The Endocrine System: Function and Structure

Function:

▪ synthesize and release hormones permitting them to act in concert and respond to changes in the body and maintain stability (homeostasis)

▪ Example organs – thyroid, pancreas (islets of Langerhans), adrenal glands, pituitary gland

Tools:

– hormones

* chemicals released by cells in one part of the body that affect cells in other parts of the body

* only a small amount needed to alter cell metabolism/function

* produced in glands and released into bloodstream

* examples include: insulin, epinephrine, growth hormone

Target cells:

▪ only cells with receptors for certain hormones will be affected

▪ cells with hormone receptors are called target cells

Steroid hormones:

> many fused rings of carbon, hydrogen, oxygen, not soluble in water

> diffuse through cell membrane and combine with receptor protein in cytoplasm

> hormone-receptor complex cause cell to respond to hormone by interacting with cell DNA and stimulating protein synthesis

Protein hormones:

> made up of amino acids, soluble in water

> combine with receptor hormones on the cell membrane

> hormone-receptor complex on the cell membrane induces an internal response by the cell which results in protein synthesis

Pituitary Gland: The Master Gland

▪ controls other endocrine glands with the hormones it releases

▪ connected to hypothalamus; composed of an anterior lobe and a posterior lobe

Anterior lobe:

> produces own hormones

> hypothalamus stimulates the release of these hormones

Posterior lobe:

> stores and releases hypothalamus hormones (ex. ADH)

> hypothalamus stimulates release of hormones