A woman is in labor. The size of the fetus combined with the contractions of the uterine muscular layer stretches the uterine wall, stimulating stretch receptors in the cervix. Signals from these receptors are conducted through nerves to the hypothalamus/posterior pituitary. The hypothalamus/posterior pituitary releases oxytocin. The oxytocin travels through the blood and stimulates the smooth muscle layer of the uterus. Oxytocin has two effects on the uterine smooth muscle: 1. Itdirectlystimulatesthesmoothmuscletocontractmorefrequentlyandmoreforcefully. 2. Itcausestheuterinewalltoreleaseprostaglandins,whichincreasethefrequencyandforceof the contractions even more. These effects push the fetus more forcefully into the cervix, stimulating the stretch receptors further. The receptors send additional impulses to the hypothalamus/posterior pituitary. The increased activation of the hypothalamus/posterior pituitary stimulates release of additional oxytocin, which further stimulates the uterus. This cycle of activation continues until the fetus is expelled from the uterus. 1. Whatisthestimulusofthiscontrolloop? 2. Whatisthecontrolcenter? 3. Whatistheeffector? 4. This is an example of (positive / negative) feedback. How could you tell?
A woman is in labor. The size of the fetus combined with the contractions of the uterine muscular layer stretches the uterine wall, stimulating stretch receptors in the cervix. Signals from these receptors are conducted through nerves to the hypothalamus/posterior pituitary. The hypothalamus/posterior pituitary releases oxytocin. The oxytocin travels through the blood and stimulates the smooth muscle layer of the uterus. Oxytocin has two effects on the uterine smooth muscle:
1. Itdirectlystimulatesthesmoothmuscletocontractmorefrequentlyandmoreforcefully.
2. Itcausestheuterinewalltoreleaseprostaglandins,whichincreasethefrequencyandforceof
the contractions even more.
These effects push the fetus more forcefully into the cervix, stimulating the stretch receptors further. The receptors send additional impulses to the hypothalamus/posterior pituitary. The increased activation of the hypothalamus/posterior pituitary stimulates release of additional oxytocin, which further stimulates the uterus. This cycle of activation continues until the fetus is expelled from the uterus.
1. Whatisthestimulusofthiscontrolloop?
2. Whatisthecontrolcenter?
3. Whatistheeffector?
4. This is an example of (positive / negative) feedback. How could you tell?
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