Posterior Pituitary

Question 1

What does oxytocin do and what is it and where is it synthesised

Answer 1

• It regulates lactation and uterine contractions
• its a neuropeptide
• synthesed by hypothalamic magnoceller neurones

Question 2

How is oxytocin secreted

Answer 2

From the paraventricular (and supraoptic) nuclei of the hypothalamus. They extend into the posterior pituitary Herring bodies where they’re stored before secreting into the extracellular space

Question 3

What is an oxytocin receptor and what does binding to it lead to

Answer 3

• It’s a Gq GPCR
• leads to Ca+ influx which acts on myosin light chain kinase (sm contraction)

Question 4

What is oxytocin’s action during the final few weeks of pregnancy and when else is it secreted

Answer 4

• increases oxytocin and receptors are more sensitive to
• baby pushes cervix which causes a pos feedback loop when sm contraction from Ca+
• suckling increases oxytocin too via afferent neurones to hypothalamus to myoepithelial cells lining breast alveoli causing contraction
• also ejaculation and orgasm

Question 5

In post pit where are precursor bodies cleaved

Answer 5

From periventricular/ supraoptic nuclei via axons of hypothalamic neurones to Herring bodies in post pt

Question 6

What does ADH do

Answer 6

Neuro peptide that acts on kidneys CD to increase water reabsorbtion based on plasma osmotic pressure and volume status detected by osmoreceptors in hypothalamus which contract when vol is low and expand when high