Endocrine System

What is a gland? Gland is a organ that produces secretion Endocrine glands secrete into blood stream Endocrine glands secrete into a lumen/duct

Functions of Endocrine System Secrete hormones that coordinate and direct activities of target cells/organs Regulates mood, growth, development, metabolism, sexual function, reproduction, blood pressure, heart rate Most systems are under combined control of endocrine and nervous systems

Negative Feedback Loops Endocrine system operates under negative feedback mechanisms - think about your home’s thermostat and furnace

Requirements for feedback Hormone – chemical released from endocrine gland that exerts effect elsewhere Target- cell that responds to hormone - must have receptor for hormone - number of receptors on target cells are in state of flux

Hormones Three categories of hormones 1. Proteins: -freely circulate in blood -available for use quickly, short lasting effects 2. Amines 3. Steroids: -Require special transport proteins -unavailable when bound -allows for a gradual, longer term response

Nervous System Control: Adrenal Medula can be stimulated to release hormones by sympathetic nervous system Example: releases epinephrine (adrenalin

Pituitary Gland Know as the master gland Major influencer of body activities Stimulated to release hormones by the hypothalamus

Thyroid Gland Butterfly shaped gland; sits inferior to cricoid cartilage Very vascular and rich in blood supply Secretes three hormones -Triliodothyronine (T3) -Thyroxine (T4) -Calcitonin

Parathyroid: Four glands found on posterior thyroid gland Secretes hormone parathyroid Involved in calcium metabolism

Thymus Gland Endocrine and lymphatic organ Secretes hormone thymosin Stimulates production of lymphocytes

Adrenal Glands Located on top of the kidneys Contains two regions: 1. Medulla - Norepinephrine – greatest effect is to cause vasoconstiction of blood vessels -increases blood pressure

Adrenal Glands 2. cortex 1. (release of corticoids – steriod hormones) 2. glucocorticoids – mediates inflammation process and reduces pain 3. androgens – male sex hormones; secreted in both men and women -post menopause women may develop some male characteristics -levels are masked by gonads

Gonads Sex glands Females produce estrogen and progesterone Testosterone causes development of male reproductive organs

Pancreas Endocrine and exocrine gland located behind the stomach Exocrine – secrete digestive enzymes into duodenum Endocrine – regulate glucose metabolism -regulates own function through paracrine signaling

Islets of Langerhans Contain endocrine cells of pancreas Alpha (A)- cells secrete glucagon Beta (B) cell secrete insulin

Pineal Gland Releases melatonin; causes sleepiness Assists with temperature regulation Involved in mood regulation - possibly linked to depression Stimulated by level of light input