Parturition, hormones

AVP plays a central role in water homeostasis of terrestrial mammals, leading to water conservation by the kidney. OT is primarily involved in milk ejection, parturition and in sexual and maternal behaviour. Both hormones are pqDtides secreted by the neurohypophysis, and both act also as neurotransmitters in the central nervous system (CNS). The major hormonal targets for AVP are the renal tubules and vascular myocytes. The hormonal targets for OT are the myoepithelial cells... 

Clapham DE, Lechleiter JD, Girard S 1993 Intracellular waves observed by confocal microscopy from Xenopus oocytes. Adv Second Messenger Phosphoprot Res 28 161-165 Martin C, Chapman KE, Thornton S, Ashley RH 1999 Changes in the expression of myometrial ryanodine receptor mRNAs during human pregnancy. Biochim Biophys Acta 1451 343—352 McLean M, Smith R 2001 Corticotrophin-releasing hormone and human parturition. Reproduction 121 493-501... 

Posterior pituitary Two hormones, vasopressin and oxytocin, are synthesised in the hypothalamus and then transported through nerve axons to the posterior pituitary, where they are stored until released. Vasopressin acts on the kidney to conserve water. Its secretion is stimulated by thirst and a decrease in blood pressure. Secretion of oxytocin initiates uterine contraction for parturition. It also stimulates milk ejection from the mammary glands. 

Gases, nutrients, hormones, electrolytes, antibodies and waste products are transported across the placenta. Many drugs and infectious agents can also cross the placenta. Maternal transfer of steroid hormones across the placenta is limited. When natural or synthetic steroid hormones do cross the placenta, developmental toxicity can result. Furthermore, hormones produced by the fetal placenta also play an important role in parturition. 

Cytochrome and insulin are not unique in their opposition to the Darwinian model of genealogy. Relaxin, a hormone of parturition in placental mammals, shows clearly that molecular structures and branching patterns do not connect. When the sequence data of all known relaxins are reviewed, several startling observations could be made. The hormone differs by about 55% in animals of purportedly... 

Pre- and postmature childbirths are each estimated to occur in almost 10% of pregnancies in the United States. The physiological processes of parturition (birth) must be precisely timed and effective to avoid harm to the mother and fetus. Like pregnancy, parturition relies on the sending and receiving of numerous hormonal signals between mother and fetus and is therefore especially susceptible to toxic insult. 

Q8 The process of birth (parturition) involves strong contractions of the uterine muscle (myometrium), which start spontaneously. Which hormones are involved in the initiation and maintenance of uterine contractions in labour ... 

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