Neuroendocrinology Flashcards
(16 cards)
List 3 Neural and humoral signalling
-endocrine
-neuroscience
-neuroendocrine
explain neurosecretory cells and neuroendocrine integration
-neuroendocrine cells are neurosecretory cells that release signal molecules from their synaptic terminals into the blood
-controlled via synaptic transmission from presynaptic neurons
Examples:
-magno and parvocellular neurons of the hypothalamus
-chromaffin cells of the adrenal medulla
Explain the embryology of the pituitary gland
-evagination of floor of 3rd ventricle (neural ectoderm)
-evagination of oral ectoderm
-rathke’s pouch pinched off
Explain the mechanism of action of the parvocellular nuclei and the magocellular nuclei
Parvocellular nuclei:
-neurosecretory cells release hormones to capillaries of median eminence (supplied by superior hypophysial artery)
-conveyed by portal veins to anterior pituitary gland where they regulate endocrine secretion
Magnocellular nuclei:
-project to posterior pituitary release to capillaries supplied by inferior hypophysial artery
Explain posterior pituitary hormones (oxytocin and vasopressin)
-PP is basically an extension of the hypothalamus, with hormones stored in hypothalamic neurone terminals.
-released under neural control into hypophysial capillaries, inferior hypophysial vein
What are the 4 hormones involved in the control of anterior pituitary secretions
1) TSH: thyroid stimulating hormone (thyrotropin)
2) TRH: thyrotropin releasing hormone
3) ACTH: adrenocorticotropic hormone
4) CRH: corticotropin releasing hormone
What are growth hormone functions
-growth and development (anabolic)
-couples growth to nutritional status
How is endocrine control of growth hormone secretion increased/decreased by
Increased by:
-GH releasing hormone (from hypothalamic parvocellular neuroendocrine cells)
-Ghrelin (hunger hormone)
Decreased by:
-GH- inhibiting hormone (known as somatostatin from hypothalamic parvocellular neuroendocrine cells)
Negative feedback control by:
-GH in circulation
-IGF-1 in circulation (released by liver in response to GH)
What are triggers of the growth hormone being released
- Hypoglycaemia (low blood sugar) and Diurnal rhythm (daily body clock) tell the hypothalamus to make signals.
-Ghrelin (a hormone from the stomach) also helps stimulate this process.
Explain what the hypothalamus and the pituitary gland does
Hypothalamus:
It releases:
GHRH (Growth Hormone Releasing Hormone) → tells the pituitary gland to release GH.
-Somatostatin → blocks GH release.
Pituitary gland:
Special cells called somatotropes release Growth Hormone (GH) into the body.
Explain growth hormone’s actions
GH acts on:
Adipose (fat) tissue → increases fat breakdown (lipolysis).
Liver → boosts glucose production and makes IGFs (Insulin-like Growth Factors).
Muscle → increases protein production.
What are results and feedback loops of growth hormone
Results:
IGFs and GH together:
Help cells grow.
Improve bone growth and chondrocyte (cartilage cell) function.
Feedback loops:
Short loop: GH itself can slow down further GH release (like a “stop” signal).
Long loop: IGFs made by the liver also send a “stop” message to the brain and pituitary to control GH levels.
What are stimulators and inhibitory factors controlling GH secretion
Stimulatory:
* GHRH
* Ghrelin
* Hypoglycemia
* Decreased fatty acids
* Fasting
* Exercise, sleep
* Stress
Inhibitory:
* Somatostatin (GHIH)
* GH
* Hyperglycemia
* Increased fatty acids
* IGF-1
Explain GH action
1) Stimulates production of IGF-1 by liver
- Increases lipolysis: raises free fatty acids (FFA)
- Increases gluconeogenesis: raises blood sugar
- Increases amino acid uptake into muscle, protein synthesis and lean body mass
- Stimulates chondrocytes: linear growth
- Stimulates somatic growth: increased organ/tissue size
Explain excess growth hormone (acromegaly)
-most commonly due to pituitary adenoma: increase in GH secreting somatotropes
-less commonly secondary: tumour elsewhere secretes GHRH
Explain metabolic consequences of acromegaly
-excess GH leads to insulin resistance
-many patients will have impaired tolerance and hyperinsulinemia
-may also have dyslipidaemia
