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Basalnucleicerebellu
Neuro Basal Nuclei & Cerebellum
| Question | Answer |
|---|---|
| The motor system is: | a massive parallel process that is initiated in the frontal lobe & executed from ventral horn |
| Sensory feedback needs to be incorporated at which levels? | @ all levels to ensure that the actual mvmt is the intended goal |
| Sensory feedback occurs both as: | local action in the GAMMA LOOP & as mass action in BASAL NUCLEI & CEREBELLUM |
| The basal nuclei: | pulse out motor commands by inhibiting & disinhibiting CST circuits |
| The cerebellum: | will simultaneously compare the motor output to unconscious sensory feedback & the vestibular & reticular nuclei prepare our bodies for mvmt in relation to gravity |
| Basal nuclei are essential for: | modulation of motor control |
| Basal nuclei consist of: | paired cell groups in each hemisphere that form multiple circuits b/w cerebral cortex, thru BN, to thalamus, & back to motor cortex again |
| BN circuits involve: | subthalamus, substantia nigra, & septal nuclei |
| Septal nuclei are: | poorly understood set of neuron pools just rostral to lamina terminalis |
| How many distinct loops are there thru the BN? | @ least 5 |
| Functionally and anatomically, the ______ & _______ (BN) are intimately related. | caudate, putamen |
| At rostral/ventral extreme of the nuclei, the _______ & ______ are fused, but separate as they move caudally. | caudate, putamen |
| Caudate and putamen together constitute: | neostriatum, named b/c it's phylogenetically new and looks striated or striped |
| Stripes of neostriatum are: | NT cell clusters, w/ excitatory & inhibitory transmitters that modulate the local activity of the striatum |
| The spiny neurons of the striatum utilize ________ NT and are _____________ (excitatory or inhibitory). | GABA, inhibitory |
| Nucleus accumbens: | sits @ base of striatum & is included in neostriatium |
| Striatum receives input from ___________ & reciprocally from the _______ _______, & outputs to the _______ _______. | cortex, substantia nigra, pallidal complex |
| Pallidal complex is mainly the: | globus pallidus |
| Globus pallidus is divided into: | inner & outer segments & is GABAergic, thus inhibitory to its targets |
| At base of pallidal complex sits the _____ _____ & the ____ _ ______. | substantia innominata, basal nucleus of Meynert |
| BN of Meynert is: | a large collection of ACh neurons that are lost in Alzheimer's disease, as are other ACh centers |
| Inner segment of globus pallidus receives input from the ______, specifically the _____ & projects to the _____. Is this direct or indirect path? | striatum, specifically the putamen & projects to the thalamus (this is DIRECT PATH) |
| Out of the inner segment of GP, what emerge? | 2 efferent tracts |
| What is the significance of the ansa lenticularis and the lenticular fasciculus? | Begin as separate paths out of the inner segment, but merge as they enter the thalamus to synapse on the AN, VN, and CM nucleus |
| What is the INDIRECT path? | The outer segment of GP; contains an extra synapse; it receives input from striatum & projects mainly to subthalamus |
| Subthalamic nuclei are ________, but they are almost continuously inhibited by the ______ segment of GP. | excitatory (glutamate), outer; (if this inhibition removed, then cells fire uncontrollably |
| Substantia nigra is reciprocally connected to what? | Almost all these structures |
| What parts of the substantia nigra are interconnected? | pars compacta and pars reticularis |
| What does the pars compacta contain? | the dopaminergic cells that can either excite or inhibit the caudate & putamen, depending on type of receptor on post-synaptic membrane |
| What does pars reticularis do? | Constantly inhibits its targets, such as neostriatum, thalamus, & superior colliculus |
| How are the direct & indirect pathways related? | They have opposing actions on the activity of the targets of the basal nuclei |
| How does the direct pathway facilitate flow thru the BN? | By releasing the brake through a process of disinhibition; this increases activity of thalamus & subsequent excitation of motor cortex |
| How does the indirect pathway work? | It inhibits this flow by (through BN) by pumping the brake; this decreases activity of thalamus & subsequent excitation of motor cortex |
| Describe direct pathway (2 things): | 1. Inhibitory connection from putamen to inner segment of GP. 2. Inhibitory connection from GP to thalamus. |
| Describe indirect pathway (4 things): | 1.Inhibitory connection from putamen to outer segment GP. 2.Inhibitory connection GP to subthalamic nucleus. 3.Excitatory connection from ST to inner segment GP. 4. Inhibitory connection to thalamus. |
| What is the function of the direct pathway? | To release thalamus from inhibition by GP, or release the brake |
| What is the function of the indirect pathway? | Disinhibits the subthalamus so it can excite the GP & therefore inhibit cortex & thalamus, or pump the brake |
| What can you trace behavioral deficits related to the BN to? | Imbalances b/w direct and indirect pathway |
| T/F. All of the loops of the BN have antagonism b/w direct and indirect pathway. | True--each loop is reciprocally connected to a unique part of the cortex, thalamus, & basal nuclei components, w/ dopamine playing an impt role in all of them. |
| In addition to the motor loop, there are 3 other loops identified, whose names are: | 1. Executive 2. Motivational 3. Visuospatial |
| What is the executive loop? | Involved in recognizing behavioral context & modulating cortical activity that's appropriate for that context, e.g. in gp setting, or in diad; damage causes cognitive dysfunction |
| What is the cingulate cortex? | It's looped into BN, along w/ other brain structures that influence motivation/emotion; current research looking how to pharmacologically manipulate this loop to control schizo, depression, other affective/emotional disorders |
| What is the visuomotor loop? | Includes connections to superior colliculi; involved in directing gaze & head orientation during behavior; Parkinson's affects these loops @ diff. stages of the disease |
| Relate Parkinson's to visuomotor loop: | e.g. motor dysfctn 1st, followed by eye disturbances, then executive fctn, lastly motivation loop affected resulting in dementia; these can result in hypo/hyperkinesia |
| What causes the hypokinetic disturbances of Parkinson's disease patients? | Lesions to neostriatum, subseq. lack of disinhibition of thalamus by direct pathway (brake won't release) & increase of inhibition of thalamus from indirect pathway (brake inappropriately applied) |
| When is the substantia nigra dopaminergic loop active? | @ same time as direct/indirect pathways (parallel distributed processes) |
| D1 receptors makes dopamine _______ in the striatum and D2 receptors are ________. | excitatory; inhibitory |
| This NT modulates the BN, sharpening the responses, & if absent, produces characteristic signs of Parkinson's disease: | dopamine! |
| Huntington's disease: | genetic, progressive, most die 15 yrs onset; sx young adult(35-45), see flattened head of caudate--MRI; affects all BN loops, behavioral deficits assoc w/ each loop; faulty gene replication causes XS glutamate permanently bind receptors, causes cell death |
| Parkinson's disease: | mean onset 55yo; resting tremor, asymmetric gait, reduced eye blink, arm swing while walking; cause is idiopathic, results in cogwheel rigidity, bradykinesia, loss of postural control, mostly affecting motor/cognitive loops of BN |
| Parkinson's disease: | these sx usually occur after majority of dopaminergic cells are dead & surviving neurons contain Lewy bodies (which can occur in other neuro diseases too); trtmt slows progress, but won't stop it; stem cell implants, surg, L-dopa to treat |
| Wilson's disease: | genetic; early onset, usually by 25yo, failure to metabolize copper, damaging liver & lenticular nucleus; Kayser-Fleisher rings, Parkinsonian behaviors, wing-flapping common signs; trt w/ chelation to remove copper, prognosis good if get trtmt early |
| What is the large superstructure that receives all unconscious sensory processing, yet doesn't contribute to sensory discrimination or interpretation and has profound influence on motor fctn (but its partial destruction won't result in paralysis)? | CEREBELLUM! |
| What does the cerebellum do? What does damage to it do? | great comparator of sensory, motor, & learned input to generate coordinated mvmt; damage causes uncoordinated (uncompared) behavior; highly convoluted, contains core of white matter w/ cerebellar nuclei |
| What are the 3 cerebellar stalks connecting cerebellum to brainstem? | Inferior cerebellar peduncle, middle cerebellar peduncle, superior cerebellar peduncle |
| What is the inferior cerebellar peduncle and what's its function? | union of juxtaform & restiform bodies & serves to connect cerebellum to medullar & vestibular nuclei (carries spinocerebellar tract) |
| What is the middle cerebellar peduncle and what's its function? | continuous w/ basal pons @ about level of trigeminal roots & carries pontocerebellar fibers |
| What is the superior cerebellar peduncle and what's its function? | sweeps up into midbrain just below level of exiting trochlear nerve (CN IV); fibers in this peduncle decussate @ level of inf. colliculi & contain cerebellar efferents from deep nuclei to stem and thalamus |
Created by:
aostromecki
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