3.1.2 circulatory systems

Question 1

why do multicellular organisms need transport systems

Answer 1

they have a low surface area to volume ratio and a higher metabolic rate so all cells cannot get everything they need

Question 2

what is a single circulatory system

Answer 2

blood only passes through the heart once for each complete circuit of the body

Question 3

what is a double circulatory system

Answer 3

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

Question 4

what is a closed circulatory system

Answer 4

the blood is enclosed in blood vessels

Question 5

what is an open circulatory system

Answer 5

blood can freely flow through body cavity at points

Question 6

how does an insect’s circulatory system work

Answer 6

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

Question 7

how does a fishes circulatory system work

Answer 7

the heart pumps blood through gills then to the rest of the body in a single circuit

Question 8

how does an mammals circulatory system work

Answer 8

heart is divided down the middle
left pumps to the rest of the body and the right pumps to the lungs

Question 9

what is the function of an artery

Answer 9

carry blood away from the heart to the rest of the body

Question 10

what is the function of a vein

Answer 10

bring deoxygenated blood back towards the heart

Question 11

what is the function of an capillary

Answer 11

exchange substances with cells such as oxygen and glucose

Question 12

what is the structure of arteries

Answer 12

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

Question 13

what is the structure of veins

Answer 13

they have wide lumen with little elastic and smooth muscle tissue
also have valves to stop blood flowing backwards

Question 14

what is tissue fluid

Answer 14

the fluid that surrounds cells in tissues. it is made from substances that leave the blood

Question 15

how is tissue fluid formed

Answer 15

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

Question 16

where does excess tissue fluid drain

Answer 16

into the lymphatic system which leads to the main lymph vessels in the thorax where it is returned to the blood

Question 17

how do valves stop blood flowing backward

Answer 17

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

Question 18

what are the valves between the atria and ventricles called

Answer 18

atrioventricular valves

Question 19

what valves link ventricles and to arteries

Answer 19

semi lunar valves

Question 20

what blood vessel brings blood from the rest of the body to the heart

Answer 20

vena cava

Question 21

what blood vessel brings blood to the heart from the lungs

Answer 21

pulmonary vein

Question 22

what blood vessel brings blood to the rest of the body from the heart

Answer 22

aorta

Question 23

what blood vessel brings blood to the lungs from the heart

Answer 23

pulmonary artery

Question 24

what is the cardiac cycle

Answer 24

the ongoing sequence of contraction and relaxation of the atria and ventricles to keep blood continuously circulating

Question 25

what is atrial systole

Answer 25

ventricles are relaxed and atria contract which decreases their volume and increases their pressure. this pushes blood through atrioventricular valves

Question 26

what is ventricular systole

Answer 26

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

Question 27

what is diastole

Answer 27

the ventricles and atria relax. high pressure in arteries shuts the semi lunar valves atria fill with blood and atrial ventricular valves to open

Question 28

what is cardiac output

Answer 28

volume of blood pumped by the heart per minute

Question 29

how do we calculate cardiac output

Answer 29

heart rate x stroke volume

Question 30

what is the stroke volume

Answer 30

volume of blood pumped during each heartbeat

Question 31

what does myogenic mean

Answer 31

it can contract and relax without receiving signals from nerves

Question 32

how is heart rhythm controlled

Answer 32

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

Question 33

what can we use to record hearts electrical activity

Answer 33

an electrocardiograph

Question 34

what causes the p wave

Answer 34

contraction (depolarisation) of the atria

Question 35

what causes the QRS complex

Answer 35

contraction (depolarisation) of ventricles

Question 36

what causes the T wave

Answer 36

relaxation (repolarisation) of the ventricles

Question 37

what is tachycardia

Answer 37

heart beat is too fast (120bpm)

Question 38

what is bradycardia

Answer 38

heartbeat is too slow (<60bpm)

Question 39

what is an ectopic heartbeat

Answer 39

an extra heartbeat caused by early contraction of the atria

Question 40

what is fibrillation

Answer 40

atria and ventricles loose rhythm and stop contractions properly

Question 41

what is haemoglobin

Answer 41

a protein the contains an iron haem group which has a high affinity for oxygen and carries oxygen around in blood as oxyhaemoglobin

Question 42

when does the oxygen load onto the haemoglobin

Answer 42

at high partial pressures of oxygen

Question 43

when does the oxygen offload from the haemoglobin

Answer 43

at low partial pressures of oxygen

Question 44

why is an oxygen dissociation curve s shaped

Answer 44

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

Question 45

what is different about foetal and adult haemoglobin

Answer 45

foetal Hb has a higher affinity for oxygen

Question 46

why does foetal haemoglobin need a higher affinity for oxygen

Answer 46

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

Question 47

how do high concentrations of carbon dioxide effect how easily haemoglobin gives up oxygen

Answer 47

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

Question 48

what is the bohr effect

Answer 48

the dissociation curve shifts right when carbon dioxide levels increase showing how more oxygen is released from the blood

Question 49

how do high concentrations of carbon dioxide effect oxygen unloading

Answer 49

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