IB DP Biology Topic 6: Human physiology : 6.2 The blood system Question Bank HL Paper 2


Explain the control mechanism of the heart rate [7]




sinoatrial node/SAN is a specialized group of muscle cells
sinoatrial node/SAN is located in the right atrium ✔


acts as a pacemaker/controls the heart rate
initiates/generates the heart beat/starts the cardiac cycle ✔

c sends out electrical signal/impulses/depolarisations 

d electrical signal stimulates contraction «of heart muscle» 

e signal passes through walls of atria/passes to AV node 

f then through walls of the ventricles g medulla «oblongata of brain» can change/increase/decrease the rate 

h through nerves/named example of nerve/autonomic/sympathetic/ parasympathetic nervous system  In mph, only accept vagus nerve for slowing heart rate and sympathetic nerve for accelerating it.

i one nerve increases the rate and the other decreases it 

j epinephrine/adrenaline increases heart rate/force of contraction 

k epinephrine/adrenaline prepares the body for vigorous activity/is part of fight or flight response

Accept the four possible blood groups of the offspring anywhere in the answer.


The human circulatory system is structured to serve the organs and tissues of the body efficiently. 

Explain how circulation of the blood to the lungs and to other systems is separated in humans and what the advantages of this separation are.


Distinguish between the composition of the blood of the renal artery and the blood of the renal vein.



a. double circulation / pulmonary and systemic circulations 

b. heart is a double pump / heart has separate pumps for lungs and other systems / left and right sides of heart are separate / no hole in heart (after birth)

c. deoxygenated blood pumped to the lungs and oxygenated to other organs/tissues/whole body (apart from lungs)

d. each side of the heart has an atrium and a ventricle

e. left ventricle/side pumps blood to the systems/tissues and right ventricle/side pumps blood to the lungs

f. left atrium receives blood from the lungs and right atrium receives blood from systems/tissues

g. left ventricle pumps blood via the aorta and right ventricle pumps blood via the pulmonary artery

h. left atrium receives blood via the pulmonary vein and right atrium receives blood via the vena cava

i. lungs require lower pressure blood / high pressure blood would damage lungs

j. high pressure required to pump blood to all systems/tissues apart from lungs

k. pressure of blood returning from lungs not high enough to continue to tissues / blood has to be pumped again after returning from lungs

l. oxygenated blood and deoxygenated blood kept separate / all tissues receive blood with high oxygen content/saturation

Points may be earned using an annotated diagram.


a. less urea/excretory waste products/creatinine in renal vein

b. less oxygen in the renal vein

c. more carbon dioxide in renal vein

d. less glucose in renal vein

e. concentration of sodium ions/chloride ions/pH at normal level in the renal vein whereas it is variable in renal artery

f. solute concentration/osmolarity/water balance at normal level in the renal vein whereas it is variable in renal artery

Allow answers in a table format. For all these mark points accept the converse as long as it is clear whether the artery or vein has the higher amount.

Answers relating to volume and pressure are not relevant to the question.



Draw a labelled diagram of the human heart showing the attached blood vessels.


Describe the action of the heart in pumping blood.


All parts of the body change the composition of the blood.  Explain how the nephron changes the composition of blood.



NB: Drawings must be correctly proportioned and clearly drawn showing connections between structures. The drawing may show the heart without contraction or in any stage of contraction. Award [1] for any correctly labelled part that has been drawn to the stated standards.
a. atria/right atrium/left atrium – shown above the ventricles and must not be bigger than ventricles;
b. ventricle/left ventricle/right ventricle – below the atria, must have thicker walls than atria;
c. vena cava/superior vena cave/inferior vena cava – connected to right atrium;
d. pulmonary artery – shown from right ventricle (to lungs);
e. pulmonary vein(s) – shown (from lungs) to left atrium;
f. aorta – shown as large artery from left ventricle out of heart;
g. AV valves/atrioventricular valves / mitral/bicuspid and tricuspid – named correctly and shown between both atria and ventricles and labelled at least on one side;
h. semilunar valves – shown in aorta/pulmonary artery;
Valves need to open in correct direction.


a. (both) atria collect blood (from veins);
b. sinoatrial/SA node sends impulses to muscle/fibres initiating contraction;
c. blood is pushed to ventricles by contraction of atria/atrial systole;
d. AV (atrioventricular) valves are open (as atria contract);
e. semilunar valves are closed so that ventricles fill with blood;
f. ventricles contract / ventricular systole;
g. AV (atrioventricular) valves close ( preventing backflow);
h. (blood is pushed through the) semilunar valves/pulmonary artery and aorta;
i. when ventricles relax /diastole, semilunar valves close preventing backflow of blood;

Do not accept the description of blood flow without a clear action.
Do not accept general statements such as systole = heart contraction and diastole = heart relaxation.
[4 max] if answer suggests that left and right sides are contracting at different times or simultaneous contraction not indicated.


Remember, up to TWO “quality of construction” marks per essay.

a. higher nitrogen/urea as blood enters nephron/Bowman’s capsule than when it leaves the nephron (in the renal vein);
b. most small soluble molecules/glucose/nutrients/ions are removed from blood in Bowman’s capsule;
c. through ultrafiltration;
d. proteins / blood cells / large molecules remain in the blood;
e. as filtrate moves through the nephron (tubule), water is returned to the blood (by osmosis);
f. glucose/nutrients is returned to blood by active transport (and diffusion) / selective reabsorption;
g. in the proximal convoluted tubule;
h. urea / uric acid remain in the filtrate / removed from blood;
i. sodium is pumped into the medulla in the loop of Henlé;
j. water reabsorption is enhanced by a high sodium gradient (in the medulla);
k. permeability of the collecting duct membrane is regulated by hormones / ADH;
l. water concentration in urine is variable to maintain homeostasis in the blood;
m. more oxygen/less carbon dioxide in blood entering (kidney) than in blood leaving (kidney);



Draw a labelled diagram to show the structure of the heart.


Outline how the human body responds to high blood glucose levels.


Explain the role of the nephron in maintaining the water balance of the blood in the human body.



Award [1] for each of the following structures clearly drawn and labelled correctly in a diagram of the heart.

a. left ventricle/right ventricle – both left and right ventricles must be shown but the mark can be awarded if either is correctly labelled. The left must be thicker walled than right and both must be larger than the atria;

b. left atrium/right atrium – both left and right atria must be shown with thinner walls than ventricles, but the mark can be awarded if either atrium is correctly labelled;

c. atrio-ventricular valves/tricuspid and bicuspid valves – positioned between atria and ventricles, with both labelled and tri/bicuspid correct if these names are used;

d. semi-lunar valves –shown at the start of the aorta and pulmonary artery, with the cusps facing in the right direction;

Award [1] for any two blood vessels clearly drawn and correctly labelled.

aorta – shown connected to the left ventricle;

pulmonary artery – shown connected to the right ventricle;

pulmonary vein – shown connected to the left atrium;

vena cava – shown connected to the right atrium;


a. (high blood glucose levels) detected by pancreas islet cells/beta cells;

b. insulin secreted in response (to high blood glucose/glucose above threshold level);

c. insulin stimulates cells to absorb glucose;

d. glucose used in cell respiration (rather than lipids);

e. glucose converted to glycogen (in liver/muscle cells);

f. glucose converted to fatty acids/triglycerides/fat;

g. negative feedback process;


a. ultrafiltration in the glomerulus produces (large volumes of) filtrate;

b. 80%/most of water in filtrate is (always) (re)absorbed in proximal convoluted tubule;

c. water reabsorbed from filtrate in descending loop of Henle;

d. pituitary gland secretes ADH if blood solute concentration is too high;

e. ADH makes the collecting duct/distal convoluted tubule more permeable to water;

f. ADH moves aquaporins into the membranes (of cells in the tubule wall);

g. more water reabsorbed from filtrate/into blood due to ADH;

h. blood becomes more dilute / small volume of urine with high solute concentration;

i. with low/no ADH less water is reabsorbed in the collecting duct;

j. blood becomes more concentrated / large volume of dilute urine;

k. water reabsorption in collecting duct due to high solute concentration of medulla;

l. active transport of Naions from filtrate in ascending limb of loop of Henle;

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