Endocrine system http kidshealth orgkidhtbwbfs ESmoviesource html Endocrine

Endocrine system http: //kidshealth. org/kid/htbw/_bfs _ESmoviesource. html

Endocrine glands are ductless therefore their products are secreted into the blood stream for transport. Exocrine Endocrine Exocrine glands secrete their products into a duct.

Types of Regulatory Molecules • Hormone—regulatory chemical that is secreted into the blood by an endocrine gland or an organ of the body exhibiting endocrine function • The blood carries the hormone to EVERY cell in the body, but only the TARGET cell can respond since it is the only one with the proper RECEPTORS.

The difference between a neurotransmitter and a hormone • Norepinephrine [a. k. a. noradrenaline] is released as a neurotransmitter by the sympathetic nerve endings AND is secreted by the adrenal gland as a hormone • As a neurotransmitter it travels a very short distance across the synaptic cleft and binds to a receptor protein to stimulate the postsynaptic cell —either another neuron, a muscle cell or a gland cell • As a hormone it travels throughout the bloodstream and can thus act across a great distance

A neurotransmitter jumps the synaptic cleft and is received by a receptor protein on an adjacent muscle cell.

Wouldn’t you know? There’s a neurohormone! • Neurohormone—a chemical messenger secreted into the blood stream by specialized neurons • The distinction between the nervous system and endocrine system blurs when it comes to such molecules • The brain can be considered an endocrine gland since some neurons in the brain secrete hormones

Norepinephrine is a hormone when secreted by the adrenal gland into the blood stream

ENDOCRINE GLANDS & HORMONES • There are organs that secrete hormones in addition to other functions • There are organs that function exclusively as endocrine glands • There’s a huge table to follow—good to know for multiple choice points • PICK A COUPLE OF THESE AND KNOW THEM WELL—IN DETAIL—FOR ESSAYS!

Figure 45. 5 Human endocrine glands surveyed in this chapter

Two big classes of hormones: WATER SOLUBLE & WATER INSOLUBLE • LIPOPHILIC—fat soluble [thus NOT water soluble!] hormones – All steroids – thyroxin • HYDROPHILIC—water soluble [thus NOT fat soluble!] hormones – All other hormones • THIS DISTINCTION IS CRITICAL since it relates structure to function

ENDOCRINE GLANDS LACK DUCTS: Products secreted into capillaries FOUR different chemical categories of products • Polypeptides—insulin and antidiuretic hormone (ADH) • Glycoproteins—follicle-stimulating hormone (FSH) and luteinizing hormone (LH) • Amines—derived from the aa’s tyrosine and tryptophan; include hormones secreted by the adrenal medulla, thyroid and pineal glands • Steroids—lipids derived from cholesterol; include testosterone, estradiol, progesterone and cortisol

Steroids further divided • Sex steroids--secreted by testes, ovaries, placenta and adrenal cortex [outer region of the gland] • Corticosteroids--secreted ONLY by the adrenal cortex – Cortisol—regulates glucose balance – Aldosterone—regulates salt balance

Figure 45. 13 Steroid hormones from the adrenal cortex and gonads

Ammine Hormones • Cholamines—secreted by the adrenal medulla [inner portion of the adrenal gland] – Epinephrine [adrenaline] & Norepinephrine [noradrenaline] the fight or flight hormone & its “antidote”; derived from tyrosine • Thyroxine—secreted by the thyroid gland; derived from tyrosine • Melatonin—secreted by the pineal gland; derived from tryptophan

Neural and Endocrine Interactions • The endocrine system cooperates with the nervous system to regulate the activities of the other organ systems of the body

Major site of neural regulation is the brain’s regulation of the anterior pituitary gland • The hypothalamus controls the hormonal secretions of the anterior pituitary which regulates other endocrine glands