Paraventricular nucleus

What is the paraventricular nucleus?

The paraventricular nucleus is an anatomical cluster of nerve cells in the central nervous system. In the hierarchy of the nervous system, the hypothalamus acts as the highest regulatory center of the autonomic nervous system.

From a neurohistological perspective, it is important to distinguish between the terms: "nucleus" as a cellular organelle (a light structure inside oval neurosecretory cells) and "nucleus" as a macroscopic cluster of neurons in brain tissue.

Topography and anatomical landmarks

In the sagittal plane, the paraventricular nucleus belongs to the anterior group of hypothalamic nuclei (along with the preoptic and supraoptic nuclei).

On frontal sections of the middle and posterior parts of the hypothalamus, its localization is determined as follows:

• The nucleus is located in the medial zone (along with the dorsomedial, ventromedial, and tuberal nuclei).
• It is adjacent to the upper part of the wall of the third ventricle.
• Spatially, the medial and lateral zones of the hypothalamus are separated by the fornix (fornix), which runs within the substance of the hypothalamus.
• The optic tract (tractus opticus) is located ventrolaterally.
• In the anterior section, the optic chiasm (chiasma opticum) is located ventrally.

Secretory function

The paraventricular nucleus is part of the hypothalamo-hypophyseal system. It belongs to the group of magnocellular nuclei (along with the nucleus supraopticus).

The magnocellular neurons of this nucleus synthesize:

• Vasopressin (antidiuretic hormone, ADH).
• Oxytocin.

Mechanism of hormone transport

The synthesized hormones are transported from the hypothalamus to the neurohypophysis. The mechanism of their secretion includes the following stages:

1. Vasopressin and oxytocin travel along the axons of neurosecretory cells.
2. Transport occurs via the supraopticohypophyseal tract—one of the main efferent pathways of the hypothalamus.
3. The hormones reach the neurohypophysis (posterior lobe of the pituitary gland). The neurohypophysis consists predominantly of neuroglial tissue, contains ependymal cells, and has a grayish-yellowish color due to a brownish-yellow pigment. It is connected to the tuber cinereum (tuber cinereum) of the hypothalamus via the infundibulum (infundibulum).
4. In the posterior lobe of the pituitary gland, the hormones are stored and subsequently released into the bloodstream.

This axonal pathway differs from the regulation of the adenohypophysis (anterior lobe), where parvocellular neurons synthesize liberins and statins that enter the hypophyseal portal system, as there is no direct neuronal connection between the hypothalamus and the adenohypophysis.

Class and exam questions

What else to study on this topic

• Supraoptic nucleus of the hypothalamus
• Neurohypophysis (posterior pituitary gland)
• Hypothalamo-pituitary system
• Vasopressin and oxytocin

Other topics in "Physiology concepts"

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