THE LIMBIC SYSTEM

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THE LIMBIC SYSTEM
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LEARNING OBJECTIVES

• Define limbic system
• Know the different parts and function of
• Limbic system
• Describe the functions of various parts of
• Hypothalamus

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LIMBIC SYSTEM

• Limbic means the structure which lies on medial
  rim of brain between cerebral cortex
  hypothalamus
• Limbic system is a set of brain structure
• including hippocampus, amygdala, ant.
  thalamic nuclei and limbic cortex

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Limbic System

• Not a separate structure but a ring of forebrain
  structures that surround the brain stem
• Responsible for
• Emotions , long term memory, olfaction
• Basic, inborn behavioral patterns related to
  survival and perpetuation of the species
• Plays important role in motivation and learning

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Schematic of the Limbic System Components
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Location of the Limbic System
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Hypothalamus

• major output pathway of the limbic system
• vegetative functions
• neurogenic control of arterial pressure
• regulation of body temperature
• regulation of fluid volume
• regulation of endocrine gland secretion
• growth hormone, thyroid hormone,
• glucocorticoid secretion, sex hormones

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Behavioral Functions of the Hypothalamus and
Related Areas

• lateral hypothalamus
• eating, thirst, general level of activity, rage
• ventromedial nucleus
• satiety, tranquillity
• periventricular nucleus
• fear, punishment reactions
• anterior and posterior hypothalamus
• sexual drive

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Functional Areas of the Hypothalamus
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Hypothalamus

• Brain area most involved in directly regulating
  internal environment
• Functions
• Controls body temperature
• Controls thirst and urine output
• Controls food intake
• Controls anterior pituitary hormone secretion
• Produces posterior pituitary hormones
• Controls uterine contractions and milk ejection
• Serves as a major ANS coordinating center
• Plays role in emotional and behavioral patterns
• Participates in sleep-wake cycle

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Behavior and its Control

• Almost all behaviors are associated with either
  reward or punishment.
• Several limbic structures are concerned with the
  affective nature of the sensory experienceis it
  pleasant or unpleasant?
• Reward center - located around medial forebrain
  bundle (the lateral and ventromedial
  hypothalamus).
• Punishment center - located in central gray
  around the aqueduct and extending into
  periventricular zones of hypothalamus and
  thalamus.
• Punishment always takes precedent over reward

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Function of Other Limbic Areas

• Amygdala
• receives input from other areas of limbic system
  as well as most areas of the cortex
• sends output back to cortex as well as into
  hippocampus, septum, and hypothalamus
• functions in behavioral awareness at the
  semiconscious level
• projects into limbic system ones status with
  respect to the surroundings and current thoughts
• helps pattern behavior appropriate for the each
  occasion

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Function of Other Limbic Areas

• Hippocampus
• originated as part of the olfactory cortex
• in lower animals the sense of smell is an
  important determinant of behavior (is it good to
  eat, does it smell like danger, is it sexually
  inviting)
• therefore, the early hippocampus was involved in
  decision making by determining the importance of
  the incoming information

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Hippocampus

• memory and learning, (in remembring recent
  events)
• damage causes anterograde amnesia
• reward and punishment determine whether or not
  information will be stored as memory
• a person becomes habituated to indifferent
  stimuli but learns any sensory experience that
  causes pain or pleasure
• hippocampus provides the drive to rehearse and
  consolidate these sensory experiences

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Limbic Cortex

• cerebral association area, Role in anger, fear
  and emotional behavior with sexual behavior
• stimulation of various portions of this area can
  elicit almost all types of behavior in an animal

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Functions of limbic system

• Part
  Function
• Amygdala aggression
  fear
• Cingulate gyrus autonomic
  functions
• Hippocampus recent memory
• Mammilary body long memory
• Prefrontal cortex personality

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Malfunction of limbic system

• Leads to psychiatry disorders e.g.
• Schizophrenia, depression and senile
  dementia
• Lesions in hippocampus
• loss of recent memory, in Alzheimers
• disease there is extensive degeneration
  of
• hippocampus
• Lesions in Amygdaloid nucleus
• loss of aggressive behavior, fear and
  anger

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References

• Human physiology by Lauralee Sherwood,
  seventh/eighth edition
• Text book physiology by Guyton Hall,
• 12th edition
• Text book of physiology by Linda .s contanzo,
  third edition