What happens to the nervous system when the dog runs up to and you get scared

The body responds by secreting the hormone adrenaline, which helps during the ‘fight or flight’ actions. In this case when adrenaline is secreted, your body responds by increased pumping of the heart as the heart is one of the target organs. This blood is sent to our muscle cells. The blood to the digestive system and skin is reduced due to contractions of small nerves in these organs and this blood is directed to our skeletal muscles. You also start breathing faster due to contraction of diaphragm and rib muscles.