Circulatory System Flashcards
What is an open circulatory system
No vessels
Direct movement of substances in and out of heart
What is a closed circulatory system
Blood enclosed within vessels- diffusion of substances only occurs in vessels
Benefits of a mass transport system
Carries raw materials from specialised exchange organs to the body cells to remove metabolic waste
Define double circulatory system
Blood flows through the heart twice for each complete circuit of the body. Maintains a high blood pressure to meet demands of a high metabolic rate
Why is a closed circulatory system more effective
Blood is forced through narrow tubes so travels faster and under higher pressure
Three disadvantages of single circulatory systems as seen in fish
Blood pressure drops as blood passes through the gill capillaries so it flows slowly and therefore the rate of delivery of oxygen to respiring tissues is limited
Order of vessels in a closed system
Arteries
Arterioles
Capillaries
Venules
Veins
Blood vessel tissue layers
Smooth muscle- contracts to control the flow of blood (vein arteries arterioles)
Elastic layer - allows the vessel to stretch and recoil (arteries arterioles veins)
Endothelium- then to inner lining which is smooth to reduce friction (all vessels)
Features of veins
Thin wall large lumen valves
Features of arteries
Thick walls small lumen elastic layer
Features of capillaries
One cell thick large number high sa
Where is blood pressure the highest
In the aorta immediately after ventricular contraction
Where is blood pressure the lowest
Vena cava final blood vessel before returning to the heart
Why does blood lose pressure going through the system
Branching into many vessels
Increase lumen size of vessels
Friction
What is a semi lunar valve and what is its purpose
From ventricle to pulmonary artery or aorta depending on which side
To prevent back flow
What are the 3 stages of the cardiac cycle
Diastole (relaxing)
Arterial systole (contracting)
Ventricular systole (contracting)
What happens is diastole
The atria + ventricular muscles are relaxed and blood enters leading to an increases in pressure
What happens in atrial systole
Atrial muscles contract increasing pressure due to the decrease in volume
Atrioventricular valves forced to open by the pressure
What happens in ventricular systole
Ventricles contract. Big increase in pressure in ventricle forces atrioventricular valve to shut and semi lunar valves to open. Blood pushed out due pressure being higher in ventricles than the atria
Describe the ventricle pressure graph
Small increase during atrial systole then during ventricular systole sharp increase then curves back down into diastole
Describe the atrial pressure graph
When the av valve shuts in ventricular systole the pressure decreases below 0 then gradually increases as the atria begins to refill then in diastole when the av ba,be opens it decreases again
Goes no higher then 2 kPa
Describe the aortic pressure graph
Begins much higher at 12.5 as opposed to others that start at just below 0
During atrial systole the gradient stays 0 then as the semilunar valve opens in ventricular systole a parabola shape forms just underneath thr ventricle pressure one. When the semi lunar valve Shuts at the start on diastole there is a little increase then decreas to the same pressure it began on
Equation for cardiac output
Heart rate x stroke volume
= the volume of blood which leaves one ventricle in one minute
Features of the heart that creates cardiac impulse
Myogenic- generates its own electrical impulse without external stimulation. The impulse is spread across the heart and causes it to contract
Journey of impulse through the heart
Starts in the sinoartrial node in the top right of the atrium called the pacemaker
Spreads through the atria walls causing them both to contract. Reaches the atrioventricular node located at the bottom right of the atrium, it helps delay the impulse to allow the atria to finish their contraction. The impulse moves down the bundle of his in the septum and branches off through the purkinje fibres. This causes both ventricles to contract
