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LIMBIC SYSTEM

LECTURE 12 DR.ZAHOOR. LIMBIC SYSTEM. LIMBIC SYSTEM. Limbic System works for 1. Emotion 2. Behavior 3. Motivation 4. Memory (we will discuss in next lecture). LIMBIC SYSTEM. We will study Limbic System under the heading 1) History

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LIMBIC SYSTEM

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  1. LECTURE 12 DR.ZAHOOR LIMBIC SYSTEM

  2. LIMBIC SYSTEM Limbic System works for 1. Emotion 2. Behavior 3. Motivation 4. Memory (we will discuss in next lecture).

  3. LIMBIC SYSTEM We will study Limbic System under the heading • 1) History • 2) Functional Anatomy • 3) Functions • 4) Experiments done in animals • 5) Chemical transmitters • 6) Clinical applications.

  4. LIMBIC SYSTEM 1- History • - Rhincephlon in RATS was first identified. • Why it was named Rhincephalon? • Because Rats are led by Olfactory stimuli. • Than name was changed to LIMBIC SYSTEM because all animals are not guided by olfactory stimuli.

  5. WHAT IS LIMBIC SYSTEM? It is ring of Fore brain structures that surround the brain stem 2. Functional Anatomy Limbic System includes i). Amgdala ii). Hippocampus iii). Cingulate gyrus iv). Portions of hypothalamus v). Portions of thalamus Vi) Portions of basal nuclei vi). Portions of lobes of cerebral cortex [limbic association cortex]

  6. Schematic of the Limbic System Components

  7. Location of the Limbic System Figure 58-4; Guyton & Hall

  8. LIMBIC SYSTEM • Limbic System nuclei are connected by neuron pathway 3. We will discuss the functionsof Limbic System 1. Emotion 2. Behavior 3. Motivation

  9. Functions 1. Emotions • Emotion means feelings, mood, anger, happiness, fear, and physical responses associated with these feeling e.g. laughing, crying Important – Input processed and giving rise to sensation of FEAR is in Amygdala, it lies in temporal lobe

  10. Functions2. Behavior • Control of behavior is under the limbic system and higher cortex e.g. behavior of survival – search for food, attack, socio-sexual behavior response

  11. Functions3. Motivation • It is well known that person reinforces behavior that has proved gratifying and suppresses that behavior which are associated with unpleasant experience • Areas in limbic system are named as - Reward center - Punishment center

  12. Functions3. Motivation [cont..] Why we call reward and punishment center? • Because stimulation in these areas give rise to pleasant and unpleasant sensations • Reward center – are found in regions of behavior activities of eating, drinking • Punishment center – are found in regions of pain

  13. LIMBIC SYSTEM – Different areas Cingulate Gyrus Cingulate Gyrus – situated above corpus callosum Functions • - Sociable adaptable • - Maternal behavior – care of offspring ( Animal who eat offspring has no cingulate gyrus) • - Emotional behavior Dysfunction causes - Addictions to drugs– seeking pleasure

  14. LIMBIC SYSTEM AMGDALA AMGDALA Functions • - Sociability – more social, more friends • - Fear response • - Pleasure • - Post traumatic stress • - Aggression • - Memory

  15. LIMBIC SYSTEM Hippocampus Hippocampus – (Sea horse) Located in Temporal lobe Functions - Memory – Short term and Long term memory. If damage to hippocampus, patient cannot make long term memory. - damage causes anterograde amnesia

  16. Hippocampus FUNCTIONS [CONT..] • reward and punishment determine whether or not information will be stored as memory • If no reward or punishment, it is hardly remembered but a person learns any sensory experience that causes pain or pleasure and makes strong memory trace • hippocampus provides the drive to rehearse and consolidate these sensory experiences IMPORTANT First area to show damage in ALZEHIMER DISEASE is Hippocampus

  17. Limbic Cortex FUNCTIONS • cerebral association area functions for control of behavior • stimulation of various portions of this area can elicit almost all types of behavior in an animal

  18. LIMBIC SYSTEM • HYPOTHALAMUS • Major part of Limbic system, it plays role in • - Behavioral control , body temperature, osmolality of body fluids, control of body weight ( eating and drinking ) • - These internal functions are called VEGETATIVE functions of brain and are closely related to Behavior.

  19. 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

  20. 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

  21. Functional Areas of the Hypothalamus Figure 58-6; Guyton & Hall

  22. Behavior and its Control • Reward and punishment causes the Limbic system so that we can learn. If no reward or punishment we ignore. • Several limbic structures are concerned with sensory experience–is it pleasant or unpleasant? • Reward center -the lateral and ventromedial hypothalamus, thalamus certain areas, Amygdala, • Punishment center - located in hypothalamus and thalamus, Amygdala and Hippocampus Punishment always takes precedent over reward. Punishment can frequently inhibit reward center.

  23. 4. Experiments done in rats • - Experiments done in animals to see behavioral response to Reward and Punishment. • - What was found ? • - It was found if electrical stimulus is rewarding, animal presses the button more often , positive reinforcement. • - But if electrical stimulus causes pain , animal decreases the rate of pressing the bar. So if punishment , we do not do the things again.

  24. Emotional Behavior • Cerebral cortex plays major role in directing many motor responses during emotional behavior e.g. to do or avoid situation, or modulation, or inhibition of emotional behavior.

  25. 5. NEUROTRANSMITTERS IN PATHWAYS OF EMOTIONS AND BEHAVIOR These are 1. Norepinephrine 2. Dopamine 3. Serotonin

  26. NEUROTRANSMITTERS IN PATHWAYS OF EMOTIONS AND BEHAVIOR • Norepinephrine and dopamine are catecholamines, that are present in regions that elicit highest rate of self stimulation – DO IT YOURSELF • That is why amphatamine [stimulant] is used in depression. It causes increased release of dopamine from dopamine secreting neurons

  27. OTHER EFFECT OF DOPAMINE • Many drugs increase dopamine in pleasure pathways in limbic system, therefore, cause intense sensation of pleasure e.g. cocaine • Cocaine blocks re-uptake of dopamine at synapses

  28. 6. Clinical Application Limbic System defects 1- Depression • It is psychiatric disorder associated with defect in limbic system neurotransmitters • In depression, neurotransmitter is decreased which is Norepinephrine or serotonin or both NOTE – Depression is not neurological disorder i.e. there is no lesion in the brain

  29. DEPRESSION Symptoms in depression are - Loss of interest - Negative mood - Inability to experience pleasure - Suicidal tendency

  30. TREATMENT FOR DEPRESSION Anti-depressant drugs are used - Prozac – blocks re-uptake of released serotonin, therefore, there is increased serotonin at synapses - Amphetamine – causes increase release of Dopamine .

  31. Clinical Application • Alzheimer disease • Memory loss- recent memory can not be converted to long term memory ( Ante grade Amnesia)

  32. THANK YOU

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