Which of the following situations could result in maternal antibodies attacking fetal blood cells during a second pregnancy?

a) On the inside of the plasma membrane: Catecholamines cannot cross the lipid bilayer, so they cannot bind to internal membrane receptors.

b) On the outside of the plasma membrane: Because catecholamines are water-soluble, they bind to extracellular receptors that initiate a second messenger cascade (e.g., cAMP).

c) In the cell cytoplasm: Only lipid-soluble hormones, like steroids, bind to intracellular receptors.

d) In the cell nucleus: Again, only lipid-soluble hormones (like thyroid hormones or steroids) reach nuclear receptors.

a) Hypothalamus: Oxytocin is synthesized by neurosecretory cells in the hypothalamus, specifically in the paraventricular and supraoptic nuclei. After production, it is transported down the axons of these neurons to the posterior pituitary gland, where it is stored and released into the bloodstream.

b) Somatic Nervous System: The somatic nervous system is part of the peripheral nervous system and controls voluntary skeletal muscle movements. It does not produce hormones and has no role in endocrine secretion.

c) Anterior Pituitary Gland: The anterior pituitary produces several hormones (like ACTH, GH, PRL, TSH, LH, and FSH), but oxytocin is not one of them. It is not produced by the anterior pituitary; instead, oxytocin is made in the hypothalamus and released from the posterior pituitary.

d) Posterior Pituitary Gland: While the posterior pituitary stores and releases oxytocin, it does not produce it. The production occurs in the hypothalamus, and the posterior pituitary acts as a storage and release site.