Thalamus/Basal Ganglia/Reticular Formation (2) Flashcards
(107 cards)
1
Q
What are the subdivisions of the basal ganglia?
A
striatum- consists of the caudate, putamen and the nucleus accumbens; globus pallidus and substatia nigra
2
Q
Where can the caudate nucleus be found?
A
C-shaped structure that is immediately adjacent to the lateral ventricle
3
Q
Where is the putamen located?
A
lateral and ventral to the caudate and is separated from it by the internal
capsule.
4
Q
Where is the nucleus accumbens located?
A
rostral-ventral to the putamen
5
Q
Where is the globus pallidus located?
A
immediately medial to the putamen
6
Q
What is jointly referred to as the lenticular nucleus?
A
putamen and globus pallidus
7
Q
What are the components of the substantia nigra?
A
pars reticulata- ventral portion of this nucleus and pars compacta- dorsal portion of the nucleus (immediately dorsal to the cerebral peduncle)
8
Q
What portion of the substantia nigra contains dopaminergic neurons?
A
pars compacta
9
Q
Glutaminergic neurons from many regions of the cerebral cortex project to where?
A
striatum via the corticostriatal pathway
10
Q
GABAergic medium spiny neurons of the striatum project to where?
A
globus pallidus
11
Q
What causes huntingtons chorea?
A
degeneration of GABAergic medium spiny neurons of the striatum, caused by a mutation in the Huntingtin gene which results in CAG repeats, codes for glutamine, polyglutamine tracts within the protein are formed
12
Q
GABAergic neurons in the internal segment of the globus pallidus project to where?
A
ventral anterior (VA) nucleus of the thalamus via the lenticular fasciculus and ansa lenticularis
13
Q
Neurons in the VA of the thalamus project to where?
A
supplemental motor cortex
14
Q
Dopaminergic neurons of the substantia nigra, pars compacta project to where? Degeneration causes what?
A
caudate and putamen via the nigrostriatal pathway; Parkinson’s
15
Q
Dopaminergic neurons of the ventral tegemental area project to where? What is this path thought to be involved in?
A
nucleus accumbens; drug addiction
16
Q
Glutaminergic neurons in the subthalamus project to where? Damage results in?
A
internal segment of the globus pallidus; hemiballismus
17
Q
What would be the effect on a patients movement be after a lesion of the striatum?
A
uncontrolled dance like movements-> Huntington’s chorea
18
Q
What would be the effect on a patients movement be after a lesion of the substantia nigra?
A
resting tremor, parkinsons, trouble initiating movement
19
Q
What would be the effect on a patients movement be after a lesion of the subthalamic nucleus?
A
hemiballismus- one limb, sharp, uncontrolled movement, cant stop
20
Q
What separates the thalamus from the hypothalamus?
A
hypothalamic sulcus
21
Q
What are the different nuclei of the thalamus?
A
Anterior division (AN), Medial division (mediodorsal N), Lateral division: Dorsal N (lateral dorsal, lateral posterior, pulvinar), Ventral N (ventral anterior, ventral lateral, ventral posterior lateral, ventral posterior medial, medial geniculate, lateral geniculate); Intralaminar N (centromedian and reticular)
22
Q
What is the input to the pulvinar and LP? ouput from the pulvinar and LP?
A
retina to pretectal n. to superior colliculus; to posterior parietal cortex
23
Q
What is the input to the LGN? ouput from LGN?
A
retina; optic radiations to striate cortex (primary visual cortex)
24
Q
What is the input to the MGN? ouput from the MGN?
A
inferior colliculus via braichi of inferior colliculus; auditory radiation to Herchel’s gyrus (primary auditory cortex)
25
What is the input to the VPL? ouput from the VPL?
gracilis and cuneatus nuclei (ST) via ML; somatosensory radiations to post central gyrus
26
What is the input to the VPM? ouput from the VPM?
solitary n, spinal n. of V, primary sensory n of V; post central gyrus
27
What is the input to the VL? ouput from the VL?
dentate nucleus of cerebellum via dentatorubrothalamic; motor and premotor cortex
28
What is the input to the VA? ouput from the VA?
basal ganglia and globus palidus via thalamic fasciculus; supplementary cortex
29
What is the input to the MD? ouput from the MD?
septal n to amygdala; prefrontal cortex
30
What is the input to the anterior nucleus? ouput from the anterior nucleus?
mammillary bodies via mammilothalamic tract; cingulate gyrus
31
Where is the lateral geniculate nucleus located?
along the banks of the calcarine fissure
32
Sensory information is conveyed by which thalamic nuclei?
lateral posterior, pulvinar, VPL, VPM, medial geniculate, and lateral geniculate
33
Motor information is conveyed by which thalamic nuclei?
ventral anterior, ventral lateral, centromedian
34
Limbic information is conveyed by which thalamic nuclei?
anterior, medialdorsal, pulvinar
35
Consciousness information is conveyed by which thalamic nuclei?
reticular and centromedian
36
What symptoms might a thalamic lesion elicit?
ataxia, loss of fine touch, pain- ex of neuropathic central pain not caused by damage to body tissues but possibly by a stroke
37
What is the input to the basal ganglia?
straitum- caudate nucleus and putamen and nucleus accumbens
38
What is the output of the basal ganglia?
pallidum- lateral and medial segment; pars reticulata of substantia nigra
39
What are the highways to the basal ganglia?
lenticular fasciculus, thalamic fasciculus, and ansa lenticularis
40
Where does the pars compacta of the substantia nigra project to?
striatum
41
What are the intrinsic nuclei of the basal ganglia?
globus pallidus-external segment, ventral pallidum-intrinsic part, subthalamic nucleus, substatia nigra pars compacta, and ventral tegmental area
42
What are the components of the direct system with the basal ganglia?
cerebral cortex (frontal lobe) to input nuclei to output nuclei to thalamus back to cerebral cortex (frontal lobe)
43
What are the components of the direct system with the basal ganglia?
Cerebral cortex (frontal lobe) to input nuclei to globus pallidus external segment/ventral pallidum to subthalamic nucleus (can go backward) to output nuclei to thalamus to cerebral cortex
44
The output nuclei of the basal ganglia projects to where besides the thalamus?
brain stem motor areas thru SCP to the parapontine area
45
What dopaminergic cell groups input to the frontal lobe prior to input nuclei and the input nuclei of the basal ganglia?
SN compacta and Ventrotegmental area
46
What is the function of the direct path of the basal ganglia?
inhibit the brake to activate desired pathway
47
What is the function of the indirect pathway of the basal ganglia?
inhibitory to the inhibitor-> more excitation to internal segment of globus pallidus to inhibit unwanted programs
48
What is the function of the subthalamic nucleus?
inhibit unwanted programs
49
What is the function of the D1 of the putamen/caudate?
excitatory reinforcing desire to move
50
What is the function of the D2 of the putamen/caudate?
reinforcing the desire for inhibition, have more unwanted movements
51
What are the 4 principle input-output loops of the basal ganglia?
skeletomotor loop, occulomotor loop, associative loop, and the limbic loop
52
What are the componnents of the skeletomotor input-output loop of basal ganglia?
somatic sensory/primary motor/premotor/supplementary motor area to putamen to GPi and SNr to VA and VL and back around
53
What type of information is input to the caudate nucleus (head)?
cognition or executive function
54
What type of information is input to the putamen?
skeletal motor
55
What is the input and output to the limbic loop of the basal ganglia?
nucleus accumbens; ventral pallidum
56
What goes wrong in the basal ganglia loops in a hypokinetic movement disorder like Parkinson's?
no SNc to D2 or D1, decreased output of D1 (GABASPDYN) to GPm/SNr, increase output from D2 (GABAENK) to GPi, GPi has a decrease in output to STN and GPm/SNr, STN has increased output to GPm/SNr which has increased output to GPi, VL/VA, tectum and rectic nuclei, all of which have decreased output
57
What is Akinesis?
delay in initiation or starting movement
58
What is Bradykinesis?
prolonged execution of movements
59
What is Hypokinesis?
paucity of normal spontaneous movements
60
What are the features of parkinsonism?
akinesis, bradykinesis, hypokinesis, rigidity, resting tremor (4-5hz, pill rolling), cogwheel rigidity (resting tremor +rigidity), and parkinsonian gait
61
What are the causes of Hypokinetic or Parkinsonian Syndrome
Idiopathic Parkinson disease, Encephalitis lethargica, Head trauma- dementia pugilistica, MPTP- designer drug, Carbon monoxide and manganese poisoning, Drug induced- neuroleptics (dopamine blocking drugs), Wilson disease- hepatolenticular degeneration, Rigidity plus other deficits in multiple neurodegenerative diseases
62
What is chorea?
spontaneous, rapid, jerky, arrhythmic involuntary movements which are purposeless or “fragments of motor programs”
63
What is Athetosis?
inability to sustain the body part in one position. Movements are writhing or snake-like. Often seen with chorea, hence the term choreoathetosis
64
What is Ballismus?
flailing, flinging movement of the whole extremity seen in lesions of the contralateral subthalamic nucleus
65
What is Dystonia?
persistence or fixing of the posture at the extreme of an athetoid movement of either the extremities or the trunk.
66
What are the changes in basal ganglia loops in hyperkinetic disorders like huntigton's?
D2 interrupted output to GPl which has an increase to GPm/SNr and STN which has a decrease to GPm/SNr which has a decrease to GPl, VL/VA, Tectum and Retic nuclei, all have increased output and motor cortex has an increased output
67
Hyperkinetic disorders are characterized by involuntary movements such as?
twitching head, grimacing movements of face, lips and tongue, gesticulating movements in distal parts of upper limbs and jerking in distal lower limbs
68
What are some causes of hyperkinetic disorders?
Huntington- loss of medium spiny stellate neurons (GABA neurons of indirect pathway), Sydenham chorea (rheumatic chorea), Drug induced, Lupus erythematous, Thyrotoxicosis
Part of other neurodegenerative diseases
69
Hypokinetic disorders occur when?
there is too little direct pathway effect and too much indirect pathway effect.
70
Hyperkinetic disorders occur when?
there is too little indirect pathway effect?
71
The reticular formation contains several populations of what?
of neurons with long dendrites surrounded by interlacing bundles of fibers.
72
The raphe nuclei include many what?
serotonergic neurons; Rostrally projecting-active in sleep, Caudally projecting- receive afferents from periaqueductal gray matter, modulate pain sensation
73
The central group of nuclei includes the cells of origin of what? Rostral projections are concerned with what?
motor reticulospinal fibers; eye movements
74
The paramedian pontine reticular formation is involved in what?
control of eye movements
75
What kind of neurons are in the locus coerulus? What processes are they involved in?
Catecholaminergic neurons; probably to increase the speed of reflexes and the general level of alertness
76
The laterally located parvocellular, parabrachial, and superficial medullary reticular areas are concerned with what?
regulation of the respiratory and circulatory systems
77
Reticular formation is activation is responsible for what?
REM stage of sleep
78
The lateral column of the reticular formation contains what? whose function is what?
small-sized cholinergic cells, parvocellular regions, receive afferent fibers from both neighboring regions of the brainstem
79
The medial column of the reticular formation contains what? These areas serve as what?
different groups of large-sized cells, called magnocellular regions; effector regions
80
The median column of the reticular formation contains groups which lie along or adjacent to what? This comprises what?
midline of the upper medulla, pons, and midbrain; raphe nuclei, Serotonergic.
81
Locus ceruleus is located in what? IT contains ½ of the brain’s what?
pontomesencephalic junction; noradrenergic neurons
82
Interneurons of the reticular formation receive what? These fibers innervate what?
some of the corticobulbar fibers from the motor cortex; innervate the three cranial nerves involved in eye movement
83
The descending reticular nuclei in the brain are involved in what?
reflexive behavior such as coughing, chewing, swallowing and vomiting
84
The ascending reticular formation is also called what? It is responsible for what? This portion projects to where?
reticular activating system; the sleep-wake cycle, mediating various levels of alertness; the mid-line group of the thalamus (wakefulness) then to cortex
85
The descending reticular formation is involved in what? Receives input from where?
posture, equilibrium, ANS activity, plays a role in motor movement; hypothalamus
86
Where in the reticular system can a lesion result in a coma?
ascending system bilaterally
87
Medullary raphe neurons receive afferents from where? project to where?
Spinal cord, Gracile and cuneate nuclei, Trigeminal nuclei, Periaqueductal gray matter (PAG); Dorsal horns, trigeminal nuclei, and preganglionic autonomic neurons of BS/SC
88
Pontine nuclei receive afferents from where? Projects to where?
Prefrontal cortex, Limbic system (hypothalamus, hippocampal formation); Forebrain, Cerebellum, Noradrenergic neurons of the brainstem
89
What are the different raphe nuclei?
medullary and pontine, nucleus raphe magnus
90
It is believed that the sensory and emotional information transmitted to the thalamus mediates affective components of pain. What is the pathway and the end result?
projection from cells in PAG to serotonergic nucleus raphe magnus (NRM), NRM projects to dorsal horn entire length of spinal cord and inhibits ST tract neuron; pain reduction
91
What are the central group nuclei of the reticular formation?
Gigantocellularis nucleus, oral pontine reticular nuclei, Paramedian pontine reticular formation (PPRF);
92
Gigantocellularis nuclei receives input from where? projects to where? Mediates what effect?
cortical input (premotor and motor) and project to the spinal cord as the lateral reticulospinal tracts in ventrolateral funiculus. Inhibitory influence on motor neurons. Inhibits extensor motor tone.
93
oral pontine reticular nuclei receives input from where? projects to where? mediates what effect?
cortical input (premotor and motor) and project to the spinal cord as the medial reticulospinal tracts in ventral funiculus. Excitatory influence facilitates extensor tone.
94
PPRF is involved in what?Receives afferents from where?
lateral conjugate movements of eyes. Saccades; contralateral cerebral cortex, the superior colliculus, and vestibular nuclei
95
PPRF projects to where and with what information?
abducens nucleus; frontal eye fields (corticoreticular) and superior colliculus (tectoreticular fibers); VI to lateral rectus and contralateral III nucleus via MLF
96
Locus coeruleus contains what kind of neurons? Receievs input from where? Project to where?
Catecholemine (NE and Epi NT); central group nuclei and nucleus prepositus; MANY areas in CNS, notably cortex, limbic system structures (excitatory modulation)
97
What is paradoxical sleep? What modulates it>
REM, muscles of the trunk and limbs are relaxed and it takes a significant sensory stimulus for arousal but the brain very active; reticular system
98
Electrical stimulus to reticular activating system results in?
sleeping to awake
99
Electrical stimulus to thalamus results in?
awake to asleep
100
What occurs in stage 1 sleep?
“drowsiness" , EEG lower frequency and increased amplitude; increase in anterior thalamic GABA and a decrease in noradrenergic and cholinergic activity
101
What occurs during stage 2 sleep?
further decrease in frequency and increase in amplitude of EEG; sleep spindles-arise as a result of interactions between thalamic and cortical neurons.
102
What occurs during stage 3 sleep?
moderate to deep sleep, the number of spindles decreases, whereas the amplitude of low-frequency waves increases still more.
103
What occurs in stage 4 sleep?
deepest, EEG activity consists of low frequency (1–4 Hz), high-amplitude fluctuations-> delta waves; 1hr to here, only first two cycles.
104
What occurs in REM sleep?
stages of sleep reverse, similar waves to stage I, lasts 10 min and cycle back to non-REM
105
What are the physiological characteristics of deep sleep? Modulated by what brain areas?
parasympathetic dominance: Decreased heart rate/respiration, Increased gastric mobility, blood pressure decrease, dysregulation of temperature; cortex and thalamus
106
REM sleep is characterized by what physiological changes? Reticular formation in REM causes what changes?
Increased eye movements (PPRF), Penile erection (female equiv.), locus ceruleus- NE signaling activates limbic system, Raphe nucleus- serotonin signaling in forebrain
107
The increase in limbic system activity, coupled with a marked decrease in the influence of the frontal cortex during REM sleep, presumably explains what?
characteristics of dreams (e.g., their emotionality and the often inappropriate social content); frontal area is area of social inhibition; possibly involved in learning
