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The limbic system. Neuronal circuitry controls of emotional behavior and motivational drives Composed of subcortical and cortical components. Limbic System. Figure 12.18. limbic. Subcortical group.
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The limbic system • Neuronal circuitry controls of emotional behavior and motivational drives • Composed of subcortical and cortical components
Limbic System Figure 12.18
Subcortical group Hypothalamus ,septum,paraolfactory area,epithalamus,ant.thalamic nuclei,hippocampus,amygdala,basal gangeli
Limbic cortex • Orbitofrontal coretx,subcallosal gyrous cingulate gyrus and parahippocamp gyrous
Limbic System: Emotion and Cognition • The limbic system interacts with the prefrontal lobes, therefore: • One can react emotionally to conscious understandings • One is consciously aware of emotion in one’s life • Hippocampal structures – convert new information into long-term memories
The hypothalamus not only influences how you feel, it influences how you interpret the consequences of those feelings.
Hypothalamic Role in Emotion HypothalamicNuclei VisceralAfferents HormonalOutput Nucleusof the Solitary Tract TargetOrgans AutonomicOutput AutonomicPreganglionicNuclei Brain StemNuclei
Hypothalamus PituitaryReleasing Factors AutonomicNervous System Sympathetic Neurohypophysis(Posterior Pituitary) Adenohypophysis(Anterior Pituitary) Parasympathetic
striaterminalis Amygdala mtt Anterior Nucleus dorsal long.fasciculus Brainstem medial forebrainbundle Cortex, septum Hypothalamus ventralroute medialforebrainbundle Brainstemspinal cord Amygdala parvo magno(SO, PV) ant. post. Pituitary
Hypothalamus,Major • Hypothalamus is the most important output sorce • It communicate with brain stem by medial forebrain bundle ,bidirectionaly between forebrain and brain stem
Hypothalamus cont. • Controls: 1-vegetative and endocrine functions 2-behavior and motivation
vegetative and endocrine functions • Cardiovascular regulation involves 1-Post. And lateral hypothalamus area, increase BP and HR. 2-preoptic area ,decrease BP and HR *1and 2 mediated by cardiovascular centre in the pontile and medullary part of reticular formation
Body temperature regulation • Preoptic area
Thermo-regulation (body temperature) • Involves autonomic nervous, endocrine, and skeletomotor systems • Body temperature detectors • Peripheral: skin, spinal cord, viscera • Central: anterior hypothalamus • Body temperature effectors • Heat retention or generation: posterior hypothalamus • Heat dissipation: anterior hypothalamus
Thermo-regulation (body temperature) • Heat dissipating mechanisms • Dilation of blood vessels in the skin • Inhibition of shivering • Heat conserving mechanisms • Vasoconstriction of blood vessels in the skin • Shivering • Increased secretion of thyroxin
Response to Cold Response to Heat Methods of thermo-regulation by the body
Regulation of body water intake • Thirst centre,lateral hypothalamus • Electrolyte concentrationmaking desire to drink • Supraopticx:urinary excrition due to ADH
Thirst • Function of serum osmolality and blood volume • Osmotic receptors in the hypothalamus • Volume receptors in the right atrium of the heart and great veins • Vasopressin release from hypothalamus • Increases water reabsorption from the kidney • Inhibited by ethanol
Circadian Rhythm • Oscillations during the course of the day • Corticosteriods • Feeding and drinking behavior • Growth hormone secretion • Lesions of the suprachiasmatic nuclei of the hypothalamus disrupts these oscillations
Feeding • Complex interaction of many systems • Regulation of energy metabolism by the Ventromedial and Lateral nuclei of the hypothalamus • Physical Lesions produce hyperphagia and obesity or reduced attention to food. • Amygdala may also be involved indirectly • Lesions produce hyperphagia-like symptoms • Ventromedial hypothalamic lesions also cause increased insulin secretion Obesity.
Feedback Mechanisms Controlling Feeding • Feedback from gut hormones • e.g. Cholecystokinin • Released from small intestine in response to feeding • Inhibits or suppresses feeding
Uterine contraction and milk ejection • Oxytocin stimulation by PARAVENTRICULAR
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Hippocampus circuit • Ent. cortex From perforant To dentate gyrous mossy fiber cA3 schaffer collaterals cA1 to subiculum to ento cortex