Lab 3 Neuroanatomy Flashcards
the three parts of the brainstem
midbrain
pons
medulla
brainstem
The brainstem connects the spinal cord to the cerebrum. Some of the cranial nerves (covered in this week’s lab) arise from the brainstem and many important nuclei associated with the motor and sensory pathways are located within the brainstem.
Most rostral part of brainstem
midbrain
most caudal part of the brainstem
medulla
Midbrain consisting mainly of
the cerebral peduncles
pons characterised by
the transverse cerebellopontine fibres
medulla containing
cranial nerve nuclei
How are the cerebral peduncles and optic tracts related to each other on the lateral surface of the brainstem?
The optic tracts wrap around the cerebral peduncles laterally, i.e. they travel from an anterior position to a posterolateral position where they enter the thalamus.
Medulla regions
open and closed
open medulla
Open medulla is at the level of the fourth ventricle
closed medulla
closed medulla is the portion below the fourth ventricle.
ventral =
anterior
dorsal =
posterior
rostral =
superior
caudal =
inferior
structures you can locate on the medulla
pyramids
olives
trigeminal fasiculus
pyramids location
medulla
The pyramids, paired ridges on either side of the midline.
olives location
medulla
The olives, more rounded bulges of the inferior olivary nucleus, lying lateral to
the pyramids
trigeminal fasiculus location
medulla
The trigeminal fasciculus and nucleus of the trigeminal nerve, lying lateral to
the olive, and inferior to the cuneate tubercle.
What type of fibres, motor or sensory, are found in the pyramids?
Pyramids are anterior, and therefore contain motor fibres
part of the corticospinal tract, the pyramids are the point of crossing over for this tract
at what level of the medulla are the olives found?
open medulla
which cranial nerve emerges from the medulla between the pyramid and olive?
hypoglossal nerve which is nerve number twelve
With which spinal cord structures are the gracile and cuneate tubercles continuous?
Gracile and Cuneate fasciculi/tracts – tubercles contain nuclei for the tracts
closed medulla
Cerebellum has two
hemispheres
hemispheres of the cerebellum are connected medially by the
vermis
surface of the cerebellar hemispheres are folded and the ridges formed by these folds are known as
folia (leaves)
Three divisions of the cerebellum
Each hemisphere has three divisions; anterior and posterior lobes divided from each other by the primary fissure and the flocculonodular lobe, which is made up of the flocculi (found in each hemisphere) and the nodule (found in the midline at the end of the vermis). Functionally the anterior and posterior lobes are important in movement coordination and the flocculonodular lobe is important for adjustments of posture to maintain balance.
With which lobes of the cerebral hemispheres is the cerebellum in contact?
Basal portions of the occipital and temporal lobes
Which brainstem regions are overlapped by the cerebellum?
Pons and medulla
Ventral aspect of the cerebellum rests on the
foramen magnum; a shallow circular groove on the cerebellar surface indicates that relationship
tonsil of the cerebellum
The portion of the cerebellar cortex between that groove and the medulla is the tonsil. In pathological conditions with rapidly increasing intracranial pressure, the tonsils may be pushed between the medulla and the edges of the foramen magnum. Death can occur by compression of the centres of the medulla controlling respiration and blood pressure.
arbor vitae
in the cerebellum, in a horizontal section, the arrangement of white matter as the arbor vitae
Note that the white matter is covered by a thin layer of cerebellar cortex (gray matter) which covers all the surface of the cerebellum.
There are four nuclei embedded within the white matter of the cerebellum….
These nuclei are known as the fastigial, emboliform, globose and dentate nuclei. Only one of these nuclei - the dentate nucleus is large enough to be seen with the naked eye.
The cerebellum is attached to the brainstem by the _______ cerebellar peduncles
3
Cerebellar peduncles in the intact brain
note that only the middle peduncle is clearly visible in the intact brain. The inferior and superior peduncles are more readily seen in isolated cerebella.
Middle cerebellar peduncle
which is continuous with the pons. This contains only afferent axons (for example, axons from the contralateral pontine nuclei as part of the cortico-pontine-cerebellar tract).
Inferior cerebellar peduncle
by which the cerebellum is attached to the dorsolateral aspect of the medulla. This contains afferent axons chiefly (eg. sensory axons from muscle proprioceptors) and some efferent axons.
Superior cerebellar peduncle
arising from the dorsal surface of the midbrain, under the cover of the occipital lobes. This contains efferent axons chiefly that arise from the deep cerebellar nuclei and can terminate in either the red nucleus or the thalamus (and then to the cerebral cortex).
Superior medullary velum
which is more substantial than the inferior, and is visualised by elevating and retracting the superior part of the cerebellum; it roofs in the space between the converging superior cerebellar peduncles and the cerebellum.
Inferior medullary velum
or its remnants, roofing in the gap between the diverging inferior peduncles and the cerebellum. Note this is not always visible.
fourth ventricle
expanding on the dorsum of the brainstem under cover of the cerebellum. This ventricle can only be seen in specimens with the cerebellum removed.
how are the superior and inferior medullary vela related to the fourth ventricle?
These structures form the roof of the fourth ventricle
Cranial nerves I and II arise from
forebrain
Cranial nerves III to XII arise from
brainstem
structures that enter/exit - foramen magnum
medulla oblongata
spinal cord
spinal root of accessory nerve
structures that enter/exit - cribriform plate of the ethmoid bone with olfactory foramen
olfactory nerves
structures that enter/exit - optic foramen
optic nerves (II)
structures that enter/exit - superior orbital fissure
cranial nerves III, IV, V1 and VI
structures that enter/exit - carotid canal
Internal carotid artery
structures that enter/exit - foramen rotundum
Maxillary branch of the trigeminal nerve
structures that enter/exit - foramen ovale
Mandibular branch of the trigeminal nerve
structures that enter/exit - foramen spinosum
middle meningeal artery
structures that enter/exit - jugular foramen
internal jugular vein
glossopharyngeal, vagus, accessory
cranial root of accessory
structures that enter/exit - hypoglossal canal
hypoglossal nerve
structures that enter/exit - internal auditory meatus
Vestibulocochlear nerve
facial
pituitary fossa in the
sphenoid bone
foramen of olfactory nerve
cribriform plate of ethmoid bone
number of olfactory nerve
1
function of olfactory nerve
sensory - smell
path of the olfactory nerve
Numerous fine nerves are attached to the olfactory bulb, which is part of the brain. The nerves, which have ascended through the cribriform plate of the ethmoid to reach the olfactory bulb, possess the characteristics of peripheral nerves.
foramen of the optic nerve
optic foramen
number of the optic nerve
2
function of the optic nerve
sensory - sight
path of the optic nerve
This is an outgrowth of brain matter (it is a tract and not a peripheral nerve) and it extends forward from the optic chiasm. At the chiasm about 50% of optic nerve fibres cross to enter the opposite optic tract.
foramen of oculomotor nerve
superior orbital fissure
number of the oculomotor nerve
3
function of the oculomotor nerve
motor - innervates most of the muscles controlling eye movement
path of the oculomotor nerve
This nerve emerges from the midbrain at the interpeduncular fossa, and supplies some of the extrinsic eye muscles.
foramen of trochlear nerve
superior orbital fissure
number of trochlear nerve
4
function of trochlear nerve
motor - eye movement
path of trochlear nerve
This is the only cranial nerve arising from the dorsal aspect of the brain, and it can be found curving around the cerebral peduncle. It is also the smallest cranial nerve. It is very difficult to see on most of the brains.
foramen of trigeminal nerve
V1= superior orbital fissure, V2=foramen rotundum, V3=foramen ovale
number of trigeminal nerve
5
function of trigeminal nerve
Sensory (V1, V2 and V3) – sensation from eye and skin of face, Motor (V3) – innervation of muscles of mastication.
path of trigeminal nerve
This large nerve arises from the pons. In addition to its large sensory component, it
possesses a small motor part, both of which should be visible.
foramen of abducens nerve
superior orbital fissure
number of abducens nerve
6
function of abducens nerve
motor - innervates lateral rectus muscles, abducts the eye
path of abducens nerve
This slender nerve will be found close to the midline at the junction of the pons and the
medullary pyramid.
foramen of facial nerve
internal acoustic meatus, stylomastoid foramen
number of facial nerve
7
function of facial nerve
Motor – muscles of facial expression, Sensory – taste from anterior tongue
path of facial nerve
This nerve passes out from the brainstem lateral to the abducens at the lateral edge of
the pontomedullary junction.
foramen of vestibulocochlear nerve
Internal acoustic meatus
number of vestibulocochlear nerve
8
function of vestibulocochlear nerve
Sensory - hearing and balance
path of vestibulocochlear
The two nerves constituting this are found at the cerebellopontine angle, immediately
lateral to the facial nerve.
foramen of glossopharyngeal
Jugular foramen
number of glossopharyngeal
9
function of glossopharyngeal
Motor – swallowing. Sensory – taste from posterior tongue
path of glossopharyngeal
This nerve is found lateral to the vestibulocochlear nerve.
foramen of vagus nerve
jugular foramen
number of vagus nerve
10
function of vagus nerve
Motor – pharynx, larynx, and heart. Sensory – visceral sensation
path of vagus nerve
This nerve arises from the medulla, just lateral to the olive.
foramen of accessory nerve
jugular foramen
number of accessory nerve
11
function of accessory nerve
Motor – pharynx, larynx and innervates trapezius and sternocleidomastoid
path of accessory nerve
These nerves emerge as a series of fine rootlets, in sequence, along the postolivary
sulcus of the medulla immediately lateral to the olive.
foramen of hypoglossal nerve
hypoglossal canal
number of hypoglossal nerve
12
function of hypoglossal nerve
motor - muscles of tongue
path of hypoglossal nerve
This nerve emerges as a series of rootlets, between the olive and pyramid.
Bell’s palsy
Paralysis of the facial nerve resulting in inability to control facial muscles on the affected side
possible causes for bells palsy
Infection of the facial nerve in the facial canal.
Common infectious causes of sudden onset facial paralysis include such conditions as Lymes disease, Epstein Barre, Herpes Simplex and HIV disease, among others.
CT scans - pros and cons
CT scans are produced using x-ray imaging techniques and give good definition of dense structures, such as bone. It is also good for imaging blood, due to the density of iron molecules found in haemoglobin. These dense structures appear bright white in CT images. Soft tissue definition is not good in CT images.
MRIs - pros and cons
MRIs use the magnetic properties of hydrogen ions within the body and their interaction with an external magnetic field or radiowaves. MRIs provide good soft tissue definition and gray and white matter structures can easily be distinguished. The lab has examples of both T1 and T2 weighted MRIs. In both T1 and T2 images the gray matter images (appears) brighter than the white matter, which appears greyish. In T2 weighted images the CSF images brightly. Thus the ventricles, in particular, appear very bright.
association fibres
Association fibres stay within the same hemisphere
commissural fibres
commissural fibres cross from one hemisphere to the other
projection fibres
projection fibres synapse in deep nuclei, the brainstem or spinal cord.
projection fibres examples
fornix
internal and external capsules
projection fibres - fornix
Fornix: Subdivided into column, body, fimbria. The column runs upwards from the mamillary bodies; merge with the body which, in a midsagittal section, disappears from sight deep to the splenium of the corpus callosum. The body reaches the roof of the inferior horn of the lateral ventricle and becomes the fimbria. Viewed as an entity the fornices of each side meet in a body as their columns come up out of each mammillary body.
projection fibres - internal and external capsules
Internal and external capsules: The internal capsule is mass of myelinated axons, lying between the lenticular nucleus laterally and the thalamus and caudate nucleus more medially. Consists of three parts - anterior and posterior limbs and a genu.
A number of important fibre bundles run in the internal capsule, including the corticospinal, corticobulbar and thalamocortical fibres . The visual radiation also runs through it. The external capsule forms the lateral border of the putamen, and fibres from all the cortical lobes enter the external capsule and connect the putamen and globus pallidus.
Commissure fibres examples
anterior commissure
corpus callosum
posterior commissure
commissure fibres - anterior commissure
Anterior commissure: Interconnects the olfactory bulbs, olfactory cortex, amygdaloid nuclei and neocortex in the region of the middle and inferior temporal gyri.
commissure fibres - corpus callosum
Corpus callosum: Largest of the commissures. Divided into a rostrum, genu, body and splenium; forms the roof of the anterior horn and body of the lateral ventricle. Connects widespread areas of the cerebral cortex.
