The diagram shows a school laboratory setup used to investigate the blink reflex. A student stands 2 m from a harmless puff of air delivered beside, but not...
Question 1 Report
The diagram shows a school laboratory setup used to investigate the blink reflex. A student stands 2 m from a harmless puff of air delivered beside, but not into, the eye. A high-speed camera records the time from the puff to closure of the eyelid. Table 1 shows mean results for five trials at two room temperatures. The eye and its surrounding structures are protected by this rapid response.
| Room temperature / degrees C | Mean blink time / ms |
|---|---|
| 18 | 152 |
| 24 | 149 |
(a) State the mean blink time at 24 degrees C. [1]
(b) Describe the difference between the two mean blink times. [2]
(c) Explain why five trials were used at each temperature. [2]
(d) Name the structure labelled T. [1]
(e) Explain how blinking helps to protect the eye. [2]
(f) Which part of the nervous system coordinates a simple reflex such as blinking: the brain or the spinal cord? [1]
(g) State one variable, other than temperature, that should be kept the same. [1]
Answer Details
(a) The mean blink time at 24 degrees C is 149 ms. [1]
(b) Blink time is lower at 24 degrees C than at 18 degrees C. The difference is \(152-149=3\) ms. [2]
(c) Repeating the test five times allows a mean to be calculated. A mean reduces the influence of anomalous results and random variation, so it is more reliable than one reading. [2]
(d) T is the eyelid. [1]
(e) Blinking closes the eyelid, helping to prevent dust and other foreign objects entering the eye. It also spreads tears over the eye surface, keeping it moist and helping remove particles. [2]
(f) A simple blink reflex is coordinated by the brain. [1]
(g) One suitable control variable is the distance of the air puffer from the eye. The strength or volume of puff, student tested, or light level would also be acceptable. [1]
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