulated

Locally changes in blood flow are regulated by changes in vascular resistance

Changes are brought about by contraction and relaxation of the narrow terminal branches of the arterial system

Question 17

Two ways to increase flow

Answer 17

Increase the driving pressure

Reduce the vascular resistance

Question 18

Right and Left Timing

Answer 18

Both atria contract at roughly the same time

Both ventricles contract at roughly the same time

The ventricles eject equal volumes of blood into the pulmonary and systemic circuits in a normal heart

Ventricular contraction is called systole

Ventricular relaxation is called diastole

Question 19

Tricuspid valve

Answer 19

sits between the right atrium and right ventricle (3 leaflets)

These valves are called ‘atrioventricular’

Their leaflets are attached to papillary muscles in each ventricle by chordae tendinae

These help support the leaflets and ensure the valves remain closed when the ventricles contract

Question 20

Mitral valve

Answer 20

sits between the left atrium and left ventricle (2 leaflets)

These valves are called ‘atrioventricular’

Their leaflets are attached to papillary muscles in each ventricle by chordae tendinae

These help support the leaflets and ensure the valves remain closed when the ventricles contract

Question 21

Aortic valve

Answer 21

sits between the left ventricle and the aorta (3 cusps)

These are called semilunar valves – their cusps are crescent shaped and are attached to the walls of the artery like pockets

Question 22

Pulmonary valve

Answer 22

sits between the right ventricle and the pulmonary artery (3 cusps)

These are called semilunar valves – their cusps are crescent shaped and are attached to the walls of the artery like pockets

Question 23

Valves Opening

Answer 23

Valves open passively when the pressure of the blood behind them exceeds the pressure in the chamber in front of them

E.g. the mitral valve opens when the pressure in the left atrium exceeds the pressure in the left ventricle

Question 24

Vales Closing

Answer 24

The valves close when the pressure of blood in the chamber behind them falls below that of the chamber in front of them

E.g. The aortic valve closes when the pressure in the left ventricle drops below the pressure in the aorta

The mitral and tricuspid valves are also helped to close by the contraction of the ventricles/papillary muscles

Question 25

Location

Answer 25

• located in the chest between the two lungs

- size of a clenched fist and is angled towards the left-hand-side.

Question 26

How many chambers does the heart have?

Answer 26

4

The artia (left and right) are the filling chambers of the heart, where blood is delivered to.

Question 27

Where does the heart sit?

Answer 27

behind the sternum. The sternum connects the ribs and forms the front of the rib-cage.

The rib-cage offers protection to the heart, lungs and major blood vessels.

Question 28

Arteries

Answer 28

vessels that always carry blood away from the heart.

They deliver oxygen rich blood to the tissues and organs of the body.

As blood leaves the left ventricle, the first artery blood travels through is the aorta.

Question 29

aorta

Answer 29

The largest artery in the body, this is where blood it at the highest pressure.

The aorta branches into a network of smaller arteries that extend throughout the body.

The arteries’ smallest branches are called arterioles.

Question 30

Veins

Answer 30

carry blood towards the heart - they deliver oxygen poor blood from the tissues and organs back to the heart.

When oxygen and nutrients have been delivered to the tissues, blood then travels into venules, these are the smallest veins.

These connect to other venules to form veins, these get progressively larger as they get closer to the heart. The largest veins are the superior and inferior vena cava (SVC and IVC).

These veins deliver blood to the right atrium

Question 31

blood vessels

Answer 31

dynamic, elastic and constantly changing.

Question 32

capillaries

Answer 32

the smallest blood vessels

these are permeable, solutes can flow out of the capillary and waste products can flow into the capillary.