circulatory system

Question 1

Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs (3)

Answer 1

1. renal vein
2. vena cava to right atrium
3. right ventricle to pulmonary artery

Question 2

tissue fluid is formed from blood at the arteriole end of a capillary bed
explain how water from tissue fluid is returned to the circulatory system (4)

Answer 2

1. plasma proteins remain
2. creates a water potential gradient/ reduces water potential of blood
3. water moves to blood by osmosis
4. returns to blood by lymphatic system

Question 3

describe 3 precautions the student should take when clearing away after a heart dissection (3)

Answer 3

• disinfect surfaces
• disinfect hands
• carry sharp instruments by holding handle

Question 4

explain how an arteriole can reduce the blood flow into capillaries (2)

Answer 4

• muscle contracts
• constricts arteriole/ lumen

Question 5

which blood vessel carries blood at the lowest pressure? (1)

Answer 5

vena cava

Question 6

there is a small increase in pressure and in rate of blood flow in the aorta
explain how this happens and it’s importance (2)

Answer 6

1. semi-lunar valves closed
2. because pressure in aorta is higher than in ventricle

Question 7

describe the advantage of the Bohr effect during intense exercise (2)

Answer 7

• increases disassociation of oxygen
• for aerobic respiration at the tissues

Question 8

explain which and how a physiological change would allow for removal of increased carbon dioxide (2)

Answer 8

-increase in breathing rate
-similar pCO2 per breath but more breaths

Question 9

EPO increases the percentage of red blood cells in blood, a heart attack is caused by a lack of glucose and oxygen being delivered to cardiac muscle, overuse of EPO can increase heart attack risk- suggest how (2)

Answer 9

• EPO causes blood to thicken
• thickened blood could block the coronary arteries

Question 10

describe and explain the effect of increasing carbon dioxide concentration on the disassociation of haemoglobin (2)

Answer 10

• more oxygen disassociation
• by decreasing blood pH

Question 11

explain how valve A (Atrioventricular) maintains a unidirectional flow of blood (2)

Answer 11

• pressure in left atrium is higher than in ventricle, causing valve to open
• pressure in ventricle is then higher than in the atrium, causing it to close

Question 12

name the blood vessels that carry blood to the heart muscle (1)

Answer 12

coronary arteries

Question 13

binding of one molecules of oxygen to haemoglobin makes it easier for a second oxygen to bind, explain why (2)

Answer 13

• binding of first oxygen changes the tertiary structure of haemoglobin
• uncovers another binding site

Question 14

explain the role of the heart in the formation of tissue fluid (2)

Answer 14

• contraction of ventricle produces high blood pressure
• this forces water and some dissolved substances out of blood capillaries

Question 15

lymphoedema is a swelling in legs which may be caused by a blockage in the lymphatic system, suggest how a blockage in the lymphatic system could cause lymphoedema (1)

Answer 15

excess tissue fluid cannot be reabsorbed/ it builds up

Question 16

explain how changes in the shape of haemoglobin result in the S-shaoed oxyhaemoglobin disassociation curve for HbA (2)

Answer 16

-first oxygen binds to Hb causing change in shape
- shape change of Hb allows more oxygen to bind easily

Question 17

explain a property of iron ions that enables these ions to carry out their role in red blood cells (2)

Answer 17

• is charged
• binds with oxygen

Question 18

how does composition of blood in the pulmonary artery of a fetus differ from composition of blood in pulmonary artery of mother (2)

Answer 18

• fetal blood has more oxygen
• because gas exchange occurs in the placenta

Question 19

hydrostatic pressure falls from the arteriole end of the capillary to the venule end, explain why (2)

Answer 19

loss of water from capillary

Question 20

high blood pressure leads to an accumulation of tissue fluid. Explain how (3)

Answer 20

1. high blood pressure means high hydrostatic pressure
2. increases outward pressure from arterial end
3. so more tissue fluid formed

Question 21

water potential of blood plasma is more negative at the venule end than at the arteriole end. Explain why (3)

Answer 21

1. water has left the capillary
2. proteins too large to leave capillary
3. increasing concentration of blood proteins

Question 22

how is tissue fluid formed (1)

Answer 22

small molecules such as amino acids and glucose are forced out of the capillary at the arterial end

Question 23

describe the quaternary structure of haemoglobin

Answer 23

4 polypeptides
each polypeptide has a haem group that contains an Fe2+ ion

Question 24

explain how DNA leads to different haemoglobin molecules having different affinities for O2

Answer 24

different base sequence so different amino acid sequence so different tertiary structure and quaternary structure = different affinities for O2

Question 25

when the body is at rest only one of the four O2 molecules carried by Hb is normally released into the tissues suggest why this could be an advantage when the organism becomes more active

Answer 25

if all O2 molecules were released there would be none in reserve to supply tissues when they were more active

Question 26

carbon monoxide occurs in car exhaust fumes. it binds permanently to haemoglobin instead of O2- suggest why a person breathing in car fumes may lose consciousness

Answer 26

CO occupies all binding sites on Hb instead of O2 so no O2 carried to tissues such as the brain these tissues cant respire and function, so person loses consciousness

Question 27

what does the curve show about Hb affinity if the curve is to the: - left -right

Answer 27

to the left: Hb has a HIGHER affinity for O2, loads O2 more readily to the right: Hb has a LOWER affinity for O2, loads O2 less readily

Question 28

what effect does an increased CO2 concentration have on the affinity of Hb

Answer 28

increased CO2 concentration REDUCES affinity of Hb, unloads O2 more easily at tissues there is high concentration of CO2 so Hb has low affinity and releases O2 more readily

Question 29

what effect does CO2 concentration have on affinity of Hb at the LUNGS

Answer 29

- low CO2 concentration as it is constantly being excreted - this raises pH - higher pH changes the shape of the Hb which enables it to LOAD O2 more readily - increased affinity of Hb

Question 30

what effect does CO2 concentration have on affinity of Hb at the TISSUES

Answer 30

- CO2 produced by respiring cells - CO2 dissolves in blood and lowers its pH - this changes shape of Hb which enables it to UNLOAD O2 more easily - decreased affinity of Hb - more O2 unloaded - more O2 available for respiration

Question 31

suggest whether disassociation curve of a pigeon is shifted to left or right of a human

Answer 31

RIGHT so Hb has a lower affinity for O2 and unloads O2 more easily at the respiring tissues quicker respiration

Question 32

diasassociation curve of a mouse is shifted to the right of a humans explain how this changes the way O2 is unloaded from mouse Hb compared to human Hb suggest an advantage this has for the maintenance of body temperature in mice

Answer 32

- unloads more easily in the mouse as it has lower affinity - O2 more easily unloaded to tissues, so more respiration means more heat is produced, which helps maintain body temperature

Question 33

ice fish live in the antarctic and are the only vertebrates to completely lack Hb. suggest 1 reason why they can survive in the seas around antarctica without Hb in their blood

Answer 33

temperatures in antarctic waters are LOW so respiration rates of cold blooded animals is also low respiration needs O2, if they respire less they need less O2 ice fish rely on water for O2- the amount of O2 dissolved in water is adequate enough to supply their needs

Question 34

why does blood return to the heart after leaving the lungs

Answer 34

after going through lungs, pressure of blood is reduced if it were to pass immediately to whole body circulation would be very slow goes to heart before to increase pressure so circulation is faster

Question 35

state 2 factors that make it more likely that the organism will have a circulatory pump e.g the heart

Answer 35

- low SA:V ratio - high metabolic rate

Question 36

state the main advantage of double circulation found in mammals

Answer 36

it increases blood pressure so increases rate of blood flow to tissues

Question 37

suggest and explain why the rise and fall in blood pressure in the aorta is greater than in small arteries (3)

Answer 37

- the aorta is directly connected to heart (LV) this creates the highest pressure - there are more elastic fibres in aorta - elastic fibres stretch and recoil to maintain high BP

Question 38

Describe and explain  four ways in which the structure of a capillary adapts it for the exchange of substances between blood and the surrounding tissue.

Answer 38

Permeable membrane Wall is single cell thick- reduces diffusion distance Flattened endothelial cells- reduces diffusion distance Fenestrations allow large molecules through Small diameter increases SA:V ratio, short diffusion distance

Question 39

Explain how tissue fluid is formed and how it may be returned to the circulatory system. (6)

Answer 39

Hydrostatic pressure of blood is high at arterial end Fluid passes out Proteins remain This lowers water potential of blood Water moves back into venous end of capillary by osmosis Lymph system collects excess tissue fluid which then returns to blood

Question 40

what makes up tissue fluid

Answer 40

water amino acids fatty acids salts sugars hormones white blood cells metabolic waste products.