Voltage-regulated Ca2+ channel Leu Pro Cys Cys Oxytocin Ty Ash le Glo Gaq/11 Oxytocin receptor PLC activation PIP2 InsP3+DAG PKC MAPK cascade ↑ Calmodulin activation activation CPLA2 activity RhoA/ROK activation Sarcoplasmic reticulum Ca2+ calmodulin complex MLC kinase Prostaglandin activation production TMLC phosphorylation Myometrial cell Contraction
When the fetus is fully developed and takes up the maximum amount of space in the uterus, the pressure that it inflicts upon the cervix activates stretch receptors to send a signal to the hypothalamus (a structure within the brain). The brain responds by producing oxytocin, which is then released by the pituitary gland (an endocrine organ in the brain). Oxytocin travels through the bloodstream; when it reaches the uterus, it signals through myometrial (uterine smooth muscle) oxytocin receptors. Activation of the oxytocin receptors on myometrial tissue causes a signaling cascade that results in the cell producing prostaglandins that facilitate myometrial contraction (Figure 2).. Contraction of myometrial tissue then reduces the intrauterine space, causing the fully developed fetus to inflict more pressure on the cervix, thus repeating this process until the fetus is delivered.
a) Fetal delivery is an example of which type of feedback loop?
b) What type of sensory receptor is the cervical stretch receptor?
c) Placental tissue has been shown to package the activated form of MAPK, a signaling molecule in the oxytocin receptor signaling pathway (Figure 2), and release it into the extracellular space. When myometrial cells take up these packages of activated MAPK, prostaglandin production is increased. By what mechanism of membrane transport does activated MAPK move from placental tissue to myometrial cells?
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