8.5 The Heart Flashcards
Name the different vessels and their functions
Aorta : oxygenated blood to the body
Vena Cava : de oxygenated blood to the heart
Pulmonary artery : deoxygenated blood to the lungs
Pulmonary vein : oxygenated blood to the heart
Which side of the heart is thinner? Why?
To make sure the delicate lung tissue isn’t damaged.
What is the function of tendinous cords?
To make sure the valves are not turned inside out by the pressure exerted when the ventricles contract
What do valves do? How do they work?
They stop blood flowing the wrong way
They one open one way.
If there is more pressure behind a valve, they are forced open.
If there is more pressure in-front of the valve, it’s forced shut.
Where are the semi-lunar valves?
Link the ventricles to the pulmonary artery and aorta
Where are the atrioventricular valves?
In between the atria and ventricles.
Describe and explain the cardiac cycle ( just for notes, other cards for revision)
Atria contract ( ventricles relax )
This decreases their volume and increases pressure
Blood pushed into ventricles through atrioventricular valves
Slight increase in ventricular pressure and volume as they receive the blood
Ventricles contract ( atria relax )
This decreases their volume and increases pressure
This pressure forces the atrioventricular valve close
This also opens the semi-lunar valves
Blood is forced into the pulmonary artery and aorta
Both atria and ventricles relax
Semi lunar valves close
Atria fills with blood and increases pressure
Ventricles continue to relax and have decreased pressure
AV valve opens and blood flows passively into ventricles
Atria contracts
What happens after the atria contract ?
This decreases their volume and increases pressure
Blood pushed into ventricles through atrioventricular valves
Slight increase in ventricular pressure and volume as they receive the blood
What happens after the ventricles contract?
This decreases their volume and increases pressure
This pressure forces the atrioventricular valve close
This also opens the semi-lunar valves
Blood is forced into the pulmonary artery and aorta
What happens after both the atria and ventricles relax?
Semi lunar valves close
Atria fills with blood and increases pressure
Ventricles continue to relax and have decreased pressure
AV valve opens and blood flows passively into ventricles
Where is the sino-atrial node and atria ventricular node located?
The right atrium
Define myogenic
Can contract and relax without receiving signals from nerves
Describe how the SAN and AVN work to make the heart contract
SAN sends out waves of electrical activity to atrial walls
This causes both atria to contract at the same time
Layer of non-conducting collagen tissue prevents waves of electrical activity behind passed directly to ventricles
Instead it is transferred to the AVN
AVN passes it onto bundle of His ( after slight delay to make sure ventricles contract after atria have emptied )
bundle of His conducts waves to Purkyne tissue
Purkyne tissue carries waves into walls of both ventricles causing them to both contract at the same time from the bottom up
What is the bundle of His?
A group of musicale fibres
What do electrocardiographs record?
When the heart contracts, it depolarises ( loses electrical charge )
When the heart relaxes, it repolarises ( regains charge )
ECG records these changes
