hypothalamus Flashcards
hypothalamus, anatomical landmarks
a division of the diencephalon that functions primarily in the maintanence of homeostasis.
Functionally related in 3 systems: ANS, endocrine and limbic
forms the walls and floor of the bottom of the 3rd ventricle, separated from each side of the hypothalamic sulcus
Delimited anteriorly by the optic chiasm and lamina terminalis and posteriorly by the mammillary bodies
hypothalamic regions and nuclei
hypothalamic regions divided into periventricular, medial, and lateral areas or zones. While there is no distinct divisions between the thin periventricular zone and the medial area, the medial and lateral zones are separated by the fornix ventrally and mammillothalamic tract dorsally
lateral zone of hypothalamus
this region is comprised of loosely arranged neuronal cell groups and is transversed by the fibers of the medial forebrain bundle, 3 major nuclei:
1. lateral preoptic nucleus: anterior portion, which is telecephalic derivation developmentally
- lateral hypothalamic area: induces eating when stimulated- ablation–> anorexia and starvation
- tuberomammillary (Lateral tuberal) nucleus: located at ventrolateral surface at level equivalent to the tuberal and mammillary levels of the medial zone. large neurons that release histamine as a NT via axonal projections to widespread portions of the forebrain- important during attention and arousal, turned off during sleep
medial zone of hypothalamus
this zone is divided into 4 anatomically distinct anteroposterior regions: the preoptic, anterior (supraoptic), middle (tuberal) and posterior mammillary regions
preoptic region: the anterior telencephalic portion contains the medial preoptic nucleus- regulate gonadotropin secretion from the adenohypophysis- contains a sexually dimorphic nucleus
Suprachiasmatic nucleus: 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: this region lies between the suprachiasmatic and paraventicular nuclei. its involved temporal regulation- cause hyperthermia
paraventricular nucleus: this complex nucleus releases neuropeptides (release arginine vasopressin, oxytocin, CRH)
Supraoptic nucleu- syntesizes AVP and oxytocin
middle region
dorsomedial nucleus- BP regulation, aggregation and savage behavior
Ventromedial nucleus- urge to eat when stimulated, satiety center
Arcuate nucleus- adenohypophyseal hormones
posterior region
posterior nucleus- neurons involved in thermoregulation
mammillary nucleus- part of limbic system, , receive input from the hippocampus via fornixp memory from involvement with hippocampus
periventricular zaone
periventricular nucleus, this layer of cells lining the wall of the 3rd ventricle mainly at anteriorly and middle levels of medial zone
major fiber tracts
the hypothalamus is extensively interconnected with many portions of the neuraxis: 1. forebrain regions that are components of the limbic system, 2. brainstem regions that serve as part of the ANS, 3. the pituitary gland
Fornix- the mammillary bodies of the hypothalamus receive a large axonal projection from hippocampus via this pathway
mammillothalamic tract-project from the mammillary bodies to the anterior nucleus of the thalamus
stria terminalis- prominent pathway interconnecting the amygdaloid complex with the medial zone of the hypothalamus
medial forebrain bundle- the most complex fiber pathway in the CNS, contianting at least 50 disting paths
supraopticohypophyseal tract- conducts fibers from the supraoptic and paraventricular nuclei, specifically-magnocellular neurons that syntesize AVP or oxytocin
Tuberoinfundibular tract- arcuate nucleus to the hypophyseal portal system at the median eminence of the infundibulum
hypothalamospinal tract- contains descending axons that regulate sp cd,
major regulatory functions of the hypothalamus
thermoregulation, stress responsiveness, feeding and energy metabolism, blood pressure and electolyte composition, reproductive functions
