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Transcript
Cell Bio 12- Hypothalamus Hypothalamus serves as an integrator of somatic, visceral, endocrine, and immune functions The hypothalamus exerts CNS and systemic influences by two mechanisms: 1. Neural (local circuits, afferent and efferent projections) 2. Neurohumoral (i.e., hormonal, vascular, neuroendocrine functions, neuroimmune influences) Cell Bio 12- Hypothalamus Afferent Connections to the Hypothalamus The fornix conveys afferent fibers from the hippocampus, it is an importat fiber tract of the limbic system The medial forebrain bundle transmits afferent fibers from the olfactory areas to the preoptic nuclei The stria terminalis conveys afferent fibers from the amygdala The peduncle of the mamillary bodies transmits visceral afferent fibers Efferent Connections from the hypothalamus The dorsal longitudinal fasciculus reaches to parasympathetic nuclei (3,7,9, 10) The mamillotegmental tract distributes efferent fibers to the tegmentum of the midbrain; these are then relayed to the reticular formation. The fibers of this tract mediate the exchange of autonomic information between the hypothalamus, cranial nerve nuclei, and spinal cord The mamillothalamic fasciculus connects to cingulate gyrus Hypothalamic - hypophyseal tract communicates with pituitary gland Cell Bio 12- Hypothalamus Pituitary Vasculature and Hypothalamic Hormone Delivery (Neurosecretion) Portal veins branch into another series of capillaries within the anterior pituitary Capillaries in anterior and posterior pituitary coalesce into veins that drain into systemic venous blood. Medial Preoptic Nucleus: Is characterized by sexual dimorphism involving hormonal influences on neuronal maturation Contains high density of gonadotropin-releasing hormone producing neurons which synthesize large peptides that are directed at target cells in the anterior pituitary Anterior preoptic region: maintains constant body temperature Suprachiasmatic nucleus.: receives direct retinal input; circadian rhythm Cell Bio 12- Hypothalamus Paraventricular and Supraoptic Nuclei: o Neurosecretory cells whose axons project to posterior pituitary o Paraventricular nucleus secrete oxytocin, o Supraoptic nucleus secrete vasopressin. Posterior Pituitary (Neurohypophysis) Paraventricular and supraoptic nuclei contain neurons that produce oxytocin or vasopressin Hormones travel down axon by axonal transport and are stored and released at terminals in the posterior pituitary Hormones released into systemic circulation upon excitation Systemic feedback to hypothalamus via CircumVentricular Organs (OVLT and SFO) Cell Bio 12- Hypothalamus Dorsomedial and Ventromedial Nuclei.: o Neurons involved in feeding, reproductive, and parenting behavior, thermoregulation Anterior nuclei: regulate appetite and food intake. Medial part lesion causes obesity, lateral part lesion causes anorexia Posterior Hypothalamic Region : Temperature regulation function has been assigned. Responds to temperature changes, such as sweating. Lesion causes hypothermia Also, arousal, shift of attention; especially as a function of behavioral states mediated by hypothalamus Mammillary body: involved in limbic forebrain and midbrain functional integration Inflammatory response-associated chemicals (cytokines) which may influence thyroid function during severe infection (sepsis) through systemic feedback to hypothalamus Cell Bio 12- Hypothalamus Lesions in certain cortical regions can be associated with severe autonomic dysfunctions Limbic system o Amygdala o Cingulate gyrus o Lateral septal nuclei o Insular cortex, others Cortical influences on hypothalamic output leading to altered behavioral states o Emotion, pain o “Drives”: hunger, thirst, sex o Fight or flight o Forms of anxiety Cell Bio 12- Hypothalamus __________________________________________________________________________________________________ Cell Bio 12- Hypothalamus _________________________________________________________________________________________________ Cell Bio 12- Hypothalamus __________________________________________________________________________________________________ Hypothalamic Nuclei Involved in sleep Activation of VLPO neurons contributes to the onset of sleep lesions tends to produce insomnia __________________________________________________________________________________________________ Cell Bio 12- Hypothalamus __________________________________________________________________________________________________