Brain Stem Flashcards
What are the 2 parts of the brainstem?
the midbrain (mesencephalon)
the hindbrain (rhombencephalon)
What is the midbrain continuous with?
the forebrain
What is the hindbrain continuous with?
the spinal cord
In older textbooks, what were the 3 divisions of the brainstem?
midbrain
pons
medulla oblongata
the brainstem controls the muscles of:
the eye, face, mouth, and throat; control of the salivary and lacrimal glands
the brainstem controls the internal organs of the:
thorax
abdomen
the brainstem controls sensations from:
the face, mouth, and throat, including taste
the special sense organs for vision, hearing and balance
the brainstem controls the coordination of movement of:
the limbs
the trunk
the brainstem has centres for controlling:
breathing
micturition
defecation
the brainstem has centers for maintenance of:
alertness
the brainstem acts as a corridor for:
long motor and sensory pathways that connect the brain with the spinal cord
the brainstem is a place of origin of:
descending motor pathways
what are all of the key functions of the brainstem?
-the control of the muscles of the eye, face, mouth, and throat; control of the salivary and lacrimal glands;
-control of the internal organs of the thorax and abdomen;
-receiving sensation from the face, mouth, and thro
at, including taste;
-receiving sensation from the special sense organs for vision, hearing and balance;
-coordination of movement of the limbs and trunk
-centers for control of breathing, micturition, and defecation;
-centers for maintenance of alertness;
-acting as a corridor for long motor and sensory pathways that connect the brain with the spinal cord;
-and as a place of origin of descending motor pathways.
The brain stem is connected with the muscles and sensory organs of the head through what?
cranial nerves 3 - 12
What is the structure of the brainstem?
The brain stem has a basic cylindrical structure, but there are major outgrowths from the dorsal surface
What are the dorsal outgrowths on the midbrain called?
the superior colliculi
the inferior colliculi
what are the superior and inferior colliculi?
two pairs of rounded bumps on the dorsal surface of the midbrain
what is the superior colliculus a receiving center for?
visual pathways
what is the inferior colliculus a receiving center for?
auditory pathways
what is the large outgrowth from the hindbrain called?
the cerebellum
During early development, where does the cerebellum grow?
the rostral part of the hindbrain
(just caudal to the midbrain)
In a brainstem section, what may be stained to show a clear picture of the main pathways in the brain stem?
myelinated fibers
When staining for myelinated fibers, what do nuclei appear as?
they do not stain and appear as pale areas in these sections
What are sections of the caudal hindbrain similar to?
sections of the cervical spinal cord
describe the pyramidal decussation:
The relocation of the corticospinal tract from its lateral position in the spinal cord to a ventral position in the pyramid of the opposite side.
what direction does the corticospinal tract travel?
descending
What level of the brainstem is the pyramidal decussation at:
caudal hindbrain
What do the gracile and cuneate fasciculi terminate in?
the gracile and cuneate nuclei
what fibers of the gracile and cuneate fasciculus cross the midline?
the internal arcuate fibers
what is the newly formed crossed tract of the gracile and cuneate fasciculus called?
the medial lemniscus
after forming, where is the medial lemniscus situated?
dorsal to the pyramids
what direction does the medial lemniscus travel, and what does it reach?
rostrally
the thalamus
what is the crossing of fibers from the gracile and cuneate fasciculus called?
the somatosensory decussation
after the gracile and cuneate fibers cross the midline, what is progressively vacated?
the dorsal region of the brainstem
once vacated, what takes up the remaining space in the dorsal region of the brainstem?
the fourth ventricle
What is the most outstanding feature at the level of the caudal end of the 4th ventricle?
the inferior olive
the caudal end of the 4th ventricle is a thin tube that is continuous with:
the central canal
in more ___ sections, the 4th ventricle expands to cover most of the ___
- rostral
- whole dorsal surface of the hindbrain
What 3 large nuclei in the hindbrain project to the cerebellum?
the external cuneate nucleus
the inferior olive
the basilar pontine nuclei
What are the 3 large nuclei in the hindbrain that project to the cerebellum collectively referred to as?
precerebellar nuclei
The fibers traveling from the inferior olive and the pontine nuclei do what to reach the cerebellum?
cross the midline
Because the pontine nuclei are huge, when they cross the midline, the crossing:
forms a massive outgrowth on the ventral surface of the hindbrain
The fibers traveling from the hindbrain to the cerebellum form 2 thick bundles called:
the inferior cerebellar peduncle
the middle cerebellar peduncle
The inferior cerebellar peduncle contains what?
the crossed olivocerebellar fibers
Where are the basilar pontine nuclei?
in the rostral hindbrain
The axons of the basilar pontine nuclei cross the midline to form:
the huge middle cerebellar peduncle
The external cuneate nucleus receives:
position sense information from the upper limb and neck
The external cuneate nucleus sends position sense information where?
to the cerebellum of the same side
The external cuneate nucleus is located medial to:
the inferior cerebellar peduncle at the dorsolateral corner of the rostral hindbrain
The inferior olive is:
a large, folded nucleus in the rostral half of the caudal hindbrain.
The inferior olive forms what on the ventral surface of the hindbrain, lateral to the pyramid?
a distinctive bulge
Axons of inferior olive cells travel to the opposite cerebellar hemisphere via:
the inferior cerebellar peduncle
What do axons of inferior olive cells provide in the opposite cerebellar hemisphere?
timing signals for coordination of movement
What is the largest group of neurons in the human brainstem?
the basilar pontine nuclei
Basilar pontine nuclei receive input from where?
the cerebral cortex
What forms a massive bulge that covers most of the rostral hindbrain?
The pontine nuclei and the crossing pontocerebellar fibers
What is the most usual landmark in the rostral hindbrain?
the fourth ventricle
The 4th ventricle is widest where?
the caudal end of the pontine expansion
The 4th ventricle becomes progressively narrower as:
it approaches the midbrain
What does the 4th ventricle form in the midbrain?
the aqueduct
Cerebrospinal fluid from the ___ travels down ___ to reach the fourth ventricle
- ventricles of the forebrain
- the aqueduct
The fluid escapes through holes in the roof of the fourth ventricle to reach ___.
- the subarachnoid space
Sections through the pontine expansion look very different from those at the level of the inferior olive because:
they are dominated by the huge pontine nuclei and crossing pontine fibers
In the pontine expansion, fibers that form the pyramid are swallowed up by:
the pontine nuclei and crossing fibers
What are the fibers that are used to be for the pyramid on the level of the pontine expansion called?
the longitudinal fibers of the pons
what do the longitudinal fibers of the pons consist of?
corticospinal and corticopontine fibers
What no longer lie vertically; and is forced to assume a horizontal position, sitting above the pontine expansion?
the medial lemniscus
the 4th ventricle separates the cerebellum from what?
the longitudinal part of the hindbrain
The cerebellum forms the roof of what?
the rostral half of the fourth ventricle
the inferior cerebellar peduncle moves dorsally to enter what?
the cerebellum, lying lateral to the fourth ventricle.
where does the middle cerebellar peduncle enter?
the cerebellum
On the left-hand side of a section of the pontine expansion, you can see the fibers of ___ as they travel through the middle cerebellar peduncle to reach ___.
- the trigeminal nerve
- the surface
What crossing is shown in sections of the rostral pontine expansion?
the decussation of the superior cerebellar peduncles
in the rostral pontine expansion, what forms a prominent bundle in the center of the basilar pontine formation
the corticospinal and corticopontine fibers (longitudinal fibers of the pons)
in the rostral pontine expansion, what still lies dorsal to the basilar pons, but has moved away from the midline
the medial lemniscus
why are the middle cerebellar peduncles not seen in sections of the rostral pontine expansion
because they have left the brainstem to enter the cerebellum
in the section of the ___, the fourth ventricle has shrunk down to a small tube that is about to become ___.
- rostral pontine expansion
- the aqueduct of the midbrain
Where does the superior cerebellar peduncle appear?
in the rostral hindbrain
In the rostral hindbrain, the superior cerebellar peduncle is ___ to the medial lemniscus
dorsal
The superior cerebellar peduncle consists of fibers that have:
left the cerebellum and are heading toward their termination in the thalamus
In the ___, the superior cerebellar peduncle is crossing the midline – the crossing is therefore called the ___.
- rostral hindbrain
- decussation of the superior cerebellar peduncle
In what hindbrain segment does the decussation of the superior cerebellar peduncle occur?
in the isthmus
what is the most rostral segment of the hindbrain?
the isthmus
In a section of the caudal midbrain, what overlapping features of the rostral hindbrain (isthmus) can be seen?
the isthmus and the rostral part of the basilar pontine formation
The dorsal part of the section of the caudal midbrain is at ___,
the caudal part of the inferior colliculus of the midbrain
the middle of the section of the caudal midbrain shows features of the ___ – which are: ___
- most rostral segment of the hindbrain
- the decussation of the superior cerebellar peduncle and the nucleus of the trochlear nerve.
The most ventral part of the section of the caudal midbrain cuts through: ___.
- the most rostral part of the basilar pontine formation
In a caudal midbrain section, lateral to the crossing pontine fibers is a very large fiber bundle called:
the cerebral peduncle (crus cerebri).
What is the cerebral peduncle formed by?
the corticospinal and corticopontine fibers
what is another name for the cerebral peduncle?
the crus cerebri
In a midbrain section at the level of the superior colliculus, what is in the center?
the aqueduct
In a midbrain section at the level of the superior colliculus, what surrounds the aqueduct?
the pale periaqueductal gray matter
In a midbrain section at the level of the superior colliculus, what is above the periaqueductal gray?
the two superior colliculi
In a midbrain section at the level of the superior colliculus, what appearance do the superior colliculus have?
a characteristically laminated appearance.
In a midbrain section at the level of the superior colliculus, what are/is below the periaqueductal gray? What does this contain?
two dark round masses
They contain the fibers of the superior cerebellar peduncle
Where does the superior cerebellar peduncle ascend towards?
the thalamus
In a midbrain section at the level of the superior colliculus, the dark, round masses containing the superior cerebellar peduncle coincides with the location of what?
large cells of the red nucleus
What does the red nucleus give rise to?
the descending rubrospinal tract
In a midbrain section at the level of the superior colliculus, what are the red nucleus cells obscured by?
the superior cerebellar peduncle fibers
In a midbrain section at the level of the superior colliculus, lateral to the red nucleus, at the lateral edge of the midbrain, is what?, which contains corticospinal and corticopontine fibers that are heading towards the hindbrain.
the very large cerebral peduncle
What does the cerebral peduncle contain?
corticospinal and corticopontine fibers
where do corticospinal and corticopontine fibers head towards?
the hindbrain
In a midbrain section at the level of the superior colliculus, lateral to the red nucleus, at the lateral edge of the midbrain, is what?
the very large cerebral peduncle
On the inner margin of the dark cerebral peduncle is an extensive pale area called:
the substantia nigra
What is the reason for the apparently contradictory name of the substantia nigra?
in fresh brain specimens, the area is stained black by iron deposits
Some of the cells of the substantia nigra contain ___, and which project to ___.
- dopamine
- motor centers in the forebrain
Between the red nucleus (superior cerebellar peduncle) and the cerebral peduncle is:
the elongated medial lemniscus
In a midbrain section at the level of the superior colliculus, which way has the medial lemniscus been pushed?
laterally
An important feature of a midbrain section at the level of the superior colliculus is the presence of streaks of fibers that start from ___ and which course through ___.
- under the periaqueductal gray
- the red nucleus
The streaks of fibers in a midbrain section at the level of the superior colliculus are of the: ,
oculomotor nerve
Where is the emergence point of the streaks of fibers of the oculomotor nerve in a section at the level of the superior colliculus?
between the two cerebral peduncles (the interpeduncular fossa).
what is the space between the two cerebral peduncles called?
the interpeduncular fossa
