Topography of the brain Flashcards
describe the formation of the midbrain, hindbrain, forebrain and spinal cord?
The forebrain vesicle gives rise not only to the diencephalon but also the cerebral hemispheres.
The midbrain vesicle doesn’t grow very much, whereas the hindbrain vesicle it grows, it falls and forms the pons and medulla in front and the cerebellum at the back.
So the entire brain stem is formed from the midbrain vesicle and then parts of the hindbrain vesicle that form the pons and the medulla.
what happens as soon as the neural tube is formed?
it divides into 3 primary vesicles
during what week does the neural tube dovide into 3 primary vesicles?
week 4
what do the three primary vesicles divide into during week 5?
5 secondary vesicles
what do the 5 secondary vesicles divide into?
the adult brain
how does the neural tube cavity persist during vesicle development?
the five secondary vesicles are formed the cavity persists within these and it is these cavities that form your ventricles.
what vesicle is found within the cerebral hemisphere?
lateral ventricles
what ventricle is found within the diacephalon?
3rd ventricle
what is found within the midbrain?
cerebral aqueduct
which ventricle is found within the hindbrain vesicle, which gives rise to the pons and medulla in front and the cerebellum at the back
fourth ventricle
What are the different ventricles?
Lateral ventricles (x2)
III ventricle
Cerebral aquaduct
IV ventricle
Where are the lateral ventricles located?
Within cerebral hemispheres
Where is III ventricle located?
Within diencephalon
Where is cerebral aquaduct located?
Within midbrain
Where is IV ventricle located?
Between pons and medulla (in front) and cerebellum (at the back)
Where is CSF found?
Inside ventricles and in the subarachnoid space
what are cerebellar peduncles?
the structure connecting the cerebellum to the brain stem and the cerebrum
label the different parts of the brainstem?
midbrain
pons
medulla
what cranial nerves emerge from the brainstem?
Cranial nerves III – XII, tracts from spinal cord, vital centres for eg: cardiorespiratory centre
what are the three functions of the brainstem?
Pathway for fibre tracts running between higher & lower centres.
Brainstem nucleii are involved with 10 of the 12 cranial nerves, so innervation of head & neck.
Brainstem centres produce the rigidly programmed automatic behaviours essential for survival.
what does medulla continue as in foramen magnum?
At the foramen magnum it becomes the spinal cord.
lum by the inferior cerebellar peduncle.
what is the cavity within the medulla?
4th ventricle, located between the medulla and cerebellum.
what are the pyramidal projections beside the 4th ventricle of the the medulla known as?
pyramids of the medulla
what are the small projections lateral to the medulla?
Lateral to that are little projections that look like olives - called olives
there are a lot of fibres that seem to be criss crossing at the lower part of the pyramids, joining up or going from one pyramid to the other what are they?
decussation of the pyramids
how do motor signals travel to the pyramids?
These fibres that you have in the ventral part of the medulla that formed this prominence here are nothing but your motor fibres,
motor fibres that originate in the cerebral hemisphere and are carrying the impulses down to your skeletal muscle.
want to move your right upper limb.
The left side of the brain controls the right and therefore motor impulses that have to go to your right upper limb muscle are originating in your left cerebral hemisphere.
They are tracking down from your cerebral hemisphere, down through these fibres just here, down through this part of the pons,
until they reach the medulla that they are going to be sitting within the pyramid.
And at the lower part of the pyramid is where they’re going to cross to the opposite side, so that when they come down
they can leave the spinal cord and then go through the brachial plexus to go to the upper limb muscles on the right.
In order to go to my right upper limb, impulses from my left brain come down from the pyramid of the medulla oblongata,
cross to the right side at the lower part of the pyramids, continues down into the spinal cord, finally leaving it through the ventral horn somewhere between C5 and T1,
goes through the brachial plexus, through the nerves of the brachial plexus and then supplies the muscles of my upper limb
connection of cerebral peduncles?
Superior cerebellum connects cerebellum to the midbrain, middle to the pons and inferior to the medulla oblongata.
describe the caudal part of the medulla section?
Closed around IV ventricle
desribe the cranial part of the medulla section?
Open with IV ventricle posteriorly.
desribe what is found within the white matter of the medulla section?
Pyramidal tract
Medial lemniscus
Inferior cerebellar peduncle
Other tracts.
desribe what is found within the grey matter of the medulla section?
Cranial n nucleii & inferior olivary nucleus
Nucleii of the Reticular formation (vital centres)
Sensory nucleii (gracile and cuneate)
From the surface of the pons what should you should see arising?
cranial nerve 5
what is cranial nerve 5?
Cranial nerve five, or trigeminal as we know, mainly carries general sensory information from all of the face.
But there are also motor fibres in its mandibular division.
Cranial nerve five at its origin from the brainstem is quite a chunky nerve.
in gross specimens, while it might sometimes be difficult to identify most of these smaller nerve rootlets, you will always be able to see where cranial nerve five emerges from.
what other cranial nerves arise from the pons?
three nerves from the pontomedullary junction.
cranial nerves six (abducent) and cranial nerves seven and eight which come together.
Seven is your facial nerve and eight your vestibulocochlear nerve.
what is located posterior to the pons?
IV ventricle
what would you find in the white matter of the pons?
1.Middle cerebellar peduncle
2.Medial lemniscus (sensory)
3.Pyramidal tract (motor)
what would you find in the grey matter of the pons?
A.Cranial n. nucleii
B.Pontine nucleii
C.Nucleii of Reticular formation