Hypothalamus, limbic system and olfactory system

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HYPOTHALAMUS, LIMBIC SYSTEM AND OLFACTORY

SYSTEM

Rimbun Meutia Maulina Desy Purwidyastuti

Ilmu Kedokteran Dasar Anatomi-Histologi Fakultas Kedokteran Universitas Airlangga

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Overview

 Olfaction (the sense of smell)  one of the oldest senses

 Lower animal  olfactory : vital for sensing the environment

 Human :

 Olfactory  non dominant

 Visuospatial  dominant

Related to limbic system

(3)

Survive

Hypothalam us

Interoceptor signals  homeostatic

responses

internal physical

& chemical environment

balanced &

stable

Limbic system

Exteroceptive information 

learning &

memory

adaptive behaviour

Association neocortices

Exteroceptive information 

adaptive

personal & social responses

Interfaces in a hierarchical fashion between the internal & external

environment

(4)

HYPOTHALAMUS

Functions :

 Able to integrate interoceptive signals from internal organ and fluid-filled

cavities

 Make appropriate adjustments to the internal environments by virtue of its input & output systems

 Close link with the limbic system &

association cortex of the frontal lobe

 influencing or overriding more complex adaptive behaviour

(5)

The hypotalamic input

Circulatory signals

* Physical

* Chemical

* Hormonal (growth &

development , readiness for action)

Neural signals

The nucleus solitarius

* Baroreceptors

* Chemoreceptor s

The state of neural arousal

* Reticular formation via thalamus

* The

monoaminergic nuclei via the medial

forebrain bundle

(6)

The hypothalamic output

Circulatory output

Hormon synthesal

is &

release (endocr system) ine

Neural output

The ANS projects 

to &

control internal

organs outside conscious

control

Connections with limbic system & corpus

striatum (nucleus accumbens)

Initiating appropria

te motor behaviou

repertoirral es of an instinctiv

e kind

Interconnections with the reticular

formation

Influencing the state of wakefulness &

sleep

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Topographical Anatomy

Median sagital section of the diencephalon

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Hypothalamic Nuclei

 Lateral hypothalamic area

 Contains fiber systems & diffuse lateral nuclei

Control of food & water intake 

equivalent to the physiologically defined feeding centre

Lesions  aphagia & adipsia

 Medial hypothalamic area

Contain s many nuclei

Divided into 3 parts

(9)

Hypothalamic Nuclei

Medial hypothalamic nuclei

Supraoptic portion

Supraoptic

Suprachiasm atic

Paraventricul ar

Tuberal portion

Ventromedial

Dorsomedial Arcuate

Mammilary portion

Posterior Mammilary

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Neuroanatomy an illustrated colour text, 2010

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The Supraoptic Portion

 The supraoptic nuclei

 Contains osmosensitive neurones  increase in osmolality causes release of vasopressin  increase water reabsorption by kidney

tubules  maintaining water homeostasis

 The paraventricular nuclei  produce

oxytocin (induce by suckling) : stimulates milk production & causes constraction of myometrium

 The suprachiasmatic nucleus  control of diurnal rhythms & the sleep/waking cycle

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Tuberal & Mammilary Portion

 Ventromedial nucleus

 Control of food & fluid intake

 Lesions  abnormally increased food intake

 Medial mammilarry nucleus

 Located within the mammillary body

 Afferent  the hippocampus

 Efferent  the anterior nuclei of the thalamus & brain stem

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The Pituitary Portal System

 The hypothalamus synthesises releasing & inhibiting factors  control hormon release by the

adenohypophysis (ACTH, LH, FSH, TSH, GH, Prolactin)

 Factors that control them are released from the terminals of hypothalamic neurones into the capillary bed of the pituitary

portal system  intrinsic to the hypophyseal stalk

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Release of hormones by the adenohypophysis and neurohypophysis

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Tumours of The Hypothalamus and Pituitary Gland

 Tumours of hypothalamus :

 Tumours of pituitary gland :

Pituitary adenomas  bitemporal visual field loss

Disorders Diseases

Produce of growth

hormones Dwarfism, Gigantism, Acromegaly Sexual function Precocious puberty,

Hypogonadism

Body water control Diabetes insipidus, Pathological drinking

Eating Obesity, Bulimia Adrenal cortical

control Cushing’s disease, adrenal insufficiency

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LIMBIC SYSTEM

 Consists of complex structures  looped

connections  projects into the hypothalamus

 The powerful input  from the neocortical association areas  links complex “goal- directed” behaviour to more primitive, instinctive & internal homeostasis

 Influence motor responses appropriate to its informational analyses  projections to the nucleus accumbes  forms part of the basal ganglia

(19)

Outside

information Special modality

Association cortex

Frontal association area (planned

behaviour) &

inferior temporal association area

Supramodal status Meaning &

interpreted

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(21)

(22)

Information to Limbic System

Indirec t

Hippocamp al formation

Permits a link to previous experience

(memory & learning)

(23)

The principal parts of the limbic system and their relationship with the hypothalamus

Cingulate gyrus

Septum Amygdala

Hippocampa l formation

Hypothalam us

Medial forebrain

bundle Ventral

amygdalofu gal

pathway Stria

termina lis Forni

x

(24)

Amygdala

Medial forebrain

bundle

ITAC Septum Olfactory tract

Amygdala

Ventral

amygdalofugal

pathway Stria terminalis

Hypothalam us

(25)

Septum

Habenular nuclei

Medial forebrain

bundle Septum

Hypothalam us

Brain stem

(monoaminergic nuclei)

Interpeduncu lar nuclei

Stria medullaris

thalami

Fasciculus retroflexus

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Hippocampal Formation

 Consist of : the hippocampus, dentate gyrus &

parahippocampal gyrus

 Formed by an infolding of the

inferomedial part of the temporal lobe into the lateral ventricle  along the line of the choroid fissure

(28)

Hippocampal Formation..

Cont’d

Hippocam ITC

pus

Hippocam pal

formation

Fornix

Anterior nuclei of thalamus

Cyngulate gyrus

Entorhinal area Fornix

system &

hippocampal commisure

(29)

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Cingulate gyrus

 The cingulate gyrus &

parahippocampal gyrus  continuity with one another around the

splenium of corpus callosum

 The principal structures of the limbic system  linked by a series of

connections  constitute the Papez circuit

Cygulat e gyrus

Parahippocam pal gyrus

Fibres of cingulu

m

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The Papez Circuit

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Limbic Lobe Disorders

Wernicke’s encephalopa

thy

• Alcohol abuse of dietary

deficiency of thiamine  capillary

haemorrhages (upper brain stem & limbic structures)  confusion &

coma

• Partial

recovery with retrograde or anterograde amnesia

Korsakoff’s psychosis

• Similar amnesic syndrome

• Occurs when billateral

• Surgical lobectomy incorporates the hippocampal formations

Temporal lobe (complex

partial seizures)

• Arising close to amygdala &

hippocampi

• Lead to complex

experiences of smell, mood, &

memory

• The states of disordered thingking,

hallucinations,

& mimic

schizophrenia

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OLFACTORY SYSTEM

Olfactory receptors

( olfactory

ephitelium of the nasal cavity )

Olfactory nerve

Olfactory bulb

(interneurones

& large mitral cells)

Olfactory tract

Lateral olfactory

stria

Primary olfactory

cortex

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Olfactory system... Cont’d

The primary olfactory cortex :

- On the inferomedial aspect of the temporal lobe - Subjacent the amygdala

- Adjacent to the uncus, the anterior part of the parahippocampal gyrus (entorhinal area)

The olfactory association cortex

- Collectivelly referred to as the pyriform cortex

- Responsible for the appreciation of olfactory stimuli

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Anosmia

 Damage to the olfactory nerve

 Frequently follows head trauma &

tumours of the meninges (meningiomas)

 Signs & symptoms :

 loss of the sense of smell, flavour of foods

Preserve elementary aspects of taste (sweet, salt, bitter, & sour)

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Hypothalamus, limbic system and olfactory system