Transport in Man Ex 2

(a) Explain why a vein is described as an organ. [1]

(b) The diagram shows a vein passing between two muscles.

(b)(i) When the muscles contract, the pressure of the blood in the part of the vein between valves A and B changes. Explain how this change in pressure, together with the action of the valves, helps the blood to flow to the heart. [2]

(ii) Suggest how blood is returned to the heart when the muscles are not contracting. [1]

(c) The graph shows the relationship between the pressure in the veins returning blood into the heart and stroke volume (the
amount of blood pumped by the left ventricle of the heart in one contraction).


(c)(i) From the graph, describe the relationship between stroke volume and pressure in the veins. [1]

(ii) What information would you need, other than that in the graph, to calculate this person’s cardiac output (the output of blood by the heart per minute)? [1]


ANSWERS
(a) It is a structure made up of different tissues (connective, muscle) working together for a specific function (transport blood).
(b)(i) Increase pressure causes valve A to shut and valve B to open.
Blood squeezed in one direction towards the heart, valves prevent backflow.
(ii) Residual pressure/suction due to action of the heart
(c)(i) Increase in stroke volume causes an increase in pressure in veins up to 4kPa/ stroke volume reaches 100cm3 then no further effect/stroke volume remain constant.
(ii) Heart rate/ pulse rate