Neuroendocrinology Flashcards
Describe the transport of a neurotransmitter from a nerve cell
Impulses from nerve cell release neurotransmitter that acts upon a neurone or effector cell
Describe the transport of a neurohormone from a nerve cell
Impulses from nerve cell cause the release of a neurohormone that is released into the blood that acts on a target cell
What is a neuroendocrine cell?
Neuroendocrine cells are neurosecretory cells that release signal molecules (hormones) from their synaptic terminals into the blood
What are neuroendocrine cells controlled by?
Give some examples of these cells
Controlled via synaptic transmission from presynaptic neurons (neuroendocrine integration)
Examples:
Chromaffin cells of adrenal medulla
Hypothalamic magnocellular neurons
Hypothalamic parvocellular neurons
Describe the Embryology of the pituitary gland
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- The floor of the third ventricle will form the hypothalamus
- We have a down swelling of the floor of the third ventricle (infundibulum) and an upswelling of the oral cavity( Rathke’s pouch). This then pinches off, connected to down swellings
- Rathke’s pouch will form the anterior lobe and the posterior lobe is a downward projection of the hypothalamus
What is the hypothalamus composed of?
Hypothalamus: composed of various nuclei (cell clusters)
What are parvocellular nuclei?
Parvocellular nuclei: neurosecretory cells release hormones to capillaries of median eminence (supplied by superior hypophysial artery); conveyed by portal veins to anterior pituitary
What are Magnocellular nuclei?
Magnocellular nuclei: project to posterior pituitary and release to capillaries supplied by inferior hypophysial artery
What is the posterior pituitary?
PP is basically an extension of hypothalamus, with hormones stored in hypothalamic neuron terminals. Released under neural control into hypophysial capillaries, inferior hypophysial vein
Remind yourself of the pathway that releases ADH
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What are the 2 functions of growth hormones?
Growth and development (anabolic)
Couples growth to nutritional status
How do we control growth hormone secretion?
What is GH where is it synthesized and secreted from?
What is GH releasing hormone produced?
What is GH controlled by?
GH (somatotropin) synthesised and secreted by somatotropes of the anterior pituitary
Ghrelin (‘hunger hormone’ secreted by endocrine cells of the stomach)
GH-releasing hormone (hypothalamic neurosecretory cells)
Somatostatin (hypothalamic neurosecretory cells)
Negative feedback control by
GH in circulation
IGF-1 (released by liver in response to GH)
Describe the growth hormone pathway
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What does GH cause?
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
What is excessive growth hormone called?
What causes excessive growth hormones to be released?
What does this eventually cause?
Acromegaly
Most commonly due to pituitary adenoma: increase in GH-secreting somatotrophs
Less commonly secondary: tumour elsewhere secretes GHRH
Excess GH leads to insulin resistance
Many patients will have impaired glucose tolerance and hyperinsulinemia
