Chapter 45 ~Hormones and the Endocrine System

Endocrine and Nervous System Regulation Nervous system - Electrical signals - Fast acting for immediate response Endocrine system - Hormones - Slower and longer acting

Negative Feedback Loops The hormonal response reduces the initial stimulus Prevents overreaction of the system and maintains homeostasis (sugar levels in the blood)

Positive Feedback Loops Reinforces the stimulus Creates a greater response

Regulatory systems Hormone~ chemical signal secreted into body fluids (blood) communicating regulatory messages Target cells~ body cells that respond to hormones Endocrine glands~ hormone secreting glands; ductless, travel through interstitial fluid or circulatory system Exocrine glands secrete chemicals through ducts; tears, mucus, saliva Neurosecretory cells~ actual cells that secrete hormones

Water and Fat Soluble Hormones Water soluble- faster acting, reversible, protein based, removed from blood quickly– insulin, ADH: attaches to cell membrane Fat soluble hormones- slower acting and longer lasting, irreversible, stimulated by a trophic hormone – steroids: enters the cell

Paracrine signaling Cell to cell communication Induces a change in nearby cells Travel in short distances Example-Hedgehog proteins

Local regulators Nitric oxide (NO)` vessel dilation, increase blood flow for more O 2 Growth factors ~ proteins for cell proliferation Prostaglandins~ immune, reproduction, blood clotting

Local Regulators Histamine- triggers dilation and increased permeability in the immune response Interleukins-a cytokine protein that activates lymphocytes Retinoic acid- necessary for vision and bone growth (anti aging hormones in cosmetics)

Trophic Hormones Growth effect on the gland it stimulates It is released in the bloodstream to travel to the target organ or gland

The pancreas- feedback for glucose Islets of Langerhans Alpha cells: glucagon~ raises blood glucose levels Beta cells: insulin~ lowers blood glucose levels Type I diabetes mellitus (insulin-dependent; autoimmune disorder) Type II diabetes mellitus (non-insulin- dependent; reduced responsiveness in insulin targets)

The adrenal glands Adrenal medulla (catecholamines): epinephrine & norepinephrine~ increase basal metabolic rate (blood glucose and pressure) Adrenal cortex (corticosteroids): glucocorticoids (cortisol)~ raise blood glucose mineralocorticoids (aldosterone)~ reabsorption of Na+ and K+

Epinephrine Release Fight or flight Stress hormone Increases blood pressure Increases diameter of blood vessels

The gonads Steroid hormones: precursor is cholesterol androgens (testosterone)~ sperm formation; male secondary sex characteristics; estrogens (estradiol)~uterine lining growth; female secondary sex characteristics Progestins (progesterone)~uterine lining growth

Gonadotropic Hormones Stimulates gonads FSH- follicle stimulating hormone (in women regulates menstruation and ovulation) LH- luteinizing hormone (ovulation in women and production of testosterone in men)

 Arthropods have extensive endocrine systems regulating molting in insects and crustaceans.  The regulation of molting in insects.  Neurosecretory cells in the brain produce brain hormone (BH), which regulates the secretion of ecdysone.  Ecdysone also promotes the development of adult features and molting Juvenile hormone (JH) promotes the retention of larval characteristics. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

I know- It’s my Pharoahmones You are so irresistible!!!