- The primary function of the Hering-Breuer reflex is to prevent lung overinflation during inspiration.
- This reflex is triggered when stretch receptors located in the walls of the bronchi and bronchioles detect excessive lung expansion.
- Upon activation, these receptors send inhibitory signals via the vagus nerve to the respiratory centers in the brainstem, which then terminate inspiration and prevent further lung inflation.

- This reflex plays a crucial protective role by ensuring that the lungs do not inflate beyond their safe capacity, which could otherwise cause damage to the delicate alveolar tissues.
- It is particularly important during deep or forceful breathing.

The other options are incorrect because:
- Bronchoconstriction during asthma is mediated by different mechanisms involving inflammatory cells and neurotransmitters, not the Hering-Breuer reflex.
- Hypoventilation in response to high CO2 levels involves chemoreceptor regulation, not the stretch receptors responsible for the Hering-Breuer reflex.
- Alveolar collapse during expiration is prevented primarily by surfactant, not by the Hering-Breuer reflex.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th Edition, Chapter 46, Pulmonary Ventilation and Control of Respiration