| Date | November 2019 | Marks available | 5 | Reference code | 19N.2.SL.tz0.6 |
| Level | Standard Level | Paper | Paper 2 | Time zone | time zone 0 |
| Command term | Apply | Question number | 6 | Adapted from | N/A |
Question
Using an example from sport, apply the concept of psychological refractory period.
Compare and contrast the structure of fast-twitch (type IIa and IIb) muscle fibres.
Describe how breathing is controlled during exercise.
Explain how the mechanics of exhalation change from rest to exercise.
Markscheme
When a stimulus is closely followed by a second stimulus, the first stimulus must be cleared before the second can be processed
OR
S2 only becomes relevant when S1 is finished with ✔
the delay in reaction time to a second stimulus is called the psychological refractory period ✔
a performer/defender has to sort out new and correct stimulus, but first they have to disregard the old and now useless stimuli, which causes the delay ✔
any other action/response must wait until the first response has been completed ✔
eg, in soccer an attacker may lean to the left/fake/dummy to move the defender; this is S1 ✔
the defender will begin to respond (R1) to S1/ to the initial stimulus first ✔
the attacker immediately moves to their right to beat the defender; this is S2 ✔
the defender cannot respond to S2 until they have completed R1 <therefore they appear to be slow and beaten by the attacker> ✔
Award max [4] if no example has been provided.
Award max [2] for an explanation of the PRP including a schematic representation if no example provided.
[Source: Psychological refractory period adapted from Multidix, https://creativecommons.org/licenses/by-sa/4.0/, Single channel hypothesis by International Baccalaureate Organization]
Award max [3] for each of contrast / compare
an increase in CO2 causes a decrease in pH ✔
decrease in pH is detected by the chemoreceptors ✔
movement is detected by the proprioceptors ✔
this stimulates the ANS to increase the depth of breathing ✔
baroreceptors inform the ANS to increase the rate of breathing ✔
the increase in rate of breathing causes the lungs to stretch further ✔
stretch receptors initiate exhalation ✔
the diaphragm and/or <internal> intercostal muscles contract more forcefully ✔accessory muscles are required to
pull the rib cage in during exercise ✔
the rib cage moves downwards and inwards further when exercising ✔increasing the depth of breathing ✔
the rate of breathing is increased ✔
the thoracic volume decreases further ✔
the thoracic cavity pressure raises higher than at rest ✔
air rushes out faster due to a greater difference between the lungs and the atmosphere ✔
Award max [5] if no mention of accessory muscles.
