Post on 31-Dec-2015
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