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66 Cards in this Set
- Front
- Back
What part of the embryological brain is the hypothalamus derived from? |
Diencephalon
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What is the primarily function of the hypothalamus?
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Maintenance of homeostasis
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What three systems is the hypothalamus related to?
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1. ANS
2. Endocrine system 3. Limbic system |
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What structures are the hypothalamus anatomically related to?
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- Forms inferior portion of 3rd ventricle
- Underneath the thalamus (separated by shallow groove named the Hypothalamic Sulcus) - Limited anteriorly by optic chiasm - Limited posteriorly by mammillary bodies - Infundibulum - stalk to pituitary |
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What is the Infundibulum? Contents?
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- Stalk of the hypophysis (pituitary gland)
- Contains hypophyseal portal vessels (to the adenohypophysis - ant. pituitary) - Contains several important tracts connecting the hypothalamus and the posterior part of the pituitary (neurohypophysis - post. pituitary) |
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Which part of the hypophysis (pituitary) is connected by neural tracts?
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Neurohypophysis - Posterior Pituitary
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Which part of the hypophysis (pituitary) is connected by portal vessels?
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Adenohypophysis (anterior pituitary)
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What flows to the anterior pituitary (adenohypophysis) via the portal vessels? How?
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Various classes of (largely peptidergic) hypthalamic neurons release regulatory factors
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What is the Tuber Cinereum?
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"Gray Protuberance" - bulge located between the optic chiasm and mammillary bodies
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What are the Mammillary Bodies?
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- Paired structures
- Functionally a part of the limbic system (i.e., Papez circuit) |
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How does blood supply the hypothalamus?
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Small branches from the Circle of Willis surrounding the ventral surface
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Why is the blood supply to the hypothalamus important (besides for nutrients/waste)?
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Key component of responsiveness of specific hypothalamic neuronal populations to the negative feedback actions of circulating hormones (e.g., adrenal and gonadal steroids)
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How is the Hypothalamus divided?
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- Lateral Zone
- Medial Zone - Periventricular Zone |
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What separates the different zones of the hypothalamus?
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- Lateral and Medial Zones separated by Fornix (ventrally) and Mammilothalamic Tract (dorsally)
- No distinct division between thin Periventricular Zone and Medial Zone |
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What are the components of the Lateral Zone of the Hypothalamus?
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- Loosely arranged neuronal cell groups
- Traversed by fibers of Medial Forebrain Bundle - Three major nuclei |
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What are the three major nuclei of the Lateral Zone of the Hypothalamus?
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1. Lateral Preoptic Nucleus
2. Lateral Hypothalamic Area (Nucleus) 3. Lateral Tuberal (Tuberomammillary) Nucleus |
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Which are the characteristics / roles of the three major nuclei of the Lateral Zone of the Hypothalamus?
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1. Lateral Preoptic Nucleus - anterior portion, telencephalic developmentally (involved in initiating sleep)
2. Lateral Hypothalamic Area (Nucleus) - induces eating when stimulated; ablation causes anorexia and starvation 3. Lateral Tuberal (Tuberomammillary) Nucleus - ventrolateral surface of medial zone - neurons release histamine to forebrain; involved in attention and arousal, inhibited during sleep |
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Which nuclei of the hypothalamus is involved in inducing eating when stimulated? Lesion?
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- Lateral Hypothalamic Area (Nucleus) - part of lateral zone
- Ablation causes anorexia and starvation |
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Which nuclei of the hypothalamus is involved in attention and arousal when stimulated? Inhibition?
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- Lateral Tuberal (Tuberomammillary) Nucleus
- Inhibition during sleep - Releases Histamine |
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What regions are a part of the Medial Zone of the Hypothalamus?
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- Preoptic Region (blue)
- Anterior (Supraoptic) Region (red) - Middle (Tuberal) Region (orange) - Posterior (Mammillary) Region (green) |
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Which nuclei is found in the Preoptic Region of the Medial Zone of the Hypothalamus? Function?
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- Medial Preoptic Nucleus (blue)
- Neurons regulate gonadotropin secretion from the adenohypophysis - Also contains interstitial nuclei of anterior hypothalamus (INAH1-4), one of which is sexually dimorphic (INAH3) and regulated by testosterone |
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What are the nuclei in the Anterior (Supraoptic) Region of the Medial Zone of the Hypothalamus? Functions?
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- Suprachiasmatic Nucleus - immediately dorsal to optic chiasm, receives input from retina; involved in circadian rhythm
- Anterior Hypothalamic Area (Nucleus) - temperature regulation, senses warmth and excess heat; also stimulatory drive of PNS - Paraventricular Nucleus - release neuropeptides AVP (water conservation), Oxytocin (milk letdown/release), and CRH (stress responsiveness); also projects to intermediolateral cell column of spinal cord (T1-L2 - SNS) - Supraoptic Nucleus - synthesizes AVP and Oxytocin - projects to neurohypophysis to release into gen. circulation (RED) |
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Which nucleus in the hypothalamus regulates gonadotropin secretion from the adenohypophysis and is developmentally regulated by testosterone?
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Medial preoptic nucleus of the Preoptic region in the Medial zone of the hypothalamus
(RED) |
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Which nucleus in the hypothalamus receives input from the retina and is important for circadian rhythm?
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Suprachiasmatic Nucleus - Anterior (Supraoptic) Region of Medial Zone of Hypothalamus
(RED) |
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Which nucleus in the hypothalamus regulates temperature by sensing heat? Lesions?
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- Anterior Hypothalamic Area (Nucleus) in Anterior (supraoptic) region of Medial Zone of Hypothalamus
- Also concerned with stimulatory drive for PNS - Lesions cause hyperthermia (RED) |
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Which nucleus in the hypothalamus regulates AVP, Oxytocin, and CRH release?
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- Paraventricular Nucleus of the Anterior (Supraoptic Region) of the Medial Zone of the Hypothalamus
- Also projects to intermediolateral cell column of spinal cord (T1-L2), to excite sympathetic preganglionic neurons (RED) |
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Which nucleus in the hypothalamus releases AVP and Oxytocin to the Neurohypophysis where it can enter the general circulation?
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Supraoptic Nucleus of the Anterior (Supraoptic) Region of the Medial Zone of the Hypothalamus
(RED) |
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What are the nuclei of the Middle (Tuberal) Region of the Medial Zone of the Hypothalamus? Functions?
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- Dorsomedial Nucleus - aggressive behavior, BP regulation
- Ventromedial Nucleus - inhibits urge to eat (satiety center) - Arcuate Nucleus - controls release of adenohypophyseal hormones via hypothalamic-releasing (and inhibiting) factors; involved in feeding behavior (ORANGE) |
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Which nucleus of the hypothalamus mediates aggressive and savage behavior as well as BP regulation?
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Dorsomedial Nucleus of the Middle (Tuberal) Region of the Medial Zone of the Hypothalamus
(ORANGE) |
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Which nucleus of the hypothalamus inhibits the urge to eat ("satiety center")? Lesion?
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- Ventromedial Nucleus of the Middle (Tuberal) Region of the Medial Zone of the Hypothalamus
- Lesion causes hyperphagia (over-eating) (ORANGE) |
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Which nucleus of the hypothalamus controls the release of various adenohypophyseal hormones via hypothalamic releasing and inhibiting factors, also involved in feeding behavior?
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Ventromedial Nucleus of the Middle (tuberal) region of the Medial Zone of the Hypothalamus
(ORANGE) |
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What are the nuclei of the Posterior (Mammillary) Region of the Medial Zone of the Hypothalamus? Functions?
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- Posterior Nucleus - thermoregulation by sensing cold
- Mammillary Nucleus - part of limbic system, input from hippocampus via fornix; projects to anterior nucleus of thalamus; also conveys sensory info to midbrain tegmentum (GREEN) |
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Which nucleus of the hypothalamus is involved in thermoregulation by sensing cold and initiating heat conservation? What happens if there is a lesion?
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- Posterior Nucleus of Posterior (Mammillary) Region of the Medial Zone of the Hypothalamus
- Poikilothermia - inability to thermoregulate if bilateral lesion (GREEN) |
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Which nucleus of the hypothalamus is part of the limbic system and receives input from hippocampus and projects to anterior nucleus of thalamus; as well as sending sensory info to midbrain tegmentum? Lesions?
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- Mammillary Nucleus of the Posterior (Mammillary) region of the Medial Zone of the Hypothalamus
- Lesions cause memory disturbances due to extensive interconnectivity with the hippocampus |
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What are the nuclei of the Periventricular Zone? Functions?
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Periventricular Nucleus - layer of cells lines the wall of the 3rd ventricle at supraoptic and tuberal levels
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The hypothalamus is extensively interconnected with what portions of the neuraxis?
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- Basal forebrain regions that are components of the limbic system
- Brainstem regions that serve as part of the ANS |
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What are the major fiber tracts of the Hypothalamus?
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- Fornix
- Mammillothalamic Tract - Stria Terminalis - Medial Forebrain Bundle - Supraopticohypophyseal Tract - Tuberoinfundibular Tract - Hypothalamospinal Tract |
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What happens in the Fornix?
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- Mammillary bodies of the Hypothalamus receive a large axonal projection from the Hippocampus
- Also contains axons that serve as inputs to the hippocampus from multiple brain regions |
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What happens in the Mammillothalamic Tract?
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- Projects from the Mammillary Bodies (nuclei) to the Anterior Nucleus of the Thalamus
- Key component of the Papez Circuit |
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What happens in the Stria Terminalis?
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Proinent pathway interconnecting the amygdaloid complex (e.g., amygdala) and the medial zone of the hypothalamus
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What happens in the Papez Circuit?
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- Fornix connects Hippocampus to Mammillary Body
- Mammillothalamic Tract connects Mammillary Body to Anterior Thalamic Nuclei - Superior Thalamic Radiation connects that to the Cingulate Gyrus - Cingulum connects CG back to Hippocampus |
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What happens in the Medial Forebrain Bundle?
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- Most complex fiber pathway in CNS w/ >50 distinct constituent parts/pathways
- Extends through entire Lateral Hypothalamic Zone, interconnecting regions from the septal nuclei (rostrally) to the brainstem (caudally) |
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What happens in the Supraopticohypophyseal Tract?
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Conducts fibers from the Supraoptic and Paraventricular Nuclei to the Neurohypophysis
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What happens in the Tuberoinfundibular Tract?
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Conducts fibers from the Arcuate Nucleus to the Hypophyseal Portal System at the Median Eminence of the Infundibulum
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What happens in the Hypothalamospinal Tract?
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Contains descending axons that regulate the spinal cord preganglionic neurons of both sympathetic and parasympaethtic divisions of the ANS; originates from the Paraventricular Nucleus
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What are the major functions of the Hypothalamus?
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- Body temperature regulation
- Stress responsiveness - Feeding and energy metabolism - BP and electrolyte composition - Reproductive functions |
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What are the fundamental capacities of the hypothalamus?
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1. Hypothalamus can access sensory information from virtually the entire body
2. Hypothalamus is thought to establish biological set points for temperature, blood osmolality, glucose, Na+, and levels of hormones 3. Deviation from set point is detected, the hypothalamus responds by adjusting autonomic, endocrine, and behavioral responses to restore homeostasis |
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Which areas of the Hypothalamus are involved in Thermoregulation? How?
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- Anterior and Posterior Hypothalamic Nuclei
- Anterior senses warmth and triggers heat dissipation (sweating, vascular dilation, increased respiration) and by activating PNS - Inflam. cytokines and pyrogens act on anterior hypothalamus to alter body temp set point causing fever - Posterior senses cold, triggering heat conservation via sympathetic outflow (shivering, stop sweating, vascular constriction, increased thyroid to increase metabolic rate - Both influenced by limbic forebrain and connected to brainstem and spinal cord - Also behavioral responses (change environment, put on / take off clothes) |
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What happens if there are lesions to the areas of the Hypothalamus regulating Thermoregulation?
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- Bilateral lesions to Ant. Hypothalamic Nuclei causes hyperthermia due to loss of warm-sensitive neurons
- Bilateral lesions to Post. Hypothalamic Nuclei causes inability to thermoregulate (poikilohermia) due to loss of cold-sensitive neurons and descending projections of warm-sensitive neurons |
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How does the Hypothalamus play a role in stress responsiveness?
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Neuroendocrine control of the release of stress hormones from adrenal cortex (e.g., glucocorticoids) as well as epinephrine and NE from adrenal medulla
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What sort of sympathetic changes are mediated by the hypothalamus in a stress response?
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- Diversion of blood from viscera to skin and muscles
- Increased cardiac output - Pupillary dilation (CN III inhibited) - Bronchodilation - Decreased GI motility and renal activity - Inhibition of PNS neurons in brainstem |
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What controls the hypothalamus stress response?
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Afferent regulatory control by pre-frontal cortex, limbic forebrain, and brainstem
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Which components of the limbic system are interconnected with the hypothalamus response to stress?
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- Amygdala
- Hippocampus |
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Which CNs are inhibited in the stress response by the hypothalamus?
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- CN III - pupil dilation
- CN VII - sublingual and submaxillary gland secretion inhibited - CN IX - parotid gland secretion inhibited - CN X - decreased HR and decreased intestinal motility |
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Which hypothalamic nuclei are involved in feeding and energy metabolism?
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- Lateral Hypothalamic Area - induces eating
- Ventromedial Hypothalamic Nucleus - inhibits eating - Arcuate Nucleus - involved in eating |
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Which hormones are involved in feeding and energy metabolism?
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- Insulin
- Glucagon - Leptin |
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How is the Arcuate Nucleus of the Hypothalamus (middle/tuberal level) involved in feeding?
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- Two distinct sets of neurons have opposite effects
- First set co-expressess agouti-related peptide (AgRP) and neuropeptide Y (NPY) w/ local hypothalamic projections to signal increased feeding and decrease in metabolism - Second set co-expresses pro-opiomelanocortin (POMC --> converted to α-melanocyte-stimulating hormone, α-MSH) and cocaine- and amphetamine-responsive transcript (CART) which signals decreased feeding and increased metabolism - Integrated at Nucleus of the Solitary Tract (NST) = Satiety Center |
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Which hormones modulate feeding in the short-term?
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- Ghrelin (released from stomach just prior to a meal)
- PPY (polypeptide Y - released from GI following a meal) - Act on two sets of arcuate neurons (AgRP/NPY and POMC/CART) to stimulate or inhibit feeding |
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Which hormones modulate feeding in the long-term?
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- Leptin - released by fat cells
- Signals a decrease in feeding - Inhibits AgRP/NPY neurons (that usually signal increased eating and decreased metabolism) |
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What are three clinical correlates regarding the hypothalamus?
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1. Craniopharyngioma
2. Hypothalamic Memory Disturbances 3. Klein-Levin Syndrome |
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What is a Craniopharyngioma? Symptoms?
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- Congenital tumor (usually calcified) originating from remnants of Rathke's pouch
- Most common supratentorial tumor in children - Pressure on chiasm results in bitemporal hemianopia - Pressure on overlying hypothalamus results in "hypothalamic syndrome" of adiposity, diabetes insipidus, temp. regulation disturbances, and somnolence (sleepiness) |
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What causes a Hypothalamic Memory Disturbance? Symptoms?
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- Posterior hypothalamic lesions involving the Mammillary complex
- Associated with inability to form new memories (episodic) for context- and time-specific events |
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What is an example of a cause of Hypothalamic Memory Disturbances?
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Korsakoff Syndrome - caused by thiamine deficiency associated with chronic alcoholism (not eating enough food)
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What is Klein-Levin Syndrome?
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- Hypothalamic lesion in adolescent males (autoimmune?)
- Episodic compulsive eating - Hypersomnolence - excessive daytime sleepiness - Hypersexuality - May result from a decrease in dopaminergic tone during the symptomatic phase of syndrome |
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Which of the hypothalamic nuclei has groups of neurons that synthesize and release Oxytocin, AVP, and CRH?
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Paraventricular Nucleus
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Which fiber pathway is a major efferent of the hippocampal formation, and also divides the medial zone of the hypothalamus from the lateral zone?
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Fornix
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