Introduktion
Hormones are chemical messengers secreted by glands in the endocrine system.

Hormones travel in the blood to work in another part of the body and they regulate many of the body functions such as regulating glucose blood level and growth in the body.

Hormones can only produce reactions in specific cells known as target cells which contain an appropriate receptor site for the hormones into.

When a hormone binds to a cell it either increases or decreases its function. One hormone that affects human behavior is adrenaline, this hormone is secreted in the adrenal glands and plays a role in the “flight and fight” response.

When we are afraid our brain signals the release of adrenaline, which stimulates the sympathetic nervous system. This increases the blood flow in the body, heart beat, and breathing rate.