Physiology of Limbic System by Dr. Roomi

7/31/2019 Physiology of Limbic System by Dr. Roomi

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PHYSIOLOGY of

LIMBIC SYSTEMBY

DR. MUDASSAR ALI ROOMI (MBBS, M. PHIL)


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Limbic system: (shown in dark pink)

Limbic = border Definition : limbic system means the

entire neuronal circuitry that controlsemotional behavior and motivationaldrives.

It consists of a core of cortical anddiencephalic structures found on themedial aspect of each hemisphere.

It is often referred to as the emotional nervous system

Limbic system is connected to thereticular formation of brainstem

through the medial forebrain bundle*** Limbic system consists of: Limbic cortex Associated deep structures


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Limbic cortex: Consists of a ring of cortical

tissue around the hilus of cerebral hemisphere.

Phylogenetically, limbiccortex is the oldest part of the cerebral cortex.

It consists of: Orbitofrontal cortex

Sub-callosal gyrus Cingulate gyrus Parahippocampal gyrus Uncus


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Associated deep structures:

Consist of: Septum area Para-olfactory area

Epithalamus Anterior thalamic nuclei Hypothalamus Portion of Basal Ganglia Amygdala Hippocampus


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Reward and Punishment Function of the Limbic System

Reward Centers:1. lateral and

ventromedial nuclei of the hypothalamus.

2. Centres are also foundin the septum, theamygdala, certain areasof the thalamus andbasal gangia.

Punishment Centers:1. central gray area

surrounding theaqueduct of Sylvius inthe mesencephalon

2. periventricular zones of the hypothalamusandthalamus.

3. some locations in theamygdala andhippocampus.


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Importance of Reward or Punishment inLearning and Memory Habituation VersusReinforcement


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Functions of Limbic System:

Olfaction Control of emotions & behavior Control of food intake, water intake & body

weight Control of sexual functions Involved in recent memory Body temperature regulation Regulation of osmolality


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Diseases of the Limbic System

There are several well known diseases that aredisorders of the limbic system. A few are:1.Psychosis2.Schizophrenia

3.Depression


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Diseases of the Limbic System SCHIZOPHRENIA Cause : An increased dopamine

response in the limbic system resultsin schizophrenia.

Symptoms of schizophrenia are: 1.Loss of touch with reality 2.Decreased ability to think and

reason 3.Decreased ability to

concentrate 4.Decreased memory 5.Regress in child-like behavior 6.Altered mood and impulsivebehavior 7.Auditory hallucinations

DEPRESSION Cause: Depression is caused by

decreased levels of NE and/orserotonin in the limbic system.

Symptoms of depression are: 1.Intense sadness and despair 2.Anxiety 3.Loss of ability to concentrate 4.Pessimism 5.Feelings of low self esteem 6.Insomnia or hypersomnia 7.Increased or decreased

appetite 8.Changes in body temperature

and endocrine gland function


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Amygdala: Has a center for

punishment Involved in olfaction

(important in animals) Control of behavior &

emotion Control of sexual function In monkeys, bilateral

destruction of amygdalaKLUVER BUCY

SYNDROME


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Effects of Bilateral Ablation of the Amygdala

The Klver-Bucy Syndrome

Excessive tendency to put objects into mouth(hyperorality)

Changes in behavior of animal (psychic blindness) has extreme curiosity about everything Animal becomes tame & placid forgets rapidly Change in dietary habits Herbivorous animal carnivorous Over-sexuality Anterograde amnesia


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Features and Functions of hippocampus:

Has a center for punishment Role in control of behavior & emotions On weak electrical stimulation epilepsy-like fit. Probably one of the reasons for this hyperexcitability of the

hippocampi is that they have a different type of cortex from thatelsewhere in the cerebrum, having only three nerve cell layers insome of its areas instead of the six layers found elsewhere.

Fit is accompanied by hallucination (tactile / visual / olfactory /auditory)

In some patients of epilepsy, removal of hippocampus gives benefit. It is our memory consolidation centre .**** Bilateral destruction of hippocampus anterograde amnesia (loss

of recent memory)


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Anterograde amnesia (loss of recent memory)

Patient is not able to learn new events orskills. Even not able to remember names & faces of

person, to whom the patient meet. Old memory remains intact. Hippocampus is involved only in recent

memory. ***


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thalamus Major part of the

diencephalon Medial wall makes the

lateral wall of the 3 rd

ventricle Lateral surface is separated

from lentiform nucleus byinternal capsule

It is divide into 3 parts by aY-shaped internal medullarylamina: anterior, medial andlateral parts.


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Main nuclei in three parts of THALAMUS

1. Anterior part : Anterior thalamic nuclei

2. Medial part: Dorsomedial nucleus

3. Lateral part: Dorsal group:

Lateral dorsalLateral posteriorpulvinar

Ventral group:Ventral anteriorVentral lateralVentral posterior (VPL,VPM)

VENTRAL POSTROLATERAL (VPL):receives nerve fibers from main sensorytracts through medial and spinalleminisci. ***

VENTRAL POSTROMEDDIAL (VPM):Receives fibers from trigeminal andgustatory pathway. ***


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Functions of thalamus

1. Main or principal sensory relay station***2. Subcortical centre for pain***3. Thalamus helps to maintain the level of

alertness and consciousness4. Also involved in the control of motor activity5. Involved in long-term memory process6. Involved in sleep mechanism

7. Anterior thalamic nuclei..parts of limibicsystem***

8. Centre for sexual sensations.


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Thalamic syndrome Due to degenration of ventral posterior (VPL, VPM) part of

the thalamus resulting from thrombosis in a branch of posterior cerebral artery.

Anterior and medial nuclei remain intact

Features fo thalamic syndrome:1. Loss of all the somatic sensations from C/L side of the body(touch, pain, temperature, proprioception, vibration)

2. Ataxia due to loss of proprioception3. Astereognosis

4. Spontaneous burning or aching pain (resistant to analgesicdrugs)5. hyperalgesia6. Amelognosia (illusion that limb is absent)

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Physiology of Limbic System by Dr. Roomi