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 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

Note Hypothalamus

Pituitary Gland

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 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

Pancreas 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