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HPA Axis, Pregnancy, Precursor molecule: POMC, Pregnancy, Hypothalamus,…
HPA Axis
Parvocellular Neuroendocrine neurons
within the
Paraventricular Nucleus (PVN)
of the
Hypothalamus
synthesise & secrete
Corticotropin-Releasing Hormone (CRH)
travels through portal system to
Anterior Pituitary
Binds to
CRHR1
on
Corticotroph
cells
synthesise & secrete
Adrenocorticotropic Hormone (ACTH)
into systemic circulation
Circulates to
Zona
Fasciculata
of the
Adrenal
Cortex
Binds to
MCR2
on cells there
2 more items...
Pregnancy
High
progesterone
levels
Myometrium contractions
Oxytocin
-producing neurons of
Supra-optic Nucleus
Oxytocin
release
Further myometrium contractions
Local prostaglandin release from
myometrial cells
High
Estrogen
levels
Number of oxytocin receptors in
myometrium
(preparing for labour)
Precursor molecule:
POMC
Cleavage
Melanocyte Stimulating Hormone (
MSH
)
Pregnancy
High levels of
Estrogen
Increase in Prolactin-secreting
Mammotrophs
Prolactin levels begin to rise
However
Placental
Estrogen
and
Progesterone
Block Prolactin's effects at
Mammary glands
Prolactin block gone
Production and secretion of milk from mammary glands
1 more item...
Hypothalamus
High levels of
Dopamine
Inhibits activity
Towards end of pregnancy
Dopamine drops
Birth
Placental steroids plummet
Physical stimulation of suckling
Strong suppression of hypothalamic
dopamine
Suckling stops
Dopamine rises
Prolactin decreases
Milk secretion ceases
End of pregnancy
Enzyme in foetal membrane becomes more active
Converting progesterone into a less active form
Decrease in progesterone receptors
Progesterone
block removed
Myometrium contractions begin
Initial contractions push baby's head against cervix
Cervical stretch
Prolactin
Milk
secretion
into mammary gland lobules
Suckling on nipple
Mechanoreceptors
Magnocellular
neurons
in
paraventricular
nucleus
Oxytocin
Acts on
myoepithelial
cells
surrounding mammary gland lobules and
milk duct smooth muscle
Contraction of these cells
Milk
ejection
Pregnancy
High
estrogen
levels
Increase oxytocin receptors
Mammotropic Axis
Oxytocin Axis
Milk Letdown Reflex