Diencephalon and Basal Ganglia Flashcards
what is the medial boundary of the diencephalon?
lateral boundary?
medial: 3rd ventricle
lateral: internal capsule (post limb)
what is the hypothalamic sulcus and why is it important
depression in the 3rd ventricle that runs from above the interventricular foramen of Monroe to the post commissure
-important bc it separates the hypothalamus from the dorsal thalamus
what are the 4 parts of the diencephalon
- dorsal thalamus
- hypothalamus
- subthalamus (STN)
- epithalamus (pineal gland)
what is the tuber cinereum
the zone that forms the floor of the 3rd ventricle
what kind of fucntions is the hypothalamus nvolved w/
endocrine functions of the body
ex. feeding, drinking, sex, emotions, growth
what is the median eminence
what emerges from it
what kind of organ is it
the central part of the tuber cinereum; the infundibulum emerges from this
-circumventicular organ (areas where there is no blood-brain barrier, allowing free communication btwn the cerebral blood, CSF of the ventricular system, and brain)
what is the diaphragma sellae
the dural fold covering the pituitary
what kind of organ is the pineal gland
what is it involved w/
what is it innervated by
circumventricular organ
circadian rhythms
sympathetic NS
when is melatonin secreted
when it’s dark outside
in the retina-scn-pineal circuit, the retina photoreceptors detect light, and fibers head to the “master pacemaker” called the ……..
where is this located
and via what tract
suprachiasmatic nucleus in the hypothalamus via the retinohypothalamic tract (RHT)
the descending hypothalamic fibers will travel down the _____ brainstem to C8-T1 of the cord where it will synapse on the _______ cell column in the latreal horn gray of the spinal cord
lateral
IML -intermediolateral cell column in the lateral horn gray of the spinal cord
what happens when the pineal gland receives its sympathetic innervation
it stops secreting melatonin
-light will stop melatonin secretion
all sensory inputs except _____ pass through the thalamus before reaching the cortex
olfaction
the thalamus receives motor info from where
deep cerebellar nuclei
basal ganglia
where do almost all thalamic projections (info leaving the thalamus) go to
-wehre do these projectoins travel in…what are they calld
cerebral cortex
-these projections travel in the internal capsule and area called “radiations
wehre do relay nuclei receive input from and wehre do they project
receive defined inputs (tracts) and project to a specific area of cortex for specific function
ex. VPL, VPM, VA, VL, LGN, MGN
where do association nuclei receive info from and where do they project
receive info from cortex and project back to cortex’s association areas in frontal and parietal lobes
ex. MD, LD, LP/pulvinar
what are the internal medullary lamina and what do they divide
Y-shaped internal medullary lamina are myelinated fibers which divide the thalamus into anterior, medial and posterior nuclear groups
what ist he lateral aspect of the thalamus covered by
a layer of myelinated axons, the external medullary lamina, which contains the reticular nucleus of the thalamus
what do the anterior and medial groups (dorsomedial nucleus (MD nucleus, medial thalamus)) have a role in
what are they connected w?
memory and emotions
-hypothalamus, limbic lobe, frontal lobe
what nuclei are in the dorsal tier
association nuclei: LD, LP, pulvinar
what nuclei are in the ventral tier
relay nuclei: VA/VL, VPL/VPM
what is the function of the dorsolateral group (LD)
unclear function, but similar to ant nuclear group
what is the function of the posterior group (LP, pulvinar)
parieto-occipital-temporal association
-role in attention needed in, for example, visuopatial tasks in the right hemisphere and language tasks in the left
LP and Pulvinar (post group) receive info from what?
they send their output projections to large parts of the association cortex called the….
LP and pulvinar receive info from all other thalamic nuclei and they send their output projections to larget parts of the association cortex called the parieto-occipital-temporal area
why is the pulvinar involved w/ the extrageniculate visual pathway
why is it called the extrageniculate visual pathway
pulvinar is involved in a “second” visual pathway that bypasses the LGN (and sues the sup colliculus and pulvinar) and is therefore called the extrageniculate visual pathway
-pulvinar is the thalamic relay in this pathway
where does the pulvinar receive its afferent projectoins from
wehre does it project to
the superfical layers of the superior colliculus and projects to visual associatoin areas in the occipital, parietal, and temporal lobes
the motor thalamus (VA, VL) receives inputs from what
cerebellum (contralateral denate) basal ganglia (GPi) substantia nigra (SNr)
where does the motor thalamus project to
projects to areas of the cortex important for motor acitivity
-helps regulate movement (planning, initiating)
what is the area in the thalamus that is important for motor function
in the VA and VL nuclei
-wehre we get inputs fcoming in from the cerebellum, BG, sub nigra
what will a lesion to the VPL do
contra loss of pain and temp (body)
contra loss of conscious proprioception/2 pt tactile/pressure/vibratory sense of the upper and lower extremities
what will a lesion to the VPM do
contra loss of pain and temp and tactile discimination in the head
-also results in loss of ipsi taste
what kind of nuclei are in the VPL?
what is its input
what is its output
relay nuclei
input: medial lemniscus, spinothalamic tract
output: post-central gyrus (arm and leg area)in pariteal lobe via internal capsule
what kind of nuclei are in VPM?
what is its input
what is its output
relay sensory nuclei
input; trigeminal lemniscus (dorsal and vtt tracts), 2ndary taste fibers from n. colitarius via CTT
output: post central gyrus (face) in parietal lobe via internal capusle and area 43
where does the vestibular system send projections to the thalamus at
VP area
-receives some vestibular inputs for conscious awareness of where your head is in space
what are the inputs and outputs of the MGN
what kind of nucleus
inputs: brachium of the inf colliculus
outputs: to primary auditory cortex (transverse temporal gyri of heschl) via auditory radiations
-auditory relay nucleus
what are the inputs and outputs of the LGN
what kind of nucleus
inputs: from retina via optic tract
output: to primary visual cortex (cuneus, lingual gyri) via optic radiations
-visual relay nucleus
what do the nuclei of the dorsal thalamus do to go to sleep
what kind of nuclei are these
inhibit thalamic nuclei (and therefore their projections to cortex)
- in sleep, can prevent sensory info from getting into cortex
- reticular nuclei
the output of the cerebellum is excitatory or inhibitory? what about the basal ganglia?
cerebellum: excitatory
BG: inhibitory
what is the pathway through the basal ganglia thought to be
a feedback loop that has a major modualtory influence on the direct output pathways of the cerebral cortex
why is the effect of the BG look contralateral
bc the effect is largely via corticospinals
what is the basal ganglia function
modulate cortical control of movement, cognition, and behavior
what will pathologic changes in the BG lead to
- abnormal involuntary movements in muscle tone and gait
- NO WEAKNESS
- dementia
- psychiatric disease
what make up the striatum
-what are they separated by
the caudate nucleus and putamen
- separated by the ant limb of the internal capsule
- caudate medially and putamen laterally
what make up the lenticular nucleus
-what are they separated by
the putamen and globus pallidus
-separted from the thalamus by the post limb of the internal capsule
what is the input of the nuclei of the basal ganglia? what is the output
input: striatum (caudate and putamen)
output: GPi and SNr (globus pallidus interna and substantia nigra pars reticularis)
how does the basal ganglia send signals
- motor cortex sends signals to the BG’s striatum
- BG manipulates that info
- GPi/SNr will send projections out of the basal ganglia to the VA/VL thalamus, which then send signal back to cortex
what is the direct pathway through the BG from the cortex?
what is the indirect pathway?
direct: which facilities the movement
indirect: which terminates the movemetns
what is parkinson’s disease due to
due to a slow, progressive degeneration of the dopaminergic neurons of the substantia nigra pars compacta
wht are the signs and symptoms of parkinson’s
Tremor
Rigidity
Akinesia
Posture
what does the SNc project onto
projects onto the striatum
influences both direct and indirect pathway
-through dominergic input onto either D1 or D2 receptors
what does lesion of Snc cause
decreased motor acitivty (bradykinesia)
ex. PD
what happens in huntington’s disease
selective loss of medium spiny GABAergic neurons of striatum whose output is through indirect pathway
what are the sympotoms of huntingtons
chorea: brief, jerklike movements
athetosis: slow, writhing movements
mental decline: executive dysfunction, slowness, memory decline
personality changes: irritable, anxious,depressed
what are the input, output, and intrinsic nuclei of the BG
input: caudate and putamen
output: GPi, SNr
intrinsic: GPe, SNc, STN
