Notes Ch. 13a Anatomy and Physiology Endocrine System Notes Ch. 13a Anatomy and Physiology

General Characteristics of the Endocrine System The endocrine system is made of endocrine glands that secrete substances into the body (the internal environment). The secreted substances are called hormones. They move from the interstitial fluid into the bloodstream and then to target cells. There are also exocrine glands that secrete fluids out of the body. – Examples of exocrine secretions would be stomach acid and sweat. General Characteristics of the Endocrine System

There are glands that secrete substances that are not called hormones There are glands that secrete substances that are not called hormones. These would be paracrine secretions – they only affect nearby cells. Autocrine secretions - affect the cell secreting substance.

The endocrine system is similar to the nervous system because it also sends messages but it sends it only to certain target cells.

Endocrine glands and hormones help regulate metabolic processes Endocrine glands and hormones help regulate metabolic processes. They aid in transporting substances through membranes, regulate water balance, electrolyte balance, and blood pressure. They are also extremely important in reproduction, development, and growth.

There are 2 types of hormones – steroids and nonsteroids. Hormone Action

These are lipids that are made of rings of carbon and hydrogen atoms. Steroids are different by the types and numbers of atoms attached to these rings and the way they are joined. The base of all hormones is cholesterol. These include sex hormones (testosterone and estrogen), secretions of the external part of the adrenal gland, Vitamin D. Steroid Hormones

Amines are nonsteroid hormones Amines are nonsteroid hormones. Examples are norepinephrine and epinephrine. They are made in the adrenal gland. Nonsteroid Hormones

Protein hormones are made of long chains of amino acids. These include hormones secreted by the parathyroid gland and the pituitary gland. Peptide hormones are short chains of amino acids.

Prostaglandins are produced to regulate neighboring cells Prostaglandins are produced to regulate neighboring cells. These are lipids (fats) that are produced in the liver, kidney, heart, lungs, thymus, pancreas, brain, and reproductive organs.

Hormones work by altering metabolic processes Hormones work by altering metabolic processes. It could change an enzyme or alter the rate a chemical is transported through the cell membrane. A hormone delivers its message by binding to a receptor on the target cells. The more receptors that bind the greater the response. Upregulation is an increase in the number of receptors on target cells. Downregulation is a decrease in the number of receptors. Actions of Hormones

Steroid Hormones and Thyroid Hormones Hormones will bind to parts of a DNA sequence and either activate or repress specific genes (turn the gene on or off). Steroid Hormones and Thyroid Hormones

Prostaglandins work a little differently because they only affect those close by. Some of the functions of prostaglandins are to relax smooth muscle in the airways of the lungs, cause labor contractions, Help regulate blood pressure, promote inflammation. Prostaglandins