Section 2 Flashcards
From where does the forebrain receive information?
from our sensors and sends controlling signals out to motor and visceral systems.
How does the forebrain perform functions?
By carrying out the complex computations we call higher cognitive processes.
Within the forebrain, what is the principal structure involved in the higher cognitive processes?
the cerebral cortex, but subcortical structures also play a role.
Cognitive deficits signal what?
forebrain, and usually, cortical pathology.
Three subcortical nuclei, are usually referred together as?
the Basal Ganglia which are major deep structures of the forebrain.
What is the striatum?
caudate, putamen, together commonly referred to as the striatum
Basal ganglia is composed of
1) caudate 2) putamen, (together commonly referred to as the striatum) 3) globus pallidus - note: besides these three subcortical structures, substantia nigra and subthalamic nucleus are part of the Basal Ganglia
What happens to the nuclei of the basal ganglia?
These nuclei are involved in motor control and diseases of the basal ganglia resulting in a variety of motor symptoms
What are some of the motor symptoms involved with damage to the basal ganglia?
difficulty in initiating movement (akinesia), abnormalities of muscle tone (rigidity), or the development of various involuntary motor movements (tremor, chorea, ballism, etc.) which are characteristic of various basal ganglia diseases.
In addition to motor control, what does the basal ganglia have a role in?
cognitive functions.
Amygdala is involved in
Another subcortical nucleus, the amygdala, is involved in controlling emotional behavior
Amygdala is an important component of what?
the limbic system
The limbic lobe comprises what?
only part of the limbic system.
The limbic system includes what?
1) amygdala 2) anterior portion of the cingulate gyrus 3) orbital and medial prefrontal gyri of the cerebral cortex 4) ventral parts of the basal ganglia 5) the hippocampus (though probably not directly involved in emotional behavior control) 6) parts of the thalamus that projects to the cortical regions
What do portions of the limbic system interact with?
the hypothalamus and autonomic areas of the brainstem
The anterior horn of the lateral ventricle lies in what?
frontal lobe
the body of the lateral ventricle does what?
extends across the frontal and parietal lobe,
The posterior horn of the lateral ventricle
there is a spur that extends into the occipital lobe.
The inferior horn lies in the
temporal lobe.
The third ventricle lies where?
At the midline where you identified the thalamus on the half-brain specimen;
What is the thalamus punctured by?
a hole where the thalamic adhesion (massa intermedia) had been.
How does the lateral ventricles communicate with the third ventricle?
by way of the interventricular foramen, sometimes called the Foramen of Monro.
How does the third ventricle communicate with the fourth ventricle?
through the cerebral aqueduct.
What is the path of the cerebral aqueduct?
This is a narrow passage (normally smaller than that represented in the model) that passes through the midbrain under the superior and inferior colliculi.
the dorsal surface of the lateral ventricles
This is where the fibers of the corpus callosum form the ventricular roof.
What is the cavity in the ventral lateral surface of the anterior horn of the lateral ventricle created by?
the head of the caudate nucleus that lies on the floor of the anterior horn.
a hollow on the ventral medial surface of the inferior horn is produced by what?
the hippocampus
The hole piercing the third ventricle is made by
the massa intermedia (or thalamic adhesion; this connection between the thalami on each side does not occur in some brains and is not a commissure).
The third ventricle extends ventrally
to a point like the beak of a bird. This point extends to the bottom of the brain where it is surrounded by the hypothalamus.
The medial surface of the posterior horn normally abuts what?
the calcarine sulcus where this sulcus extends inward from the medial surface of the occipital lobe
What is the tectum?
(superior and inferior colliculi)
Where is the tectum?
(superior and inferior colliculi) lies dorsal to the aqueduct, and the tegmentum lies below it.
Where is the cerebellum relative to the ventricles?
It lies above the fourth ventricle, forming its roof,
What forms the floor of the fourth ventricle?
the continuation of the tegmentum into the pons region forms the floor of this ventricle.
What does the blood brain barrier (BBB) do?
maintains a stable environment for neurons to function effectively, protecting the CNS from severe fluctuations in ionic concentrations, excludes many toxic compounds, and protects central neurons from circulating hormones and neurotransmitters released in other parts of the body
What is the actual locus of the BBB?
it is the capillary endothelium
How is the capillary endothelium specialized?
by having: 1) tight junctions between capillary endothelial cells, 2) few endocytotic vesicles for intracellular transport, 3) a high number of mitochondria indicative of high levels of oxidative metabolism.
This barrier is selective, how is entry into the brain is achieved?
1) by diffusion of lipid-soluble substances 2) by facilitative and energy-dependent transport of specific water soluble substances (e.g. glucose and amino acids) 3) by ion channels.
Give an example for diffusion of lipid soluble substances across the blood brain barrier?
(e.g. lipid soluble gases O2 and CO2)
Diffusion of lipid soluble substances across the blood brain barrier is related to what (give an example)?
generally to their oil/water partition coefficient, (e.g. Penicillin -hydrophilic- does not transport well, while diazepam –very hydrophobic- does)
How do substances get out of the brain?
Besides carrying substances to the brain, there is also a reverse pump
Where are the reverse pumps for the blood brain barrier?
intracellular transporters within astroglia that move lipophilic molecules of the brain into the blood
Example of the BBB reverse pumps.
glycine, glutamate which may limit the accumulation of these neurotransmitters within the brain
Why is the reverse pump within the astroglia?
This is probably related to the processes of astroglial cells that encase the capillaries.
Can whole cells cross the BBB?
Some whole cells can migrate across a healthy BBB, especially lymphocytes and macrophages,
What is the mechanism by which whole cells cross the BBB?
probably by a mechanism that opens the tight junctions. Unfortunately, this mechanism also permits the entry of the myelin-reactive lymphocytes of multiple sclerosis, and HIV-infected macrophages.
Several regions of the CNS do not have a BBB, all of which need to be able to do what?
sense fluctuations in the blood, because they are part of the circuitry for regulating these fluxes (e.g. the area postrema of the 4th ventricle may detect poisons in the blood and initiate the vomiting reflex).
What happens to the BBB in many brain tumors?
The BBB breaks down in many brain tumors, with bacterial invasion, and during ischemia.
What is the most common cause of BBB breakdown?
Ischemia
The pathology of a stroke
stems not only from the loss of tissue oxygenation, but also from the introduction of toxins to the brain, and from ionic fluxes.
Ischemia directly damages what?
the cells’ Na and K pumps.
In ischemia, what causes the cells to fill with water?
Na and K pumps together with the ionic influx causes the cells to fill with water.
What does the swelling result in?
The resulting brain swelling (edema) with its attendant increase in intracranial pressure will, if unchecked, eventually lead to coma and death.
Cerebrospinal fluid (CSF) is in equilibrium with
brain extracellular fluid and maintains a constant external environment for cells of the CNS, preserving homeostasis.
In addition to preserving homeostasis what else does the CSF do?
It also provides buoyancy for the brain, decreasing the weight of the brain on the skull, and serves as a mechanical cushion, protecting it from impact with the bones of the skull.
CSF drains what?
unwanted substances from the brain, serving as the brain’s lymphatic system.
The total volume of the CSF is estimated at
~140 ml,
What is the rate of formation of CSF?
the rate of formation of CSF is about 500 ml per day,
So the entire volume of CSF is turned over how many times?
three or four times a day.
CSF is secreted primarily by the
choroid plexus
What does the choroid plexus consist of?
a specialized capillary network surrounded by a cuboidal or columnar epithelium.
What maintains the chemical stability of the CSF?
Choroid plexus
The capillaries of the choroid plexus are freely permeable to what?
plasma solutes
What are the epithelial cells of the choroids plexus responsible for?
Its a barrier that is responsible for carrier-mediated active transport that is bi-directional.
What does the choroid plexus account for?
For the continuous production of CSF and active transport of metabolites out of the CNS and into the blood.
CSF and the extracellular fluids of the brain are in
a steady state normally and differ from blood plasma
How does the CSF compare to the blood plasma?
concentrations of K+, Ca2+, bicarbonate, glucose and protein in CSF are lower than in the blood plasma, and CSF is also more acidic
CSF is normally
clear and does not contain red blood cells and few, if any, white blood cells.
The choroid plexus is found within
the floor of the inferior horn and body of the lateral ventricle, the roof of the third ventricle, and the inferior part of the roof of the fourth ventricle
CSF is made in the
lateral ventricles flows into the third ventricle and this CSF, along with that added by the choroid plexus in the roof of the third ventricle, flows through the cerebral aqueduct to reach the fourth ventricle.
Does most of the CSF continue down the central canal of the spinal cord?
Most of the flow does not continue down the central canal of the spinal cord, which is vestigial in adults, but exits the fourth ventricle through three foramina; 1) the Foramen of Magendie 2) Foramina of Luschka (two of them)
Foramen of Magendie
a midline opening at the caudal end of the fourth ventricle,
Two Foramina of Luschka
at the lateral edge of the ventricle at its widest extent where cranial nerve VIII lies, adjacent to the flocculus.
What happens to the CSF after it exits the foramen?
it continues to flow over the whole brain and spinal cord beneath the arachnoid mater in the subarachnoid space
Describe the CSF flow in the subarachnoid space.
It flows slowly over the convexities of the cerebral hemispheres until it reaches the arachnoid villi in the walls of the dural sinuses, most notably the superior sagittal sinus.
Where does absorption of the majority of the CSF into the venous system occur?
through the arachnoid granulations or villi (in the walls of the dural sinuses, most notably the superior sagittal sinus)
The flow of CSF can be obstructed, especially at what point?
the interventricular foramen or at the cerebral aqueduct.
What is obstruction of CSF flow called?
This produces an obstructive or non-communicating hydrocephalus.
Obstruction of CSF flow such as a tumor, occurs most frequently where?
Wherever the ventricular system narrows (interventricular foramen, cerebral aqueduct, or at the outlet of the 4th ventricle)
Communicating hydrocephalus
occurs when there is no blockage of ventricular flow, but the arachnoid villi are diseased and absorption fails.
In either type of obstruction, the continued buildup of CSF (~20 ml/hr) causes what?
increased ventricular pressure, expanding the ventricles and putting pressure on brain tissue.
Clinically when can increased intracranial pressure be seen?
when inspecting the fundus of the eye with an ophthalmoscope.
What is seen in the eye under conditions of increased ICP?
The retinal vessels of the optic nerve become engorged and the optic nerve head becomes dilated. This effect is called papilledema.
What are the symptoms resulting from increased intracranial pressure?
headache, nausea, vomiting, cognitive impairment, a decreased level of consciousness, and may include impaired vision and sixth nerve palsies.
How might the frontal lobe function be affected with increased ICP?
it is often compromised including the descending white matter pathways from the frontal lobe
ICP compromising the descending white grey matter pathways from the frontal lobe may lead to what?
a characteristic unsteady gait where the feet barely leave the floor (magnetic gait) as well as incontinence.
The composition of the CSF
has clinical significance since it may be altered in different disease states.
An increased white cell count in the CSF
(greater than 4/mm3) indicates pathology and may be a thousand-fold greater in acute bacterial meningitis
Why might the white cell count in the CSF be a thousand fold greater in acute bacterial meningitis?
BBB breaks down in this case allowing entry of antibiotics to address the infection
How might protein content be increased in the CSF?
by many pathological processes due to changes in vascular permeability or CSF dynamics.
In multiple sclerosis what happens to the CSF?
the gamma globulin content of CSF is disproportionately increased to more than 13% of total protein, due to the production of immunoglobulin.
The presence of red blood cells in the CSF may be indicative of what?
a hemorrhagic stroke in the CNS.
What are the three categories for the deep white matter of the cerebrum?
1) association fibers 2) commissural fibers 3) projection fibers
association fibers
connect different areas of cortex in the same hemisphere
commissural fibers
connect homologous areas of cortex of the two hemispheres
projection fibers
connect areas of cortex to lower areas of the neuraxis.
What does damaging the white matter (axons) that connects areas of cortex often produce?
similar symptoms as damaging the area of cortex itself.
How are the different areas of cortex within the same hemisphere connected?
There are four “long” association fiber tracts connecting them
What are the 4 long association fibers that connects the areas of the cortex within the same hemisphere?
1) superior longitudinal fasciculus = arcuate fasciculus 2) inferior longitudinal fasciculus 3) uncinate fasciculus 4) cingulum
What is the largest of the association fibers?
it is the superior longtitudinal fasciculus, commonly known as the arcuate fasciculus.
Superior longtitudinal fasciculus
extends from the frontal lobe arcing (hence its name) inferiorly into the temporal lobe and also posteriorly to the occipital lobe.
What are the areas that are interconnected via the superior longitudinal fasciculus?
They are Broca’s motor speech area, Wernicke’s area and auditory cortex.
Path of the Inferior longitudinal fasciculus
it extends from the occipital lobe to the temporal lobe along the inferior aspect of the hemisphere deep to the occipitotemporal gyrus.
limen insulae
the anterior border of the insula
Path of the uncinate fasciculus
runs deep to the limen insulae connecting frontal and temporal cortices.
It is hypothesized that the uncinate fasciculus does what?
interconnects orbital frontal cortex-based reward and punishment centers with temporal lobe-based memory representations.
What is the location of the cingulum?
found on the medial aspect of the hemisphere deep to the cingulated gyrus.
What does the cingulum do?
it interconnects structures of the limbic system such as the subcallosal gyrus, cingulate gyrus, parahippocampal gyrus and uncus.
What is the cingulum hypothesized to be involved in?
process of learning to avoid painful stimuli
Why is the cingulum thought to be involved in the process of learning to avoid painful stimuli?
Because of its connections to areas of the thalamus that receive pain fibers via the spinothalamic tract
Describe the path of the association fibers.
It is important to realize that the association fiber systems are not one-way, direct pathways. They can be likened to an interstate highway.
Give an example of short versus long association fibers.
While some axons from neurons in the frontal lobe enter the system and travel longer distances to the parietal lobe, occipital lobe or temporal lobe, some “short” association fibers travel only short distances, perhaps to an adjacent gyrus (“U” fibers) or to a nearby gyrus
Importantly, like an interstate highway, these fiber systems are
bidirectional.
Give an example of how the association fibers are bidirectional.
While axons of some neurons in the frontal lobe carry information to the occipital lobe, for instance, axons of neurons in the occipital lobe carry information to the frontal and parietal lobes.
Reciprocal connections
they are the rule rather than the exception.
What are the 4 important commisures?
1) corpus callosum 2) anterior commisure 3) hippocampal commisure 4) posterior commisure
The largest of the commissural fiber tracts is the
corpus callosum
The corpus callosum interconnects what?
homologous areas of cortex the two hemispheres in a spatially oriented fashion.
The frontal lobes are connected through what?
the genu of the corpus callosum
Parietal lobes are connected through what?
the body of the corpus callosum,
Occipital lobes (notably visual cortex) are connected via
the splenium facilitating binocular vision.
anterior commissure connects
the anterior poles of the two temporal lobes containing the primary olfactory cortices.
hippocampal commissure is comprised of
axons of the fornix that cross where the two fornices approach one another (crura of the fornices) between the splenium of the corpus callosum and the posterior part of the thalamus.
The hippocampal commissure connects the two hippocampi, structures that are involved in what?
the consolidation of long-term memory.
Posterior commissure
connects the two sides of rostral midbrain.
What is the posterior commisure involved in?
It is involved in the pupillary light reflex and is essential in mediating upward gaze.
Projection fibers interconnect what?
the cortex with nuclei at lower levels of the neuraxis.
In the cerebral hemispheres the posterior commusure projection fiber axons are collectively known as what?
the corona radiate
How did the corona radiata get its name?
because in a dissected specimen they have the appearance of radiating (in a crown-like fashion) to all areas of the cortex.
An important component of the corona radiata are what?
the thalamic radiations
What are the thalamic radiations?
interconnections between the thalamic nuclei and their cortical targets.
What are the interconnections between the thalamic nuclei and their cortical targets?
These include sensory projections (somatosensory, visual and auditory) from sensory nuclei of the thalamus to their respective cortical centers in the parietal, occipital and temporal lobes.
Internal capsule
As the axons of the corona radiata pass medial to the lenticulate nucleus they are called the internal capsule.
Crus Cerebri
Axons whose targets are in the brainstem and spinal cord descend onto the anterior aspect of the midbrain as the crus cerebri.
The internal capsule and crus cerebri contain what?
1) corticospinal fibers, 2) corticobulbar fibers 3) corticopontine fibers
For the corticospinal fibers of the internal capsule and crus cerebri, where do they originate?
axons originating in the pre- and post- central gyri
For the corticospinal fibers of the internal capsule and crus cerebri, where do they terminate?
They go to dorsal and ventral horn neurons in the spinal cord;
corticobulbar fibers of the internal capsule and crus cerebri
motor axons that control cranial nerve nuclei in the brainstem;
corticopontine fibers of the internal capsule and crus cerebri
axons from motor cortex to the pontine nuclei in the base of the pons which in turn project to the contralateral cerebellar hemisphere.
corticopontine fibers project to where after the pontine nuclei
the contralateral cerebellar hemisphere
The bulge in the anterior horn of the lateral ventricle under that lays the head of what?
the caudate.
Then look at the roof of the anterior horn of the lateral ventricle and see the crossing fibers of the
corpus callosum.
Then identify the hippocampus that lies where?
on the medial part of the floor of the inferior horn of the lateral ventricle
The inferior horn lies in
the temporal lobe
the hippocampus slopes
ventrally, widening and curving medially as it goes anteriorly.
Look on the inferior surface of the temporal lobe and identify what structure?
the parahippocampal gyrus
The hippocampus is a
cortical structure that rolls up in the ventricle.
The hippocampus is believed to have a special role in what?
certain memory functions, especially the memory for spatial relationships.
Axons of hippocampal neurons form what?
a large fiber tract that emerges from the hippocampus
What is the route of the hippocampal neurons?
It takes a circular route connecting the hippocampus in the temporal lobe to the hypothalamus.
What does the hippocampal neuron connect to?
Connects prominently to the mammillary bodies, which are part of the hypothalamus.
What is the fiber tract that connects prominently to the mammillary bodies?
the fornix.
What is the path of the fornix?
You can see this tract forming on the surface of the hippocampus then, leaving the hippocampus, it curls posteriorly around the “C” shape of the lateral ventricle. It spreads out in a sheet there and proceeds, rostrally, at the floor of the lateral ventri
Where is the anterior commissure located?
between the two descending columns of the fornix, at the rostral end of the third ventricle.
The head of the caudate
This is a large cluster of cell bodies that is part of the basal ganglia, and is associated with motor and cognitive functions.
What happens to the caudate posteriorly?
It narrows posteriorly as the body of the caudate nucleus and follows the course of the lateral ventricle into the temporal lobe, somewhat like the trajectory of the fornix.
Where does the caudate end?
in the roof of the inferior horn abutting the amygdala.
The thalamus is
a collection of nuclei, most of which project (send their axons) and receive projections from the same distinct parts of the cerebral cortex, so they all have different functions.
A major function of the thalamus is to
relay sensory and motor information to the specific sensory and motor regions of the cortex.
Anterior tubercle
a bulge on the thalamus dorsal surface anteriorly
Pulvinar
The thalamus shape has a pillow shape at its posterior end, and this is called the pulvinar.
The anterior tubercle and pulvinar each mark what?
nuclear groups within the thalamus.
Two particularly important thalamic nuclei are
1) the medial geniculate nucleus, 2) Lateral geniculate nucleus
medial geniculate nucleus
relays auditory information to the transverse or Heschl’s gyri
lateral geniculate nucleus
which receives its information from the eye via the optic tract and projects to the visual cortex surrounding and within the calcarine fissure.
Where can the MGN and LGN be seen?
on the ventral surface of the thalamus.
How do you find the Lateral geniculate nucleus?
follow the optic tract to its end.
medial geniculate nuclei are
prominent bulges lateral to the superior colliculi but with a large fiber tract connecting it to the inferior colliculus, called the brachium of the inferior colliculus.
brachium of the inferior colliculus
prominent bulges lateral to the superior colliculi but with a large fiber tract connecting it to the inferior colliculus
The amygdala is
a large nuclear structure located near the uncus at the anterior medial part of the temporal lobe, across the anterior end of the inferior horn of the lateral ventricle.
What is the amygdale associated with?
It is closely connected to the hypothalamus on the one hand and the cerebral cortex on the other, communicating visceral information such as hunger, thirst, anger, fear and sexual feelings between brainstem, hypothalamus and cortex.
What does bilateral damage of the amygdala produce?
a flattening, or blunting of emotional and sexual behavior.
What divides the internal capsule?
The knee of the end of bend of the anterior end of the thalamus divides it into the anterior and posterior limb
The internal capsule is
it is the neck of the funnel in which massive cables of axons (corona radiata) carry information from thalamus to cortex and from cortex to thalamus, basal ganglia (putamen, caudate and globus pallidus), brainstem and spinal cord
septum pellucidum
separates the two anterior horns of the lateral ventricles
anterior limb of the internal capsule
carries mostly information to and from the frontal lobes
posterior limb of the internal capsule
carries somatic sensory and motor information from each side of the central sulcus
Visual radiations
Further posteriorly (to the posterior limb of the internal capsule) visual information passes through this region on the way to the occipital lobes from the lateral geniculate nucleus (LGN) in the visual radiations.
Auditory radiations
Auditory information to the primary auditory cortex in the superior temporal gyrus from the medial geniculate nucleus (MGN) also passes through this region (auditory radiations)
lesions in the posterior limb of the capsule produce
dramatic symptoms of sensory loss and paralysis
The putamen is joined medially by the
globus pallidus
Putamen + globus pallidus =
lenticular nucleus
Caudate + putamen =
corpus striatum
What does the striatum send projection to?
Globus pallidus
Where does the globus pallidus sends much of its information to?
areas of the thalamus that project to motor areas of the cortex.
the midbrain and hypothalamus are ventral to the
thalamus
the hypothalamus appears on both sides of the
third ventricle
What marks the anterior boundary of the third ventricle and hypothalamus?
anterior commissure at this point
What forms the crus cerebri?
the posterior limb of the internal capsule is beginning to form the crus cerebri
Crus cerebri carries what?
much of the motor functions coming from the cortex destined for the brainstem and spinal cord
What wraps around the posterior limb of the internal capsule (or crus cerebri)?
Optic tract
ventral portion of the basal ganglia is called what?
the ventral striatum,
ventral extension of the globus pallidus is called what?
the ventral pallidum
The ventral portion of the basal ganglia receives information from what?
the amygdala and is involved in emotional (limbic system) function rather than motor control
Why does the hippocampus show up at each level and what is it surrounded by?
slants down anteriorly in the temporal lobe, so it shows up in single cross section at each level surrounded by the inferior horn of the lateral ventricle
The cingulum
extends between the subcallosal gyrus in the frontal lobe and the parahippocampal gyrus in the temporal lobe.
U-fibers,
run only between adjacent gyri.
In the brain, the shorter fibers will be the
most superficial
In the brain, the longest fibers will be the
deepest
Superior longitudinal fasciculus is also known as
the arcuate fasciculus
What does the superior longitudinal fasciculus interconnect?
cortex of the frontal, parietal, occipital and temporal lobes
In the left hemisphere the superior longitudinal fasciculus interconnects what?
Wernicke’s area with Broca’s motor speech area
Damage to the superior longitudinal fasciculus between Broca’s and Wernicke’s will cause what?
symptoms similar to Broca’s aphasia.
The superior longitudinal fasciculus connects what?
all of the sensory cortices to one another and to the language centers
INFERIOR LONGITUDINAL FASCICULUS runs between what?
the occipitial and temporal lobes on the inferior surface of the brain
The uncinate fasciculus interconnects
between the frontal and temporal lobes and passes superficially through the very anterior part of the insula, known as the limen insulae
Limen insulae
the very anterior part of the insula
projection fibers of the cerebrum
These axon systems interconnect the cerebral cortex with lower areas of the neuraxis. Intuitively, these axons run “up and down” rather than “across” like the association fibers.
CORONA RADIATA comprised of the
entire population of fibers that “radiate” in a crown-like fashion between the cortex and lower centers
What are the posterior-most fibers of the corona radiata?
the OPTIC (or VISUAL) RADIATION extending to the occipital lobe.
What do the posterior-most fibers of the corona radiata carry?
These carry visual information from the lateral geniculate nucleus (body) of the thalamus to the primary visual cortex on the banks of the calcarine sulcus.
Deep to the insular cortex is
a very thin band of white matter, the extreme capsule, followed by a very thin band of gray matter, the claustrum.
EXTERNAL CAPSULE is
another thin sheet of projection fibers that covers the LENTICULATE NUCLEUS
The extreme and external capsules are comprised of
projection fibers similar to the much larger and vastly more important internal capsule
The lenticulate nucleus is
a descriptive name for the gray matter that includes the putamen more laterally, and the globus pallidus situated medial to it
AUDITORY RADIATION
carrying auditory information from the medial geniculate nucleus of the thalamus to the primary auditory cortex (Heschl’s gyri).
crus cerebri is comprised of
the fibers of the internal capsule as they project to lower centers
What are the long fiber bundles passing through the base of the pons from the crus cerebri to the pyramid?
These bundles are mostly comprised of the axons of corticospinal and corticobulbar neurons in the primary motor cortex (upper motor neurons) whose targets are (lower) motor neurons in the brainstem and spinal cord
Where is the red nucleus?
in the tegmentum of the midbrain
What are the axons of the inferior cerebellar peduncle?
Axons emerging from the anterior aspect of the cerebellum adjacent to the middle cerebellar peduncle that cross to medial cerebellum (vermis and paravermal areas)
On myelin sections in caudal pons the inferior cerebellar peduncle lies between what?
the middle and superior cerebellar peduncles.
DENTATE NUCLEUS
the largest of the deep cerebellar nuclei
deep cerebellar nuclei mediate what?
the great majority of the cerebellar outflow
What forms the bulk of the SUPERIOR CEREBELLAR PEDUNCLE? What forms the rest of it?
1) the axons emerging from the rostral end of the dentate nucleus 2) The rest of the superior cerebellar peduncle is comprised mostly of axons from the globose and emboliform deep nuclei
DECUSSATION OF THE SUPERIOR CEREBELLAR PEDUNCLE is comprised of what?
axons from the deep cerebellar nuclei
What are the targets for the axons from the deep cerebellar nuclei that comprise the decussation of the the superior cerebellar peduncle?
whose targets are the contralateral red nucleus in the midbrain and the ventral lateral and ventral anterior nuclei in the contralateral thalamus.
