Fig. 1 shows an experiment using three sections of artificial tubing to model blood vessels. Each section had the same length. Water was pumped through at a...
Question 1 Report
Fig. 1 shows an experiment using three sections of artificial tubing to model blood vessels. Each section had the same length. Water was pumped through at a constant rate, and the pressure was measured at the start and end of each tube. Table 1 shows the results. The model helps a class compare resistance to flow in vessels of different internal diameter.
| tube internal diameter / mm | pressure decrease / kPa |
|---|---|
| 2 | 18 |
| 4 | 7 |
| 6 | 3 |
(a) Describe the relationship between tube diameter and pressure decrease. [2]
(b) Which blood vessels have the smallest internal diameter? [1]
(c) Explain why narrowing of an artery can increase blood pressure before the narrowing. [2]
Fig. 1 shows an artificial heart valve being tested in a transparent tube. Water is pushed from left to right and then the pump is stopped. The flexible flaps should open when pressure is greater on the left side and close when pressure becomes greater on the right side. Heart valves work in a similar way to keep blood moving in one direction.
(a) Describe what happens to the valve flaps when water flows from left to right. [1]
(b) Explain why the flaps close if pressure becomes greater on the right side. [2]
(c) Give one place in the human circulatory system where valves are found. [1]
Answer Details
Tube diameter and resistance
- (a) As tube diameter increases, pressure decrease decreases. For example, the pressure decrease falls from \(18\text{ kPa}\) at \(2\text{ mm}\) to \(3\text{ kPa}\) at \(6\text{ mm}\). [2]
- (b) Capillaries have the smallest internal diameter. [1]
- (c) Narrowing increases resistance to blood flow. Consequently, pressure builds up before the narrow region. [2]
Artificial heart valve
- (a) When water flows from left to right, the flexible flaps open. [1]
- (b) If pressure is greater on the right side, it pushes the flaps together. This prevents reverse flow, or backflow. [2]
- (c) Valves are found in veins. They are also found between atria and ventricles and at the bases of arteries leaving the ventricles. [1]
Download The App On Google Playstore
Everything you need to excel in your exams
