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A snapshot of the summary - 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
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)
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
What 3 types of cells are there in the anterior pituitary?
What hormones are secreted by the basophils of the anterior pituitary? What are the characteristics of these hormones?
- Luteinizing hormone (LH)
- Follicle-stimulating hormone (FSH)
- 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.
- Luteinizing hormone (LH)
What are the functions of LH and FSH?
- In males: stimulates Leydig cell development and testosterone production.
- In females: stimulates corpora lutea development and production of progesterone.
- In males: stimulates spermatogenesis
- In females: stimulates development of ovarian follicles and the secretion of estrogens