Hypothalamus Flashcards
Main function of the hypothalamus
Maintain homeostasis
What three systems is the hypothalamus functionally related to?
Autonomic nervous system
Endocrine system
Limbic system
What are the three zones that the hypothalamus is divided into?
Periventricular
Medial
Lateral
What anatomical structures separate the medial and lateral zones?
Fornix (ventrally) and mammillothalmic tract (dorsally)
Major nuclei of Lateral zone
Lateral preoptic nucleus
Lateral Hypothalamic area
Tuberomammillary (lateral tuberal) nucleus
Function of Lateral hypothalamic area
Induces eating when stimulated
Ablation causes anorexia and starvation
Contains important peptide ntms that increase food intake
Function of Tuberomammillary Nucleus
Contains large neurons that release histamine as a ntm via axonal projections to widespread portions of the forebrain
Thought to plan an important role in attention and arousal processes
Actively inhibited during sleep
Major nuclei of the Medial zone
Preoptic Region: Medial preoptic nucleus
Anterior Region: Suprachiasmatic nucleus, Anterior hypothalamic nucleus, Paraventricular nucleus, Supraoptic nucleus
Middle Region: Dorsomedial nucleus, Ventromedial nucleus, Arcuate nucleus
Posterior Region: Posterior nucleus, Mammillary nucleus
Function of the Medial Preoptic Nucleus
Houses neurons that regular gonadotropin secretion from the adenohypothysis
Contains the interstitial nuclei of the anterior hypothalamus, only of which is sexually dimorphic and developmentally regulated by testosterone
Function of Suprachiasmatic Nucleus
Immediately dorsal to optic chasm, receives direct input from retina
Plays critical role in control of circadian rhythm
Function of Anterior Hypothalamic Nucleus
Between suprachiasmatic and paraventricular nuclei
Involved in temp regulation, contains neuron that sense warmth and initiate response to dissipate excess heat
Bilateral lesions result in hyperthermia
Function of paraventricular nucleus
Contains neurons that synthesize and release arginine vasopression, oxytocin, and CRH
Additional neurons project to interomediolateral cell column of the spinal cord (T1-L2) exciting sympathetic preganglionic neurons, as well as projections to brainstem
Function of Supraoptic nucleus
Contains neuron that synthesize AVP and oxytocin
Project to neurohypophysis where they release these hormones into circulation
Function of dorsomedial nucleus
involved in BP regulation, aggression and savage behavior result
Function of ventromedial nucleus
Inhibits the urge to eat when stimulated
Bilateral destruction results in hyperphagia
Neurons play an important role in relaying ingestion-related signals to the brainstem
Function of Arcuate Nucleus
Controls the release of various adenohypophyseal hormones
Produce hypothalamic-releasing factors and play prominent role in feeding behavior
Function of Posterior Nucleus
Involved in thermoregulation
Sense cold and initiate heat conservation and heat production responses
Bilateral lesions result in an inability to thermoregulate (poikilothermia)
Function of the Mammillary Nucleus
Series of nuclei within the mammillary bodies (part of limbic system)
Receive major input from hippocampus via the fornix
Project to the anterior nucleus of the thalamus via the mammillothalmic tract
Damage to the regions is associated with memory disturbances due to extensive interconnectivity with the hippocampus
Mammillary bodies of the hypothalamus receive large axonal projection from the hippocampus via this pathway
Fornix
Projects from the mammillary bodies to the anterior nucleus of the thalamus
Mammillothalamic tract
Prominent pathway interconnecting the amygdaloid complex with the medial zone of the hypothalamus
Stria terminalis
Most complex fiber pathway in the CNS
Contains at least 50 distinct constituent parts of pathways
Extends through the entire lateral hypothalamic zone, interconnecting regions from the septal nuclei to the brainstem
Medial forebrain bundle
Conducts fibers from the supraoptic and paraventricular nuclei to the neurohypophysis
Magnocellular neurons that synthesize either AVP or oxytocin
Supraopticohypophyseal tract
Conducts fibers from the arcuate nucleus to the hypophyseal portal system at the median eminence of the infundibulum
Carry neuropeptide release or inhibiting factors which act upon anterior pituitary cells
Tuberoinfundibular tract
Contains descending axons that regulate spinal cord preganglionic neurons of both sympathetic and parasympathetic division of the ANS
Hypothalamospinal tract
Major Regulatory functions of the hypothalamus
Body temp Feeding and energy metabolism Emergency responses to stress BP and electrolyte composition Reproductive functions
Bilateral destruction of anterior hypothalamus leads to…
hyperthermia
Bilateral destruction of posterior hypothalamus leads to…
inability to thermoregulate
Function of AgRP and NPY
increase feeding and decrease metabolism
Function of POMC and CART
decrease feeding and increase metabolism
Function of grehlin
Released from stomach prior to meal, stimulates feeding
Function of polypeptide Y (PPY)
Released from GI tract after a meal, inhibits feeding
Function of CCK
Released from GI tract, produces satiety at brainstem level
Function of Leptin
Released from fat cells, decreases feeding
Function of Orexin and melanin-concentrating hormone
produced by neurons in the lateral hypothalamic area, induces feeding
What is a craniopharyngioma?
congenital tumor originating from Rathke’s pouch, common in children, bitemporal hemianopia
What causes hypothalamic memory disturbances?
Posterior hypothalamic lesions involving mammillary bodies
What is Klein-Levin syndrome?
Hypothalamic disorder, common in adolescent males, leads to bulimia, hypersomnolence, hypersexuality
