Transport in Animals

Question 1

What are the atria?

Answer 1

Thin muscular walls receiving (low pressure) blood returning to the heart in veins

Question 2

What are ventricles?

Answer 2

thick muscular walls contract to move blood (at high pressure) into arteries

Question 2

What does the right ventricle do?

Answer 2

contracts to move deoxygenated blood from the right atrium to the pulmonary artery

Question 3

What does the left atrium do?

Answer 3

receives oxygenated blood via the pulmonary veins

Question 3

What does the right atrium do?

Answer 3

Receives deoxygenated blood via the vena cava

Question 4

What does the left ventricle do?

Answer 4

contract to move oxygenated blood into the aorta

Question 4

What does the left atrium do?

Answer 4

receives oxygenated blood via the pulmonary veins

Question 5

describe the function of the arteries?

Answer 5

-carries blood away from the heart

-elastic tissue in the aorta stretches when the left ventricle contracts

-when left ventricle relaxes the artery wall recoils due to its elasticity and forces blood to body tissues

Question 5

Which ventricle has a thicker wall and why?

Answer 5

The left ventricle has a much thicker muscular wall as it has to pump oxygenated blood towards the rest of the body. (right ventricle only supplies the lungs)

Question 5

Function of veins?

Answer 5

• carry blood under low pressure towards the heart

Question 5

Features of arteries

Answer 5

• Blood is carried under higher pressure than veins
• do not posses valves except for the aorta and pulmonary artery
• thicker wall and smaller lumen than veins + more elastic fibres and smooth muscle fibres
• carry oxygenated blood except for the pulmonary arteries

Question 6

What is the function of tendinous cords?

Answer 6

prevents valves turn inside out when ventricle contracts

Question 6

what are AV and Semi-lunar valves?

Answer 6

AV (atrioventricular) valves - between atrium and ventricles

Semi-lunar valves - between ventricles and arteries

Question 6

How to work out Cardiac Output?

Answer 6

stroke volume (cm^3) x heart rate (min^-1)

Question 7

Why don’t arterioles have to withstand the very high pressure found in main arteries?

Answer 7

• they posses a higher proportion of smooth muscle than elastic fibres and so can control the flow of the blood to different tissues or relaxation of the smooth muscle in their walls

Question 7

What is vasoconstriction and vasodilation?

Answer 7

Vasoconstriction - the contraction of smooth muscle causes narrowing of the arterioles reducing blood flow to the capillaries

Vasodilation - the relaxation of smooth muscle that causes widening of the arterioles increasing blood flow to the capillaries

Question 7

Features of veins?

Answer 7

• thinner walls than arteries
• less elastic fibres and smooth muscles than arteries
• larger lumen than in arteries so even at low pressure the blood flows back to the heart at the same rate that it leaves the heart

Question 7

What is venous return?

Answer 7

• skeletal muscles that surround veins contracting and compressing the veins pushing the blood along

Question 7

what is the function of the capillaries?

Answer 7

to exchange of materials such as oxygen & carbon dioxide between the blood and body cells.

Question 8

what is haemoglobin made up of?

Answer 8

4 haem units and 4 polypeptide chains ( quaternary protein structure)

• each haem unit can combine with one oxygen molecule so one Hb molecule can transport 4 oxygen molecules

Question 8

describe the features of the capillaries? (6)

Answer 8

one endothelial cell thick- short diff pathway

gaps between endothelial cells (fenestrations) - increase permeability

many capillaries/highly branched - large surface area

high total cross-sectional area=more frictional resistance=slower blood flow which allows more time for substance exchange

small diameter means RBC’s are squeezed against the endothelial wall - short diff pathway

Question 8

differences between tissue fluid and lymph

Answer 8

• TF contains less WBC’s than lymph

Question 8

Describe the process of the formation of tissue fluid

Answer 8

• at arteriole end of capillary the hydrostatic pressure of the blood plasma is much higher than the osmotic pressure of the tissue fluid so water and small molecules osmose into and forms the tissue fluid
• plasma protein and blood cells stay in the capillary
• loss of fluid and high frictional resistance reduces blood pressure
• the large plasma proteins which remain in the blood reduce the water potential of the blood plasma causing the osmotic uptake of water into the capillaries
• less hydrostatic pressure at the venule end of the capillary means that due to the osmotic pressure of the tissue fluid some of the water is reabsorbed by osmosis

Question 9

equation for oxyhaemoglobin?

Answer 9

Hb + 4O2 ⇌ Hb(O2)4

Question 9

what is lymph + why does it form?

Answer 9

- this process is too slow to re-absorb all the filtered plasma and some of the tissue fluid enters ;lymph capillaries - this tissue fluid is now called lymph which eventually return to the blood when the lymph capillaries join to form lymph vessels

Question 10

differences between tissue fluid and blood plasma

Answer 10

- TF contains no large plasma proteins - TF contains more CO2 than blood plasma

Question 10

what is haemoglobin?

Answer 10

An iron containing pigment, which loosely and reversibly combines with oxygen to form oxyhaemoglobin

Question 11

what is the oxyhaemoglobin dissociation curve

Answer 11

a graph showing the relationship between the partial pressure O2 and percentage saturation of haemoglobin normally an S shape

Question 12

Describe the Loading, transport and unloading of oxygen (3)

Answer 12

- deoxygenated blood enters the lung capillaries - alveoli contain a high conc of oxygen = conc gradient for diffusion of O2 - O2 enters RBC and combines with Hb to form OxyHb

Question 13

what is the Bohr effect

Answer 13

-increased respiration = more CO2 which dissolves into the blood and lowers the pH (carbonic acid) - this changes the quaternary structure of Hb and lowers its affinity for O2 and shifts the curve to the right

Question 13

why is the HbO2 dissociation curve an S shape

Answer 13

- a molecule of O2 binds to one of the four haem units - this causes a slight change in the tertiary structures of the other haem units - this change increases the affinity for O2 allowing the second and third O2 molecules to bind easier - the 4th O2 is harder to bind than the second and third

Question 14

what happens when the HbO2 dissociation curve shifts to the right

Answer 14

- at the same partial pressure of O2, the affinity of Hb for O2 decreases - more O2 is dissociated from the Hb to the tissues

Question 15

what happens when the HbO2 dissociation curve shifts to the left

Answer 15

- at the same partial pressure of O2, the affinity of Hb for O2 increases - more O2 is loaded at lower partial pressures

Question 16

Why does foetal haemoglobin have a curve shifted to the left

Answer 16

- low ppO2 in the placenta - shift to left = higher affinity for O2 - more loaded at lower ppO2

Question 17

why do animals at high altitudes have a curve shifted to left

Answer 17

- low ppO2 in high altitudes - shift to left = higher affinity for O2 - more loaded at lower ppO2