The air outside your body because when you tried to hold your breath the pressure builds and forces your body to breath by letting out the air but depending the altitude you are the pressure can change hope this helps
Answer:
b. epinephrine on beta 2 receptors causes bronchodilation
Explanation:
This is because epinephrine is an hormone and neurotransmitter that stimulate beta 2 receptors which causes signaling and their in presence in airway smooth muscle causes bronchodilation, which counter the activation of the M3 muscarinic receptors in cardiovascular. When stimulate in skeletal muscles it can lead to increased contractility and also to muscle tremors.
Protein builds muscle.
So it's gonna be the last one.
