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What are the 4 important regulatory influences of the hypothalamus?
HEAL: Homeostasis; Endocrine control via pituitary; Autonomic control; Limbic mechanisms
Embryologically - what is the anterior pituitary formed from? Posterior pituitary?
Anterior - from Rathke's pouch. Posterior- from invagination of ventricular system
Anterior pituitary is made up of? Posterior pituitary?
Anterior - made of glandular cells. Posterior - made of axons and nerve terminals of neurons whose cell bodies are in the hypothalamus.
What is relationship between hypothalamus and 3rd ventricle?
Hypothalamus forms walls and floor of the inferior part of third ventricle
Where are mamillary bodies?
Posterior part of the hypothalamus
What is the tuber cinereum?
Bulge between the optic chiasm and the mamillary bodies
What two structures does the infundibulum connect?
Tuber cinereum (hypothalamus) to Pituitary stalk
What is the median eminence? What is its physiologic significance?
Anterior part of infundibulum. This is where the hypothalamic neurons secrete regulatory factors that are carried by portal vessels to the anterior pituitary
What are the borders of the pituitary fossa / sella turcica?
Anterior and posteroir clinoid processes; Sphenoid bone inferiorly; Cavernous sinuses laterally.
What divides the hypothalamus into medial and lateral hypothalamic areas?
Fibers of the fornix passing through on the way to the mamillary bodies
Describe the pathways involved in hypothalamic control of the autonomic nervous system
Inputs to hypothalamus via: amygdala; limbic cortex (orbital frontal; insular; anterior cingulate; temporal). Outputs: Paraventricular nucleus (hypothalamus) sends fibers in Medial Forebrain Bundle that go to the brainstem and periaqueductal gray matter. Synapse on: 1) Pregangionic parasympathetic nuclei in brainstem and sacral spinal cord; 2) Preganglionic sympatheic neurons in intermediolateral cell column of thoracolumbar spinal cord
Describe the pathways involved in hypothalamic-limbic system
Hippocampus (subicular formation) sends fibers via the Fornix to the Mamillary bodies in posterior hypothalamus. The Mamillary bodies in posterior hypothalamus project via the mamillothalamic tract to the anterior thalamic nucleus which projects to the limbic cortex and cingulate gyrus.
Name the hypothalamic region involved in the function: circadian rhythms
Suprachiasmatic nucleus
Name the hypothalamic regioninvolved in the function: appetite stimulation
Lateral hypothalamus
Name the hypothalamic region involved in the function: appetite inhibition
Medial hypothalamus
Name the hypothalamic region involved in the function: thirst
Anterior hypothalamus
Name the hypothalamic region involved in the function: heat dissipation
Anterior hypothalamus (lesions here can cause hyperthermia)
Name the hypothalamic region involved in the function: heat conservation
Posterior hypothalamus (lesions here can cause poikilothermia)
Describe the hypophysial-portal system
Hypothalamic neurons near the 3rd ventricle secrete regulatory factors at the median eminence; These factors enter the capillary plexus of the median eminence and are carried by hypophysial portal veins to the anterior pituitary to exert their influence.
What hypothalamic nuclei secrete regulatory factors for the anterior pituitary?
Arcuate nucleus; Paraventricular nucleus; Periventricular nucleus; Medial preoptic nucleus.
What hypothalmic nuclei have the axons and nerve terminals in the posterior pituitary?
Supraoptic nucleus; Paraventricular nucleus.
Why do prolactinomas often cause amenorrhea?
Elevated prolactin inhibits hypothalamic release of LHRH causing decreased LH and FSH secretion. (This is also why women who are breastfeeding do not have menses)
What is Cushing syndrome? What is Cushing disease?
Syndrome - increased cortisol. Disease - from an ACTH-secreting pituitary tumor
What are common effects of cortisol excess? (18)
Moon facies; truncal obesity; buffalo hump; acne; hirsutism; easy bruising; poor wound healing; HTN; DM; edema; immunosuppression; osteoporosis; avascular necrosis of femoral head; amenorrhea; decrased libido; myopathy; fatigue; psychiatric disturbance
Do all lesions in the posterior pituitary cause diabetes insipidis?
NO. Remember posterior pituitary is just axons/nerve terminals - lesion in posterior pituitary needs to be high enough to cause retrograde degeneration of hypothalamic neurons in supraoptic and paraventricular nuclei
What is the ""triphasic"" response often seen after pituitary surgery?
First get DI - then followed by SIADH - then end up with DI which may gradually improve.
Causes of panhypopituitarism?
Very large pituitary adenomas; Hypothalamic tumors; Metastatic disease; Sarcoidosis; Infection; Autoimmune disorders; pituitary apoplexy (rare)
What is pituitary apoplexy?
Spontaneouss hemorrhage in the pituitary
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