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Lecture 09
Terms, Vocabulary & Concepts
27
Anatomy
Undergraduate 2
02/15/2012

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Term
Gland
Definition

One or more cells that makes and secretes an aqueous fluid

 

 

Term
Gland: Endocrine
Definition
A type of gland that secretes internally, directly into the area rather through than a duct. It is a ductless gland. Secretes directly into either the blood  or nearbly tissue/interstitial fluid.
Term
Gland: Exocrine
Definition
A gland that secretes externally by way of ducts that lead directly into thier external environment.
Term
Glands: Exocrine - Modes of Secretion
Definition

These modes differ by how much the cell is affected by the excretion

 

  • Merocrine (no damage): products to be excreted are contained in vesicles and are secreted by exocytosis. No part of the gland is damaged or lost. (e.g. a sweat gland)
  • Apocrine (Some membrane lost): A portion of the plasma membrane buds of the cell, continting the secrition. (e.g. lipid secretionfrommamary  gland
  • Holocrine (Cell ruptures): In order to release the secretionthecell ruptures. (e.g. sebaceous glands of the skin)
Term
Glands: Exocrine Glands
Definition
  • More numerous than endocrine glands.
  • Secrete their products: onto body surfaces (i.e. skin) ((e.g. sweat)), into body cavities (pancreas), or into the lumen of an organ.
  • Exocrine glands include mucous and goblet cells which are unicellular composed of simple columnar epithelial cells that function to secrete mucus using both apocrine and merocrine methods of secretion.
  • Multicellular exocrine glands are composed of a duct and secretory unit.
  • Other types of glands:
    • sweat glands
    • salivary glands
    • mammary glands
    • stomach-pyloric glands, gastric chief cells
    • pancreas
    • liver
Term
Hormone
Definition

Any chemical, irrespective of whether it is produced by a special gland or not, for export or cellular use that "controls andd regulates the activity of certain cells or organs"

 

  • Old/Classic definition: A substance released by an endocrine andtransportedthrough the bloodstream to a target issue where it has effects on regulating the function of that tissue.

 

 

Term
Hormones: Hormonal Control and Body Functions
Definition
  • Reproduction
  • Growth and development
  • Mobilizationof body defneses
  • Maintenance of electrolyte, water, and nutrient balance
  • Regulation of cellular metabolism
  • Regulation of energy balance
Term
Glands: Endocrine - Hormone Actions
Definition
  • Autocrine Hormone Actions
    • Auto - self.The hormon acts on the same cell type in which it was produced.
    • E.g. Insulin - pancreatic islet B cells
  • Intracine Hormone Actions
    • intra - within. The hormone acts within the specific cell in which it was produced (within the cell's cytoplasm) without ever being released
    • E.g. Adipocyte
  • Paracrine Hormone Actions
    • The hormonehasits effects locally on cells other thanthose in which the hormone was produced. These hormones areproducedwithinone tissue yet regulate a differenttissueofthesameorgan

 

Term
Glands: Endocrine - Types of Stimuli - Humoral Stimuli
Definition
Humoral - liquid
 
  • It is the section of hormonesindirectresponseto changing blood levels of ions and nutrients.
  • Example: Concentration of calcium ions in the blood
    1. There is a decline in the blood Ca2+ concentration which stimulatesthe parathyroid glands to secrete parathyroid hormone (PTH).
    2. PTH causes Ca2+ concentrationsto rise back to appropriate levels and the stimulus is then removed
Term
Hormones: Mechanisms of Hormone Action - Non-Genomic
Definition

Where the hormones primary target is the cell memberane.

 

  • Activation/repressionofpre-existing cellproteins
  • Rapidonsetofaction
  • Rapid adaptationtochangeinthemilieu.
  • Effects:
    • Binding of hormoneto membrane receptor activates a cascade of second messengers

Term
Non-Genomic Effect
Definition
  1. A hormone (1st messenger) binds to the receptor.
  2. The receptor activates G protein
  3. G-protein activates the transmembrane protein adenylate cyclase.
  4. Adenylate cyclase converts ATP to cAMP (2nd messenger.
  5. cAMP activates protein kinases which triggers the responses of the target cell.
Term
Hormones: Mechanisms of Hormone Action - Genomic 
Definition

Primary action through specific intracellular receptors. Hormones are circulated to all tissues but only activate cells referred toa s target cells.


  • Sent to nucleus
  • Gene expression and new protein synthesis
  • Relatively long latency of onset
  • Organization of cell networks for complex functions
  • Hormon response receptors
Term
Genomic Effect
Definition
  1. The steroid hormone diffuses through the plasma membrane and binds to an intracellular receptor.
  2. The receptor-hormone complex enters the nucleus.
  3. The receptor-hormone complex binds to a hormone response element-a specific DNA sequence.
  4. This binding initiates transcription of the gene to mRNA.
  5. The mRNA then directions protein synthesis.
Term
Hormone Transport
Definition
  • In most cases it is the free hormone that is biologically active.
  • Hormones circulating bound to plasma protein:
    • Cortiscosteroid-binding protein - cortisol, progesterone
    • Sex-hormone-binding protein - testosterone, estradiol
    • Vitamin D binding protein - vitamin D
Term
Hormones: Inhibitary Hormones
Definition
Hormonesusedto inhibit anteriorpituitary
Term
Adenylate Cyclase
Definition
An effector enzyme activated by the G protein. It generates cAMP.
Term
cAMP
Definition
A second messenger in the Adenylate cyclase-cAMP system. It is converted from ATP by Adenlyte Cyclase. Then cAMP activates protein kinase.
Term
Hormones:Target Cell Specificity
Definition
  • Hormones circulate to all tissues but onl
Term
Parathyroid Gland - Chief/Principal cells
Definition
functionis to secrete PTH
Term
Effects of the Parathyroid Hormone
Definition
  1. Low Ca2 levels (Hypocalcemia) stimulates Chief cells in the parathyroid gland to release PTH.
  2. PTH activates osteoclast in the bone and calcium and phosphate ions are released from the bone into the blood.
  3. PTH stimulates the kidney to increase calcium reabsorption-->decrease urinary Ca loss.
  4. PTH stimulates the kidney to increase the enzyme that makes the active form of vitamin D, 1,25(OH)2D.
  5. ActiveVitamin D causes increased calcium absorption from food.
Term
Intracrine Hormone Actions
Definition
When the hormone acts within the specific cell (within the cytoplasm) without ever being released.
Term
Autocrine Hormone Actions
Definition
When the hormone acts on the same cell type in which it was produced.
Term
Paracrine Hormone Actions
Definition
When the hormone has its effect locally on cells other than those which they were produced. Produced within one tissue asnd regulate a different tissue of the same organ.
Term
active vitamin D 1,25(OH)D, 1,25-dihydroxyvitamin D3
Definition
  • Produced in the kidneys with the stimulation of the enzyme 1-alpha hydroxylase.
  • Stimulates the gup to increase Ca absorption from diet and thus increase Ca in the blood.
  • Also stimulates bones to breakdown to release calciu
Term
Vitamin D Metabolism
Definition
  1. Make D3 in skin or ingest D2 or D3 in diet.
  2. It binds to a Vitamin-D Binding Protein (DBP) and travels to the liver.
  3. It is then hydroxylated in the liver at 25-position by 25-OHase to form 25(OH)D.
  4. 25(OH)D travels bound to DBP to the kidneys where it is hydroxylated at 1-position by 1-aslphOHase to form 1,25(OH)2D.
  5. This then binds to DBP (some is free) and travels to target tissues wehre it has its affects through genomic and non-genomic mechanisms
Term
Rickets
Definition
  • A disease of impaire bone mineralization in children (before epiphyses of long bones fuse) caused by too little Ca or P in the blood, vitamin D deficiency, genetic disorder of Ca, D, or P metabolism.
  • Symptoms are bowing of legs and growth retardation.
  • UV radiation therapy is often used for rickets to stimulate bone mineralization.
  • Vitamin D Rickets (VDR) Mutations  - Type 1
    • A defect in the 1-alpha hydroxylase enzyme which converts 25(OH)D into the biologically active 1,25(OH)2D.
    • Normal  25(OH)D, low 1,25(OH)2D
  • VDR Mutations - Type II (Genomic)
    • Defectin the hormone receptor (HR) interaction
      • Hormone binding defects
      • Deficient nucleur localization
      • Normal binding to receptor but abnormal binding of HR complex to DNA
    • Normal 25(OH)D and normal or high 1,25(OH)2D
Term
Vitamin D - Hormone
Definition
two types: D2 from diet and D3 from epidermal synthesis
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