Expiration occurs when the lungs recoil.
Answer:
1. First of all, a squirrel would make sure to stash lots of food before and during the winter.
2. The squirrel would claim its own tree hollow/burrow.
3. They wrap themselves into a tight ball and go into a state of torpor (Torpor is a state where their body temperature becomes about the same temperature as their surrounding hibernaculum. This causes their heart rate to slow and causes them to use less energy)
4. Squirrels get up after 20 or so days to rewarm themselves up, and perhaps eat something to regain their energy. After that they will head back to their hibernaculum to continue hibernation.
5. When spring approaches they will fully wake up, go eat, regain their energy, and prepare themselves for the mating season.
Hope this helps :)
The nucleus resembles the brains function.
