Read the summary and the most important questions on Chapter 2 - The endocrine system

• 2 Chemical communication

• Explain the different types of chemical mediation

  • Intracrine cells: mediation of intracellular events.
  • Autocrine cells: secrete products that may feed back to affect processes in the cells that originally produced them.
  • Paracrine cells: releases chemical mediators that induce a biological response in an adjacent cell.
  • Endocrine cells: secrete chemicals into the bloodstream, where they may travel to distant target cells.
  • Ectocrine substances (pheromones etc.): released into the environment to communicate with other individuals. 

• 4.1 Protein and peptide hormones

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• What are the characteristics of protein and peptide hormones?

  • Soluble in blood
  • Don't need carrier proteins to travel to target cells
  • Removed from the blood through degradation or excretion

• What does the term "biological half-life" mean?

  The metabolism of a hormone is expressed as the biological half-life of a hormone, which is the amount of time required to remove half of the hormone from the blood.

• 4.1.1 Hypothalamic hormones

• What do hormones from the hypothalamus do?

  They are a special class of neurotransmitters that act on a variety of cells in the anterior pituitary.

• What are the inhibitory hormones that are secreted by the hypothalamus?

  • Growth hormone inhibitory hormone or somatostatin (GHIH)
  • Gonadotropin inhibitory hormone (GnIH)

• What are the releasing hormones that are secreted by the hypothalamus?

  • Tyrotropin-releasing hormone (TRH)
  • Growth hormone releasing hormone (GHRH)
  • Gonadotropin-releasing hormone (GnRH)
  • Melanotropin-releasing hormone (MRH)
  • Corticotropin-releasing hormone (CRH)
  • Kissepeptin

• What other hormone does the hypothalamus secrete?

  Dopamine (DA) also known as prolactin inhibitory factor (PIH) or melanotropin inhibitory factor (MIF). Technically a monoamine.

• 4.1.2 Anterior pituitary hormones

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• What 3 types of cells are there in the anterior pituitary?

  1. Acidophils
  2. Basophils
  3. Chromophobes

• What hormones are secreted by the basophils of the anterior pituitary? What are the characteristics of these hormones?

  1. Luteinizing hormone (LH)
     
  2. Follicle-stimulating hormone (FSH)
     
  3. Thyroid-stimulating hormone (TSH)
     

  
  
  

  • They are known as glycoproteins and consist of an alfa and a beta subunit. The alpha subunits of all 3 are the same, and the beta subunits are unique. 
    
  • LH and FSH are gonadotropins.
  • TSH is released in response to TRH from the hypothalamus and stimulates the thyroid gland to release thyroid hormones. 

• What are the functions of LH and FSH?

  • LH:
    - In males: stimulates Leydig cell development and testosterone production.
    - In females: stimulates corpora lutea development and production of progesterone.
  • FSH:
    - In males: stimulates spermatogenesis
    - In females: stimulates development of ovarian follicles and the secretion of estrogens