Question

ing labor, uterine stretch is detected by sensory neurons. the hypothalamus bonds, and oxytocin is released.
ich sequence best describes the physiological pathway leading to uterine ntraction?
) uterine stretch → sensory input → paraventricular nuclei → oxytocin release → binds uterine smooth muscle receptors → stimulates uterine contraction.
uterine stretch → sensory input → paraventricular nuclei → adh release → binds uterine smooth muscle receptors → stimulates uterine contraction.
uterine stretch → sensory input → anterior lobe of pituitary releases oxytocin → binds skeletal muscle receptors in uterus → uterine contraction occurs.
uterine stretch → sensory input → anterior lobe of pituitary releases adh → binds smooth muscle receptors in uterus → uterine contraction occurs.

Explanation:

To determine the correct sequence, we analyze each option:

• Option 1: Uterine stretch is detected by sensory neurons, sending input to paraventricular nuclei (in hypothalamus) which release oxytocin. Oxytocin binds to uterine smooth muscle receptors, stimulating contraction. This matches the physiological pathway (oxytocin is involved in uterine contractions, paraventricular nuclei in hypothalamus produce oxytocin, and uterus has smooth muscle).
• Option 2: ADH (antidiuretic hormone) is for water balance, not uterine contractions. Eliminate.
• Option 3: Oxytocin is released from the posterior pituitary (not anterior), and uterus has smooth (not skeletal) muscle. Eliminate.
• Option 4: ADH is not involved in uterine contractions, and pituitary release of ADH is incorrect for this pathway. Eliminate.

Answer:

The correct option is the first one: Uterine stretch → sensory input → paraventricular nuclei → oxytocin release → binds uterine smooth muscle receptors → stimulates uterine contraction.