Lecture 13: Contributions of Cerebellum and Basal Nuclei to Motor Function II Flashcards
Dopamine in indirect pathway (Caudate circuit) vs. in the direct pathway (Putamen Circuit)
- Dopamine is inhibitory on the indirect pathway
- uses D2 receptors
- Dopamine is excitatory on the direct pathway
- uses D1 receptors
- The action of dopamine overal is excitatory
What is agnosia? With what lesion is it associated?
- inability to accurately perceive objects through normally functioning sensory mechanisms
- caused by lesions of the posterior parietal cortex
Define Parkinson’s disease and relate it to respective lesions:
- AKA: Paralysis agitans
- characteristics
- rigidity of much of body musculature
- involuntary tremors of involved areas even at rest at a fixed rate
- serious difficulty in initiating movement (akinesia)
- Postural instability
- Dysphagia, speech disorders, GAIT disturbances, fatigue
- results from widespread destruction of pars compacta of substantia nigra that sends dopaminergic fibers to caudate nucleus and putamen
- dopaminergic pathways to direct and indirect pathways are lost. the direct pathway loses some of its excitatory input and the indirect pathway loses some of its inhibitory input. In both cases there is decreased motor activity
Define Athetosis and relate it to respective lesions:
- lesions in the globus pallidus frequently lead to spontaneous and often continuous writhing movements of a hand, an arm, the neck, or the face.
Define hemiballismus and relate it to respective lesions:
- A lesion in the subthalamus often leads to sudden flailing movements of an entire limb
What are the most important functions of the basal nuclei (ganglia)?
- The basal nuclei help to paln and control complex patterns of muscle movement, controlling relative intensities of the separate movements, directions of movemnts, and sequencing of multiple successive and parallel movements
- Plan and execute motor commands in convert with cerebral cortex; help cotex execute subconscious but learned pattern
- help plan multiple parallel sequential patterns
- control complex patterns of motor acitvity
Define Huntington’s disease and relate it to respective lesions:
- indirect pathway no longer has inhibitory influence on direct pathway and motor activity is increased
- Caused by the loss of most of cell bodies of GABA-secreting neurons of caudate nucleus and putamen and of Ach neurons in other parts fo the brain
- GABA neurons normally inhibit parts of the globus pallidus and substantia nigra
- Characteristics
- Flicking movements of individual muscles
- Progressive severe distortional movements of entire body
- Severe dementia
- Motor dysfunctions
- Usually beocmes symptomatic around 30-40 years of age
Be able to diagram the direct and indirect pathways of the basal nuclei and the neurotransmitters involved and whether they are inhibitory or excitatory. This includes the role of the substantia nigra reticularis and compacta and the subthalamic nuclei
- Putamen circuit (direct)
- for subconscious execution of learned patterns of movement
- overall excitatory - tends ot increase motor activity
- pathway
- Cerebral cortex (premotor, supplementary motor, somatosensory) uses acetylcholine to activate —-> Putamen(can also be ativated by dopamine d1 from the substantia nigra compacta) then uses GABA to be inhibitory on the —> Globus pallidus (internal) and substantia nigra reticularis, which use GABA to be inhibitory on the —-> Thalamic relay nuclei (ventroanterior and ventrolateral nuclei) which uses glutamate to be excitatory on the —> primary motor cortex (and premotor/supplementary)
- (note that this pathway bypasses the caudate nucleus
- Caudate nucleus circuit (indirect)
- For cognitive planning of sequential and parallel motor patterns.
- Plays major role in cognitive control of motor activity.
- Overal inhibitory– tends to decrease motor activity
- Pathway
- Cerebral cortex (premotor, supplementary motor, somatosensory) uses acetylcholie to activate —> Caudate nucleus (the substantia nigra compacta uses dopamine via D2 receptors to inhibit the Caudate nucleus) then uses GABA to inhibit —> Glbus pallidus (external) wich uses GABA to inhibit —> Globus pallidus (internal) which uses GABA to inhibit —> Thalamic relay nuclei (ventroanterior and ventrolateral nuclei) uses glutamate to activate —–> premotor and supplemental motor cortex
What is personal neglect syndrome
Example: a person with a lesion in the right posterior parietal cortex might try to copy drawlings. In these cases, the patient’s ability to copy the left side of the drawings is severely impaired. Also, such a person will always try to avoid using his or her left arm, left hand, or other portions of his or her left body for the performance of tasks, or even to wash this side of the body, almost not knowing that these parts of his or her body exist.
Neurotransmitters in the basal ganglial system
- Dopamine pathways
- from the substantia nigra to the caudate nucleus and ptuamen
- GABA pathways
- form the caudate nucleus and putamen to the globus pallidus and substantia nigra
- Acetylcholine pathways
- form the cortex ot the caudate nucleus and putamen
- Mulitple general pathways from the brain stem that secrete
- norepinephrine, serotonin, enkephalin, and several other neurotransmitters in the basal ganglia, as well as in other parts of the cerebrum
- Multiple glutamate pathways
- Provide most of the excitatory signals
Describe lesions associated with each of the basal nuclei
- Lesions in globus pallidus
- frequently lead to spontaneous and often continuous writhing movements of a hand, an arm, the neck, or the face. These movements are called athetosis
- Lesions in subthalamic nuclei
- often leads to sudden flailing movements of an entire limb, a condition called hemiballismus
- Lesions in striatum
- Lesions in substantia nigra
- lead to the common and extremely severe disease of rigidty, akinesia, and tremors known as Parkinson’s disease
- Lesions in Putamen
- lead to flicking movements in hand, face, and other parts of the body, called chorea
Define Chorea and relate it to respective lesions:
- Multiple small lesions in the putamen lead to flicking movements in the hands, face, and other parts of the body
