The chemicals of the endocrine system typically travel to their target cells by way of the

Correct Answer: C

Rationale: Hormones travel via the bloodstream (e.g., thyroxine to cells), ensuring distant delivery in endocrine signaling. Lymphatic system aids immunity/fluid, not primary hormone transport secondary at best. Nerve axons carry neurotransmitters, not hormones neural domain. Cell membranes host receptors, not travel routes. Bloodstream's circulatory path distinguishes it, key to endocrine distribution, unlike lymphatic, neural, or static options.

Correct Answer: C

Rationale: Oxytocin release (e.g., labor) uses positive feedback uterine contractions increase oxytocin, amplifying delivery. Negative feedback stabilizes (e.g., cortisol). 'Neutral' isn't a mechanism undefined. 'Hormonal' isn't feedback type control mode. Positive feedback distinguishes oxytocin's escalating role, critical for childbirth, unlike stabilizing or vague options.

Correct Answer: D

Rationale: Thyroid gland uses iodine to synthesize T3/T4 from thyroglobulin metabolic hormones. Adrenal cortex (cortisol) uses cholesterol, no iodine. Pancreas (insulin) needs amino acids. Parathyroids (PTH) regulate calcium, no iodine. Iodine's thyroid necessity distinguishes it, critical for hormone synthesis, unlike steroid, peptide, or calcium glands.

Correct Answer: B

Rationale: PTH doesn't decrease blood calcium it raises it via bone release, kidney reabsorption, and vitamin D activation (1,25-DHC) all increase Ca²⁺. Decreasing calcium is calcitonin's role, not PTH opposite action. PTH's consistent elevation distinguishes it, critical for hypocalcemia correction, unlike erroneous lowering claim.

Correct Answer: A

Rationale: Cortisol, a glucocorticoid, is produced by adrenal cortex's zona fasciculata stress/metabolism regulation. Medulla makes epinephrine, not steroids. Anterior pituitary releases ACTH, stimulating cortisol, not producing. Pancreas secretes insulin/glucagon glucose focus. Cortex's steroid synthesis distinguishes it, critical for cortisol's role, unlike neural, regulatory, or metabolic glands.