Honors Anatomy & Physiology

 act together to coordinate body’s activities  both:  use chemical messengers to communicate cell to cell  major function: homeostasis  endocrine: slower response time  hormones transported thru circulatory system  target cells (any cell with hormone receptor) anywhere in body  nervous: quicker conduction of signals  neurotransmitters  act on cells close by

EndocrineExocrine  no ducts  secretions released and diffuse into blood capillaries  have ducts  secretions released onto surface  example: sweat glands, salivary glands

PeptideSteroid  bind to protein receptors in cell membranes (do not enter cell)  receptor-hormone activate enzyme in cytoplasm  series of reactions result in cell response  enter cell & bind to receptor in cytoplasm or nucleus  Activates transcription of gene  protein produced  generally action slower than peptide hormone

 part of brain  secretes “releasing” hormones that act on pituitary gland  axons that store the 2 posterior pituitary hormones end there

 2 lobes: posterior & anterior

 stimulated by TSH  secretes thyroxin (T4) and triiodothyronine (T3)  (-) feedback inhibition  both have similar effects on target cells

 Thyroid produces too little hormone  several causes: Hashimoto’s autoimmune/ lack of Iodine in diet  goiter (enlargement of thyroid due to increased TSH stimulation  Symptoms:  Adults: lethargy, weight gain, anovulatory cycles  Infants:cretinism: dwarfism, low IQ, failure to reach sexual maturity

 excessive secretion of thyroid hormones

 4 small glands embedded in posterior surface of thyroid gland  secrete: parathyroid hormone (PTH)  regulated by serum Ca++ levels  actions: 1. stimulates removal of Ca++ from bone 2. increases kidney tubules reabsorption of Ca++ 3. activates vit D which enhances Ca++ absorption from food

 outer layer  produces 2 kinds of steroid hormones 1. Glucocorticoids  major 1 – cortisol:  reduces swelling by inhibiting immune system/ raises serum glucose (stimulates liver to make glucose from proteins or lipids 2. Mineralocorticoids  major 1- aldosterone  acts on kidney to promote absorption of Na+ & excretion of K+