3.1.2 circulatory systems Flashcards
why do multicellular organisms need transport systems
they have a low surface area to volume ratio and a higher metabolic rate so all cells cannot get everything they need
what is a single circulatory system
blood only passes through the heart once for each complete circuit of the body
what is a double circulatory system
blood passes through the heart twice for each complete circuit of the body
left side pumps to rest of the body, right to the lungs
what is a closed circulatory system
the blood is enclosed in blood vessels
what is an open circulatory system
blood can freely flow through body cavity at points
how does an insect’s circulatory system work
the heart is segmented and contacts in a wave from the back, pumping blood into a single main artery which opens up into the body cavity
blood flows around the organs making its way back into the heart through valves
does not supply oxygen
how does a fishes circulatory system work
the heart pumps blood through gills then to the rest of the body in a single circuit
how does an mammals circulatory system work
heart is divided down the middle
left pumps to the rest of the body and the right pumps to the lungs
what is the function of an artery
carry blood away from the heart to the rest of the body
what is the function of a vein
bring deoxygenated blood back towards the heart
what is the function of an capillary
exchange substances with cells such as oxygen and glucose
what is the structure of arteries
walls are thick and muscular and contain elastic tissue to withstand and maintain high pressure
the endothelium is folded so it can expand to maintain pressure
arterioles have less elastic tissue but have smooth muscle to control blood flow
what is the structure of veins
they have wide lumen with little elastic and smooth muscle tissue
also have valves to stop blood flowing backwards
what is tissue fluid
the fluid that surrounds cells in tissues. it is made from substances that leave the blood
how is tissue fluid formed
at the arteriole end hydrostatic pressure in capillaries is greater than the hydrostatic pressure in the tissue fluid so fluid is forced out
as fluid leaves hydrostatic pressure in the capillaries decreases so it is lower at the venule end
oncotic pressure generated by plasma proteins and it lowers the water potential
at the venule end water potential in capillaries is lower than water potential in fluid so some water reenters the capillaries
where does excess tissue fluid drain
into the lymphatic system which leads to the main lymph vessels in the thorax where it is returned to the blood
how do valves stop blood flowing backward
the valves only open one if there is a higher pressure behind a valve they’re forced open if there is a higher pressure in front it forced shut
what are the valves between the atria and ventricles called
atrioventricular valves
what valves link ventricles and to arteries
semi lunar valves
what blood vessel brings blood from the rest of the body to the heart
vena cava
what blood vessel brings blood to the heart from the lungs
pulmonary vein
what blood vessel brings blood to the rest of the body from the heart
aorta
what blood vessel brings blood to the lungs from the heart
pulmonary artery
what is the cardiac cycle
the ongoing sequence of contraction and relaxation of the atria and ventricles to keep blood continuously circulating
what is atrial systole
ventricles are relaxed and atria contract which decreases their volume and increases their pressure. this pushes blood through atrioventricular valves
what is ventricular systole
atria relax and ventricles contract increasing their pressure. pressure in ventricles increases so atrioventricular valves shut and opens the semi lunar valves and forces blood out
what is diastole
the ventricles and atria relax. high pressure in arteries shuts the semi lunar valves
atria fill with blood and atrial ventricular valves to open
what is cardiac output
volume of blood pumped by the heart per minute
how do we calculate cardiac output
heart rate x stroke volume
what is the stroke volume
volume of blood pumped during each heartbeat
what does myogenic mean
it can contract and relax without receiving signals from nerves
how is heart rhythm controlled
electrical impulse from SAN in the wall of right atrium cause atria to contract
non conducting collagen tissue prevents waves passing directly from atria to ventricles
electrical impulses reach AVN which delays it slightly so ventricles contract after atria have emptied
electrical impulse travels down bundle of his to the purkyne fibres causing ventricles to contract
what can we use to record hearts electrical activity
an electrocardiograph
what causes the p wave
contraction (depolarisation) of the atria
what causes the QRS complex
contraction (depolarisation) of ventricles
what causes the T wave
relaxation (repolarisation) of the ventricles
what is tachycardia
heart beat is too fast (120bpm)
what is bradycardia
heartbeat is too slow (<60bpm)
what is an ectopic heartbeat
an extra heartbeat caused by early contraction of the atria
what is fibrillation
atria and ventricles loose rhythm and stop contractions properly
what is haemoglobin
a protein the contains an iron haem group which has a high affinity for oxygen and carries oxygen around in blood as oxyhaemoglobin
when does the oxygen load onto the haemoglobin
at high partial pressures of oxygen
when does the oxygen offload from the haemoglobin
at low partial pressures of oxygen
why is an oxygen dissociation curve s shaped
when Hb combines with the first oxygen molecule its shape alters in a way that makes it easier for other molecules to join
as it becomes more saturated it becomes harder for oxygen molecules to join
what is different about foetal and adult haemoglobin
foetal Hb has a higher affinity for oxygen
why does foetal haemoglobin need a higher affinity for oxygen
the foetus gets blood from the mother but oxygen saturation has decreased by the time it reaches the placenta so it needs a higher affinity for oxygen so that it can take up enough
how do high concentrations of carbon dioxide effect how easily haemoglobin gives up oxygen
in high partial pressures of carbon dioxide Hb offloads oxygen more readily.
this means active cells offload more oxygen which is needed for increased respiration
what is the bohr effect
the dissociation curve shifts right when carbon dioxide levels increase showing how more oxygen is released from the blood
how do high concentrations of carbon dioxide effect oxygen unloading
CO2 enters red blood cells and combines with water to form carbonic acid. (enzyme carbonic anhydrase is used to catalyse). around 10% is carried in Hb to the lungs
the carbonic acid dissociates into H+ and HCO- ions
the H+ causes HbO8 to unload oxygen so Hb can take up H+ ions. this forms haemoglobinic acid
the HCO- diffuse out of the cell and are transported in plasma. to maintain the charge Cl- ions diffuse in (chloride shift)
in the lungs the low pCO2 causes some H+ and HCO- to recombine into CO2 which leaves via alveoli
