Oxytocin Flashcards
Oxytocin
nonapeptide synthesized by MC neurons and secreted by the PP gland
Very similar structure to AVP; but different effects
Involved in the process stage 2 of parturition
Critical for milk letdown b/c without cause neonatal death by dehydration
Critical for parental bonding and maternal behavior
Myometrium
2 layers of muscle for contractibility
- dilation
contraction
Oxytocin in Parturition
- Higher estrogen to progesterone ratio
- increase OTR in myometrial cells and increase tissue response to OT
- both are necessary for coordinated and strong myometrial contraction
Role of progesterone
hormone for gestation
blocks oxytocin actions and keeps uterus soft and not contracted
Role of estrogen
positive feedback effect on oxytocin synthesis
stimulates OTR and OT
Stage 2 parturition
fetus starts pushing adding pressure against cervix
cells send signals to mechanical receptors signals spinal cord which travels to the brain and stimulate oxytocin release
stimulates muscle and receptors for contraction
Ferguson reflex
Positive feedback
pressure against cervix dilation stimulates release of OT
Stage 1 of parturition
Dilation»_space; preparation for fetal expulsion
Effects of Oxytocin
OTR: more abundant in the fundus of the uterus
OT: promotes the synthesis of prostaglandins to break down cervical opening
OT; promotes gap junctions expression to make contraction more effecinent
Milk Letdown
Suckling (20 % of milk release w/out OT)
stimulates mechanoreceptors in the breast
send afferent signal through the spinal cord
stimulation of MC neurons for pulsatile OT release
Pumping action in the alveoli
MAX secretion of milk
epithelial cells
produce the milk
myoepithelial cells
muscle cells
Location of OTR in mammary gland
located around myoepithelial cells
Prolactin’s role and location
production of milk
located in epithelial cells
