Hypothalamo-Neurohypophysial System Flashcards
What is a hypothalamic nucleus?
A collection of cell bodies that send their axons to a particular place.
State the two main hypothalamic nuclei.
Supraoptic
Paraventricular
What is the other hypothalamic nucleus where the biological clock resides?
Suprachiasmatic
What two molecules are produced by the neurohypophysis?
Vasopressin
Oxytocin
What are the two types of neurone and how do they differ?
Parvocellular: Average sized Terminate in the median eminence and other parts of the brain ONLY from paraventricular nucleus Magnocellular: LARGE Terminate in neurohypophysis Nuclei in both paraventricular AND supraoptic nuclei
Describe supraoptic neurones.
They are ALL MAGNOCELLULAR and terminate in the neurohypophysis
They are either oxytocinergic or vasopressinergic. The neurosecretions are hormones because they release directly into the circulation.
What is a key feature of magnocellular neurones?
Herring Bodies - areas where neurosecretions can be stored on their way down to the neurohypophysis
Describe the synthesis of Vasopressin. What other molecules are produced when the prohormone is cleaved?
Vasopressin is synthesised from Pre-provasopressin Cleaved to produce: Arginine vasopressin Glycopeptide Neurophysin
Describe the synthesis of Oxytocin.
Synthesised from pre-prooxytocin Cleaved to produce: Oxytocin Neurophysin (different to that produced from pre-provasopressin) Does NOT produced glycopeptide
State the main differences between Arginine Vasopressin and Oxytocin.
AVP has PHENYLALANINE instead of ISOLEUCINE
AVP has ARGININE instead of LEUCINE
State some similarities between Arginine Vasopressin and Oxytocin.
They are both nonapeptides
They are both synthesised from prohormones
Prohormones are cleaved to produce neurophysin
What is the main effect of vasopressin?
Increased water reabsorption in the kidney collecting ducts
What are some other effects of vasopressin?
Vasoconstriction
Synthesis of blood clotting factors
Corticotrophin release
Hepatic glycogenolysis
What are the different types of vasopressin receptor and which cells express these receptors?
V1a MOST IMPORTANT Vasculature Brain V1b Involved in control of corticotrophin release Adenohypophysial cells (corticotrophs) V2 Involved in antidiuretic effect Kidney collecting duct cells
Describe how V1 and V2 receptors work.
V1 = Gq protein linked receptor (PLC; PIP2 ---> IP3 + DAG; increase in [Ca2+]) V2 = Gs protein linked receptor (adenylate cyclase; increase cAMP; PKA)
