Endocrine System Coordinates and directs the activity of the body’s cells through the release of hormones into the bloodstream
What does this system do? -regulates mood -regulates growth and development -regulates tissue function -regulates metabolism -regulates sexual function -regulates reproduction
Characteristics -uses hormones to send messages -hormones secreted by glands -hormones transported through blood -organs/glands are small compared to other systems
Chemistry of Hormones 1. Amino acid-based hormone 2. Steroid hormones (protein and peptide based) peptide -2 or more amino acids proteins-10 or more amino acids 2. Steroid hormones (made from cholesterol) -consist of sex hormones made by gonads (ovaries and testes) and hormones made by adrenal gland
How Hormones Work? General Info -hormones affect only certain tissue cell or organs called target cells or target organs -target cells must have protein receptors present on the cell membrane to allow the hormone to attach -hormone must bind to the target cell to influence the cell
How do hormones work? Second Messenger System (amino acid-based) Hormone binds to receptor on the target cell membrane Receptor with the hormone activates an enzyme inside the cell Enzyme activates various reactions inside the cell
How do hormones work? Direct Gene Activation (Steroid hormones) Diffuse through the cell membrane of the target cell Enters the nucleus of the cell Binds to a protein receptor inside the nucleus Hormone and receptor attach to the DNA Activates mRNA mRNA leaves nucleus and makes new proteins
How are the endocrine organs activated to release hormones? Hormone release is triggered through negative feedback mechanisms 3 ways hormones are released Hormonal stimuli Humoral stimuli Neural stimuli
Hormonal stimuli -most common -endocrine organs are activated by other hormones
Neural stimuli -nerve fibers stimulate hormone release Example: sympathetic nervous system stimulates adrenal gland to release hormones (fight or flight: adrenaline rush)
Humoral Stimuli -hormone release is activated by changing blood levels of certain nutrients -word humor indicates the various body fluids (blood, bile, and others) Example: 1. Calcium levels trigger parathyroid hormone 2. Glucose levels trigger release of insulin from pancreas
Major organs of Endocrine System
Pituitary Gland -approximately the size of a pea -hangs on inferior surface of hypothalamus on the brain -has 2 lobes anterior pituitary (gland tissue) posterior pituitary (nervous tissue)
Anterior lobe of Pituitary Gland Release 6 hormones 2 stimulate nonendocrine target Growth hormone (GH)-bone/muscle growth Prolactin-milk production in breast 4 stimulate endocrine glands (tropic hormones) Adrenocorticotropic (ACTH) –adrenal gland Thyroid-stimulating hormone (TH)-thyroid 3 & 4) Gonadotropic hormone –gonads (testes and ovaries) 3. follicle-stimulating hormone (FSH)-sex cell production 4. Luteinizing hormone-ovulation of egg