Median preoptic nucleus

The Median preoptic nucleus (MnPO) is a small but significant structure located in the preoptic area of the hypothalamus in the brain. It plays a crucial role in the regulation of body temperature, fluid balance, and cardiovascular function.

Anatomy

The MnPO is situated at the midline of the anterior hypothalamus, adjacent to the third ventricle. It is bordered by the organum vasculosum of the lamina terminalis (OVLT) and the anterior commissure. The MnPO is part of the lamina terminalis, a region that includes the OVLT and the subfornical organ (SFO).

Function

The MnPO is involved in several critical physiological processes:

Thermoregulation

The MnPO plays a pivotal role in thermoregulation. It receives input from thermoreceptors in the skin and spinal cord and integrates this information to maintain homeostasis of body temperature. The MnPO sends projections to other hypothalamic nuclei, such as the paraventricular nucleus (PVN) and the dorsomedial hypothalamic nucleus (DMH), which are involved in the autonomic and endocrine responses to temperature changes.

Fluid Balance

The MnPO is essential in the regulation of fluid balance and osmoregulation. It detects changes in blood osmolarity and sodium concentration and coordinates the release of antidiuretic hormone (ADH) from the posterior pituitary gland. This process helps to maintain blood pressure and fluid homeostasis.

Cardiovascular Function

The MnPO also contributes to the regulation of cardiovascular function. It receives input from baroreceptors and chemoreceptors and modulates the activity of the sympathetic nervous system to control heart rate and blood pressure.

Connections

The MnPO has extensive connections with other regions of the brain, including:

• The paraventricular nucleus (PVN)
• The dorsomedial hypothalamic nucleus (DMH)
• The organum vasculosum of the lamina terminalis (OVLT)
• The subfornical organ (SFO)
• The anterior commissure

Clinical Significance

Dysfunction of the MnPO can lead to various disorders, including hypertension, diabetes insipidus, and thermoregulatory disorders. Research on the MnPO is ongoing to better understand its role in these conditions and to develop potential therapeutic interventions.

See Also

• Hypothalamus
• Thermoregulation
• Fluid balance
• Cardiovascular system
• Lamina terminalis