Term
| What functions are overseen by the hormones released in the pituitary gland? |
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Definition
1. Somatic growth
2. Lactation
3. Thyroid function
4. Gonadal function
5. Adrenal function
6. Body fluid homeostasis |
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Term
| What two major functions do pituitary hormones normally have at their target organs? |
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Definition
1. Growth of target tissues
2. Secretion of more hormones |
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Term
| What does growth hormone releasing hormone do? |
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Definition
| Activates release of growth hormone by the somatotroph |
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Term
| What does somatostatin do? |
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Definition
| Inhibits the release of growth hormone by the somatostatin |
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Term
| What does prolactin releasing hormone do? |
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Definition
| Activates the release of prolactin by the lactotroph |
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Term
| what does prolactin inhibiting hormone (dopamine) do? |
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Definition
| Inhibits the release of prolactin by the lactotroph |
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Term
| What does gonadotroph releasing hormone do? |
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Definition
| activates the release of FSH and LH by the gonadotroph |
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Term
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Definition
| stimulates the release of thyroid stimulating hormone by the thyrotroph |
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Term
| what does cortical releasing hormone do? |
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Definition
| Stimulates the release of adrenocorticotropic hormone by the corticotroph |
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Term
| What types of molecules are the pituitary hormones? What is the exception to this rule? |
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Definition
1. peptides
2. PIT (dopamine) is a catecholamine |
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Term
| What neurons in the hypothalmus trigger the release of RH and RIH that affect the anterior pituitary? |
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Definition
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Term
| explain how the releasing hormones get to the anterior pituitary to stimulate the release of trophic hormones in the anterior pituitary |
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Definition
1. Neural stimulation by parvacellular neurons stimulate the release of releasing hormones
2. The superior hypophyseal artery has a capillary bed that surround the stalk where these hormones are released, so they diffuse into the bloodstream. 3. They then migrate through the bloodstream to the anterior pituitary and stimulate trophic cells to release hormones |
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Term
| Describe the "pulse generator" system of making and putting out releasing hormones |
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Definition
1. Neuroendocrine cells make hormones in their cell bodies and send them to axon terminals
2. several times over a day a network of neuroendocrine cells function IN UNISON to provide a synchronized release of the hormones
Note: Interneurons modulate the frequency of these releases, and feedback inhibition loops stop their activity as well |
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Term
| Describe how somatotrophs respond to activating releasing hormones. How does this differ from their response mechanism to inhibitory release hormones? |
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Definition
Activation hormones:
1. Binding of hormones to surface receptors activates cAMP
2. cAMP causes sodium channel induced cell depolarization as well as Calcium influx (which is also aided by the sodium depolarization)
3. Increased calcium levels in the cell cause fusion of granules to cell membrane and exocytosis of hormones
INHIBITING:
1. Binding of hormone to surface receptor inhibits cAMP and promotes potassium efflux, hyperpolarizing the cell
2. Hyperpolarization inhibits calcium influx, lowering calcium levels in the cell and decreasing hormone release |
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Term
| What types of hypothalmic cell bodies manufacture posterior pituitary hormones? |
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Definition
| Magnocellular cell bodies |
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Term
| Describe the process of hormone manufacture and release in the magnocellular pathway |
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Definition
1. Hormones are manufactured in the cell bodies (found in the paraventricular and supraoptic nuclei)
2. Hormones are packaged and transported down axons to nerve terminals in the pituitary, where they are stored
3. Excitation of the nerve triggers their release directly into the bloodstream
Note: The magnocellular (posterior pituitary) pathway DOES NOT have the large signal amplification associated with the anterior pituitary. The hormones are released directly into the bloodstream for target organs |
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Term
| What benefits are provided by the superior hypophyseal artery? |
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Definition
1. Its capillary plexus that surrounds the median eminence provides a larger surface area for hormonal diffusion
2. It travels directly to the anterior pituitary before returning to normal circulation, allowing minimal inactivation and loss of hormone signals meant for the anterior pituitary |
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