BASAL GANGLIA Flashcards
Collection of gray matter nuclei located deep within the cerebral white matter
BASAL GANGLIA
Main 5 Components that participate in regulation of movement:
Caudate nucleus
Putamen
Globus pallidus (GP)
Subthalamic nucleus (STN)
Nucleus accumbens
Nucleus Accumbens parts
Ventral Striatum
Similar embryonic development and input/output connections
Limbic system
Other parts involved: amygdaloid nuclear complex (limbic system) and claustrum
Amygdaloid nuclear complex - does not participate in the modulation of movement as well as claustrum; only included d/t its location (on tail of caudate) and Claustrum (on side of basal ganglia)
Primary Components of Basal Ganglia
Caudate
Putamen
Globus Pallidus
Subthalamic nucleus (nucleus of Luys)
Substantia nigra is divided into
reticula and compacta
Globus pallidus = aka paleostriatum or pallidum
Neostriatum
Caudate & Putamen
Lentiform Nucleus
Putamen & Globus Pallidus (more medial)
Corpus Striatum
Caudate, Putamen, Globus Pallidus
HORIZONTAL SECTION FROM LATERAL TO MEDIAL
INSULA
EXTRE CAP (extreme capsule)
CLAUSTRUM
EXTER CAP (external capsule)
PUTAMEN
EXTER ML ( external medullary lamina)
GPe (globus pallidus externa)
INTER ML (internal medullary)
GPi (globus pallidus interna)
INTER CAP (internal capsule)
Elongated arched gray cellular mass related throughout its extent to the lateral ventricle
C-shaped
CAUDATE NUCLEUS
Most lateral part of the corpus striatum
Darker and larger
PUTAMEN
Wedge shaped with apex directed medially
Kind of cone shaped
Broad convex base is directed laterally
LENTIFORM NUCLEUS
C-shaped
Lies lateral to the thalamus
CAUDATE NUCLEUS
Outer putamen, inner globus pallidus
Between the internal and external capsule
LENTIFORM NUCLEUS
Between the external capsule and the lateral medullary lamina of the globus pallidus
PUTAMEN
Lateral surface is related to internal capsule which separates it from lentiform nucleus
CAUDATE NUCLEUS
Related medially to internal capsule
Related laterally to external capsule which separates it from claustrum
LENTIFORM NUCLEUS
Rostral part is continuous ventromedial with the head of the caudate
PUTAMEN
enlarged, protrudes into anterior horn of lateral ventricle (part of caudate nucleus)
Head
follows the curvature of the inferior horn of lateral ventricle and enters the temporal lobe; terminates in the region of the amygdaloid complex
(part of caudate nucleus )
Tail
dorsolateral to the thalamus near the lateral wall of the lateral ventricle (part of caudate nucleus )
Body
What separates 2 segments of globus pallidus (interna/externa)
medial / internal medullary lamina
Receives inputs to basal ganglia
STRIATUM
Lateral to the thalamus
CORPUS STRIATUM
Most medial part of the lentiform nucleus
Lighter, inner portion
GLOBUS PALLIDUS
CORPUS STRIATUM:
Almost completely divided by __________ into:
Caudate nucleus
Lentiform nucleus
Internal Capsule
High concentration of myelinated fibers
Diencephalic origin
GLOBUS PALLIDUS
Anteriorly and ventrally, putamen is fused with head of the caudate
ventral striatum
Caudate and putamen separated by internal capsule but remain joined in some places by cellular bridges
STRIATUM
Stripes or striations
STRIATUM
part of anterior part of striatum
(ventral striatum)
Nucleus accumbens
Dorsal to the crus cerebri (found in midbrain)
SUBSTANTIA NIGRA
NEURO TRANSMITTER of Substantia Nigra
Dopamine
lies Under the thalamus
Spindle- or cigar-shaped
SUBTHALAMIC NUCLEUS
Ventral portion
Cells are similar to cells of globus pallidus interna (GPi)
Bc it is close to GPi
Separated by internal capsule from GPi
Substantia nigra pars reticulata
Dorsal
secretes Darkly pigmented dopaminergic neurons
Substantia nigra pars compacta
Main input/receptive site of basal ganglia
striatum (caudate, putamen)
motor, mainly goes to putamen
Main output site of basal ganglia
GPi and substantia nigra pars reticulata
Excitatory NT
Glutamate
Other input sources of basal ganglia
Intralaminar nuclei of thalamus (mainly centromedian and parafascicular nuclei) - released (+) glutamate
Raphe nuclei serotonin in reticular formation releases serotonin
Inhibitory NT
GABA
Where does GPi and SNPR sends their axons ?
Thalamus
associated with motor output of the rest of the body
GPi
leads and necessitates output
Substantia nigra pars reticulata
GPi and SNPR both releases
GABA
All the outputs are sent to
ventral lateral (VL) and ventral anterior (VA) of thalamus via thalamic fasciculus
Anterior part of thalamic fasciculus send out to:
anterior portion of VL (VL pars oralis)
Posterior part of thalamic fasciculus send out to:
posterior portion of VL (VL pars caudalis) from cerebellum
Thalamus convey information from basal ganglia to entire….
frontal lobe especially premotor cortex, supplementary motor area and primary motor cortex.
After outputs were sent to thalamus it goes to…
Intralaminar nuclei of thalamus (centromedian and parafascicular) project back to striatum
Mediodorsal nucleus - limbic pathways
To pontomedullary reticular formation
influencing reticulospinal tract
To superior colliculus - influencing tectospinal tract
from striatum directly to GPi or substantia nigra pars reticulata
Direct pathway
striatum to GPe to STN to GPI
Indirect pathway
The net effect of direct pathway
excitatory which facilitates movement in targeted muscles/ wanted movements
Indirect pathway and Hyperdirect pathway
Inhibitory = inhibition of unwanted movement
Net effect of both pathway
Coordinated, smooth movement
Activates ST directly from motor cortex without intervening striatum
Inhibitory
Hyperdirect pathway
Rom cortex to subthalamic nucleus to striatum
STN releases glutamate to GPi and SNR which will stimulate cortex
Hyperdirect pathway
excitatory; stimulates adenyl cyclase; stimulates the direct pathway
D1 receptor
inhibitory; inhibits the indirect pathway
D2 receptor
TRIAD for parkinson’s disease
Bradykinesia, Rigidity and Rest Tremor
Dopamine-containing neurons in substantia nigra pars compacta degenerate
Parkinson’s Disease
Increase inhibition of thalamic nuclei and reduce excitation of cortical motor system
Parkinson’s Disease
Degeneration of striatal neurons
Indirect pathway is more severely affected
Huntington’s Disease
Regulation of eye movements
Oculomotor Channel (VA, MD)
Limbic regulation of emotions and motivational drives
Limbic Channel (MD, VA)
“Brake and Switch” concept of movement
Motor Channel (VI, VA)
Passes slightly rostrally as it loops around the inferior medial edge of the internal capsule, and it then turns back towards the thalamus
Ansa lenticularis
Sweeps around the internal capsule
Ansa lenticularis
Traverse the internal capsule in a number of small fascicles and then continues medially and caudally to join the ansa in the prerubral field
Fasciculus lenticularis
Penetrate straight through the internal capsule
Fasciculus lenticularis
Looping course ventrally under the internal capsule before passing dorsally to thalamus
Ansa lenticularis
Then pass dorsal to the subthalamic nucleus and ventral to the zona incerta before turning superiorly and laterally to enter the thalamus
Fasciculus lenticularis
thalamic fasciculus
H1
lenticular fasciculus that is dorsal to the subthalamic nucleus
H2
carries fibers of the indirect pathway from GPe and STN, and from STN to GPi
Subthalamic fasciculus
region where the ansa lenticularis and lenticular fasciculus join together
H (prerubral field)
Brake
tonic inhibitory action preventing unwanted motor activity
Switch
select which of the available motor programs will be active at a given time
FUNCTIONAS OF BASAL GANGLIA
Acts as “brake or switch”
Initiation, sequencing, modulation of motor activity (motor programming)
Participate in constant priming of motor systems for rapid execution of motor acts without premeditation
corticospinal or upper motor neuron pathways (Type of movement disorder)
Pyramidal
from disorders of basal ganglia
Extrapyramidal
Unilateral movement disorders
Unilateral movement disorders because it crosses
Most obvious movement abnormalities cease during sleep except….
palatal myoclonus, periodic leg movement of sleep and some tics
Increased resistance to passive movement of the limb
Matigas siya all throughout the movement
Vs Spasticity - UMN lesion
RIGIDITY
more continuous throughout attempts to bend the limb
Lead pipe rigidity
ratchet-like interruptions in tone
Cogwheel rigidity
frontal lobe dysfunction actively resist movement of their limbs; more active, inconsistent or almost voluntary quality
Paratonia or gegenhalten
Assumes abnormal, often distorted positions of limbs, trunk or face that are more sustained or slower than athetosis
DYSTONIA
Generalized, unilateral or focal
Focal - torticollis, blepharospasms, spasmodic dysphonia, writer’s cramp
Spasm of eyelids - blepharospasms
Generalized - XDP
XDP is generalized type
DYSTONIA
slow, writhing, twisting movements usually of the fingers and extremities (can also be seen on face, trunk) that sometimes merge with faster choreic movements (choreoathetosis)
Athetosis
“dance”, characterized by nearly continuous involuntary movements that have a fluid or jerky, constantly varying quality
Chorea
Movement of the proximal limb muscles with large-amplitude or more rotatory flinging quality
BALLISMUS
unilateral flinging movements of extremities contralateral to the lesion in basal ganglia
Hemiballismus
leading to decreased pallidal inhibition of the thalamus
Subthalamic nucleus lesion
Becomes subtler choreoathetotic movements over days or weeks after infarct
BALLISMUS
Sudden brief action preceded by urge to perform it and is followed by a sense of relief
Sequence of movements identical each time
TICS
more often face or neck, less often extremities
Motor tics
brief grunts, coughing, sounds, howling, barking or vocalizations (coprolalia - obscene words)
Vocal tics
persistent motor and vocal tics; most common
Tourette’s syndrome
Fastest of all movement disorders
Fastest type of motor problem
Sudden, rapid muscular jerk
Shock-like, lightning fast contractions of muscles or groups of muscles
MYOCLONUS
intermittent brief flexion movements of the wrists bilaterally as patient attempts to hold “stop the traffic” position; caused by brief interruptions in contraction of the wrist extensors = negative myoclonus; hepatic encephalopathy, other metabolic-toxic encephalopathies and other structural lesions of cerebello-thalamo-cortical circuits
Asterixis (flapping tumor)
Causes of myoclonus
anoxic brain injury, encephalitis, toxic/metabolic encephalopathies
primary is brain injury
most prominent when limbs are relaxed, decreases or stops when patient moves their limbs
Resting tremor (3-5Hz)
most prominent when limbs are actively held in a position, disappears at rest
Postural tremor
familial, benign, or senile tremor
Most commonly involves the hands or arms, can also affect jaw, tongue, lips, head, vocal cords and legs or trunk
Essential tremor (5-8 Hz)
No problem in basal ganglia
Physiological tremor (8-13 Hz)
occurs as patient attempts to move their limb toward a target and has irregular, oscillating movements in multiple planes throughout trajectory; cerebellar disorder
Intention tremor or ataxic tremor (2-4Hz)
low amplitude at rest but becomes more violet as limbs are abducted slightly or attempts are made to hold a position or perform a movement
lesion in superior cerebellar peduncle or cerebellar circuitry
Rubral tremor (2-4 Hz)
marked psychomotor retardation in patients with schizophrenia or severe depression; not a basal ganglia lesion
CATATONIA
