The limbic system

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The limbic system

• Neuronal circuitry controls of
  emotional behavior and motivational drives
• Composed of subcortical and cortical components

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Limbic System
Figure 12.18
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limbic
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Subcortical group

• Hypothalamus ,septum,paraolfactory
  area,epithalamus,ant.thalamic nuclei,hippocampus,a
  mygdala,basal gangeli

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Limbic cortex

• Orbitofrontal coretx,subcallosal gyrous cingulate
  gyrus and parahippocamp gyrous

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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 ones life
• Hippocampal structures convert new information
  into long-term memories

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The hypothalamus not only influences how you
feel, it influences how you interpret the
consequences of those feelings.
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limbic
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Hypothalamic Role in Emotion
HypothalamicNuclei
VisceralAfferents
HormonalOutput
Nucleusof the Solitary Tract
TargetOrgans
AutonomicOutput
AutonomicPreganglionicNuclei
Brain StemNuclei
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Hypothalamus
PituitaryReleasing Factors
AutonomicNervous System
Sympathetic
Adenohypophysis(Anterior Pituitary)
Neurohypophysis(Posterior Pituitary)
Parasympathetic
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I feel fear!
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striaterminalis
Amygdala
mtt
Anterior Nucleus
dorsal long.fasciculus
Brainstem
medial forebrainbundle
Cortex, septum
Hypothalamus
ventralroute
medialforebrainbundle
Brainstemspinal cord
Amygdala
magno(SO, PV)
parvo
post.
ant.
Pituitary
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Hypothalamus,Major

• Hypothalamus is the most important output sorce
• It communicate with brain stem by medial
  forebrain bundle ,bidirectionaly between
  forebrain and brain stem

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Hypothalamus cont.

• Controls
  1-vegetative and endocrine
  functions 2-behavior and
  motivation

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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
  

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Body temperature regulation

• Preoptic area

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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

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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

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Response to Cold
Response to Heat
Methods of thermo-regulation by the body
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Regulation of body water intake

• Thirst centre,lateral hypothalamus
• Electrolyte concentrationmaking desire to drink
• Supraopticxurinary excrition due to ADH

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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

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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

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Control of Feeding
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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.

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Feedback Mechanisms Controlling Feeding

• Feedback from gut hormones
• e.g. Cholecystokinin
• Released from small intestine in response to
  feeding
• Inhibits or suppresses feeding

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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