topic 1 - lifestyle, health, and risk Flashcards
what is a single circulatory system
the blood only passes through the heart once
what types of animals may have a single circulatory system
fish/animals with gills to oxygenate the blood
what is a double circulatory system
the blood passes through the heart twice
what is a closed circulatory system
blood flows through vessels (arteries, veins, capillaries, etc)
what is an open circulatory system
blood pumped through cavities surrounding the animals organs
which side of the heart receives deoxygenated blood, and pumps it to the lungs
right
where do the pulmonary veins pump blood
from the lungs to the left side of the heart
which side of the heart receives oxygenated blood and pumps it to the body
left
where does the vena cava pump blood
from the body into the right side of the heart
where does the aorta pump blood
from the left side of the heart to the body
where does the pulmonary artery pump blood
from the right side of the heart to the lungs
what’s the bottom of the heart called
apex
what are the valves called at the entrance to the pulmonary artery and aorta
semilunar valves
what is the difference between the superior and inferior vena cava
superior vena cava brings in deoxygenated blood from the head and arms, but the inferior vena cava bring deoxygenated blood from the lower body
what are the differences between arteries and veins?
arteries have a more narrow lumen, thicker walls, more collagen, more smooth muscle, and more elastic fibres (has thicker walls as more of this), and no valves, whereas veins have valves
what is a small artery called?
arteriole
what is a small vein called?
venule
what is systole?
the contraction of the heart
what is diastole?
the relaxation of the heart
how are artery walls well adapted for the cardiac cycle?
when blood is forced into arteries during systole, their elastic walls can stretch to accommodate the blood. they can withstand the high pressure generated. during diastole, the elasticity of the artery walls causes them to recoil behind the blood, pushing it forward
why are capillaries good for gas exchange?
walls one cell thick - short diffusion pathway
narrow lumen - blood flows slower due to friction if the blood against capillary walls allows for more gas exchange
how is blood drawn into the heart from the veins?
low pressure in the thorax when breathing
how is blood flow through the veins assisted?
contraction of skeletal muscles (during movement and breathing) pushes blood forward
what are the three phases of the cardiac cycle?
atrial systole, ventricular systole, and cardiac diastole
what happens during atrial systole?
blood returns to the heart. blood under low pressure flows into the atria, from the pulmonary veins and vena cava. as the atria fill, pressure increases, and the blood pushes open the atrioventricular valves, and blood begins to leak into the ventricles. the atria walls then contract to force more blood into the ventricles.
what happens during ventricular systole?
after a slight delay, the ventricles contract from the base of the heart upwards, which increases ventricular pressure. this forces open the semilunar valves, pushing blood up and out through the pulmonary arteries and aorta. the pressure of blood against the atrioventricular valves closes them and prevents backflow into the atria.
what happens during cardiac diastole?
the atria and ventricles relax. elastic recoil of the relaxing heart walls lowers pressure. blood under high pressure in the pulmonary arteries and aorta is drawn back towards the ventricles, closing the semilunar valves and preventing backflow into the ventricles. the coronary arteries fill. low pressure in the atria helps draw blood into the heart from the veins.
what happens in atherosclerosis?
the endothelium becomes damaged (maybe due to high blood pressure or toxins from cigarettes), which causes an inflammatory response. white blood cells move into the artery wall, and accumulate chemicals from the blood, particularly cholesterol, and build up a fatty deposit called atheroma. calcium salts and fibrous tissue also build up, resulting in a hard plaque on the inner wall. the fibrous tissue build up causes the artery wall to lose some elasticity. plaques cause the lumen to narrow, which will increase blood pressure. this could lead to a positive feedback loop
what could atherosclerosis lead to?
stroke, myocardial infarction (heart attack), or tissue death
what is the purpose of a blood clot?
seals the break in the blood vessel, limits blood loss, prevents entry of pathogens
how do platelets change during blood clotting?
they change from flattened discs to spheres with long thin projections when they come into contact with the damaged vessel wall
what happens during the clotting cascade?
platelets stick to damaged wall and each other, forming a platelet plug. platelets and damaged tissue release a protein called thromboplastin. thromboplastin activates an enzyme which catalyses the conversion of the protein prothrombin into an enzyme called thrombin (vitamin K and calcium ions must also be present). thrombin catalyses the conversion of soluble fibrinogen into insoluble fibrin. a mesh of fibrin forms that traps more platelets and red blood cells, causing a clot
what is the role of thromboplastin in the clotting cascade?
released from damaged tissue and platelets. when calcium ions and vitamin K present, activates an enzyme that catalyses the conversion of prothrombin into thrombin
what is the role of thrombin in the clotting cascade?
converted from prothrombin. enzyme which catalyses conversion of soluble fibrinogen into insoluble fibrin, which is used to form the mesh for the clot
how does atherosclerosis lead to myocardial infarction?
narrow arteries limit amount of oxygen-rich blood reaching the heart. this may result in chest pain (angina), as the cardiac muscle is working harder and needs to respire more. lack of oxygen means the heart muscle must respire anaerobically.
if a plaque in the coronary arteries rupture, collagen is exposed, leading to rapid clot formation, potentially blocking blood supply to the heart (heart is now ischaemic (without blood)). this is a heart attack. if muscle cells starved of oxygen for long, could cause permanent damage
how does a stroke occur?
if a blood clot blocks one of the arteries leading to the brain, a full stroke will occur. if brain cells starved of oxygen for more than a few minutes, they will be permanently damaged, and it can be fatal.
if blood supply to the brain only briefly interrupted, mini-stoke will occur. same symptoms but just shorter
what are the symptoms of coronary heart disease?
shortness of breath, angina, heaviness, burning, fatigue
what are the symptoms of a stroke?
numbness, dizziness, confusion, slurred speech, blurred/lost vision, paralysis on one side of the body
