Hypothalamus Flashcards
forms wall and floor of inferior part of 3rd ventricle and is under thalamus (seperated by hypothalmic sulcus).
Hypothalamus
stalk of hypophysis (pitiutiary) and has phophyseal portal vesles and tracts connecting hypothalamus and posterior part of hypophysis
Infundibulum
Where classes of hypothalmic neurons release regulatory factors carried by portal vessels to ant. Pit.
Median eminence of anterior part
bulge btwn optic chaism and mammilary bodies
Tuber cinerum
Hypothalamus is highly vascularized by
Small branches off circle of Willis
Vascularity in hypothalamus is key component of
responsiveness of hypothalmic neuronal populations to negative feeback of circulating hormones
No distinction btwn pereventricular and medial zones of hypothalamus but
Medial and lateral separated by
fornix (ventrally) mammillothalamic tract (dorsally)
Lateral Pre-optic Nucleus is part of Lateral zone
from the:
developmentally:
Anterior part, telencephalic devo
induces eating when stimulated; ablation causes anorexia, starvation and originally thought to serve as the feeding center
Lateral hypothalmic nucleus in the Lateral Zone
Lateral hypothalmic nucleus in the Lateral Zone
induces eating when stimulated; ablation causes anorexia, starvation and originally thought to serve as the feeding center
located at ventrolateral surface at tuberal and mammillary levels of medial zone
Tuberomammillary nucleus
contains large neurons that release histamine as NT via axonal projections to portions of the the forebrain
Tuberomammilary nucleus
Key for attention and arousal, actively inhibited during sleep
Tuberomammillary nucleus
Three parts of the Lateral zone in hypothalamus
Lateral Preoptic Nucleus
Lateral Hypothalmic
Tuberomammillary Nucleus
The Medial zone contains
Preoptic
Anterior or suprachaismic
Middle tuberal region
Posterior mammilary region
This layer of cells lining the wall of the third ventricle at supraoptic and tuberal levels.
Periventricular nucleus.
Periventricular nucleus consists of several very small nuclei that are often also considered by some authors as parts of nuclei of
the medial zone (preoptic, suprachiasmatic, paraventricular, arcuate).
The hypothalamus is extensively interconnected with many portions of the neuraxis, most notably:
1) basal forebrain regions that are components the limbic system,
2) brainstem regions that serve as part of the autonomic nervous system, and
3) the pituitary gland (hypophysis).
the mammillary bodies of the hypothalamus receive a large axonal projection from the hippocampus via this pathway. (Also contains axons that serve as inputs to the hippocampus from multiple brain regions)
Fornix-
Mammilothalamic tract:
projects from the mammillary bodies (nuclei) to the anterior nucleus of the thalamus
- prominent pathway interconnecting the amygdaloid complex (i.e. amygdala) with the medial zone of the hypothalamus.
Stria terminalis
Stria terminalis prominent path that interconnects the _______ with the ________
amygdaloid complex with the medial zone of the hyopthalamus
the most complex fiber pathway in the central nervous system, containing at least 50 distinct constituent parts or pathways.
Medial forebrain bundle
Location of the medial forebrain bundle
It extends throughout the entire lateral hypothalamic zone, interconnecting regions from the septal nuclei (rostrally) to the brainstem (caudally)
– conducts fibers from the supraoptic and paraventricular nuclei to the neurohypophysis.
Supraopticohypophyseal tract
What is special about the axons of the supraopticohypophyseal tract
these are axons of the large (magnocellular) neurons that synthesize either AVP or oxytocin.
conducts fibers from the arcuate nucleus to the hypophyseal portal system at the median eminence of the infundibulum.
Tuberoinfundibular tract –
These axons carry neuropeptide releasing or inhibiting factors which act upon anterior pituitary cells (corticotrophs, lactotrophs, gonadotrophs, somatotrophs, thyrotrophs)
Tuberioinfundibular tract
Tuberoinfundibulum tract conducts fibers from the _______to the _________at the median eminence of the infundibulum.
arcuate nucleus
hypophyseal portal system
– contains descending axons that regulate spinal cord preganglionic neurons of both sympathetic and parasympathetic divisions of the autonomic nervous system.
Hypothalamospinal tract
Damage to this tract as it descends through the brainstem may induce Horner’s syndrome
Hypothalamospinal tract
Hypothalamospinal tract originates primarily from the
paraventricular nucleus.
Major Regulatory Functions of the Hypothalamus
Body Temperature Feeding and Energy Metabolism Emergency Responses to Stress Blood Pressure and Electrolyte Composition Reproductive Functions
serves to integrate________ and ________ functions with behavior, particularly those behaviors concerning basic homeostatic requirements of everyday life.
autonomic
endocrine
the hypothalamus can access sensory information from
the entire body
(For example, visual information is relayed there (to the suprachiasmatic nucleus), as are pain inputs from the
spinal cord and via the trigeminal nerve, as well as affective stimuli from components of the limbic system.)
The hypothalamus contains _______ neurons that are responsive to changes in local temperature, osmolality, and glucose and sodium concentrations.
internal sensory
circulating hormones act on hypothalamic neurons either
directly or indirectly
hypothalamus is thought to establish biological set points for
temperature, blood osmolality, glucose, sodium and levels of hormones.
When a deviation from set point is detected by the hypothalamus, it responds by adjusting an array of
autonomic, endocrine, and behavioral responses to restore homeostasis.
How does the hypothalamus maintain homeostasis
extensively interconnected with sites of autonomic and endocrine outflow, as well as limbic areas that affect behavioral responsiveness, all of which are coordinated to accomplish this complex regulation.
Thermoregulation:
_______ for heat dissipation
________ for heat conservation
Anterior nucleus
Posterior nucleus
Mech of heat dissipation by the anterior nucleus
sweating, cutaneous vascular dilatation and accelerated respiration and by activating portions of the parasympathetic nervous system.
Mech of heat conservation by the posterior nucleus
shivering, cessation of sweating, cutaneous vascular constriction and activation of appropriate endocrine (e.g. thyroid) responses to alter (increase) metabolic rate.
The hypothalamic regions sensitive to heat and cold are under influences of the________ and are also interconnected with brainstem and spinal cord regions that mediate these effects.
limbic forebrain,
bilateral destruction of the anterior hypothalamic area results in
hyperthermia
bilateral lesions of the posterior hypothalamic nucleus and surrounding area cause
an inability to thermoregulate altogether (a condition termed “poikilothermia”)
an inability to thermoregulate altogether or poikothermia in the posterior hypothalamic nucleus is due to
due to the loss of both the cold- sensitive neurons in the region, and the descending projections of the warm-sensitive neurons (from the anterior hypothalamus) which course through the region en route to the brainstem.
Hypothalamus role in stress resposne
coordinating the classic ‘fight-or-flight’ response
This involves neuroendocrine control of the release of stress hormones from the adrenal cortex (e.g. glucocorticoids) as well as epinephrine and norepinephrine from the adrenal medulla.
hypothalamus is under afferent regulatory control by numerous brain regions such as the
pre-frontal cortex, limbic forebrain, and brainstem.
Hypothalamus integrate signaling from these pre-frontal cortex, limbic forebrain, and brainstem and the input from which varies according to the nature of the stressor (physical, psychogenic, visceral, etc.), and to produce an appropriately coordinated set of responses involving
outflow through autonomic, endocrine and other systems.
Two prominent components of the limbic system, the ________ and________, are extensively interconnected with the hypothalamus.
amygdala
hippocampus
Feeding: a central role is played by neurons of the______ , located at the ventral surface of the hypothalamus at the middle or tuberal level.
arcuate nucleus
Lateral hypothalamic area is for _______
ventromedial hypothalamic nucleus ________
feeding
satiety
Two distinct sets of neurons within the arcuate nucleus have opposing effects upon food intake.
- AgRP (agoiuti-related peptide) + neuropeptide Y
2. MSH (melanocyte stimulating hormone) and CART (cocaine and amphetamine responsive transcript
What is the role of AgRP and neuropeptide Y in feeding
These cells have a number of local hypothalamic projections that serve to signal increased feeding and a concomitant decrease in metabolism.
What is the role of MSH/POMC and CART in feeding
synthesize and release and act upon secondary hypothalamic neurons. Activation of POMC/CART neurons signals decreased feeding accompanied by increased metabolism.
These neurons synthesize and release and act upon secondary hypothalamic neurons. Activation of POMC/CART neurons signals decreased feeding accompanied by increased metabolism.
MSH/POMC and CART
Output from both sets of neurons is integrated in the brainstem, specifically, at the _________ which appears to act as a satiety center.
nucleus of the solitary tract (NTS)
hormones ghrelin is released when?
has what affect on feedin
(released from the stomach just prior to a meal)
stimulates feeding
PPY (polypeptide Y) released from the GI tract is released when?
Acts on AgRP/NPY and MSH/CART how?
immediately following a meal,
inhibit feeding
Gastric distension and CCK release from the gastrointenstinal tract act to
produce satiety at the brainstem (NTS) level
produce satiety at the brainstem (NTS) level
CCK
In the longer term, the hormone______ is released by fat cells, signaling a decrease in feeding. This appears to occur through at the arcuate nucleus by_____ of the AgRP/NPY neurons and______ of MSH/CART neurons.
leptin
inhibition
stimulation
The peptides orexin and melanin-concentraing hormone (MCH), both of which are produced by neurons located mainly within the
lateral hypothalamic area
peptide and hormone that induce feeding when released.
MCH
orexin
______has been shown decrease food intake, as has_____ secretion in response to stress.
central oxytocin secretion
CRH
- Congenital tumor (usually calcified) originating from remnants of Rathke’s pouch.
- Most common supratentorial tumor in children
- Pressure on optic chiasm results in bitemporal hemianopsia
- Pressure on overlying hypothalamus results in “hypothalamic syndrome” of adiposity,
diabetes insipidus, temperature regulation disturbances, and somnolence
Craniopharyngioma
posterior hypothalamic lesions involving mammillary bodies associated with
inability to form new memories (episodic) for context- and time-specific
events.
hypothalamic (autoimmune?) disorder primarily in adolescent males
- hypersomnolence
- episodic compulsive eating
hypersexuality
- associated with decrease in dopaminergic tone during symptomatic phase
Klein-Levin Syndrome
Klein-Levin Syndrome
hypothalamic (autoimmune?) disorder primarily in adolescent males
- hypersomnolence
- episodic compulsive eating
hypersexuality
- associated with decrease in dopaminergic tone during symptomatic phase
