The Heart Flashcards
What type of circulatory system do humans have
They have a double circulatory system
Where is blood pumped in the double circulatory system of humans
Deoxygenated blood is pumped form the heart to the lungs where oxygen diffuses into the blood.
The oxygenated blood then passes to the heart again where it is then pumped to the tissues and oxygen diffuses to them
The deoxygenated blood then passes back to the heart and the cycle continues.
What type of muscle is the heart formed from and how many chambers does it have
It is formed from cardiac muscle and has 4 chambers.
What are the top 2 chambers called and what is a feature of them and what are the bottom two chambers called and what is a feature of them
The top 2 chambers are called atria and have relatively thin muscular walls.
The bottom two chambers are called ventricles and have thicker muscular walls than the atria.
What are the atria separated front he ventricles by
Atrioventricular valves
What is the left and right AV valves called
The left AV valve is the bicuspid valve
The right AV valve is the tricuspid valve
What the AV valves attached to and what do what they are attached to do
They are attached to tendons ensuring that the valves open in the right direction.
What are the right and left side of the heart separated by and what does this do
They are separated from each other by a wall called the septum, and it prevents blood from passing directly between the two sides of the heart.
What does deoxygenated blood enter the right atrium through and what are do the two different branches do
The vena cava
The vena cava has two branches, the superior vena cava which brings in blood from the head and upper parts of the body and the inferior vena cava which brings in blood form the lower parts of the body.
Where is the deoxygenated blood pumped to once in the right atrium
It is pumped from the right atrium to the right ventricle, the right ventricle then pumps the deoxygenated blood out of the heart to the lungs through the pulmonary artery. In the lungs the blood becomes oxygenated.
Where does the oxygenated blood return to the heart from
The blood then returns from the lungs to the heart through the pulmonary vein, the pulmonary vein brings blood into the left atrium and the blood then passes into the left ventricle, it then passes out of a large blood vessel called the aorta.
What does the aorta do
The aorta then transfers the oxygenated blood to all the parts of the body including the head.
What is a feature of the contraction of the right and left side of the heart
They contract at the same time
Why does the right ventricle have a thinner muscular wall than the left ventricle
Because the left ventricle pumps blood around the whole body. Whereas the right ventricle only pumps blood to the lungs.
What do the pulmonary artery and aorta both contain
They both contain valves
What does the coronary artery do
It supplies the heart muscle with oxygen and nutrients.
What does systole and diastole mean
systole mean contracting and diastole means relaxing
What are the atria and ventricle at the start of the cardiac cycles
They are at diastole and are relaxed at the start of the cardiac cycle
At the start of the cardiac cycle what occurs
Blood flows into the atria through the vena cava and the pulmonary vein causing the pressure in the atria to rise.
What is the second stage of the cardiac cycle
At a point the pressure in the atria is greater than the ventricles, causing the atrioventricular valves to open, allowing blood to flown down from the atria into the ventricles. The atria then contract and atrial systole takes place.
What is the third stage of the cardiac cycle
This pushes the remaining blood from the atria down into the ventricles, and after a short period of time the ventricles contract (ventricular systole)
What is the fourth stage of the cardiac cycle
The pressure in the ventricles rises and because It is greater than the atrial pressure the AV valves close preventing back flow. The semilunar valves in the pulmonary artery and aorta also open and blood is pumped from the ventricles out of the heart.
What is a feature of the ventricles and atria
When the ventricles have contracted the atria are relaxed.
What is the last stage of the cardiac cycle
The ventricles relax entering ventricular diastole
The pressure in the ventricles falls below the pressure in the pulmonary artery and aorta. Causing the semi lunar valves to shut preventing blood flowing back into the ventricles.
Annotate the graph of the pressure of the heart with the different stages in one note.
Check with notes
What does the heart not need to beat
It doesn’t need an external signal to beat and because the heart triggers its own beat the heart muscle is myogenic.
What is present in the wall of the right atrium
There is a group of specialised cells called the silo atrial node or SAN (also called the pacemaker)
What do the cells in the SAN do
They depolarise (becoming electrically excited) this triggers a wave of electrical excitation to spearhead across the atria, causing the atria to contract. This contraction of the atria is called atrial systole.
What can the wave of electrical excitation in the atria not pass into and why
It can’t pass directly down into the ventricles, as the ventricles are separated from the atria by a layer of non-conducting tissue
What is present between the atria
There is the presence of another group of specialised cells called the atrio-ventricular node or AVN, and this is connected to conducting fibres called perkyne fibres, which are initially bundled together and called the bundle of his, but then branches with the purkyne fibres running down the apex and then up the walls of the ventricles.
What does the AVN do
It detects the electrical excitation passing over the atria and after a short delay it then transmits the electrical excitement down the purkyne fibres. Causing the ventricles contract
In what direction do the ventricles contract and what does this do
They contract from the apex upwards and ensures the maximum volume of blood is pumped out of the ventricles.
Why is there a delay before the AVN triggers the electrical excitation
There is a slight delay before the AVN triggers the electrical excitation down the purkyne fibres ensuring that the ventricles contract after the atria has contracted.
