Hello Ram
I believe you have downloaded the model from the below attached file exchange link.
In the review section of the link, Josh Potter has provided insights on the model. He has mentioned that model is based on Mauro Ursino's paper "Interaction between carotid baroregulation and the pulsating heart: a mathematical model," published in 1998 by the American Physiological Society.You can go through his review for more insights.
Additionally, you can reach out to songtao, In the review section itself he has mentioned that he is working on this model and is open for discussion. Adding mentioned email id for reference: dousongtao@stu.pku.edu.cn
I hope this helps you to get started.