44 - Hypothalamus Flashcards
Hypothalamus - Blood Supply
PCA
Hypothalamus - Periventricular Zone
Parvocellular cells projecting to Anterior Pituitary via median eminence, influencing secretion
Hypothalamus - Medial Zone
Diffuse ass nuclei:
Preoptic Nucleus Paraventricular Nucleus Dorsomedial Nucleus Ventromedial Nucleus Arcuate Nucleus Supraoptic Nucleus SupraChiasmatic Nucleus Mammilary Body
Preoptic Nucleus
Just inferior to anterior commisure, superior to Optic Chiasm
Magnocellular neurons project to posterior pituitary
Dorsomedial Nucleus
Ventromedial Nucleus
Magnocellular, oxy & vas to PP
SupraChiasmatic Nucleus
Circadian Rhythms
Location of Medial Forebrain Bundle
Lateral Hypothalamus
Magnocellular nuclei in Hypothalamus
Paraventricular Nucleus
Supraoptic Nucleus
Project axons to posterior pituitary
Release Oxytocin & Vasopressin
Parvocellular Cells in Hypothalamus
Everywhere!
Project to median eminence, release in anterior pituitary, trigger release of hormones!
Inputs to the hypothalamus
Cingulate Gyrus Orbital cortex Ventral striatum Septal Nuclei Hippocampus Amygdala
Outputs from the hypothalamus
Widespread cortical areas Septal nuclei Anterior nucleus Mammilothalamic tract Amygdala
Hypothalamic Pathways
DLF MFB ST & VAP Fornix, Mammilothalamic and Mammilotegmental Tracts Optic Nerve
Descending Hypothalamus regulates the ANS
Info comes in
HypoThalamus projects down via VLF & MFB
Regulating Dorsal Motor Nucleus of X and Solitary Nucleus
Areas around Nucleus Ambiguus affect heart function.
Additionally, large projection down to spinal cord from HT to regulate PS and S preganglionics through spinal cord to regulate postganglionics
Hypothalamic Regulation of PNS
Mediated through dorsal motor nucleus of X.
Regions in reticular formation near nucleus ambiguus project to gut and heart.
Motor Nucleus of X - Inputs
VLF and MFB
Hypothalamus Four Fs
Fighting
Fleeing
Feeding
FUCKINGGGGGG
6 physiologic needs controlled by Hypothalamus
BP & Electrolytes
Temperature (ANS & motivated behavior, metabolic pathways)
Energy metabolism (eating, behavior, metabolic rate)
Reproduction (hormonal control of mating, pregnancy and lactation)
Responses to stress (directing blood flow nad stimulating adrenal se(x)cretions)
Adaptive emotional responses
Hypothalamus - Location
Lining the walls of the 3rd ventricle, above the pituitary
Not too far from VTA
Fornix
Divides Hypothalamus into medial and lateral regions
Anterior border of the hypothalamus
Line between Anterior Commisure and Mammilary Bodies
Paraventricular Nucleus
Microcosm of HT function
Both endocrine and neural regulation
Parvocellular:
Medial - secrete CRH
Dorsal/Ventral - neurons project to medulla & spinal cord to exert autonomic control. Se(x)crete oxytocin and vasopressin (neuromodulators)
Magnocellular:
Two distinct populations control endocrine function, se(x)creting right into the posterior pituitary
Visceral afferents
CN VII IX X contain visceral info
They project to the nucleus of the solitary tract.
Relayed to parabrachial nucleus
Projects to hypothalamus and other limbic structures.
Indirect control of autonomic responses
Comes from cortex, amygdala, periaqueductal grey
Hypothalamus - Neural Input, Neural Output
Controls ANS (emotion)
Hypothalamus - Neural Input, Hormonal Output
Oxytocin release for galactorrhea
Hypothalamus - Hormonal Input, Neural Output
Drives and motivated behavior (SEXXXXXX)
Hypothalamus - Hormonal Input, Hormonal Output
Vasopressin release for anti-diuresis
Servo-Control Systems
Thermostat
Receives sensory info and feedback signals
Compares with biological set points
Adjusts ANS, endocrine and behavioral responses aimed at maintaining homeostasis
Temperature Regulation
Systemic pyrogens such as IL-1 can cross BBB and increase biological set point, causing fever.
HT contains feedback detectors.
Peripheral receptors transmit info through temperature pathways to CNS.
Central receptors in anterior hypothalamus that modulate their activity related to blood temperature.
Combination of peripheral and central receptors
Lesion Anterior hypothalamus
Chronic hyperthermia
Anterior HT decreases internal temperature
Stimulate Anterior Hypothalamus
Dilate blood vessels, suppress shivering.
Anterior HT decreases internal temperature
Lesion Posterior hypothalamus
Hypothermia if placed in cold environment
Posterior HT increases internal temp
Stimulate Posterior Hypothalamus
Shiver & constrict blood flow
Posterior HT increases internal temp
Long term exposure to cold
Increased HT secretion of TRH, resulting in increased TSH and T4, increasing body heat by increasing tissue metabolism
Animals adjust their food intake to achieve normal body weight
Cool
Hypothalamic contribution to food intake
Feeding center
Satiety center.
Lesions of Ventromedial hypothalamus
Hyperphagia & obesity
Ventromedial must control satiety
Lesions of Lateral hypothalamus
Aphagia & starvation
Lateral must control food intake
Caloric homeostasis
Arcuate Nucleus
Paraventricular Nucleus
Lateral Hypothalamic Area
Insulin & Leptin hit the ARC
In response to these particular signals, ARC INHIBITS NPY/AgRP because they are anabolic, stimulating LHA and inhibiting PVN
Meanwhile, ARC EXCITES Alpha-MSH/CART, stimulating PVN & inhibiting LHA
PVN releases CRH & Oxytocin
LHA releases MCH & Orexins
PVN
Catabolic
LHA
Anabolic
Adiposity Signals Pathways
Leptin and Insulin circulate in concentrations proportional to body fot content and energy balance
Act on central effector pathways in the hypothalamus
Activating catabolic pathways, inhibiting anabolic pathways
Chronic Leptin Deficiency
Less PVH innervation from ARC
Can be rescued by leptin treatment DURING DEVELOPMENT
