[Vocabulary] Shook off the response

[krisstte]

Please, help me to understand the meaning of "shake off the response".

Nick had just tucked in his shirt in preparation for dinner when the knock sounded on the door to his bedchamber. He snapped around at the sound, immediately on edge, then shook off the response.

Sarah MacLean "[FONT=&quot]Ten Ways to Be Adored When Landing a Lord"
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Does it mean, that Nick was startled by the noise, but then relaxed? Literally saying, shook off bad thoughts?

 

[Tdol]

It means that he controlled his reaction to the sound, so he was no longer on edge.