1. THE LIMBIC SYSTEM

2. LEARNING OBJECTIVES Define limbic system
Know the different parts and function of
Limbic system
Describe the functions of various parts of
Hypothalamus

3. 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

4. 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

5. Schematic of the Limbic System Components

7. Location of the Limbic System

8. 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

9. 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

10. Functional Areas of the Hypothalamus

11. 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

12. 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 experience–is 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

14. 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 one’s status with respect to the surroundings and current thoughts
helps pattern behavior appropriate for the each occasion

15. 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

16. 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

17. 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

18. Functions of limbic system
Part Function
Amygdala aggression & fear
Cingulate gyrus autonomic functions
Hippocampus recent memory
Mammilary body long memory
Prefrontal cortex personality

19. Malfunction of limbic system
Leads to psychiatry disorders e.g.
Schizophrenia, depression and senile dementia
Lesions in hippocampus:
loss of recent memory, in Alzheimer’s
disease there is extensive degeneration of
hippocampus
Lesions in Amygdaloid nucleus:
loss of aggressive behavior, fear and anger

20. 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