The atria and ventricular muscles are relaxed. This is when blood will enter the atria via the vena cava and pulmonary vein. The blood flowing into the atria increases the pressure within the atria.
what happens during atrial systole?
The atria muscle walls contract, increasing the pressure further. This causes the atrioventricular valves to open and blood to flow into the ventricles. The ventricular muscular walls are relaxed (ventricular diastole)
what happens during ventricular systole?
After a short delay, the ventricle muscular walls contract, increasing the pressure beyond that of the atria. This causes the atrioventricular valves to close and the semi-lunar valves to open. The blood is pushed out of the ventricles into the arteries (pulmonary and aorta)
what is the cardiac output?
the volume of the blood which leaves one ventricle in 1 minute
how do you calculate the cardiac output?
cardiac output = heart rate X stroke volume
what is the heart rate?
beats of the heart per minutemin-1
what is the stroke volume?
volume of blood that leaves the heart each beat per dm^3
what is the order of structures that blood passes through on the right side of the heart?
how does blood return to the heart from the lungs?
via the pulmonary vein then enters the left atrium then passes into the left ventricle through the atrioventricular valve.Finally, blood passes through the semi-lunar valve before exiting the heart through the aorta.
what is the role of the coronary arteries?
supply the heart with blood
where are coronary arteries found?
outside of the heart
Explain how a myocardial infarction occurs.
A myocardial infarction occurs when blood flow in the coronary arteries reduces.
This means the amount of oxygen reaching the heart muscle also reduces.
As a result, the heart cells respire less and start to die.
what are 2 factors associated with cardiovascular disease?
smoking and high blood pressure
What happens in the cardiac cycle?
blood enters the atria
the atria contract
the ventricles contract
how does blood enter the atria?
pulmonary vein
vena cava
what happens when the pressure of the blood in the atria is greater than the ventricles?
the atrioventricular valves open
what happens during atrial systole?
the atria contract causing the volume of the atria to decrease whilst the pressure increases
When the pressure in the ventricles is greater than the pressure in the atria, the atrioventricular valves…
close
When the pressure in the ventricles is greater than the pressure in the blood vessels, the...
semi-lunar valvesopen
what happens during ventricular systole?
When the pressure in the ventricles is greater than the atria, the atrioventricular valves close. prevents the back-flow of blood into the atria.
The semi-lunar valves open. allows blood to be pushed into the pulmonary artery and aorta.
What is the movement of blood through the heart is controlled by?
the opening and closing of valves
what is the opening and closing of the heart valves is caused by?
differences in pressure between chambers of the heart
describe and explain ways in which the structure of a capillary adapts it for the exchange of substances between blood and the surrounding tissue (4)
permeable capillary wall
single cell thick walls reduces diffusion distance
small diameter gives a large SA:V diffusion distance
What is tissue fluid?
Fluid containing water, glucose, amino acids, fattyacids, ions and oxygen which bathes in tissues/cells
How is tissue fluid formed?
Capillaries have small gaps in the walls so that liquid and small molecules can
be forced out.
As blood enters the capillaries from arterioles, the smaller diameter results in a
highhydrostaticpressure so water, glucose, amino acids, fatty acids, ions and oxygen are forced out. This is known as ultrafiltration.
What remains in the capillaries (blood)?
Red blood cells, platelets, largeproteins
How is it reabsorbed?
Large molecules remain in the capillaries and therefore create a lowered water potential.
Towards the venule end of the capillaries, the hydrostatic pressure is lowered due to the loss of liquid, but the water potential is very low.
Water re-enters the capillaries by osmosis.
Capillaries are numerous and highly branched. How does this support their function?
They provide a large surface area for exchange
Capillaries have a narrow lumen. How does this support their function?
They have a short diffusion pathway
Most of the tissue fluid that forms returns to the circulatory system by osmosis. How does any remaining fluid get returned to the circulatory system?
lymphatic system
Describe the structure of haemoglobin and how it binds to oxygen.
Human haemoglobin is a protein with a quaternary structure because it contains four polypeptide chains. Each polypeptide chain is bonded to a haem group containing an iron ion, which can bind to one oxygen molecule. This means that one molecule of haemoglobin can carry up to four molecules of oxygen. Haemoglobin bound to oxygen is called oxyhaemoglobin.
define positive cooperativity?
When the binding or unbinding of one particle makes it easier for another to bind or unbind
where does positive cooperativity speeds up the transfer of oxygen from?
air in the alveoli to red blood cells.
red blood cells into aerobically respiring tissue.
what happens when the partial pressure of oxygen is high?
association takes place
what happens when the partial pressure of oxygen is low?
dissociation takes place
what happens when a molecule of oxygen binds to haemoglobin?
the quaternary structure of haemoglobin changes.
other oxygen molecules can bind more easily.
what leads to rapid oxygen association in the lungs?
positive cooperativity
what leads to rapid oxygen dissociation in respiring tissues?