(a) Fig. 4.1 is a photomicrograph of a human blood smear. [Figure 4.1]

1. (a)Name the cells labelled A and B in Fig. 4.1. A B [2]
2. (b)Blood and lymph are both fluids that transport substances within the human body.
3. (b)(i)Table 4.1 shows components found in both blood and lymph. Complete Table 4.1 to show whether the concentration of each of these components is higher or lower or the same in the lymph, when compared with the concentration in the blood in the aorta. You may use the words higher or lower or same once, more than once or not at all. [Table 4.1][2]
4. (b)(ii)The presence of a pathogen infecting the body leads to an increase in the concentration of protein in lymph. Suggest an explanation for this increase in protein concentration.[2]
5. (c)Blood is circulated around the body by the heart. The action of the heart is coordinated and controlled by structures located in its walls, such as the sinoatrial node (SAN) and the atrioventricular node (AVN).
6. (c)(i)Describe the role of the SAN.[2]
7. (c)(ii)In a healthy heart, the AVN provides the only pathway for electrical impulses to travel from the atria to the ventricles. The bundle of Kent is a structure found in the heart in a small number of people. Some electrical impulses do not pass through the AVN but travel directly from the atria to the ventricles through the bundle of Kent. Suggest and explain the effects that the presence of the bundle of Kent may have on heart rate.[3]

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