Hypothalamus Flashcards
The hypothalamus is functionally related to 3 major systems
- ANS
- Endocrine system
- limbic system
Infundibulum
- stalk of the hypophysis (pituitary)
- contains hypophyseal portal vessel and several important tracts connecting the hypothalamus and posterior part of the hypophysis
- anterior portion is slightly elevated and is known as the median eminence and serves as the site where the various classes of hypothalamic nuerons release regulatory factors carried by the portal vasculature to the anterior pituitary
Tuber cinereum
a bulge between the optic chiasm and mammillary bodies
mammillary bodies
paired structures that functionally are part of the limbic system (ie papez circuit)
explain the vascularity of the hypothlamaus
the hypothalamus is highly vascularized and blood supply comes from small branches of vessel forming th circle of willis which surround its ventral surface
-this vascularity is a key component of the responsiveness f the specific hypothalamic neuronal populations to the ngeative feedback actions of circulating hormones
what are the three zones that the hypothalamus is divided into
- periventricular
- medial
- lateral
what separates the medial and lateral zones of the hypothalamus
the fornix
Nuclei of the lateral zone of the hypothalamus
- lateral preoptic nucleus
- lateral hypothalamic area
- tuberomammillary (lateral tuberal) nucleus
Lateral preoptic nucleus
- lateral zone
- anterior portion which is telencepahlic derivation developmentally
Lateral hypothalamic area
- lateral zone
- induces eating when stimulated
- ablation causes anorexia and starvation and was originally thought to serve as a feeding center
- contains important neurotransmitters that increase food intake
Tubermammillary (lateral tuberal) Nucleus
- located at the ventrolateral surface at the level equivalent to the tuberal and mammillary levels of the medial zone
- contains large neurons that release histamine as a neurotransmitter via axonal projections to widespread portions of the forebrain
- the area is thought to play an important role in attention and arousal processes and is actively inhibited during sleep
what is the only place in the brain that produces histamine and the releases it globally
-tuberomammillary nucleus. gives arousal! and is inhibited right before you fall asleep
Medial zone regions
divided into four anatomically distinct regions
- preoptic
- anterior (supraoptic)
- middle (tuberal)
- posterior (mammillary)
preoptic region
- medial zone
- the anterior telencephalic portion contains the medial preoptic nucleus, which among other things houses neurons that regulate gonadotropin secretion from the adenohypophysis
- contains the interstitial nuclei of the anterior hypothalamus on of which is sexually dimorphic (larger in males) and developmentally regulated by testosterone
anterior region contains what nuclei
- sruprachiasmatic nucleus
- anterior hypothalamic nucleus
- paraventricular nucleus
- supraoptic nucleus
suprachiasmatic nucleus
- anterior region
- this compact nucleus is located immediately dorsal to the optic chiasm and receives direct input from the retina. -it plays a critical role in the control of circadian rhythmicity
anterior hypothalamic nucleus
- anterior region
- this region lies between the suprachiasmatic and paraventricular nuclei
- involved in temperature regulation (containing neurons that sense warmth and initiate response to dissipate excessive heat)
- bilateral lesions of this area result in hyperthermia
- concerned with stimulatory drive of the parasympathetic division of the autonomic nervous system
paraventricular nucleus
- this complex nucleus contains distinct populations of neurons that release neuropeptides that regulate a variety of functions
- included are neurons that synthesize and release arginine vasopressin (AVP, water conservation) oxytocin (milk let down and release and also regulation of food intake) and corticotropin releasing hormone (CRH;stress responsiveness)
- additional neurons project to the interomediolateral cell column of the spinal cord (between T1-L2) where they excite sympathetic preganglionic neurons as well as project to the brainstem
supraoptic nucleus
- anterior region
- contains neurons that synthesize AVP and oxytocin
- similar to neurons in the paraventricular nucleus that contain AVP and oxytocin
- these cells project to the neurohypophysis where they release these hormones into the general circulation
