THALAMUS

DR NILESH KATE

MBBS,MDASSOCIATE PROF

ESIC MEDICAL COLLEGE, GULBARGA. DEPT. OF PHYSIOLOGY

THALAMUS.

OBJECTIVES Physiological

Anatomy. Functions of thalamus. Applied aspects.

Friday, February 27, 2015

Physiological Anatomy. Thalamus proper. Diencephalon.----

dorsal thalamus, ventral thalamus, epithalamus & hypothalamus.


External features. Large ovoid structure. Lateral to 3rd ventricle.

Ends Anterior Posterior.

Surfaces Superior Inferior. Medial Lateral.


Internal structure.White matter

Stratum zonules. – Thin layer covering superior surface of thalamus.

External medullary lamina. -- Thin layer covering lateral surface of thalamus

Internal medullary lamina. – “Y’ shaped sheet of white matter

--- consists of internuclear thalamic connections.

Grey matter.

3 masses of nuclei Anterior Lateral. Medial.


Classification of Thalamic nuclei. Anatomical

classification. Anterior. Lateral.

Ventral Dorsal

Medial.


Functional classification. Non- specific

From RAS to Neocortex. 2 types

Midline nuclei. Centromedian nucleus.

Specific From specific sensation

to Neocortex or limbic system

Types. Specific sensory Motor Visceral efferent. Integrative & perceptual


Connections of Thalamus.Non –specific projection nuclei.

Causes diffuse thalamic projection to entire Neocortex.

Produces electrical activity of cortex. Afferents – from RAS, & Basal Ganglia Efferents –stratum & entire Neocortex.


Connections of Thalamus. Specific.

Sensory Motor Visceral Integrative.


Sensory Medial geniculate

body. Destruction of small

part --- deafness for particular band of sound frequency.


Sensory Lateral geniculate

body. Orderly organized

representation of retina.


Sensory Ventral posterior

nucleus. VPL -- from N. gracilis,

cuneatus, Spinothalamic tract

i.e. somatosensory impulses from trunk & limbs except face.

VPM – trigeminal laminiscus & taste.


Motor. Ventral lateral

nucleus. From cerebellum Dentothalamic fibres

from opp side. Proprioceptive

information & voluntary motor functions.


Motor. Ventral anterior

nucleus. Programming of

movements.


Visceral. Anterior nucleus. From hippocampus

through mammilary body.

Concerned with recent memory & emotions.


Visceral. Concerned with

thinking, memory, judgment & emotional behaviour.

Dorsal medial nucleus.


Integrative & perceptual function control.

Pulvinar nucleus. Integration of visual,

auditory & other sensation.


Integrative & perceptual function control.


Lateral posterior nucleus.

Lateral dorsal nucleus.

Functions of thalamus. Sensory relay centre. Crude centre for perception

of sensation. Arousal & alertness

reaction. Language. Emotional aspect of

behaviour. Sexual sensation. EEG Synchronization. Reflex activity centre

Integration of Sensory impulses. Motor functions. Visceral & somatic

function.

SCALE –SERINTEGRATION --3


Sensory relay centre. All except olfactory. Head ganglion of all

sensory system. Thalamic radiations.

—projection fibres.


Crude centre for perception of sensation.

2 Qualities of sensation Discriminative nature. Type, location --- by

cerebral cortex. Affective nature.

Pleasant, unpleasant, agreeable, disagreeable– by thalamus.


Arousal & alertness reaction. Control level of

consciousness. Maintain state of

alertness & wakefullness.


Language.


Emotional aspect of behaviour. Acts as a part of limbic

system & papez circuits.

Concerned with recent memory & emotions.


Sexual sensation. Centre for perception

of sexual sensation.


EEG Synchronization. Genesis of

synchronization of EEG.


Reflex activity centre As relay of sensory

fibres in Thalamus.


Integration of Sensory impulses.


Integration of Motor functions.


Integration of Visceral & somatic function.


Applied Aspects. Thalamic syndrome. Korsakoff’s syndrome Frontal lobotomy.


Thalamic syndrome. Disturbance of emotional response to

sensory experience. Cause .

Thrombotic blockage of Thalamogeniculate branch of Posterior Cerebral Artery.

Damage to Posteroventral & Posterolateral nuclei.


Signs & symptomsSensory symptoms

Thalamic Phantom limb.- unable to locate position of limb with closed eye. Due to loss of kinaesthetic sensation.

Asteriognosis. Thalamic over-reaction.–

sensation to touch, pain , temp exaggerated.

Amelognosis. – illusion of absent limb.

Motor symptoms

Thalamic hand or Athetoid hand – Moderate flexion of the wrist with hyper extended fingers.

Ataxia.-- muscle tone & profound muscle weakness.

Involuntary movements.– chorea, athetosis & intension tremors.


Korsakoff’s syndrome Difficulty in remembering new information. Due to – lesions of mediodorsal nucleus of

thalamus.


Frontal lobotomy.

To relieve intractable pain.

Dividing dorsal nuclei of thalamus from the frontal lobe.


Thank You

THALAMUS

Health & Medicine

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