Lec 4 - Posterior Pituitary gland + Oxytocin Flashcards
name the 2 ppg hormones
- oxytocin
- vasopressin
how do the 2 differ
= only 2 of the 9 amino acids differ
- but acc function is very different
where does synthesis of the 2 hormones occur
- hypothalamus
- in supraoptic and paraventricular nuclei
how are these hormones packaged and processed
packaged into granules as large precursor molecules
then carried with NEUROPHYSINS to ppg down the hypothalamic–hypophyseal tract
what receptor pathway does oxytocin activate
- binds to GPCR
- PIP2, IP3 etc. –> intracellular Ca2+ release
3 phsyiological effects of oxy
- stim milk ejection
- stim contractions
- maternal behaviour
in mammary gland, where is milk initially secreted
small sacs called lobules or alveoli
what are groups of alveoli surrounded by
smooth muscle (myoepithelial) cells
(which is the target for oxytocin)
how does oxytocin affect myoepithelial cells
stimulates contraction
causing milk to be ejected into surround ducts
what positively feedbacks on oxytocin secretion in milk secretion
nursing/suckling
relayed via spinal reflex arc to the brain
= stimulates oxytocin secreting neurons = more release of oxytocin = more contraction of myoepithelial cells
what inhibits release of oxytocin
fear
anxiety
pain
alcohol
what do neurosecretory neurones from hypothalamus connect to
sensory neurones in the breast and surrounding vascular system
during later stages of gestation, where does oxytocin act
on uterine smooth muscle cells
when is oxytocin released during labour
when fetus stimulates the cervix
what happens in later stages of gestation in terms of oxy receptors
increase on the uterine smooth muscle cells
what is triggered on the cervix
when baby pushes against in- sensory neurons which send signal back to hypothalamus to cause more oxy release
example of synthetic oxy
pitocin
can be given to stimulate contractions
inducing labour
what might be given to inhibit premature labour
oxy antagonist
atosiban
side effects of pitocin
- Uneven heart rate
- Excessive bleeding after birth
- Birth injuries to baby
rat experiment: 2 findings
- oxy into virgin rats induces maternal beh
- antibodies of oxy OR oxy antagonists given to mother rat will prevent her accepting her pups
what experiment went kinda against the rat experiment
mice one
- wehn their oxy gene was disrupted
- still showed normal maternal beh
- but deficits in milk ejection
- and some social beh changes
= so oxy is seen as FACILITATOR of mat beh, but not absolute initiator
oxy effect in males
- facilitate sperm transport by acting on smeiniferous tubules
- and may have similar effects on social behaviour
what 2 things supress oxy secretion
- catcholamines (released in stress from sdrenals)
- sex steroids (during birth pregesterone will decline to allow oxy to increase)
