Anatomy II: Neuroanatomy IV - Basal ganglia and Limbic system

…: large strongly interconnected nuclear masses deep within the cerebral hemispheres, diencephalon, and midbrain that have a dual function in regulating movements

Basal ganglia

The basal ganglia have a dual function in regulating movements; … desired movements to occur and simultaneously … competing, non-intended movements from occurring

enabling, inhibiting

Movement disorders due to abnormalities of the basal ganglia: … (2)

Parkinson, Huntington

The basal ganglia are the … in the cerebral hemisphere, the … in the diencephalon, and the … in the midbrain

corpus striatum, subthalamic nucleus, substantia nigra

The corpus striatum is subdivided anatomically into: … (2)

Caudate, lentiform nuclei

The caudate and lentiform nuclei are two large nuclear masses are deep within the cerebral hemisphere, with the … located in the wall of the lateral ventricle

comma-shaped caudate nucleus

…: Caudate nucleus & putamen

Striatum

Connections of the basal ganglia: … (3)

Input from outside sources, interconnections between nuclear masses that form basal ganglia, output from the basal ganglia to motor centers

The basal ganglia receive input mainly from the …, virtually all areas of the cerebral cortex project in an orderly manner to the striatum

cerebral cortex,

… reach the caudate nucleus and putamen directly from the adjacent white matter, most via the anterior limb of the internal capsule

Corticostriate projections

Corticostriatal projections from …, …, and … of the cerebral cortex project somatopically to the putamen

motor, premotor, somatosensory

A direct cortical projection passes from the … and … to the subthalamic nucleus

motor, premotor

Important connections between individual nuclei of the basal ganglia: … (3)

Reciprocal striatum and substantia nigra, reciprocal pallidum and subthalamic nucleus, striatopallidal projection

…: the chief output nucleus of the basal ganglia, exerts a strong influence on the thalamus

Medial pallidum

…: Lenticular fasciculus and ansa lenticularis joined together and travel into the thalamic fasciculus to the ventral anterior nucleus

Pallidothalamic fibers

the medial pallidum sends … to the thalamus

inhibitory signals

The output from the Globus pallidus internus reaches the thalamus through two fiber bundles: …

Lenticular fasciculs, ansa lenticularis

…: the lenticular fasciculus and ansa lenticularis together

thalamic fasciculus

The inhibitory signals from the the GPI travel through the thalamic fasciculus to the …

ventral anterior nucleus of the thalamus

The ventral anterior nucleus then sends … to the premotor cortex

excitatory projections

The premotor cortex then sends signals to the …, to activate the upper motor neurons for movement

primary motor cortex

Pathway of basal ganglia output: … → … → … → … → … → … → … → … (8)

Medial globus pallidus, lenticular fasciculus + ansa lenticularis, thalamic fasciculus, ventral anterior nucleus, premotor cortex, motor cortex, spinal cord, muscles

Main components of the Basal Ganglia: … (5)

caudate nucleus, putamen, globus pallidus, subthalamic nucleus, substancia nigra

…: a C-shaped gray matter structure that curves around the lateral ventricles, part of the striatum, receives input from the cortex and is involved in motor control, learning, and cognition

Caudate nucleus

…: large, rounded structure on the lateral side of the basal ganglia, fused with the head of the caudate nucleus anteriorly, functions as part of the striatum (input from the cortex), involved in regulating movement and motor skills

Putamen

…: lacted medial to the putamen, many myelinated fibers (pale color), two parts, controls voluntary movement by modulating thalamic activity

Globus pallidus

Two parts of the Globus Pallidus: …

Globus pallidus lateral, Globus pallidus medial

…: Involved in the indirect pathway

Globus pallidus lateral

…: Main output of the basal ganglia to the thalamus

Globus pallidus medial

Lentiform is composed of: … (2)

Putamen, globus pallidus

…: looks like a lens shaped, nit functionally distinct but a convenient anatomical grouping

Lentiform nucleus

…: a small lesn shaped nucleus just below the thalamus, part of the indirect pathway, excites the Globus pallidus medial → supressing unwanted movements

Subthalamic nucleus

…: located in the misbrain, just below the thalamus and basal ganglia,two parts, degerates in parkinsons disease leading to movement disorders

Substantia nigra

Substantia nigra is composed of: … (2)

Pars compacta, pars reticulata

…: males dopamine which modulate the striatum

Pars compacta

…: acts like globus pallidus medial, sending output to the thalamus

Pars reticulata

…: a large paired structure in the diencehalon, acts as a relay center for sensory and motor signals to the cortex, the ventral anterior nucleus recieves output from the basal ganlia and sends it to the premotor cortex

Thalamus

…: located in the frontal lobe, just anterior to the primary motor cortex, involved in planning movemetns and sending signals to the motor cortex

Premotor cortex

…: located in the precentral gyrus of the frontal lobe, contains upper motor neurons that control voluntary movement via the pyramidal tract

Motor cortex

…: neural pathways allows the basal ganglia to initiate and fine-tune goal directed movement, facilitate motor learning, like forming habits or patterns, select or suppress certain actions or behaviors, influence memory and emotion via connections to limbic system

Cortico-basal ganglia-thalamic cortical loops

…: large masses of grey matter buried within the white matter

Basal ganglia

…: caudate nucleus and putamen

Striatum

Basal ganglia participate in multiple neural pathways that … in the cerebral cortex

arise and terminate

Basal ganglia are involved in … (3)

movement, memory, emotion

Depending on the connections the basal ganglia can: … movement (3)

Start, stop, modulate

The cerebral cortex sends … to you the striatum and subthalamic nucleus, these inputs start the motor command and activate the basal ganglia circuit

glutamate (excitatory)

The substantia nigra par compacta sends … the striatum

dopamine to modulate

…: excitatory (facilitates movement), in the direct pathway, found on the striatum

D1 receptors

…: inhibitory (suppresses unwanted movement), in the indirect pathway, found on the striatum

D2 receptors

… balances both pathways (direct and indirect)

dopamine

The striatum sends … to the pallidum and substantia nigra

GABA (inhibitory)

The striatum shuts down … to release motor inhibition

downstream structures

The subthalamic nucleus sends glutamate (excitatory) to the …, this strengthens the inhibition on the thalamus (part of the indirect pathway)

globus pallidus internal segment

The globus pallidus medial and Substantia nigra send GABA (inhibitory) to the …, keeps movement suppressed unless the direct pathway lifts the inhibition

ventral anterior nucleus of the thalamus

The Ventral anterior nucleus sends glutamate (excitatory) projections to the …, final step that allows movement planning and execution in the cortex

premotor cortex

…: promotes desired movement by reducing inhibition on the moor cortex

Direct pathway

Direct pathway: … → … → … → … → … → … → … → … → … → … (9)

Cortex, glutamate, striatum (stimulated), GABA, Globus pallidus medial and Substantia Niagra (inhibited), thalamus (now disinhibited), glutamate, motor cortex (excite), activates movement

The direct pathway … → so the thalamus can be disinhibited and can activate movement

inhibits the inhibitor

…: suppresses unwanted or competing movements

Indirect pathway

Indirect pathway: … → … → … → … → … → … → … → … → … → … → … → … (12)

Cortex, glutamate, striatum (stimulates), GABA, globus pallidus lateral (silenced), subthalamic nucleus, glutamate, Globus pallidus medial (excited), GABA, thalamus (inhibited), unstimulated motor cortex, reduced movement

in the indirect pathway the …

more inhibition on the thalamus = less movement

The abnormalities associated with malfunctions of the basal ganglia are the result of an imbalance in activity in the direct and indirect pathways as a result of the loss of control normally exerted on the … or on the …

striatum by the substantia nigra, pallidum by the striatum and subthalamic nucleus

The striatum relieves the cortex from … necessary for a desired action and concomitant suppression of conflicting movements

sequencing all the specific movement programs

the … permits and controls movement through the …, which projects to the … via the … of the motor thalamus

striatum, medial pallidum, premotor cortex, ventral anterior nucleus

The premotor cortex programs complex voluntary movements through connections with the motor cortex and its upper motor neurons, honing of striatal and pallidal output occurs through … with the substantia nigra and the subthalamic nucleus respectively

reciprocal connections

…: actions the patient wants to perform but cannot

negative signs

…: spontaneous actions the patient does not want to preform but cannot prevent

positive signs

The negative signs occur becuase the abnormal neurons can no longer …

elicit an activity

The positive signs occurs because of the … or the release of other parts of the motor system → producing an abnormal pattern of movement

loss of control

Negative signs: … (3)

akinesia, bradykinesia, abnormal postural adjustments

…: hesitancy in starting a movement

akinesia

…: slowness of movement

Bradykinesia

Positive signs of basal ganglia disease include alterations in … and various forms of …

muscle tone, dyskinesia

…: the loss of pallidal inhibition of thalamic neurons

“release” phenomena

…: tone in all of the muscles acting on a joint is increased

rigidity

Dyskinesia: … (3)

Chorea, athetosis, ballismus

…: abnormal involuntary movement

chorea

…: condition in which the extremities preform slow, involuntary motions

athetosis

…: Jerky or shaking movements of the arms or legs, especially such movements occurring in chorea

Ballisums

…: the combination of tremor, rigidity, akinesia, bradykinesia, and abnormal postural adjustments occurs

Parkinsons disease

Parkinsons disease is associated with degeneration of the …

dopamine neurons in the substantia nigra

Parkinsons disease pathway: … → … → … → … → … → … → …

failure of the substantia nigra, disinhibition of the striatum, increased inhibition of lateral pallidum, disinhibition of the subthalamic nucleus, increased excitation of the medial pallidum, increased inhibition of the thalamus, decreased excitation of the cerebral cortex

…: associated with degeneration of striatum, neuronal degeration, presents with chorea and athetosis (associated with abnormalities in pallidum), autosomal dominant gene

Huntingtons disease

Huntington disease pathway: … → … → … → … → … → … → … (7)

Failure of the striatum, disinhibition of the lateral pallidum, increased inhibition of the subthalamic nucleus, decreased excitation of the medial pallidum, disinhibition of the thalamus, increased excitation of the cerebral cortex

…: separates the lentiform nucleus from the caudate nucleus and the thalamus

internal capsule

…: the upper portions of the cerebral white matter

corona radiata

… enter the corona radiate and descend toward the internal capsule

axons from the cerebral cortex

In addition to the corticospinal tract, the cerebral white matter converys … between differtn cortical areas, and between cortex and deep structures (basal ganglia, thalamus, and brainstem)

bidirectional information

Parts of the internal capsule: … (4)

anterior limb, genu, posterior limb, visual radiation

…: separates the head of the caudate from the globus pallidus and putamen (lentiform nucleus)

anterior limb of internal capsule

…: separates the thalamus from the globus pallidus and putamen

posterior limb of internal capsule

…: transition from the anterior limb to the posterior limb, at the level of the foramen of monro

genu

The … lie in the posterior limb of the internal capsule

corticospinal tract

…: preserves in the internal capsule, motor fibers for the face are more anterior and those of the arms and legs are progressively more posterior

somatotopic map

The patient with pyramidal patter of weakness has suffered a large right hemisphere stroke leading to weakness and spasticity affecting the left side of his body; the upper limbs are … because these muscles are stronger than the …, the lower limb is …

flexed, extensors, extended and ridged

Main blood supply to the basal ganglia: …

middle cerebral artery

…: main artery that supplies the basal ganglia coming off the middle cerebral cerebral artery

Lenticulostriate arteries

minor supply of the basal ganglia: … (2)

anterior cerebral artery, anterior choroidal artery

Substantia nigra and sub thalamic nucleus are more posterior and thus receive blood supply from branches of: … (2)

posterior cerebral artery, posterior communicating arteries

Venous drainage of the basal ganglia: … → … → …

striate branches. internal cerebral vein, great cerebral vein