Thalamus
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Transcript of Thalamus
THALAMUS
Dr. M. Anbarasi
ML
DM
IL
PUL
PL
VPL
DL
VL
VA
EXTERNAL MEDULLARY LAMINA
RETICULAR NUCLEUS
LGN
MGN
NUCLEI OF THALAMUS
PARTS OF THALAMUS
EPITHALAMUS
DORSAL THALAMUS
VENTRAL THALAMUS
EPITHALAMUS
Comprises of PINEAL BODY and HABENULAR COMPLEX
Receives projection from Supra chiasmatic nuclei Sympathetic nervous system Olfactory areas
DORSAL THALAMUS
FOUR TYPES OF NUCLEI
1. Specific sensory relay Nu.
2. Nu. Concerned with efferent control
3. Nonspecific projection Nu.
4. Nu. Concerned with higher functions.
SPECIFIC SENSORY RELAY NU.
projects to specific areas of neocortex.
VENTROBASAL GROUP [VBG]
ventroposterolateral
ventroposteromedial
- ventrolateral & ventromedial
Relay somaesthetic information to postcentral gyrus from entire body.
Spinal lemniscus Medial lemniscus
Trigeminal lemniscus
VPM
VPL
3,1,2
MEDIAL & LATERAL GENICULATE BODIES
171819
41
THALAMUS
LGNMGN
RETINA
COCHLEA
NUCLEI CONCERNED WITH EFFERENT CONTROL MECHANISMS
Mainly ventrolateral & ventroanterior Nu.
Relay motor impulses from basal ganglia and cerebellum
Projects to motor and association cortex
Participate in cognition,planning and coordination of motor activities.
THALAMUS
CEREBELLUM
STRIATOLENTICULAR NU
MOTOR & ASSOCIATION AREAS
VA & VL
NONSPECIFIC PROJECTION NUCLEI
Receive inputs from diff. ascending tracts and projects to all parts of neocortex, some specific cortical areas and also to limbic system.
Examples – Midline – behavioural responses Intralaminar – thru reticulo-thalamo-cortical and cortico-thalamo-reticular connections, thalamus influences
Alertness Sleep and wakefulness Consciousness EEG
v
SPECIFIC AREA
NONSPECIFIC CORTEX
NONSPECIFIC THALAMIC NU.SPECIFIC THALAMIC NU.
TECTUMAUDITORY
VISUAL
ARASSPECIFIC ASCENDING
TRACTS
NUCLEI CONCERNED WITH HIGHER FUNCTIONS
Anterior nucleus: participates in ‘PAPEZ CIRCUIT’ concerned with recent memory and emotions
Association Nu.
Dorso medial – AFFECTS THE MOOD
DorsolateralPulvinar Posterolateral Nu.
LANGUAGE & INTELLECTUAL FNS
PAPEZ CIRCUIT
ANTERIOR NU. CINGULATE GYRUS
HIPPOCAMPUSMAMILLARY BODY
VENTRAL THALAMUS{RETICULAR NUCLEUS}
A thin curved sheet of cells present between External Medullary lamina and the posterior limb of Internal capsule.
Modifies the exchange of signals between the thalamus and the cortex thru thalamo-cortical and cortico-thalamic fibres.
Comparison between specific & nonspecific thalamic projections
NON SPECIFIC SPECIFIC
Thalamic Nu, Intralaminar & Reticular Nu.
VPL, VPM,MGB, LGB.
Projection to the cortex
Diffuse to all parts of the neocortex
Specific cortical areas like 3,1,2,5 & 7, 41, 17,18 &19
No. of synapses
Multi {> 4} < 4
Conduction rate
Slow Fast
Termination in the layers of the cortex
Mainly 1st layer Mainly 4th layer
Effect of
lesion
Coma or unconsciousness
Loss of particular sensation
Function Arousal Specific sensation
FUNCTIONS OF THALAMUS
Sensory relay center: tactile, vibration, pressure, stereognosis, conscious
proprioception and sexual sensation. Centre for crude sensation – crude touch, pain and
temperature. Controls smooth, slow and coordinated movements Relay center for auditory and visual sensations: lesion in both MGB – deafness lesion of LGB – homonymous hemianopia Role in emotions and short term memory Role in sleep-wakefulness cycle, alertness and production
EEG
THALAMIC SYNDROMESigns and symptoms:
Loss of sensations Astereognosis Sensory ataxia Thalamic over-reaction Thalamic phantom limb Ameliognosia Hypotonia Choreoathetosis or tremor Loss of recent momory and emotions Sleep disturbances Thalamic hand