During erythropoiesis in the bone marrow, which is the last cell to have a nucleus?

a) Stimulates the formation of white blood cells: This is associated with bone marrow and not parathyroid hormone (PTH).

b) Parathyroid hormone (PTH) increases blood calcium levels by stimulating bone resorption, increasing calcium reabsorption in the kidneys, and activating vitamin D to increase calcium absorption from the gut.

c) Increases the level of sodium ions in the blood: Aldosterone regulates sodium levels, not PTH.

d) Increases the level of potassium ions in the blood: This is also regulated by aldosterone and the kidneys, not PTH.

e) Increases the level of glucose in the blood: Glucagon and cortisol are more directly involved in increasing blood glucose.

a) Entering the nucleus of a cell and initiating or altering the expression of a gene: Steroid hormones (e.g., cortisol, estrogen) are lipid-soluble and can pass through the cell membrane to bind intracellular receptors, influencing gene transcription.

b) Finding an appropriate cell receptor and initiating cAMP activity: This describes non-steroid hormones (e.g., catecholamines, peptide hormones) using second messenger systems, not steroids.

c) Stimulating the synthesis of glycogen: This is an effect of some hormones (e.g., insulin), but it’s not how steroid hormones act.

d) Increasing blood pressure: While some steroid hormones (like aldosterone) may affect blood pressure, this is not their mechanism of action.