Topic 4 - Circulatory System In Mammals Flashcards
What is the pulmonary circulation
The circuit going from the heart to the lungs and back
What is systemic circulation
The circuit from the heart to the rest of the body
Why is it a double circulation in the heart
Because there are two circuits, and blood gets pumped out of the heart twice
Where does blood get pumped out of from the heart
The right ventricle to the lungs
The left ventricle to the body
Why does the left ventricle have thicker cardiac muscle than the right ventricle
The blood pumped out of the left ventricle needs to go to the body, and therefore needs a greater amount of pressure
What are the advantages of the two-pressure system in the heart
The low pressure in the pulmonary circulation pushes blood slowly to the lungs allowing more time for gas exchange
The high pressure in the systemic circulation ensures blood is pumped to all the other body organs and allows tissue fluid to form in each organ
What is the only artery that pumps deoxygenated blood, and what is the only vein that pumps oxygenated blood
Pulmonary artery
Pulmonary vein
What is the coronary circulation
The circulation that provides the cardiac muscle in the heart with oxygen and nutrients
What are the 3 main stages during each beat of the heart, and what occurs during each
Atrial systole - atria contract
Ventricular systole - ventricles contract
Diastole - both atria and ventricles are relaxed
What makes the first heartbeat sound
The first heart sound is produced by closure of the atrioventricular valves
What causes the second heartbeat sound
The second, sharper sound is produced by the clapping shut of the semilunar valves
What is the difference between a phonocardiogram and a electrocardiogram
A phonocardiogram shows the sounds of the heart, an electrocardiogram records the electrical activity of the heart
On an electrocardiogram, what does the Wave T, QRS, and Wave P represent
Wave P shows the excitation of the atria
QRS indicates the excitation of the ventricles
Wave T corresponds to diastole
What are the events that occurs during Atrial Systole
Atria contract pushing more blood into the ventricles. This is essentially topping up the ventricles.
What events occur during Ventricular systole (a)
Ventricular pressure increase causes the atrioventricular valves to bulge into the atria increasing pressure there, thought this is not great enough to cause blood to exit the major arteries; the falls of the atrioventricular valves are prevented from turning inside out by the chordae tendinae, aided by contraction of the papillary muscles
What events occur during ventricular systole (b)
Ventricular pressure increases to exceed that in the major arteries, pushing the semilunar valves open and causing the ejection of blood from the heart; blood is returned to the atria from the major veins and so atrial pressure gradually increases
What events occur during Diastole (a)
Ventricular pressure drops to become lower than that in the main arteries, so the semilunar valves are forced shut. Blood continues to the be returned to the atria though it cannot enter the ventricles since the ventricular pressure is still greater than that in the atria, so the atrioventricular valves remain closed
What events occur during diastole (b)
Ventricular pressure drops to a point where it becomes lower than that in the atria. Therefore, the atrioventricular valves are forced open and blood enters the ventricles from the atria
How is the heartbeat myogenic
Contraction originates in the heart itself and does not depend on nervous stimulation
What is the sinoatrial node, and what is its function
It is what the heartbeat starts with, it is a small patch of tissue in the right atrium that acts as a pacemaker
What does excitation of the SA node cause
It causes the atria to contract together
Where is the non-conductive tissue located, and what is its function
Between the atria and ventricles, it prevents the spread of the wave of excitation passing directly from atria to the ventricles
Where must the wave of excitation go to to reach the ventricles
The atrioventricular node
What do excitation of the AV node cause
A short time delay before the waves of excitation pass down to the base of the ventricles