NEURO,PYRAMIDAL,EXTRAPYRAMIDAL

8/7/2019 NEURO,PYRAMIDAL,EXTRAPYRAMIDAL

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PYRAMIDAL TRACT

AND

EXTRAPYRAMIDAL TRACT



Basal Gangliasubcortical nuclei (gray matter) within the cerebral hemispheres.

Components1. Caudate nucleus2. Putamen ,3. Globus pallidus4. Amygdala (amygdaloid nuclear complex)5. Claustrum

Groupings of the basal ganglia1. Striatum (neostriatum)

caudate nucleus and the putamen,2. Lentiform nucleus

putamen and the globus pallidus.3. Corpus striatum

lentiform nucleus and the caudate nucleus.



Str iatal Mo tor System extrapyramidal motor system .plays a role in the initiation and execution of somatic motor activity, especially

willed movement.

involved in automatic stereotyped motor activity of a postural and reflex nature.exerts its influences on motor activities via the

thalamus,motor cortex,corticobulbarcorticospinal systems.

Comp on ents of the Str ia tal s ystemconsist of the following nuclei1. Striatum - neostriatum

Caudate nucleusPutamen

2. Globus pallidus - paleostriatumMedial (internal) segment - adjacent to the internal capsule.Lateral (external) segment - adjacent to the putamen.

3. Subthalamic nucleuslies between the internal capsule and the thalamus and between the internal

capsule and the lenticular fasciculus.



4. ThaJa mu sVentral anterior nucleusVentral lateral nucleus

Centromedian nucleus

5 . Sub stan t ia nig raPars compacts - contains dopaminergic neurons, which contain the

pigment melanin.Pars reticularis - contains gamma-aminobutyric acid (GABA) -ergic

neurons.6 . Pedu nc rlopon t ine nucleu s

lies in the lateral tegmentum of the caudal midbrain.





Major connections of the striatal systemStriatum

receives its largest input from theneocortex, from virtually all neocortical areas.

thalamus (centromedian nucleus)substantia nigra.

projects fibers to two major nucleiglobus palliduspars reticularis

Globus pallidusreceives input from two major nuclei:

striatum and the subthalamic nucleus.projects fibers to three major nuclei:

subthalamic nucleus, the thalamus (ventral anterior, ventral lateral, andcentromedian nuclei), and the pedunculopontine nucleus.

Subthalamic nucleusreceives input from the

globus pallidusmotor cortex.

projects fibers to the globus pallidus.



Thala mu sA. Input to the thalamus

Globus pallidus - projects to the ventral anterior, ventral lateral, andcentromedian nuclei.

Substantia nigra - projects from the pars reticularis to the ventral anterior,ventral lateral, and the mediodorsal nuclei of the thalamus.

B. projections from the thalamusventral lateral and centromedian nuclei to Motor cortex (area 4)ventral anterior and ventral lateral nuclei to Premotor cortex (area 6)ventral lateral and ventral anterior nuclei to Supplementary motor cortex (area 6)centromedian nucleus to Striatum

Sub stan t ia nig rarecieves major input from the Striatum.project fibers to the

Striatum

thalamus (ventral anterior, ventral lateral, and mediodorsal nuclei).Pedu nc ulopon t ine nucleu s .

receives GABA-ergic input from the globus pallidusprojects glutaminergic fibers to the

globus pallidussubstantia nigra.



Ventr al s tr iatopallidal co mp lex an d it s conn ect ionsplay a role in initiating movements in response to motivational and emotional

activityVentral striatum

consists of the nucleus accumbens and the olfactory tubercle.receives input from the olfactory, prefrontai, and hippocampal cortices.projects to the ventral pallidum.

V entral pallidumconsists of the substantia innominata.

receives input from the ventral striatum.projects to the medial dorsal nucleus of the thalamus.



Basal GangliaPathways and Nuclei:

Cortex » s tr iatum > glo bu s pallidu s > th ala mu s > Co rtexstr ia tum (caudate and putamen) - major site of input to the basal ganglia.

presence of Inhibitory and excitatory interneurons1. receives afferents

via theco rt icos tr ia te pr oject ions - excitatory.

sensorimotor cortex (areas 4, 1,2, and 3),premotor cortex (area 6)frontal eye fields (area 8)

2. receives inputs from the intralaminar thalamic nuclei,substantia nigra, and midbrain raphe nuclei

3. send inhibitory (GAB Aer-gic) axons to theglo bu s pallidu s - major outflow nucleus of the corpus striatum.

axon ansa lenticularis and the lenticular fasciculus - H 2 field of Forelsends inhibitory axons (GABAergic) to theventr al n ucle i (ventral anterior, VA; and ventral lateral, V L)

thalamus (which also receives input from the cerebellum, thesubthalamic nucleus, and substantia nigra)

VA and V L thalamic nuclei complete the feedback circuit by sending axonsback to the cerebr al co rtex



sub stan t ia nig ra,dopaminergic neurons in the pars compacta

1. project to the striatum (the nigrostriatal projection) form inhibitory

synapses

striatonigral projection - reciprocal projections travel from the striatumto the substantia nigra and are also inhibitory

co rtex > s tr iatum > s ub stan t ia nig ra > s tr iatum > > co rtex

2. dopaminergic neurons in the substantia nigra also project to thethalamus (ventral anterior and ventral lateral), which, inturn, sends projections to the sensorimotor cortex - this pathway

involves the following circuit:co rtex > s tr ia tum > s ub stan t ia nig ra > th ala mu s > co rtex

subth ala m ic n ucleu salso receives inhibitory inputs from the globus pallidus and from the cortex;

efferent fibers return to the globus pallidus.co rtex > glo bu s pallidu s > s ubth ala m ic n ucle i > » glo bu s pallidu s > co rtex



A no ther loo p involv es the cerebe llum .

Portions of the thalamus project by way of the central tegmental tract to theinferior olivary nucleus

sends fibers to the contralateral cerebellar cortex.

loop to the thalamus is closed via the dentate andcontralateral red nuclei.

thalamus > inferior olivary nucleus > contralateral cerebellar cortexvia dentate and contralateral

red nucleithalamus

Although there are no direct projections from the caudate nucleus, putamen, orglobus pallidus to the spinal cord,

subthalamic region, including the pre-rubral field and the red nucleus, is an

important relay and modifying station.Projections from the globus pallidus to the

red nucleus converge with inputs from the motor cortex and the deepcerebellar nuclei.

Efferent fibers from the red nucleus descend in the spinal cord as therubrospinal tract, which modulates the tone of flexor muscles



Majo r neur otr ans m itter s of the neur ons of the str iatal s ystem Glutamate-containing neurons

project from thecerebral cortex to the striatum.

subthalamic nucleus to the globus pallidus.excite striatal GABA-ergic and cholinergic neurons.

GABA-containing neuronspredominant neurons of the striatal system.found in the

striatum, globus pallidus, and substantia nigra (pars reticularis).give rise to the following GABA-ergic projections:

striatopallidal, striatonigral, pallidothalamic, and nigrothalamic projections.degenerate in Huntington disease.

Dopamine-containing neuronsfound in the pars compacta of the substantia nigra.

give rise to the dopaminergic nigrostriatal projection .thought to regulate the production of striatal peptides and peptide mRNA

degenerate in Parkinson disease.Neurons containing acetylcholine

local circuit neurons found in the striatum



Neuropeptide-containing neuronsenkephalin, dynoiphin, substance P, somatostatin, neurotensin, neuropeptide Y,

and cholecystokinin.also found in the basal ganglia.

coexist with the major neurotransmitters



Clinical co rre lat ionsPa rkinson diseas e

degeneration and depigmentation of neurons in the substantia nigra.results in the depletion of dopamine in the caudate nucleus and putamen .

clinical manifestations of bradykinesia and hypokinesia

(difficulty in initiating and performing volitional movements);rigidity (cog-wheel and lead-pipe rigidity); andresting tremor (pill-rolling tremor).

MPTP-in du ced parkinsonis mcaused by l-methyl-4-phenyl-l,2,3,6-tetrahydropyridine (MPTP), a meperidine

analog found in illicit recreational drugs.results in the destruction of dopaminergic neurons , which are located in the

substantia nigra.Prog re ssiv e supr an uclear p als y

associated with Parkinson disease.Parkinson-plus syndrome - progressive supranuclear palsy together with Parkinson

diseasecharacterized by

supranuclear ophthalmoplegia, primarily downgaze paresis, which is followedby paresis of other eye movements.



As the disease progresses, the remainder of the motor cranial nerves becomeinvolved, resulting in the clinical picture of pseudobulbar palsy.

characterized by neuronal cell loss in the globus pallidus, red nucleus,substantia nigra, periaqueductal gray, and dentate nucleus .

spares the cerebral and the cerebellar cortices.results in: neurofibrillary tangles, in the surviving neurons.

H unt ing ton dise as e inherited autosomal dominant movement disorder associated with severe

degeneration of the cholinergic and GABA-ergic neurons , which are located inthe caudate nucleus and putamen.

usually accompanied by gyral atrophy in the frontal and temporal lobes.can be traced to a single gene defect on chromosome 4.characterized by impaired initiation and slowness of saccadic eye movements;

patients cannot make a volitional saccade without moving the head.results in, clinical manifestations of choreiform movements and progressive

dementia.results in hydrocephajus ex vacuo due to the loss of neurons located in the head

of the caudate nucleus, and to a lesser extent in the putamen.



O ther chore ifo rm dy skinesiasSydenham chorea

most common cause of chorea overall.occurs mainly in girls as a sequela to rheumatic fever,

Chorea gravidarumoccurs usually during the second trimester of pregnancy.in many cases, a history of Sydenham chorea can be obtained.

Ballis m an d hem iballis mextrapyramidal motor disorders most often resulting from a vascular lesion

(infarct) of the subthalamic nucleus.characterized by violent flinging (ballistic) movements of one or both extremities;

symptoms appear on the contralateral side.may be treated with dopamine-blocking drugs or with GABA-mimetic agents,may be treated surgically by ventrolateral thalamotomy.

H ep atolent icular de gener at ion (Wilson diseas e)

autosomal recessive disorder due to a defect in the metabolism of copper(ceruloplasmin).

gene locus on chromosome 13.results in clinical manifestations of tremor, rigidity, and choreiform or athetotic

movements. Tremor is the most common neurologic signmarked by lesions in the liver (cirrhosis) and in the lentiform nuclei

(necrosis and cavitation of the putamen).



Tardive dyskinesiasyndrome of repetitive choreic movements affecting the face, limbs, and trunk.

results from treatment with antipsychotic drugs



Pyram idal tr ac tLater al co rt icos pinal tr ac t

not fully myelinatcd until the end of the second year.Function:

concerned with volitional skilled motor activity, primarily of the digits of theupper limb.

modulates the transmission of sensory input via the ascending sensorypathways.

receives input from the paracentral lobule, a medial continuation of themotor and sensory cortices, and subserves the muscles of thecontralateral leg and foot,

Origin and termination:arises from lamina V of the cerebral cortex from three cortical areas, inequal proportions

premotor cortex (area 6)

precentral motor cortex larea 4)postcentral sensory cortex (areas 3, 1, and 2).

terminates via interneurons on ventral horn motor neurons and sensoryneurons of the dorsal horn.

Fibers number approximately 1 million,usually (90%) between 1 and 4 um in diameter.usually (67%) mvelinated.



axons of the gian t ce lls of B etz - represent 4% of the fibers of the tract, withdiameters greater than 20 um.

precentral gyrusanterior paracentral lobule.

Course:passes through the posterior limb of the internal capsule.passes through the middle three-fifths of the crus cerebri of the mid-brain. 'passes through the base of the pons.

constitutes the pyramid of the medulla.undergoes a 90% de cussa t ion in the caudal medulla.lies in the dorsal quadrant of the lateral funiculus of the spinal cord.

Transectionresults in spastic hemiparesis with the Babinski sign.

Ventr al co rt icos pinal tr ac t

small uncrossed tract that decussates at spinal cord levels in the ventral whitecommissure.

concerned with the control of axial muscles. :.









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NEURO,PYRAMIDAL,EXTRAPYRAMIDAL