LIMBIC SYSTEM

DR NILESH KATE
MBBS,MD
ASSOCIATE PROF
ESIC MEDICAL COLLEGE, GULBARGA.
DEPT. OF PHYSIOLOGY
LIMBIC SYSTEM

OBJECTIVES.
 Limbic system
 Physiological anatomy
 Functions
 Physiology of Emotions.
 Components
 Theories of genesis
 Emotional behavior.
 Neural substrate.
 Physiology of Motivation.
 Physiological basis of psychotic disorders.

PHYSIOLOGICAL ANATOMY
 Components of limbic
system.
 Limbus – Ring.
 That part of cortex &
subcortical structure that
form ring around brain
stem.
 Earlier called –
Rhinencephalon – related
to Olfaction.
Wednesday, April 25, 2018

 Limbic cortex –
Phylogenetically
older part
(allocortex)
 Composed of
 Orbitofrontal cortx
 Subcallosal gyrus
 Cingulate gyrus.
 Parahippcampal gyrus.
 Uncus.

 Sub cortical structures
includes –
 Hypothalamus
 Septum
 Paraolfactory area
 Anterior nuclei of thalamus.
 Amygdala
 Portions of basal ganglia
 Hippocampus.

CONNECTIONS
 Papez circuit
 Closed circuit formed by
connections between 4
nuclei.
 Responsible for resting
EEG.
 For emotions & behaviour
for preservation of species
& individuals.

EFFERENT PROJECTIONS OF
LIMBIC SYSTEM.

CHARACTERISTIC FEATURES
OF CONNECTIONS.
 Very little connections with Neo-cortex.
 So Emotions & Instinctual behaviour not under
voluntary control.
 Prolonged After discharge – So emotional response
continue long after end of stimuli which produces
them.

FUNCTIONS
 Autonomic functions.
 Regulation of feeding behavior.
 Regulation of sexual behavior and reproduction.
 Neural control
 Endocrinal control.
 Maternal behavior
 Emotional behavior.
 Motivational behavior.

AUTONOMIC FUNCTIONS.
 Stimulation of mainly
– Amygdala through
Hypothalamus causes
Autonomic response.
 During emotional
state mainly affect
 Cardiovascular system
 Respiratory system
 GIT.

REGULATION OF FEEDING
BEHAVIOR.
 Hypothalamus – Regulate
food intake through feeding
centre & satiety center.
 Amygdala – stimulation
produces movement
associated with eating
(chewing, swallowing,
licking)
 Lesion – Produces
Hyperphagia.

REGULATION OF SEXUAL
BEHAVIOR AND REPRODUCTION.
 Basic sex drive (urge to copulate) is
instinctual behaviour as food intake.
 Function of limbic system & Hypothalamus,
influenced by sex hormones & cortex.
 Controlled by Neural & Endocrinal factors.

NEURAL CONTROL
 Role of Neo cortex &
Limbic cortex
 Mainly frontal region
stimulate sex
behaviour.
 Pyriform cortex
overlying Amygdala
inhibits sex drives in
males.

NEURAL CONTROL
 Role of Hypothalamus
 Ant Hypothalamus & median
Forebrain bundle elicit sex
behaviour
 Role of Encephalization –
Largely Encephalized –
perception that sexual act
produces pleasure – is a big
cause
 Also sexual Behaviour is
strongly influenced in human
being – by social customs,
rules & social taboo.

ENDOCRINAL CONTROL
 Role of Gonadal hormones.
 In Males – Testosterone stimulate
 In Females – Oestrogen raised during oestrous period.
Sexual activity slightly increased during ovulation.
 Role of Pheromones –
 Chemicals by their smell acts as sex attractant.

MATERNAL BEHAVIOR
 Function of Cingulate
Gyrus & Retro splenial
portion of limbic cortex.
 In animals mainly
Neurogenic – Depend
on olfactory, auditory,
visual & Themotactile
stimuli from younger
ones.

EMOTIONAL BEHAVIOR.
 Most important
function of limbic
system.

MOTIVATIONAL BEHAVIOR.
 Most important
function of Limbic
system.

PHYSIOLOGY OF EMOTIONS
 Emotions – Aroused
state having intense
feeling, Autonomic
activation & related
behaviour.
 Components
 Mental
 Physical (exa- Response
of individual to sudden
very loud sound)

MENTAL OR SENSORY
COMPONENT
 Cognition – by which
one become aware &
recognises the sound.
 Affect – German word
means development of
feeling. (frightening)
 Conation – force which
direct to take some
action (Run away)

PHYSICAL OR EXPRESSIVE OR
PERIPHERAL COMPONENTS
 Motor side of emotional
behaviour
 2 components
 Somatic – changes in skeletal
muscle, running away is somatic
part.
 Autonomic – includes
coordinated activity of
sympathetic & parasympathetic
 HR, BP, Respiratory rate

THEORIES OF GENESIS OF
EMOTIONS
 Arnold theory.
 By Cognition – aware &
recognition
 By Unconcious
evaluation – Judged as
harmful or Beneficial.
 Affect – Concious
reflection of unconscious
appraisal. (Fear, Joy,
Grief or Rage)

EMOTIONAL BEHAVIOUR
 Behaviour – is
expression of
emotions.
 Rage, fear and
Placidity.
 Sexual behaviour
 Feeling of Reward and
Punishment.

NEURAL SUBSTRATE OF
EMOTIONS
 Role of central Nervous system.
 Role of cerebral cortex.
 Role of Hypothalamus.
 Role of Amygdala.
 Role of Hippocampus.
 Role of peripheral Nervous system.
 Autonomic
 Somatic motor.

ROLE OF CEREBRAL CORTEX.
 Frontal, cingulate &
parahippocampal
cortices play imp role in
Affective component.
 Provide mechanism by
which Memory and
imagination evoke
Emotional feeling.

ROLE OF CEREBRAL CORTEX.
 Also directs Motor responses to external
events.
 It also helps in Modulation, Direction,
Understanding or inhibition of emotional
behaviour.

LIMBIC CORTEX
 Ant temporal cortex
– Gustatory &
Olfactory association.
 Parahippocampal
Gyrus – Auditory
association.
 Post singulate cortex
– Sensory motor
association.

ROLE OF HYPOTHALAMUS.
 Lat hypothalamus– stimulation – Rage & Aggression
 Ant & Post portion – Sexual arousal
 Reward center – Feeling of reward, tranquility & pleasure.
 Punishment center – Feeling of punishment, fearing &
aversion.

ROLE OF AMYGDALA.
 Amygdala – cells located above inferior horn of
lat ventricle in uncus.
 2 subdivisions – Corticomedial & Basolateral (play
role in Behavioral activities)

ROLE OF AMYGDALA.
 Afferent – from cortex & Limbic system – so called
“WINDOW” through which limbic system sees place
of person in the world.
 Efferent – To cortex, Hippocampus, septum,
Thalamus & Hypothalamus.

KLUVER BUCY SYNDROME
 Bilateral destruction of temporal lobe –
 Extreme orality
 Loss of fear
 Decreased aggressiveness.
 Change in eating behaviour
 Hypersexuality
 Psychic blindness.

ROLE OF HIPPOCAMPUS.
 Connections – Mainly to cerebral cortex.
 Stimulation – evoke Rage, Passivity & excessive
sexual drive.
 Functions – Provide signal for memory
consolidation, transformation from short term to
long term memory.

ROLE OF PERIPHERAL
NERVOUS SYSTEM.
 Autonomic nervous system
 Canon described response of ANS in emergency
 Somatic motor nervous system
 Involved in physical component of emotions – skeletal
muscle movements.

PHYSIOLOGY OF MOTIVATION.
 Neural mechanism of
Motivation based on
 Concept of reward &
Punishment.

ROLE OF
NEUROTRANSMITTERS
 Drugs that increases stimulation of reward center.
 Amphetamine
 Nicotine & Alcohol
 cocaine
 Drugs that Decreases stimulation of reward center.
 Drugs which inhibit activity of Catecholamines – Chlorpromazine
Hydrochloride.

PHYSIOLOGICAL BASIS OF
PSYCHOTIC DISORDERS
 Depression
 Mania
 Schizophrenia.

DEPRESSION
 When Mood
chronically remains
down without any
specific reason
 Signs & symptoms –
lack of interest,
suicidal tendency,
excessive sleep &
overeating.

DEPRESSION
 Causes – decreased
activity of
noradrenergic or
serotonergic fibres.
 Treatment –
 MAO inhibitors,
tricyclic
antidepressants.

MANIA
 Mood remain
chronically Elated
without any reason.
 Due to over activity of
Nor-adrenergic fibre
activity.

SCHIZOPHRENIA.
 There is false
perception of sensation
(Hallucination)
without any anatomical
lesions in sensory
pathways.
 Cause – excessive
activity of
Dopaminergic
mesolimbic pathway.

SCHIZOPHRENIA
 Characteristic
features
 Hallucinations –
Auditory & Visual
 Grandeur Delusions,
intense fear, paranoia
 Withdrawl from society
 Treatment –
 Drugs decreasing
Dopamine conc in brain

LIMBIC SYSTEM

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LIMBIC SYSTEM