Endocrine System

As we learned before, all the systems within our body works in order to maintain homeostasis. The endocrine system is responsible specially for the distribution of hormones, which are chemical messengers. The endocrine system has a slower, however, longer effects in the body than the nervous system. Nevertheless, these two systems has their similarities:

• Some nervous system tissues actually secrete hormones, for example the hypothalamus.
• Several chemicals works as both neurotransmitters and hormones, depending on their location in the body.
• Both systems are regulated by negative feed back loops.
• The regulation of several process inside our body involves the conjunction of these two systems.

Hormone Action

The cells that are effected by the hormones are called target cells, they have what is called receptors proteins that will bind with hormones. The result of this bind is the start of several chemical reaction within the cells.

There are two types of hormones: lipid-soluble hormone and water-soluble hormone 

Lipid-soluble hormones, also called as lipid-based hormone or steroid hormones, can diffuse through the lipid bilayer of cell membrane. The receptors proteins for these hormones are located inside the cell. 

Water-soluble hormone, also known as amino-acid based hormones are unable to diffuse through the cell membrane, so their receptors proteins are located out side the cell.

The action of hormones is regulated by negative feedback loops, that works when a certain blood concentration of hormone is reached, or when target cells have responded to specif hormones, the endocrine gland will inhibit the releasing of the hormone.