Neuroendocrinology Flashcards
What are neuroendocrine cells?
Neurosecretory cells that release signal molecules (hormones) from their synaptic terminals into the blood
How are neurosecretory cells regulated?
Synaptic transmission from presynaptic neurons (neuroendocrine integration)
Examples of neurosecretory cells
Chromaffin cells of adrenal medulla
Hypothalamic magnocellular neurons
Hypothalamic parvocellular neurons
Embryology of the pituitary gland
- Evagination of floor of 3rd ventricle (neural ectoderm)
- Evagination of oral ectoderm (Rathke’s pouch)
- Rathke’s pouch pinched off
What makes up the hypothalamus?
Composed of various nuclei (cell clusters)
Parvocellular nuclei
Neurosecretory cells release hormones to capillaries of median eminence (supplied by superior hypophysial artery); conveyed by portal veins to the anterior pituitary
Magnocellular nuclei
Project to posterior pituitary and release to capillaries supplied by inferior hypophysial
Posterior pituitary hormones
Oxytocin and vasopressin (ADH)
What stimulates GH secretion
GHRH, Ghrelin, hypoglycemia, decreased fatty acids, Fasting, exercise, sleep, stress
What inhibits GH secretion
Somatostatin (GHIH), GH, hyperglycemia, increased fatty acids IGF-1
Growth hormone functions
Growth and development (anabolic)
Couples growth to nutritional status
Control of growth hormone secretion
Where is GH synthesised?
Somatotropes of the anterior pituitary
What is released by the liver in response to GH?
IGF-1 -
- Increases lipolysis raises free fatty acids,
- 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
Excess growth hormone
Acromegaly
- Most commonly due to pituitary adenoma: increases in GH - secreting somatotrophs
- Less commonly secondary: tumor elsewhere secretes GHRH
Acromegaly
Excess GH leads to insulin resistance
Many patients will have impaired glucose tolerance and hyperinsulinemia
