click below
click below
Normal Size Small Size show me how
Basal Ganglia & Conn
Basal Ganglia & their connections
Question | Answer |
---|---|
What are the basal ganglia? | Masses of gray matter within each cerebral hemisphere |
Corpus Striatum in general | Divided by internal capsule into Caudate nucleus & Lentiform nucleus & globus pallidus + putamen) |
Basal ganglia... | Corpus Striatum; Amygdaloid nucleis; Claustrum |
Caudate Nucleus | Head = lateral wall of anterior horn of lateral ventricle (butterfly wing); Head continuous inferiorly with putamen; Cell bridges = striated; Body; Tail ends anterior to amygdala |
Lentiform Nucleus relationship to internal capsule | Lateral to internal capsule; IC separates lentiform from thalamus |
Lentiform Nucleus relationship to external capsule | Medial; EC separates it from thin sheet of gray matter (claustrum) |
Lentiform relationship to putamen | Putamen is more lateral |
What system is the amygdala part of? | Limbic System |
Amygdala function | Body's response to environmental changes (tied to reticular formation) |
Substantia Nigra & Sub-Thalamic Nuclei | Closely related functionally, situated near BG (NOT part of BG) |
Neurons of the Substantia Nigra are? | Dopaminergic & Inhibitory; have many connections to corpus striatum |
Neurons of the Sub-Thalamic nuclei are? | Glutaminergic & excitatory; have connections to GP & SN |
What is the function of the claustrum? | Unknown |
What is the substantia nigra? | Pigmented mass of neurons b/t cerebral peduncle & midbrain tegmentum; 2 main areas: Dorsal/Ventral |
Dorsal Substantia nigra is aka, & contains what? | Pars Compacts; contains dopamine |
Ventral Substantia Nigra is aka, & contains what? | Parts Reticulata; contains iron pigments |
SN serves as a "fence" & fences off what? | Corticospinal tract & tegmentum of upper pons/lower midbrain |
If afferent fibers arrive from the caudate nucleus & putamen to SN-Pars Compacta where is info sent? | Right back |
If afferent fibers arrive from caudate nucleus & putamen to SN-Pars Reticulata, where is info sent? | Processed & sent outside BG to control head/eye movements |
Afferent fibers arrive mostly from? | Cerebral cortex; also from globus pallidus & sub-thalamic nucleus |
What neurons are lost in pts with Huntington's disease? | Pigmented & non-pigmented |
Parkinson's patients only lose what? | Dopamine (pigmented) |
What are the main sites receiving input to the BG? | CN & Putamen |
what is the major site from which output leaves BG? | Globus Pallidus |
Do the BG nuclei receive input form SC? | No direct input from SC; little direct input to SC |
Afferent Connections of Corpus Striatum | Corticostriate (ipsilateral; input from sensory-motor cortex); Thalamostriate (intralaminar nuclei of thalamus to CN/putamen); Nigrostriate (from SN to CN & putamen); Brainstem striatal fibers |
Efferent connections of corpus striatum | Striatopallidal & Striatonigral |
Afferent connections of GP | Striatopallidal |
Efferent connections of GP | Pallidofugal fibers |
Corpus striatum receives afferent info from where? | cerebral cortex (esp pre-motor/supp motor area/primary sensory cortex); Thalamus; Sub-thalamus; Brainstem (including SN) |
Outflow of BG is channeled through what & influences what? | GP; influences activities of motor area of cerebrum or motor centers of brainstem |
BG control what by influencing cerebral cortex? | Muscle mvmts |
BG has no direct control through? | Descending paths to brainstem & SC |
Destruction of primary motor cortex prevents what? | Performance of fine discrete mvmts of hands/feet contralaterally (pt can still perform gross mvmts contralaterally) |
The thalamus is inherently active & all info from thalamus back to cortex is | Positive |
Can the cerebral cortex receive constant positive feedback from the thalamus? | No, it has to be modulated/relatively inhibited by various neurotransmitters such as GABA |
Indirect motor loop | More negative signals via GABA than direct motor loop; Less excitatory info to thalamus (slow process due to extra step) |
Parallel BG paths for mvmt, eye mvmt, congition, emotion (all have direct/indirect components) | Motor; Oculomotor; Pre-frontal; Limbic |
Oculomotor Path/Loop Cortical Sources | Frontal eye fields; Supplementary eye fields; Dorsolateral pre-frontal cortex; Posterior parietal cortex |
Inputs of oculomotor path directed where? | Mostly to the body of the caudate nucleus, which projects to GP-I & SN-PR |
Oculomotor Path- Thalamic targets are? | Dorsomedial & VA |
Oculomotor Path- Dorsomedial thalamus | Determines behavioral important of inputs; Inhibits motor response when task requires delaying response; Influences affective behavior, decision making, judgment, memory |
What completes the oculomotor loops? | Thalamocortical projections to frontal eye field & supplementary eye fields |
Which loop is important in cognitive processes involving frontal lobes? | Pre-Frontal Loop |
What are cortical sources of input in pre-frontal loop? | Posterior parietal cortex & pre-motor cortex |
Inputs of pre-frontal loop directed mostly where? | Head of caudate nucleus, which projects to GP-I & SN-PR |
Thalamocortical parts of pre-frontal loop projects to what? | Pre-frontal cortex, esp pre-frontal heteromodal assn cortex |
Pre-frontal loop- pre-frontal cortex does what? | Responds to behavioral importance of inputs; Intergrates emotional events with complex sensory stim; Helps with emotional processing, planning, & decision making |
Limbic Loop function | Regulation of emotions & motivational drives |
Cortical sources of input to limbic loop are? | Temporal cortex, hippocampus, amygdala |
Inputs f limbic loop mostly directed where? | Nucleus accumbens, ventrla caudate, ventral putamen |
Limbic Loop- thalamocortical projections to where? | Anterior cingulated, orbital frontal cortex (part of limbic system |