limbic system2.ppt physiology mbbs 1st year

Physiology

1. LIMBIC SYSTEM
A group of nuclei, cortical regions and
connecting tracts concerned with the functions
like motivation, emotions and certain kind of
memory. ( emotions make the struggle for survival
stronger )
( In primitive animals these functions are
closely related to purely chemical stimulation)

9. Most advanced part of primitive brain
Concerned with neural control of instinctual
behavior and emotions
1. Instinctual behavior –
Actions based on inner urge and not
on training or learning. e.g. sexual behavior,
maternal protective instinct, search for food
when hungry.
In man instinctual behavior is controlled by
highly developed neocortex.

10. Emotions
Mental components Physical component
Cognition
awareness of
sensation and its
cause
Affect
reflection
of mental
state -
feeling
Conation
urge to act
Coordinated
visceral and
skeletal actions
through ANS &
PNS
Emotions – aroused state involving feelings,
autonomic activation & related behavior

11. Isthmus
Parahippocampus
Mamillary bodies

12. Anatomy – ring around brain stem
Cortical structures –
neocortex – orbitofrontal lobe
` - part of parietal & temporal
lobe
Archicortex – subcallosal gyrus
- cingulate gyrus
- isthmus
- parahippocampal gyrus
- uncus

13. Subcortical nuclei –
- amygdala,
- hippocampus
- septal nuclei
- hypothalamus
- ant. nucleus of thalamus

14. Connections of limbic system – Comparatively
less connections with association areas of cortex
and more with brain stem reticular formation –
rider on the horse without rains.
Plenty of connections between parts of limbic
system. Closed circuit connections produce
prolonged emotional response
I.Fornix – uncus, amygdala & hippocampus

mammillary bodies of hypothalamusMB
HP
U
AMD

15. Subcallosal gyrus
Septum
Ant.
thalamus
Paraolfact
ory area
Hypothala-
mus
O
rbito
frontal
cortex
Part of temporal
& parietal cortex
Amygdala
hippocampus
un

16. ii. Papez circuit – closed circuit connection between
cortex and limbic system. Indicate influence of thought
over emotions and how emotions come to conscious
level,

Prefrontal Association areas
Cingulate gyrus
hippocampus
amygdala
hypothalamus
Mamillary bodies
Ant. N. thalamus
Mamillothalamic tract
fornix

17. hippocampus
Mammillary
bodies
Ant. N. of
thalamus
Cingulate
gyrus
fornix
Mamillothalamic
tract

18. iii. Amygdala receives olfactory and other
sensory connections and send signals to
sensory association areas – addition of
emotional component to the sensation
iv. Efferents of limbic system
hypothalamus
Bulbar autonomic
centers Reticular
formation
Association
cortex

20. Functions of limbic system
1)Emotional exteriorization – through ANS
causes changes in HR, BP, R.R, GI
movements, pupillary dilation during
various emotions
2)Regulates feeding behaviour – edible Vs.
nonedible .Lesions of amygdala causes
hyperphagia and oral tendency – Kluver-
Bucy syndrome
3)Regulates sexual behaviour – lesions of
amygdala produce hypersexuality

21. 4)Responsible for maternal behaviour
5)Amygdala produces emotions like fear,
rage (in hostile environment),
stimulation of amygdala – fear reaction –
sweating, pupillary dilation, turning head
post. Hypothalamus – rage – growling,
piloerection, biting tendency

22. 6) Reward (ventromedial nucleus) related
to pleasant experience and punishment
centers (lateral hypothalamus) related to
unpleasant experience
7) Olfaction
8) memory
Limbic system generates emotions, and
adds feelings to sensory experience and
then behavior is decided.

23. Applied –
1. Papez circuit – indicates influence of will
over emotions and how the emotions come
to conscious level
Prefrontal Association areas
Cingulate gyrus
hippocampus
amygdala
hypothalamus
Mamillary bodies
Ant. N. thalamus
Mamillothalamic tract
fornix
Prefrontal Association areas
Cingulate gyrus
hippocampus
amygdala
hypothalamus
Mamillary bodies
Ant. N. thalamus
Mamillothalamic tract
fornix

24. 2. Rabies virus attacks hippocampus so
profound changes in emotions –terror,
fear etc.
3. Kluver – Bucy syndrome – bil. Lesions
of amygdala – aggressive behavior,
emotional instability, no fear,
restlessness, increased interest in food,
oral tendency, hypersexuality.

25. 4. Psychosomatic disorders – emotions
produce strong effect on ANS. Prolonged
emotional disturbances lead to peptic ulcer,
ulcerative colitis or other somatic disorders
5. Norepineprine, serotonin , Dopamine are the
neurotransmitters in the pathways of emotions &
behavior. Amphetamine increases release of
Dopamine and NE which are involved in pleasure
pathway.

26. 6. Cocain gives intense sense of pleasure.
With prolonged use of cocain - tolerence –
desensitization because of decreased no. of
dopamine receptors --> high dose is required to
get same amount of pleasure – addiction and
withdrawal effects

27. 7. Schizophrenia – due to excess of
Dopamine formation – delusion,
hallucinations, inappropriate emotions,
apathy, social withdrawal
8. Deficiency of serotonin or NE leads to
Depression – no motivation, & pleasure.
Antidepressant drug Prozac blocks reuptake
of serotonin and NE & thus increase conc. Of
them at synapse.