Neuroanatomy Flashcards
Where do the superior and inferior colliculus sit?
On the dorsal brainstem in the midbrain, just medial to the thalami
Where do the pyramids sit?
On the ventral brainstem, in the medulla just below the pons. Medial to the olives
Where are the olives found?
Ventral brainstem medulla - lateral to the pyramids
What demarcates the midbrain from the pons on the dorsal brainstem?
The inferior border of the inferior colliculus
Which cranial nerve nuclei are found in the midbrain?
Oculomotor
Trochlear
Which autonomic nucleus is found in the brainstem?
Edinger-Westphal nucleus - parasympathetic fibres
How do the parasympathetic fibres originate and travel to the eye and what do they innervate?
Originate in the EW nucleus in the midbrain. Travel with CN3 to the ciliary ganglion and then sphincter papillae and the ciliary muscles
Which cranial nerve nuclei are found in the pons?
Trigeminal motor nucleus Part of the trigeminal sensory nucleus Abducens Facial motor nucleus Part of the vestibular and cochlear nuclei
What autonomic nucleus is found in the pons? Which type are they?
Superior and inferior salivatory nuclei
Parasympathetic
Where is the nucleus accumbens found?
In the basal ganglia - ventral striatum, underneath the caudate nucleus and putamen
Where is the nucleus ambiguus found? What does it do?
In the medulla
Contains CN 9, 10 and 11 information - hence innervates the pharynx and larynx
Which brainstem nucleus is responsible for nerves to the pharynx and larynx?
Nucleus ambiguus - CN9, 10 and 11
What is the nucleus solitarius?
Responsible for visceral sensory afferents including taste
ANS information including baroreceptors, chemoreceptors to hypothalamus
Where is the nucleus solitarius found?
Medulla
What nucleus is responsible for visceral afferents, including taste?
Nucleus solitarius
What cranial nerve nuclei are found in the medulla?
Nucleus solitarius Part of the trigeminal sensory nucleus Part of the vestibular and cochlear nucleus Nucleus ambiguus Vagus nucleus Hypoglossal nucleus
Where are the mammillary bodies found?
Ventral surface of the hypothalamus - rostral to the midbrain, visible on the ventral surface
Where is the pineal gland found?
Postero-superior to the thalamus
Where are the specific thalamic nuclei found?
The ventral portion of the lateral nuclear group
What are the afferents and efferent to the ventral posterior nucleus of the thalamus?
Afferents - spinothalamic, medial lemniscus and trigeminothalamic tracts
Efferent - primary somatosensory cortex
What are the afferents and efferent of the lateral geniculate nucleus?
Afferents - visual (optic tract) - contralateral 1/2 of visual field
Efferent - primary visual cortex via the optic radiations
What are the afferent and efferent of the medial geniculate nucleus?
Afferent - auditory info (from inferior colliculus of midbrain)
Efferent - primary auditory cortex
What is the inferior colliculus for?
Projects afferent auditory information to the thalamus
What are the afferent and efferent of the ventral anterior nucleus of the thalamus?
Afferent - ipsilateral basal ganglia and substantia nigra
Efferent - premotor association cortex
What are the afferents and efferents of the ventral lateral nucleus of the thalamus?
Afferents - ipsilateral globus pallidus, substantia nigra and contralateral dentate nucleus of cerebellum
Efferents - primary motor cortex
What part of the thalamus projects to the primary motor cortex?
Ventral lateral nucleus
What part of the thalamus projects to the premotor association cortex?
Ventral anterior nucleus
What part of the thalamus projects to the primary somatosensory cortex?
Ventral posterior nucleus
What part of the thalamus projects to the auditory cortex?
Medial geniculate nucleus
What part of the thalamus projects to the visual cortex?
Lateral geniculate nucleus
Which parts of the thalamus have limbic connections?
Anterior nuclear group - afferents from mammillary bodies via mammillothalamic tract, efferents to the cingulate gyrus
Lateral dorsal nucleus - afferent from the hippocampus, efferent to the cingulate gyrus
What is the pulvinar region of the thalamus connected to?
Parietal, temporal and occipital association cortices
What does the lateral posterior nucleus of the thalamus connect to?
Sensory association cortex of the parietal lobe
What are the afferents and efferent of the medial nuclear group of the thalamus?
Afferents from hypothalamus, amygdala, prefrontal cortex and other thalamic nuclei
Efferents to the prefrontal cortex
Which part of the thalamus is responsible for connections with the prefrontal cortex?
Medial nuclear group
What are the intralaminar nuclei of the thalamus involved with?
Afferents from brainstem (reticular activating formation), spinothalamic and trigeminothalamic tract
Efferents to cortex, caudate nucleus and putamen
Involved in ‘activation’ of the cortex
What part of the thalamus is involved with activating the cerebral cortex via connections with the brainstem reticular activating formation?
Intralaminar nuclei
What does the pineal gland do?
Produces melatonin; involved in sleep wake regulation
What do lesions of the subthalamus cause?
Hemiballismus
What constellation of symptoms do thalamic lesions cause?
Contralateral sensation loss, often in face, limbs
Thalamic pain in the anaesthetic areas
‘Focal’ cortical lesions
Which part of the thalamus has connections with the parietal, occipital and temporal association cortices?
Pulvinar
What forms the lenticular nucleus anatomically?
Putamen and globus pallidus
What forms the neostriatum functionally?
Putamen and caudate nucleus
How are the basal ganglia arranged?
Putamen connects to head of caudate anteriorly, which extends posteriorly and medially
Globus pallidus sits medial to putamen, lateral to anterior limb of internal capsule
What is the amygdala attached to?
Sits at the end of the caudate nucleus anteriorly
Which part of the basal ganglia is functionally related to the substantia nigra?
Globus pallidus
Which part of the basal ganglia receives most of the afferents? What are these afferents?
Striatum - putamen and caudate nucleus
Afferents from corticostriatal fibres (motor to putamen), thalamostriatal projections from the interlaminar nuclei and nigrostriatal projections
Where do striatal efferents project to?
Globus pallidus
Pars reticulata of substantia nigra
Where does the globus pallidus receive afferents from?
Striatum
Subthalamic nuclei
Where do efferents from the globus pallidus project to?
Inhibitory fibres to subthalamic nucleus
Pallidus and pars reticulata of substantia nigra project jointly to the thalamus
What are the major functional efferents from the basal ganglia?
Pallidothalamic fibres to the ventral anterior and lateral thalamic nuclei
How does Huntington’s disease result in abnormal movements?
Scarcity of striatal neurones which project to the external segment of the globus pallidus (the inhibitory, indirect pathway)
This leads to disinhibition of external pallidal neurons, leading to inhibition of the subthalamic nucleus
Internal pallidal neurons become underactive leading to unwanted movements
What are the targets for DBS in PD?
Internal pallidus
Subthalamic nucleus
What are the anterior-most hypothalamic nuclei and where do they project?
Paraventricular and supraoptic nuclei
Project directly to the neurohypophysis
Where is the lateral hypothalamus and what does it control?
Just medial/ventral to the subthalamus
Controls food and water intake, so lesions may lead to anorexia or adipsia
What does the medial hypothalamus contain?
Nuclei:
Paraventricular produces oxytocin
Supraoptic produces vasopressin
Suprachiasmatic nucleus - sleep wake cycle
Ventromedial nucleus - food and fluid intake
What do lesions of the ventromedial nucleus of the hypothalamus cause?
Abnormally increased food intake
What is the major input to the limbic system?
Modal-specific sensory information collected and referred to the inferior parieto-occipital association areas (perceptuospatial functions)
This is then conveyed to the inferior frontal association areas (planned behaviour regulation) and the inferior temporal association areas (supramodal status and meaning - semantic processing)
What are the major amygdala afferents?
Inferior temporal association cortex
Septum
Olfactory tract
What are the 2 major amygdala efferents?
Amygdalofugal tracts to hypothalamus Stria terminalis (via wall of third ventricle) to hypothalamus
What comprises the hippocampal formation?
Hippocampus
Dentate gyrus
Parts of parahippocampus
Where is the dentate gyrus?
Between the hippocampus and parahippocampus
What are the 2 major hippocampal afferents?
Inferior temporal cortex
Entorhinal area of temporal lobe
What is the major hippocampal efferent and where does it go?
Fornix - to mammillary bodies
Where is the fornix?
Sits just inferior/inside the corpus callosum
What are the two major efferents from the mammillary bodies?
Anterior nuclear group of thalamus
Brainstem via medullotegmental tract
What is the structural relationship between the cingulate gyrus, parahippocampus and corpus callosum?
Cingulate gyrus and parahippocampus are continuous with one another above/outside the corpus callosum
Neural activation of the anterior and posterior hypothalamus generally causes what?
Anterior - parasympathetic activity
Posterior - sympathetic activity
What are the 3 major inputs to the striatum and where do they come from?
Thalamostriatal - interlaminar nuclei
Corticostriatal - cortex
Nigrostriatal - from SNc
Of the four major frontal subcortical loops, which afferent to the putamen and which input to the caudate?
Motor -> putamen
Oculomotor, limbic and prefrontal -> caudate
What are the 4 major frontal subcortical circuits?
Motor
Limbic
Prefrontal
Oculomotor
What are the striatal efferents?
Indirect pathway to GPe and STN
Direct pathway to GPi
SNr
What are the overall striatal efferents?
GPi and SNr
Where do the GPi and SNr project? What nuclei, in what way and what neurotransmitter?
Thalamus motor nuclei (ventral anterior and lateral) - inhibitory via GABA
What are the two major divisions of the substantia nigra and which neurotransmitters do they utilise?
Pars reticulata - GABA
Pars compacta - DA
Describe the pathology of Huntington’s chorea in terms of direct and indirect pathways in the basal ganglia?
HD is characterised by loss of GABAergic indirect pathway neurons projecting from the striatum to the GPe
This results in underactivity of the inhibitory indirect pathway; disinhibition of the GPe, increased inhibition of GPi/SNr neurons and loss of inhibition of involuntary movements via thalamic outputs
How does DBS for PD work in terms of the schematic BG model?
Stimulators inhibit either GPi or STN; either way the net result is loss of inhibition of the thalamus leading to reduction of unwanted movements
What are the afferents in the Oculomotor frontal-subcortical loop?
Frontal eye fields (FEF) and supplementary eye fields (SEF)
How do the FEF and SEF effect gaze and saccades?
They activate gaze centres for voluntary saccades
They activate the Oculomotor loop, disinhibiting the superior colliculus
What relationship does the SNr have with eye movements? When is it active?
SNr has inhibitory projections to the superior colliculus; it is active when the eyes are at rest
What are the two primitive eye reflexes involved in gaze and saccades?
Visual Grasp Reflex VGR - causes eye movement in direction of a suddenly approaching stimulus
Fixation reflex - anchors the eye on a foveated stimulus
What and where are the neurons that govern the fixation and VGR reflexes?
Fixation and saccade neurons respectively, both found in the superior colliculus
What process is associated with voluntary control over the fixation and VGR reflexes?
Maturation of the frontal-nigral (SNr)-collicular pathways
What is the relationship between the SNc and the corticostriatal pathways?
Dopamine differentially regulates the activity of the direct and indirect pathways; the direct pathway neurons express excitatory D1 receptors, and the indirect pathway neurons express inhibitory D2 receptors. Decreased dopaminergic activity therefore decreases direct pathway activity and increases indirect pathway activity
What is Fahr’s disease?
Idiopathic autosomal dominant calcification of the basal ganglia, mostly GPi
What names are given to the corticospinal tract as it runs down through the body?
Above basal ganglia - part of corona radiata
Between BG and pons it is crus cerebri
Below pons it is CS tract
What is contained in the external capsule?
Corticocortical association fibres
Cholinergic fibres from basal forebrain to cerebral cortex
What 2 connections are made in the extreme capsule?
Association fibres between Broca and Wernicke, and the claustrum and insula
What is the claustrum thought to do?
Seamless quality of conscious experience
Intersense integration
Where is the claustrum?
Between the putamen and external capsule, and the extreme capsule and insula
What is notable about the cytoarchitecture of the claustrum?
Poverty/uniformality of cell types
What are the four major commissures in the brain?
Corpus callosum
Anterior and posterior commissures
Fornix
