Hypothalamus Flashcards
What is the major function of the hypothalamus:
Serves to integrate autonomic and endocrine functions with behavior, particularly those behaviors concerning basic homeostatic requirements of everyday life.
To which major systems is the hypothalamus functionally related?
- ANS
- Endocrine
- Limbic
The hypothalamus forms the walls and floor of the:
3rd ventricle
Separates the thalamus from the hypothalamus:
Hypothalamic sulcus
Hypothalamus us delimited anteriorly by the ______ and posteriorly by the ______.
Optic chiasm, mammillary bodies.
The medial and lateral zones of the hypothalamus are separated by the _______ (ventrally) and ________(dorsally).
Fornix, mammillothalamic tract.
The lateral zone of the hypothalamus is transversed by the fibers of the ________.
Medial forebrain bundle.
This hypothalamic nuclei induces eating when stimulated, and causes anorexia and starvation when ablated. Contains important peptide NTs that increase food intake.
Lateral hypothalamic area
This hypothalamic nucleus contains large neurons that release histamine. Thought to play an important role in attention and arousal, and is actively inhibited during sleep.
Tuberomammillary (lateral tuberal) nucleus.
This hypothalamic nucleus houses neurons that regulate gonadotropin secretion from the adenohypophysis. It also contains the interstitial nuclei of the anterior hypothalamus, one of which is sexually dimorphic and developmentally regulated by testosterone.
Medial preoptic nucleus - located within the preoptic region.
This hypothalamic nucleus receives direct input from the retina. It plays a critical role in the control of circadian rhythmicity. Lesions result in insomnia.
Suprachiasmatic nucleus
This hypothalamic nucleus contains neurons that sense warmth and initiate responses to dissipate excessive heat. Inflammatory cytokines and pyrogens also act here to alter body temperature set points. Bilateral lesions result in hyperthermia.
Anterior hypothalamic nucleus
This hypothalamic nucleus contains neurons that synthesize and release AVP, oxytocin, CRH.
Paraventricular nucleus
This hypothalamic nucleus contains neurons that synthesize AVP and oxytocin.
Supraoptic nucleus
This hypothalamic nucleus is involved in blood pressure regulation. May produce aggression when stimulated.
Dorsomedial nucleus
This hypothalamic nucleus inhibits the urge to eat when stimulated.
Ventromedial nucleus
This hypothalamic nucleus controls the release (or non-release) of various adenohypophyseal hormones.
Arcuate nucleus
This hypothalamic nucleus contains neurons that sense cold and initiate heat conservation/production responses. Bilateral lesions produce poikilothermia (inability to thermoregulate).
Posterior hypothalamic nucleus
This hypothalamic nucleus receives a major input from the hippocampus via the fornix. Damage here is associated with memory disturbances due to extensive interconnectivity with the hippocampus.
Mammillary nucleus
Function of the fornix:
Fiber tract that connects the mammillary bodies of the hypothalamus to the hippocampus. Also structurally divides the medial zone from the lateral zone.
Interconnects the amygdaloid complex with the medial zone of the hypothalamus:
Stria terminalis
The most complex fiber pathway in the CNS. Extends throughout the entire lateral hypothalamic zone, interconnecting regions from the septal nuclei to the brainstem.
Medial forebrain bundle.
This tract conducts fibers from the supraoptic and PVN to the neurohypophysis. Axons of the large neurons that synthesize either AVP or oxytocin.
Supraopticohypophyseal tract
This tract conducts fibers from the arcuate nucleus to the hypophyseal portal system. Axons that carry neuropeptide release or inhibiting factors which act upon anterior pituitary cells.
Tuberoinfundibular tract
This tract contains descending axons that regulate spinal cord preganglionic neurons of both sympathetic and parasympathetic divisions of the ANS. Damage here may induce Horner’s syndrome.
Hypothalamospinal tract.
What is the role of the hypothalamus in stress responsiveness?
Serves to integrate signaling from different areas of the brain, the input from which varies according to the nature of the stressor, and to produce an appropriately coordinated set of responses involving outflow through autonomic, endocrine, limbic, and other systems.
Clinical: child with bitemporal hemianopia, adiposity, diabetes, temperature regulation disturbances, somnolence.
Craniopharyngioma
Lesions involving mammillary bodies:
Associated with inability for form new memories for context and time-specific events.
Clinical: Adolescent male with hypersomnolence, episodic compusive eating, hypersexual.
Klein-Levin Syndrome
Input to the hypothalamus comes through:
Lateral region
Output to the hypothalamus goes through:
Periventricular region
Outcome of anterior/posterior hypothalamus activation:
Either behavioral or physiological.
Function of medial hypothalamus:
Regulates feeding behavior. Lesion causes overeating. Prader-Willi syndrome, craniopharyngioma.
Describe lateral medullary syndrome:
Loss of pain and temperature sensation on contralateral body and ipsilateral face.
Most often due to stroke involving PICA.
Common things that result in Horner’s syndrome (2):
- Pancoast tumor (ipsilateral lung and eye constricted)
2. Damage to ICA (ipsilateral side)
Major function of PAG:
Implements basic behavior based on safe/threatening environment.
