BRS

Chapter 13 Diencephalon: Thalamus and Hypothalamus

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D. Food intake regulation

1. Ventromedial nucleus ■ two hypothalamic nuclei play a role in the control of appetite: ■ satiety center. ■ destruction is involved in overeating and obesity.

2. Lateral hypothalamic nucleus ■ the hunger or feeding center . ■ destruction causes starvation and emaciation .

E. Hypothalamic-releasing and release-inhibiting factors ■ produced in the arcuate nucleus of the median eminence. ■ transported via the tuberohypophyseal tract to the hypophyseal portal system. ■ effect the release or nonrelease of adenohypophyseal hormones. ■ with the exception of dopamine, they are all peptides , which include:

1. thyrotropin-releasing hormone. 2. gonadotropin-releasing hormone. 3. somatostatin (growth hormone–inhibiting hormone). 4. growth hormone–releasing hormone. 5. corticotropin-releasing hormone. 6. prolactin-inhibiting and prolactin-releasing factor.

XIV. CLINICAL CONSIDERATIONS

A. Craniopharyngioma ■ originates from embryonic pituitary gland tissue. ■ usually calcified. ■ the most common supratentorial tumor found in children.

■ pressure on the optic chiasm results in a bitemporal hemianopia . Pressure on the hypothalamus causes hypothalamic syndrome , with adiposity, diabetes insipidus, disturbance of temperature regulation, and somnolence. B. Pituitary adenoma ■ constitutes 10% to 20% of all intracranial tumors; 1:10 people will get in lifetime. ■ pressure on the chiasm results in a bitemporal hemianopia (most cases show asymmetry of field defects). Pressure on the hypothalamus may cause hypothalamic syndrome . C. Wernicke encephalopathy ■ results from thiamine (vitamin B 1 ) deficiency. ■ characterized by the triad: ocular palsies , ataxic gait , and mental confusion . ■ lesions are found in the hypothalamus (primarily in the mammillary bodies) and in the periaq ueductal gray of the midbrain.

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