Endocrine System

• Endocrine glands secrete hormones into interstitial fluid surrounding cells, diffusing through capillaries, then into the bloodstream
• Exocrine glands secrete into ducts then to the target site
• Autocrine signaling takes place within the same cell
• Paracrine signaling effects neighboring cells
• Name all the main endocrine glands

  Hypothalamus, Anterior and Posterior Pituitary, pineal gland, Thyroid, Thymus, Adrenal Glands, Pancreas, Ovaries, and Testes
• Receptors are constantly synthesized and broken down
• The posterior pituitary stores oxytocin and antidiuretic hormone (ADH) from the hypothalamus
• The anterior pituitary secretes growth hormone, thyrotropin-releasing hormone, adrenocorticotropic hormone, follicle stimulating hormone, luteinizing hormone, prolactin
• Oxytocin stimulates uterine contractions during childbirth and milk ejection during breastfeeding.
• Antidiuretic Hormone regulates water balance by increasing reabsorption of water in the kidneys.
• The two classes of hormones based on solubility are lipid soluble and water soluble
• Lipid soluble hormones mainly consist of steroids and thyroid hormones
• Water soluble hormones consist of Aminos/proteins, catecholamines, and peptides
• Lipid soluble hormone bind to and activate receptors in the cytoplasm of the cell
• Water soluble hormones activate and bind to receptors on the plasma membrane
• A first messenger is a molecule that is released from a receptor site on the membrane and a second messenger is what is released inside the cell fluid
• Hormone secretion is controlled by signals from the nervous system, chemical changes in blood, and other hormones.
• Follicular cells in the thyroid produce thyroxine and triiodothyronine
• Thyroid hormones regulate oxygen use, basal metabolic rate, cellular metabolism, growth and development
• Calcitonin is released in response to a rise in blood calcium levels
• Calcitonin decreases calcium levels by inhibiting osteoblast activity, increasing osteoclast activity, decreasing calcium absorption in intestines, and increasing calcium loss in urine
• The parathyroid glands release parathyroid hormone (PTH)
• Parathyroid hormone increases calcium levels by stimulating osteoblast activity, reducing calcium excretion in kidneys, and increasing calcium reabsorption in intestines.
• Adrenal medulla releases epinephrine and norepinephrine
• Epinephrine and norepinephrine increase heart rate, contractility of cardiac muscle, dilation of bronchioles, constriction of arterioles, increased glucose production, and mobilization of fatty acids
• Name the adrenal cortex layers from outermost to innermost

  Zona glomerulosa, Zona Fasciculata, Zona Reticularis
• Glomerulosa secretes mineralocorticoids, Fasciculata secretes glucocorticoids, and Reticularis secretes androgens
• The Pancreas has both endocrine and exocrine portions
• The pancreatic islets of Langerhans are clusters of endocrine cells that secrete insulin and glucagon
• The pancreas has Alpha cells, Beta cells, delta cells, and PP cells
• Alpha cells secrete glucagon to increase blood glucose
• Beta cells secrete insulin to lower blood glucose
• delta cells inhibit the release of both insulin and glucagon
• PP cells playa role in appetite regulating both the exocrine and endocrine portions