Topics 7-8 Basal Ganglia anatomy and pathology Flashcards
List the components of the Basal Ganglia
-Caudate nucleus
-Putamen
-Globus pallidus (GPe -lateral/external GABA
(GPi -medial/internal GABA
-Substantia nigra(Pars compacta SNc Dopamine
(Pars reticularis SNr GABA
-Subthalamic nucleus
Striatum= caudate + putamen
lentiform nucleus= putamen + globus pallidus
Direct pathway in the Basal Ganglia
Direct pathway-Excitatory in nature(^ motor activity)
Cortex
excites
**Striatum
Inhibits
**GPi & SNr
disinhibits
**Thalamus ( VA)
Excitatory ( increased firing from thalamus to cortex)
**Cerebral Motor cortex
Indirect pathway in the Basal Ganglia
Indirect pathway-Inhibitory in nature(^ motor activity)
Cortex
excites
**Striatum
Inhibits
GPe
Disinhibits
**Subthalamic nucleus
excitates
GPi
Inhibits
**Thalamus (VA/VL)
Reduced firing from thalamus to cerebral cortex
**Cerebral cortex
Indirect pathway in the Basal Ganglia
Indirect pathway-Inhibitory in nature(^ motor activity)
Cortex
excites
**Striatum
Inhibits
GPe
Disinhibits
**Subthalamic nucleus
excitates
GPi
Inhibits
**Thalamus (VA/VL)
Reduced firing from thalamus to cerebral cortex
**Cerebral cortex
Which parts of the Basal ganglia are excitatory and which are inhibitory?
Excitatory (use glutamate)
Cerebral cortex
Subthalamic nucleus
Thalamus
Inhibitory (use GABA)
Striatum
Globus pallidus GPe
Globus pallidus GPi
Dopaminergic modulation of Direct and indirect pathways
OVERALL INCREASE MOTOR ACTIVITY
Substantia nigra produces dopamine and releases it to the striatum
Dopamine> Excitatory effect on direct pathway
Dopamine> Inhibitory effect on indirect pathway
Choliergic (ACh) modulation of Direct and indirect pathways
OVERALL DECREASE IN MOTOR ACTIVITY
Cholinergic neurons live in striatum and synapse with neurons projecting into the GPi & GPe
Inhibit the direct pathway
Excite the indirect pathway
Connections from basal ganglia to rest of the body
BASAL GANGLIA affect movement on the contralateral side of the body.
circutry occurs on ipsilateral side of brain so basal ganglia affect functin mediated by the ipsilateral motor cortex buuuut the motor cortex affect the contralateral side of the body
Connections within the basal ganglia
cerebral cortex> striatum>
GPe >subthalamic nucleus (Indirect pathway)
Globus pallidus internus >ventral thalamus>cerebral cortex
Parkinsons disease
Hypokinetic disorder
Loss of dopaminergic neurons in the SUBSTANTIA NIGRA t/f decrease in dopamine in brain
decreased activity in direct pathway
increased activity in indirect pathway
decreased cortical motor output (Hypokinesia)
Rigidity Bradykinesia(hypokinesia) Akinesia(freezing) Resting tremor Postural instability Flexed/stooped posture Visuospacial deficits Festinating gait Mask like face Dribbling Postural hypotension Autonomic changes Personality changes
Huntingtons disease
Hyperkinetic disorder
Cause & symptoms
Caused by faulty gene on chromosome 4
Atrophy of striatum (caudate & putamen)
loss of striatal GABAMinergic neurons
1)starts in indirect pathway
)loss GABAminergic neurons in direct pathway
Chronic progressive chorea Athetosis Stumbling and clumbsiness Lack of concentration Short term memory loss Depression Dementia Dystonic posturing Emotional changes Impulsiveness Moodiness Antisocial behaviour Loss of drive
Chorea define
Continous series of rapid jerky involintary movements that are fragments of purposeful movement.
may become athetosis as in huntingtons
Athetosis define
Continual uncontrolled WRITHING. usually involve hands and face. Spontaneous movement blends in the next creating constant and purposeless motion. Movement combinations of alternating antagonistic motions eg pronation/supination
Ballisms define
Violent involintary movement of proximal muscles that result in flinging of extremities. Evolves into a form of chorea or athetosis
Cause:descrete lesion to STN contralat to affected side
Tics
Uncontrollable compulsive behaviour. Quick fragments of purposive movement endlessly repeated in a steriotyped manner. eg sniffing, throat clearing
