Name the structures labelled P, Q and R shown in Figure 4.

P

Q

R

Two students (A and B) investigated reaction time in response to touch.

• Student A sat with her eyes shut and her forearm resting on a worktop so that her hand was over the edge. • Student B held a ruler vertically between student A's thumb and first finger, with the ruler at 0 mm lightly touching student A's first finger. • Student B released the ruler. • As soon as student A felt the ruler fall, she closed her thumb and first finger to catch the ruler as shown in Figure 5. • Student B measured the distance the ruler had fallen to the nearest mm

The test was repeated three more times using the same hand to catch the ruler. Table 3 shows student A's results.

The student was able to convert these distances into reaction times using Table 4.

Calculate the percentage uncertainty in the measurement of Trial 1 in Table 3.

Put a tick (✓) in the correct box below.

☐ 0.633%

☐ 1.27%

☐ 2.53%

☐ 12.6%

In this investigation, it is not possible for a student to react in less than 45 ms

Suggest one explanation for the value recorded in Trial 3 in Table 3.

Student A estimated that the length of the nerve pathway involved was 175 cm

Use Table 3 and Table 4 to calculate the mean speed of nerve impulse transmission.

Do not use the value for Trial 3 in your calculation.

Answer ______________ m s−1

In response to touch, nerve impulses can be transmitted at speeds of 76.2 m s−1

Suggest three reasons why, in this investigation, the estimated speed of student A's impulse transmission was less than 76.2 m s−1

1

2

3