Endocrine Drugs and Medications Q 31
During labor induction with oxytocin, the nurse knows that relaxation of vascular smooth muscle can cause:
A. Hypertension, premature atrial contractions
B. Hyperglycemia, premature ventricular contractions
C. Hyperglycemia, hypertension
D. Hypotension and flushing
Correct Answer: D. Hypotension and flushing
Relaxation of vascular smooth muscle will cause vasodilation leading to hypotension and flushing. Oxytocin is an oligopeptide hormone that contains nine amino acyl residues, or in other words, a nonapeptide hormone. It is one of the two hormones stored and released from the posterior pituitary gland but created in the hypothalamus. It is specifically released from the paraventricular nucleus of the hypothalamus into the posterior pituitary gland for later use.
Option A: Oxytocin also has both antidiuretic and vasodilatory effects, increasing cerebral, coronary, and even renal blood flow. Not only does oxytocin stimulate uterine contractions, but it also causes contractions of the myoepithelial cells in the female breasts. This activity occurs in the alveolar ducts. Such contractions are what force milk from these ducts into even larger sinuses, which enable milk expulsion.
Option B: Most hormones create negative feedback loops after they are released, but oxytocin is one of the few that exhibit positive feedback loops, i.e., that the release of oxytocin leads to actions that stimulate even more of a release of oxytocin. This feedback is comparable to antidiuretic hormone (ADH), also known as vasopressin (the second and the only other hormone stored and released from the posterior pituitary), which exhibits a negative feedback loop after release. Less of this hormone will be released after it exhibits its effect on the body.
Option C: Exogenous oxytocin causes the same response in the female reproductive system as that of endogenous oxytocin. Both types of oxytocin stimulate uterine contractions in the myometrium by causing G-protein coupled receptors to stimulate a rise in intracellular calcium in uterine myofibrils. Oxytocin receptor activation is what causes many signals that then stimulate uterine contraction by increasing levels of intracellular calcium, which is where positive feedback comes into play.