lOMoARcPSD|5944176 BI459 - Endocrinology Notes Endocrinology (Wilfrid Laurier University) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by Rayanna Rymes (Ryme2480@mylaurier.ca) lOMoARcPSD|5944176 Introduction Anatomy - Main Concepts ● CELL: Basic element (unit) of living organism ● TISSUES: Group of cells having same functions ● ORGANS: Functional units composed of tissues (e.g. glands) ○ Parenchyma vs. stroma ● SYSTEMS: Group of organs with related functions Physiology - Main Concepts ● Secretion vs. Excretion ○ Both are involved in the passage or movement of materials ○ Both involved in homeostasis ● “Excretion”: removal of material from a living thing ○ (mostly body wastes; e.g.: tears, urine, carbon dioxide, feces) ● “Secretion”: movement of materials (that can be metabolized and used by our bodies) from one point to another ○ e.g. hormones, saliva Endocrine vs. Exocrine Glands ● Gland: organ that releases certain substances for use in the body or for discharge into the surroundings a. Endocrine ■ separated from surface (no ducts) ■ secretions (usually) transported via circulatory system b. Exocrine ■ maintain connection to surface ■ secretions empty to surface through ducts Cellular Patterns of Secretion Secretory Pattern Description Example Endocrine Secretion into the blood for transport internally to target Hormones Downloaded by Rayanna Rymes (Ryme2480@mylaurier.ca) lOMoARcPSD|5944176 tissues Exocrine Secretion into a duct that opens onto an external or internal surface Sweat Merocrine Secretion without visible damage to the secretory cell (involves exocytosis) Peptide hormones Apocrine Release by sloughing of “outer” or apical portion of secretory cell Mammary gland - milk Holocrine Release through cell death and lysis Sebaceous gland secretion (skin) Cytogenous Release of whole, viable cells Spermatozoa Endocrinology - Overview ● Endocrinology: study of endocrine glands/tissues & their products (hormones) ○ endocrine (‘internal secretion’) ● Hormone: A chemical signal/messenger synthesized by an endocrine organ (gland) or tissue ○ secreted in the bloodstream to act on specific target cells and elicit a specific physiological response ■ Water-soluble: via exocytosis (vesicles) ■ Lipid-soluble: via diffusion (simple or facilitated) Endocrine System - General Organization ● Includes a number of different cells, tissues, and organs (glands) ● Components are functionally related ● Synthesizes & secretes hormones that: ○ Regulate ○ Coordinate ○ Integrate ○ All are functions of target cells (in most cases long-distance targets) Endocrinology Overview (Fig Blue) ● Not ALL vertebrates have the same glands/endocrine tissues!! ● E.g. Mammals: ○ Glands: pituitary, thyroid, parathyroid, adrenal, pineal ○ Tissues: (structures/organs with some endocrine function): hypothalamus, thymus, pancreas, gonads, kidneys, stomach, liver, small intestine, adipose tissue Downloaded by Rayanna Rymes (Ryme2480@mylaurier.ca) lOMoARcPSD|5944176 Endocrine System - Cellular Organization ● Cords (most common) ○ Linear arrangement ■ e.g. pituitary gland; adrenal cortex ● Follicles ○ Spherical masses → product (h) inside (lumen) ■ e.g. thyroid gland ● ● Scattered clumps or clusters ○ e.g. I. of Langerhans (pancreas; Leydig cells in testes) Single cells (unicellular gland) ○ e.g. cells within the epithelial lining of digestive and respiratory tract Hormone Delivery - Overview ● Endocrine - via circulation (distant delivery) Downloaded by Rayanna Rymes (Ryme2480@mylaurier.ca) lOMoARcPSD|5944176 ● ● ● ● Autocrine - act on the same cell that secreted it Paracrine - act on neighboring cells Intracrine – act within the same cell that made it Neuroendocrine - “neurohormones” released via synapses (neurosecretory cells) into bloodstream Neuroendocrine System ● Allow the nervous system to coordinate endocrine systems and to communicate with peripheral tissues ● Neurosecretory cells are different from regular neurons: ○ secrete neurohormones ○ large size of secretory vesicles ○ terminals on blood vessels (Release hormones into interstitial space close to bed of capillaries (neurohemal organ) Neurosecretory Cells & Neurohormones ● Magnocellular (large neurons) of hypothalamus produces the hormones ● Axons in neurohypophysis ● Secrete ADH (vasopressin) & oxytocin Downloaded by Rayanna Rymes (Ryme2480@mylaurier.ca) lOMoARcPSD|5944176 ○ ○ Vasopressin (ADH) ■ Vasoconstriction ■ water reabsorption (kidney) Oxytocin ■ contraction of smooth muscle of uterus ■ contraction of myoepithelial cells (milk ejection) Endocrine System - Main Functions ● Maintains the internal environment in the body (optimum biochemical environment; “homeostasis”). (W. Cannon; 1929) ● Regulates growth, development, and metabolism ● Controls sexual reproduction, including gametogenesis, fertilization, fetal growth and development, and nourishment of the newborn ● Regulates the response to stimuli (e.g. stress and/or injury) Endocrine vs. Nervous System ● Nervous & endocrine systems share responsibility for maintaining body health ● Nervous system sends nerve impulses (action potentials) & responds to stimuli to adjust body processes ● Endocrine system sends hormones but responds more slowly. ● The ability to control the cells is dependent on the amount of receptors on the cell ● Hormones secreted by the hypothalamus Experiments on Endocrine Function of a Gland/Organ/Tissue ● Removal of tissue should produce deficiency/effect (can be difficult if it has more than one function, e.g., heart) ● Replacement should reverse deficiency/effect ● Deficiency/effect relieved when suspected hormone is injected (most important criterion) ● First recorded endocrine experiment (~1849): demonstrated that the combs of roosters is androgen dependent ○ Arnold Berthold (1803-1861) ○ Testosterone (purified ~1935) Downloaded by Rayanna Rymes (Ryme2480@mylaurier.ca) lOMoARcPSD|5944176 Pheromones ● These hormones act on other individuals rather than the one secreting them ● Summary: ○ Organic compound (CH-Skeleton) ○ Different types of transmission (diffusion; current-borne; contact) ○ Medium: air or water ○ Invertebrates and vertebrates ○ Differ in size, shape, composition, and polarity ○ Examples of animal that use pheromone: wasps, dogs, cats, butterflies, rats, ants ● How does it work? 1. Our bodies naturally secrete fluids through glands in our body that contain natural pheromones 2. The vomeronasal organ detects the pheromones and sends a signal to the olfactory nerves 3. The olfactory nerves stimulate the hypothalamus in the cortex of the brain which stimulates emotions 4. The pheromone scent triggers illicit emotions in the hypothalamus such as attraction, sexual desire, arousal Hormone Delivery ● Endocrine hormones ○ Intracrine, autocrine, and paracrine hormones, neurohormones ○ (endo hormones) ● Pheromones ○ Exocrine signals released externally to initiate response in another organism ○ (ectohormones) Hormone Delivery: Pheromonal Communication ● Pheromones = exocrine signals released externally to initiate response in another organism; odorless; well studied in wildlife ● Example: Fish use pheromones to assist social behavior: Downloaded by Rayanna Rymes (Ryme2480@mylaurier.ca) lOMoARcPSD|5944176 ○ ○ ○ Schooling Identification of conspecifics Potential mates & in reproduction. ■ Prostaglandins (i.e., PGF2a) are released by female fish around the time of ovulation and influence male spawning behavior Downloaded by Rayanna Rymes (Ryme2480@mylaurier.ca)
