Oxytocin and ADH Flashcards
What is the difference between OT and AVP?
Two different AA side chains
Where are both AVP and OT synthesized?
Supraoptic nucleus (mainly AVP) Paraventricular nucleus (mainly OT)
How is OT transported?
Created in the paraventricular nucleus and sent in vesicles down the magnocellular axon to the posterior pituitary
When does OT have a burst in males?
At ejaculation to produce contractions for sperm release
Mechanism which OT binds and causes smooth muscle contraction?
OT bind OTR-> GPCR-> IP3 (Ca channels open) and DAG-> Prostaglandin (PGF2a)-> uterine and smooth muscle contraction
What is the Ferguson reflex?
- ) Head of baby pushes against cervix
- ) Nerve impulses from cervix transmitter to brain
- ) Brain stimulates release of oxytocin (hypothalamus)
- ) Oxytocin carried in bloodstream to uterus
- ) Oxytocin simulates uterine contractions and pushes baby towards cervix
What is the secretory unit of the breast?
The alveolus
What surrounds the alveolus of the breast?
Myoepithelial cells
What does OT cause contraction of to cause the let down reflex?
Myoepithelial cells
Characteristics of the four stages of labor:
0: Uterine tranquility and refractoriness
1: Uterine awakening, extending to complete cervical dilation
2: Active labor, from complete cervical dilation to delivery of newborn
3: From delivery of fetus to expulsion of placenta
What physiologically is occurring during each of the four stages of labor?
0: Progesterone and relaxin promote inactivity
1: Estrogens increase OT receptors by 80x at 36 weeks
2: Oxytocin, prostaglandins, estrogen increases OT receptors 200X during early labor
3: Oxytocin increases especially in last stage of labor
What effect does estrogen have in the OT cycle?
It up regulates OT
What affect does progestogens have in the OT cycle?
Decreases response of smooth muscle from OT
How does suckling cause OT release?
Suckling stimulates PRL release by removing the inhibition of DA
How does suckling affect the menstrual cycle?
GnRH is inhibited by suckling reducing LH and FSH release inhibiting the ovarian menstrual cycle
When is relaxin released and what are its affects?
It is released during pregnancy to keep the uterus in a quiet state also during labor in the cervix to dilate it
What is the half-life of OT?
3-6 minutes
Where is ADH mainly produced?
Supraoptic nucleus
What is ADH produced as?
A preprohormone
What does the preprohormone of ADH consist of?
Signal peptide
ADH
Neurophysin II
What causes the most cases of hereditary hypothalamic diabetes insipidus?
A point mutation in neurophysin II
What is neurophysin II?
A carrier of ADH
What is the primary signal for secretion of ADH?
An increase in ECF osmolality
What inhibits ADH release?
High fluid volume or blood pressure
