Extrapyramidal Motor System Flashcards
Medium Spiny neurons
Neurons in the neostriatum that utilize GABA
Extrapyramidal Motor System
Plays a role in habitual learning and modulating movement
*Actions are unconscious
Aspiny Neurons
Interneurons found in the neostriatum that are excitatory and utilize Ach
Globus Pallidus
Derived from the diencephalon
*GPi=major output division
Afferent projections of neostriatum
- Cortex (via IC)
- Thalamus
- Substantia Nigra (uses dopamine)
Efferent projections of Neostriatum
- Globus pallidus
- Substantia Nigra
(Uses GABA)
GP and SN projections
VA/VL
-These axons then project to the motor cortex to modulate the firing of neurons in the corticospinal tract
“Direct” Pathway
Normal projection of Extrapyramidal System
*Dopamine= EXCITATORY
“Indirect Pathway”
Neostriatum projects to GPe, then to subthalamic nuclei, before reaching GPi
*Dopaimine= INHIBITORY
Net result= Increased inhibition of VA/VL
Substantia Nigra projections
- Red Nucleus
- muscle tone - Superior Colliculus
- Adjusts eyes to - Reticular Formation
- Turns attention to - VA/VL- influence cortex firing of UMNS
Parkinson’s Disease
*Mostly idiopathic cause
Loss of pars compacta => loss of dopaminergic input to neostriatum
- Increased activity of indirect pathway; decreased of direct
Symptoms include: "TRAP" Akinesia Parkinsonian Stare Festinating gait Dyskinesia Resting tremor Cogwheel rigidity of muscles Drooling, increased sebaceous secretion
*Pt will have normal reflexes when startled
Lewy Bodies
Inclusion bodies found in the SN in pts. w/ Parkinson’s Disease
*Synuclein= major component caused by point mutation
Parkinsonism due to known insult
- Encephalitic inflammation
- Stroke of ACA, MCA, or PCA
- CO Poisoning
- Toxic substances
- Toxic manifestation of Thorazine/ long-term methamphetamine use
Huntington’s Chorea
Abnormal expansion in length of CAG sequence on chromosome 4
=>degeneration of medium spiny neurons (Neostriatum); excess activation of GPe
Overall decreased inhibitory input to VA/VL
Symptoms: Degeneration of Prefrontal Cortex Chorea -especially of face, tongue, and extremities; pt. may try to hide these Paranoia
*Highest suicide rate for neurological illness
Ballismus
Severe movement disorder including flinging of extremities; fatal disorder within 12 months
-Caused by lesion in subthalamic nucleus
=>Decreased inhibitory input to VA/VL
*Movements will disappear during sleep