The Heart Flashcards
What are the components of the heart?
Vena cava (superior and inferior), right and left pulmonary artery, cardiac muscle, right and left atrium, tricuspid valve, right and left ventricle, very thick left muscular wall, bicuspid valves, semilunar valves, pulmonary veins, aorta
Where does blood enter/leave the heart?
Deoxygenated enters the right side of the heart via the vena cava and leaves to the lungs via the pulmonary artery, oxygenated blood enters the left side of the heart via the pulmonary vein and leaves to the rest of the body via the aorta
What happens in the cardiac cycle?
Diastole and systole (atrial and ventricular)
What is diastole?
When the entire heart relaxes so the atria and ventricles fill with blood
What is atrial systole?
Atrium contracts so blood flows into the ventricles
What is ventricular systole?
Ventricles contract so blood flows into the arteries
What are the atrioventricular valves?
Bicuspid and tricuspid valves
What valves are open in diastole?
Atrioventricular valves are open and semi lunar valves are closed
What valves are open in atrial systole?
Atrioventricular valves are open and semi lunar valves are closed
What valves are open in ventricular systole?
Atrioventricular valves are closed and semi lunar valves are open
How long is the cardiac cycle?
~0.8 seconds
How does pressure effect valves in the heart?
High pressure behind causes valves to open, high pressure in front causes valves to close
Define the term myogenic
Contraction and relaxation not controlled by the brain
What is the beats per minute of the pacemaker cells?
60 bpm
What is the beats per minute of the heart? (usually)
70 bpm
Why is the bpm higher in the heart than the pacemaker cells?
Because other factors like exercise, excitement and stress also effect our heart rate
What are the factors used in the electrical conduction in the heart?
Sino-atiral node (SAN), atrio-ventricular node (AVN), Purkyne fibres, bundle of His, right and left bundles of Purkyne tissues
How is the rhythm of the heart maintained via electrical excitation?
- wave of electrical excitation begins in pacemaker area called the sino-atrial node (SAN)
- this causes the atria to contract, but a layer of non-conductive tissue prevents the excitation effecting the ventricle
- electrical activity in the SAN is picked up in the atrio-ventricular node (AVN). There is a slight delay before the signal stimulates the bundle of His
- this penetrates the septum between the ventricles
- the bundle of his splits into two branches and carries wave of excitation to the apex (bottom) of the heart
- the wave of excitation spreads through the Purkyne fibers at the apex up, causing a contraction of the ventricles starting from the bottom up
Why is it important the wave of excitation starts at the apex then travels up?
So the blood is emptied from the ventricles efficiently
What is an electrocardiogram?
A measure of electrical differences in your skin which result from the activity in the heart to measure the spread of electrical excitation
What are electrocardiograms used for?
Diagnosing heart conditions/recognising irregular heart patterns
In electrocardiography, what is the P wave?
Depolarisation of the atria in respone from signalling at the SAN
In electrocardiography, what is the QRS complex?
Depolarisation of ventricles triggered by signals at the AVN
In electrocardiography, what is the T wave?
Repolarisation of the ventricles and completion of a heart beat
