Heart & Circulatory System Flashcards
Why is a mammals double circulation more efficient than a fish’s?
Because the double system allows for different pressures in different areas so that both lungs and body can have blood pass through them optimally.
Thickness of muscle wall in atria
Thin as it contracts to only exert a small / low pressure to push the blood a small distance into the ventricles.
Thickness of muscle wall in right ventricle
It has a medium thickness as it must be enough pressure to push the blood to the pulmonary artery and the lungs and back.
Left ventricle muscle wall thickness
This muscle is the thickest because it must contract to exert a high pressure to push the blood into the aorta and then a long distance to the whole body.
What happens in an open circulatory system?
The heart pumps blood into spaces, haemocoel, in the body cavity. Tissues bathe in blood directly and exchange materials - no vessels. The blood flows slowly back to the heart. It moves to the Head region with assistance from the movement of muscles and valves. No respiratory pigment as no need to transport O2 in insects (and maybe all open circulatory systems….?)
What are the two types of circulatory system?
Open and closed. Within the category of closed circulatory systems, they’re also single and double systems.
Give examples of open and closed circulatory systems
Insects and humans
Describe a closed circulatory system
Blood is in blood vessels and is pumped by muscular heart at high pressure resulting in rapid flow. Tissues are not in Direct contact with the blood but bathe in tissue fluid which can exit out the walls of capillaries. Blood contains haemoglobin pigment.
Describe the single circulatory system
Blood from anywhere in the body may pass once through the heart before returning since gas exchange capillaries and those of other body systems are in the same circulation. E.g. fish
Describe a double circulatory system
Blood must pass at least twice to the heart before returning to the same location, since it must complete a separate pulmonary circulation to the systematic circulation. This is the system of mammals.
What is the systematic circulation?
Heart - body – heart
What is the pulmonary circulation?
Heart-lungs-heart
Advantages of double circulation?
the heart can increase the pressure post lungs so blood flows quicker at a higher pressure to body tissues. Therefore it is more efficient in the delivery of oxygen and nutrients. SYSTEMATIC CIRCULATION CAN CARRY BLOOD AT A HIGHER PRESSURE THAN PULMONARY
What is the function of the heart?
To contract and relax, pumping blood as result. It is a muscles (cardiac). It is myogenic, meaning it beats from within the muscle itself.
Ventricular systole basic happenings
Ventricles contract, volume decreases, and pressure increases. Atrioventricular valves are closed, semilunar open. Atria relax
What are the stages of the cardiac cycle?
Diastole, atrial systole, ventricular systole -> diastole
What happens at ventricular systole ?
Blood is forced through the semilunar valves (pulmonary and aortic valves) into the aorta and pulmonary artery.
What happens at diastole?
Blood enters from the vena cava and pulmonary vein into the atria by venous return. The atrioventricular valves are open and semilunar are closed. Atria and ventricles are relaxed
What are the basic happenings of atrial systole?
Atria contract, volume decreases, pressure increases, blood enters the ventricles down a pressure gradient. Atrioventricular valves are open and semilunar are closed. Ventricles relax
When do the atrioventricular valves open?
when the pressure in the atria is greater than the pressure in the ventricles. The valves cusps are pushed open to allow blood to flow down a pressure gradient from the atria to the ventricles.
When are the atrioventricular valves closed?
when the pressure in the ventricles is greater than the pressure in the atria. The valves cusps are pushed closed to prevent backflow of blood from the ventricles to the atria. When the atrioventricular valves closed they make a lub sound
When are the semilunar valves open?
When the pressure is greater in the ventricle than in the pulmonary artery aorta. the valve cusps are pushed open to allow blood to flow down a pressure gradient from the ventricles to the body / lungs / heart/ head arteries
When are the semilunar valves closed?
when the pressure is greater in the aorta / pulmonary artery than in the ventricles. The valve cusps are pushed closed to prevent backflow of blood from the aorta / pulmonary artery to the ventricles. When the semilunar valves close they make a dub sound.
Tachycardia
An increased heart rate
Heart block
Decreased heart rate
Atrial fibrillation
Problem with atrial contraction
Ventricular fibrillation (heart attack)
Problem with ventricular fibrillation
Repolarisation
Restored to having no electricity across it
Depolarisation
When something has electricity travel across it
Non conductive connective tissue
Terminates the impulse, causes diastole , blood enters the ventricles from the veins.
Purkyne fibres
cause ventricular systole, transmit the impulse up through the ventricles from the base upwards. Blood flows from the ventricles to the arteries through the semilunar valves.
Sinoatrial node - SAN - pacemaker
Causes atrial systole, blood flows from the atria to the ventricles through the atrioventricular valves.
Atrioventricular node - AVN
Delays impulse before sending it down the bundle of his, allows atria to fully contract before ventricle contracts.
Bundle of His
Transmits impulse down the septum to the apex of the heart. it then starts to travel up the Purkyne fibres. For a split second there is enough pressure from the contraction of the base of the ventricles to shut the atrioventricular valve but not enough to open the semilunar. At this point there is no blood flow through the heart.
