Hormones & Endocrine System

Introduction Endocrine System – Sum of all hormone secreting cells and tissues Endocrine Gland – ductless glands that secrete hormones directly into body fluids Hormones – chemical signals that cause a response in target cells Affect body tissues or other endocrine glands (tropic hormone) Endocrine secretion is determined by Positive & Negative Feedback

Hormones Can affect 1 tissue, multiple tissues or entire body Can also have a direct effect on non-endocrine tissues OR affect other endocrine tissues Called tropic hormones

Target Cell Receptors Cell-Surface Receptors Intracellular Receptors Most common receptor for initiating a signal transduction pathway Receptor  Transduction  Response Intracellular Receptors ONLY lipid-soluble ligands are able to pass through the membrane & bind intracellular receptors Testosterone & estrogen (transcription factors)

Hypothalamus & Pituitary Hypothalamus gets info from the brain or nerves Hypothalamus initiates endocrine signal response Pituitary – Anterior & Posterior Posterior - Extension of the hypothalamus that stores and secretes hormones Anterior – tropic hormones (say what???)

The Boss… Hypothalamus Receives signals from nervous system Initiates endocrine signal response

Pituitary Gland Note Hypothalamus

Anterior Pituitary Gland Regulated by hypothalamus Tropic hormones Growth hormone (GH) & Thyroid- stimulating hormone (TSH) – seriously? ACTH – Adrenocorticotropic hormone Stimulates adrenal cortex to secrete glucocortocoids Glucocortocoids raise the blood sugar level

Anterior Pituitary Gland (page 2) FSH – (Follicle stimulating Hormone) Stimulates development of ovarian follicles (female) or spermatogenesis in seminiferous tubules (male) LH – (Luteinizing Hormone) Triggers ovulation in females Stimulates testosterone production in testes PRL – (Prolactin) Stimulates growth of mammary glands milk production & synthesis of milk protein

Posterior Pituitary Oxytocin ADH – (Antidiuretic Hormone) Stimulates uterine contractions Stimulates milk release by mammary glands ADH – (Antidiuretic Hormone) Acts on collecting ducts in Kidneys Increases water reabsorption from the filtrate

Thyroid & Parathyroid T3 – (Triiodothyronine) & T4 – (Thyroxine) Stimulates & maintain metabolic processes Calcitonin Lowers calcium level in blood Parathyroid Gland PTH – (Parathyroid) Raises calcium level in blood

Adrenal Gland Epinephrine & norepinephrine – Increase metabolic level by: Constrict blood vessels Raise blood glucose levels Glucocorticoids Elevate blood glucose level ACTH

Pancreas & Pineal Gland Insulin – Lowers blood glucose level Makes cells permeable to glucose Glucagon – Raises blood glucose level Breaks down glycogen Pineal Gland Melatonin – Involved in biological rhythms