what is the difference between magnocellular neurosecretory and parvicellular neurosecretory cells

Answer 1

Magnocellular neurosecretory cells and parvicellular neurosecretory cells are two types of neurosecretory cells located in the hypothalamus of the brain. The main difference between these two types of cells lies in their anatomical location and the hormones they secrete.

1. Magnocellular neurosecretory cells: These cells are larger in size compared to parvicellular neurosecretory cells and are typically found in the supraoptic nucleus and the paraventricular nucleus of the hypothalamus. They release hormones directly into the bloodstream through the posterior pituitary gland. The two main hormones released by magnocellular neurosecretory cells are oxytocin and vasopressin (also known as antidiuretic hormone or ADH). Oxytocin is involved in various reproductive functions like labor induction and milk letdown, while vasopressin regulates water balance and blood pressure.

2. Parvicellular neurosecretory cells: These cells are smaller in size and are predominantly located in the parvocellular division of the hypothalamic paraventricular nucleus. Parvicellular neurosecretory cells release their hormones into a network of blood vessels called the hypophyseal portal system, which carries them to the anterior pituitary gland. From there, the anterior pituitary releases several hormones into the bloodstream to regulate various physiological processes. The main hormones secreted by parvicellular neurosecretory cells include releasing hormones (e.g., corticotropin-releasing hormone, thyrotropin-releasing hormone) and inhibiting hormones (e.g., dopamine). These hormones control the release of other hormones from the anterior pituitary, such as adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), and prolactin.

In summary, magnocellular neurosecretory cells release their hormones directly into the bloodstream via the posterior pituitary gland, while parvicellular neurosecretory cells release hormones into the hypophyseal portal system to regulate the secretion of hormones from the anterior pituitary.