Anatomy of Basal ganglia

Basal Ganglia

18-03-2015Dr Laxman Khanal

Assistant professor , department of anatomy

Nuclei

Introduction

• Comprise multiple sub-cortical nuclei withineach cerebral hemisphere.

• Comprises –corpus straitum, claustrum andamygdaloid nucleus.

• primary function is likely to control andregulate activities of the motor and pre-motorcortical areas so that voluntary movementscan be performed smoothly.

Does it have direct connection to motor nuclei ??Does it affect ipsi lateral or contra lateral side of body ?

Traditional classification

• Caudate nucleus

• Lentiform nucleus

• Amygdaloid body

• Claustrum

Clinical classification

• Caudate nucleus

• Lentiform nucleus

• Subthalamus

• Substantia nigra

Corpus straitum: caudate nucleus + lentiform nucleus

Lentiform nucleus: putamen (L) + globus pallidus

Striatum (or neostraitum): caudate + putamen

Palleostraitum: globus pallidus

Corpus straitum

• Lies lateral to thalamus

• Divided by band of nerve fibers (int capsule) into caudate and lentiform nucleus.

• Corpus straitum= caudate + lentiform nuclei

• Lentiform nucleus= globus pallidus + putamen

Caudate + putamen VS globus pallidus (=pale)or

Input Vs Output

c

Caudate nucleusHead – attached with putamen of lentiform nucleusBodyTail- attached with amygdaloid nucleus

What lies lateral to internal capsule ?What lies medial to internal capsule ?What lies lateral to lentiform nucleus ?

Lentiform Caudate + thalamusClaustrum

1. Third ventricle2. Thalamus and head of caudate3. Internal capsule4. Lentiform nucleus5. External capsule6. Claustrum7. Extreme capsule8. Insula9. Lat sulcus of brain

Motor cortexsensory cortex

striatum

Globus pallidus

Nucleus of thalamusSubstantia nigraBrain stem

Cranial nerve nuclei of brain stemAnterior horn cells of spinal cord

Motor function

Ansa lenticularis

Striatum

Globus pallidus

Direct pathwayIndirect pathway

Direct pathway turns up motor activityIndirect pathway turn down motor activity

?

Majority of neuron In corpus straitum areGABAergic and only few are cholinergic.

cerebrum

Thalamus

Straitum + GP

Glutamate Glutamate

GABA Direct pathway

Glutamate

Glutamate

GABA

Glutamate Indirect pathway

Glutamate

Glutamate

Glutamate

D1

D2

Role of substantia Nigra

ACH

Fine tuning of muscle activity is only possible bybalance between ACH and Dopamine

Lets summarize the pathways

• Direct pathway involves GP internus.

• Direct pathway is stimulatory to movement.

• Indirect pathway in involve GP externus and subthalamus in addition to structures of direct pathway.

• Indirect pathway is inhibitory to movement

• Dopamine stimulate direct pathway and inhibit indirect pathway; while ACH has opposite function.

Direct pathway Differences in- Indirect pathway

Form striatum to GP internus

Pathway From striatum to GP externus

Not involved Subthalamus Involved

Turn up motor activity

Function Turn down motor activity

Turns up via D1 Effect of Dopamine Turns down via D2

Turns down Effect of acetylcholine

Turns up

Parkinsonism

Hypokinesia

•Release of dopamine from Substantia nigra is less.•Less activation of direct pathway and less inhibition ofindirect pathway•May be associated with heroine addiction andantipsychotic drugs

Rigidity Restig tremor

Glutamate

Glutamate

Glutamate

D1

D2

Hyperkinesia disorders

• Hyperkinetic diseases are

– Chorea – caudate nucleus is involved

1. Huntington’s

2. Sydenham’s

3. Wilson’s disease

– Athetosis

– Ballismus (hemi) – subthalamus involved

Basal ganglia lesion are characterized bya. Ipsilateral movement disordersb. Spastic paralysisc. No atrophy of muscled. Hyper reflexia

Involuentary, quick ,jerky and nonrepetitive movement is called asa. Athetosis b. Choreac. Dystonia d. Tremor

What are the constituents of straituma. Caudate + globus pallidus b. caudate nucleusc. Caudate + lentiform d. caudate +putamen

Caudate nucleus is functionally similar witha. Globus pallidus b. Putamenc. Lentiform d. Claustrum

All the structures lie lateral to internal capsule except.a. Lentiform nucleus b. caudate nucleus c. External capsule d. Claustrum

Midbrain structure which give afferent to straitum is a. Crus cerebri b. Substantia nigrac. Tectum d. Tegmentum