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.

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.