Neuroanatomy

Although neuroanatomy, neurochemistry and neurophysiology do not fall within the day-to-day knowledge required from gynaecologists, a basic understanding is useful to understand hypothalamo-pituitary function and the effects of various steroid hormones and neuroendocrine modulators in the pathophysiology of psychological disorders. Neuroanatomy and neurophysiology are complex and only broadly relevant to the obstetric and gynaecological trainee. Although it is extremely unlikely that direct questions on knowledge of the following neuroanatomy or neurophysiology will be asked in a clinical RCOG examination, it is valuable to be aware of the terminology.

HYPOTHALAMUS

The hypothalamus is located within the ventromedial portion of the diencephalon. It is situated inferior to the thalamus and in close proximity to the pituitary gland (Figure 2.1). This brain region is important for fluid regulation, thermoregulation, food intake, reproduction, sympathetic and parasympathetic function and the control of circadian rhythms. Many of these actions are mediated through hypothalamic control of anterior and posterior pituitary function.

Hypothalamic nuclei

A nucleus refers to an aggregation of neuronal cell bodies. The major hypothalamic nuclei are the preoptic area, suprachiasmatic nucleus, supraoptic nucleus, paraventricular nucleus, ventromedial nucleus and arcuate nucleus. Each of these nuclei is involved in a specialised function (Figure 2.2).

The paraventricular nucleus produces the hypothalamic hypophysiotrophic hormones. These peptides are transported into the anterior pituitary (adenohypophysis), via a portal vessel system, where they either stimulate or inhibit the release of other hormones.