Brain stem Flashcards
BRAIN STEM COMPONENTS:
Midbrain:most rostal part
Pons
Medulla oblongata:most caudal part
EMBRYOLOGICAL ORIGIN of the Midbrain
It arises from mesenphalon
Embryological origin of the Pons & medulla:
arise from
rhombencephalon or hindbrain (together with cerebellum
The midbrain is continuous
rostrally with _____
diencephalon of the forebrain
The pons is continous rostrally with ____& caudally with ____
midbrain
medulla
The brain stem lies on the ___ part of the occipital bone
Basilar part of the Ossipital bine
The midbrain is continuous rostrally with
diencephalon of forebrain
The pons is continous rostrally
with ___ & caudally with ____
midbrain
medulla
The medulla is continuous
caudally with spinal cord at the margin of foramen magnum
What’s the brainstem CONNECTION TO CEREBELLUM
Midbrain via superior cerebral peduncle
Pins via middle cerebral peduncle
Medulla via inferior cerebral peduncle
The brainstem is the site of
origin & emergence of nuclei
of cranial
nerves
(from 3rd to 12th)
Contains groups of nuclei & related fibers known as reticular formation
reticular formation
responsible for:
control of level of
consciousness, perception of pain,
regulation of cardiovascular &
respiratory systems
List all the cranial nerves
Oh, Oh, Oh, To, Try, And, Feel, Very, Good, Valet, Ah, Heaven
Location and function of those nerves
The ventral surface of the medulla
The median fissure
The lower part of this fissure is not easily visible because it is covered by the crossing of the pyramidal fibers____ fibres
pyramidal (corticospinal) fibers.
These fibers are nerve pathways that originate from the cerebral cortex and cross over to the opposite side of the body, controlling voluntary muscle movements.
Features of the ventral surface of the medulla
Pyramidal discussion
Olive
Ventral median fissure
The olive is found on the lateral side of the pyramid and is separated from it by a groove called the _____.
ventrolateral sulcus
The olive is also an elevation or bulge and is produced by the presence of the _____.
inferior olivary nucleus
The olive is involved in ____
motor coordination and learning.
Nerves emerging from the Medulla are?
Hypoglossal, glossopharyngeal, vagus, cranial part of assesory nerve
The hypoglossal nerve emerges from ______
And it’s function is _____
Hypoglossal nerve (12th cranial nerve): This nerve emerges between the pyramid and the olive.
It controls the muscles of the tongue, allowing for movements such as swallowing and speech.
Glossopharyngeal nerve (9th cranial nerve),
Vagus nerve (10th cranial nerve),
Cranial part of the Accessory nerve (11th cranial nerve):
These nerves emerges from
Emerges dorsolaterally (towards the back and side) to the olive, in a top-to-bottom arrangement.
Glossopharyngeal nerve (9th cranial nerve),
Vagus nerve (10th cranial nerve),
Cranial part of the Accessory nerve (11th cranial nerve):
What are the function of these nerves
controlling functions related to the throat, larynx, and various organs in the chest and abdomen, including swallowing, breathing, and heart rate.
Features of the ventral surface of the pons
Basilar sulcus
Transverse Pontine (Pontocerebellar) Fibers
What’s the basilar sulcus, it’s content & function of the content
The basilar sulcus is a groove running along the midline of the pons, dividing it into two halves. It is occupied by the basilar artery, which supplies blood to the brainstem and cerebellum.
Transverse Pontine (Pontocerebellar) Fibers
These are groups of neurons located in the pons. These fibers cross the midline and pass through the contralateral (opposite) middle cerebellar peduncle to enter the opposite hemisphere of the cerebellum.
Function of the Transverse Pontine (Pontocerebellar) Fibers
They are involved in connecting the pons with the cerebellum and play a role in motor coordination and balance.
Nerves emerging from the Pons are
Where they emerge from
Trigeminal nerve (5th cranial nerve):
Abducent nerve (6th cranial nerve):
Facial nerve (7th cranial nerve) and vestibulocochlear nerve (8th cranial nerve)
Nerves emerging from the Pons & Where they emerge from
5th -The trigeminal nerve emerges from the middle of the ventrolateral aspect of the pons
6th- emerges at the junction between the pons and the pyramid
7 & 8th- emerge at the cerebellopontine angle, which is the junction between the pons, medulla, and cerebellum.
The trigeminal roots and it’s function
It has two roots: a small medial motor root and a large lateral sensory root.
The trigeminal nerve is responsible for sensations in the face and controlling the muscles involved in chewing
Function of the abducent nerves
It controls the movement of the lateral rectus muscle, which is responsible for outward eye movement.
The facial nerve has a motor root and a sensory root, while the vestibulocochlear nerve has two parts: the vestibular part and the cochlear part.
The facial nerve controls facial muscles and is involved in taste sensation, while the vestibulocochlear nerve is responsible for hearing and balance.
The midbrain contains important structures involved in motor control, sensory processing, and various other functions.
Features of the midbrain
Descending Fibers (Crus Cerebri or Basis Pedunculi)
Interpeduncular Fossa: The two crura cerebri,
The midbrain is primarily composed of a large column of nerve fibers known as the crus cerebri or basis pedunculi
These fibers are responsible for transmitting signals from the cerebral cortex (the outer layer of the brain) to the spinal cord and other parts of the body. They form a pathway for motor commands, enabling voluntary movement and muscle control.
Interpeduncular Fossa: The two crura cerebri, which are the descending fibers mentioned above, are separated by a depression or groove called the interpeduncular fossa.
What are the Nerve emerging from the Midbrain & emerges from____
And it’s function
Occulomotor Nerve (3rd Cranial Nerve):
It emerges from the medial aspect (inner side) of the crus cerebri.
The oculomotor nerve is responsible for controlling the movement of certain eye muscles, including those that control eye position, pupil size, and focusing.
The dorsal surface of the medulla is divided into
• Caudal 2/3: Closed Medulla:
• Rostral 1/3: Open Medulla
Features of the dorsal surface of the medulla
CLOSED MEDULLA
Dorsal median sulcus
Fasciculus gralis
Fasciculus cuteanus
The fasciculus gracilis is located closer to ____, and an elevation called the ____ can be seen at the upper part of this bundle.
the midline
gracile tubercle
Gracile tubercle marks the site of the ____, which is does what function
gracile nucleus
the processing of sensory information related to touch, vibration, and conscious proprioception
fasciculus cuneatus is situated on the sides (lat.)of the fasciculus gracilis, and the cuneate tubercle is an elevation seen at its upper part. This tubercle indicates the location of the cuneate nucleus, which also plays a role in processing _____
sensory information from touch, vibration, and conscious proprioception, but primarily from the upper body.
Moving on to the open medulla, which forms the lower part of the floor of the fourth ventricle
On either side of the open medulla, there is an inverted V-shaped sulcus that divides this area into ____ parts when viewed from the mid. To lat.
3
The three parts are
And their function
Hypoglossal triangle, which overlies the hypoglossal nucleus. The hypoglossal nucleus is responsible for controlling the movements of the tongue.
Vagal triangle, which overlies the dorsal vagal nucleus. The dorsal vagal nucleus is involved in regulating functions of the autonomic nervous system, including the parasympathetic control of various organs in the body.
Vestibular area, which overlies the vestibular nuclei. The vestibular nuclei are associated with processing sensory information related to balance and spatial orientation.
___ Forms the upper part of floor of 4th ventricle
The dorsal surface of the pons
The dorsal surface of the Pons is seperated from the medulla by
Is separated from the medulla by an imaginary line passing between the caudal margins of
middle cerebellar peduncle
In the dorsal surface of the Pons
On either side, a sulcus divides the area into 2 parts (from medial to lateral):
Which are?
Medial eminence:
Vestibular area:
Medial eminence & vestibular area overlies
Medial eminence:overlies abducent
nucleus
Vestibular area: Overlies vestibular nuclei
The dorsal surface of the midbrain is characterized by ___ elevations, which are structures that are elevated or raised above the surrounding areas.
4
These four elevations:
& are involved in , their function
.
Two superior colliculi, which are involved in visual reflexes.
Two inferior colliculi, which are part of the auditory pathway.
The superior colliculi coordinate eye movements and attention based on visual stimuli.
The inferior colliculi process auditory information, helping with sound localization and auditory reflexes
What nerve emerges from the dorsal surface of the midbrain
The trochlear nerve (4th cranial nerve) emerges from the midbrain’s dorsal surface, just below the inferior colliculus.
The trochlear nerve innervates the superior oblique muscle of the eye, contributing to eye movements and coordination.
Medulla@ olive
Principal olivary nucleus, dorsal asessory olivary nucleus is pst. to principal
&medual olivary nucleus is medial to principal
Together forms inferior olivary complex
Pyramid is located@ the ant. Surface of the medulla
In the pyramid@ the ant. Side is the Accurate nucleus
PST PART OF THE MEDULLA
@ the floor of the 4th ventricle anteriorly is the hypoglossal nucleus close to the mid line
Lat to the hypoglossal is the dorsal nucleus of vagus
Medial vestibular nucleus is the lat. To it
Then inferior vestibular nucleus & nucleus solitarus is also present in the pst medulla
PST PART OF THE MEDULLA
the inferior cerebellar peduncle is located@ what part
Pst lat part
PST PART OF THE MEDULLA
Inferior spinocerebelar tract is located@
Close to the surface & Lat. In between the inferior cerebellar peduncle & olive
Medial to the inferior spinocerebelar tract is
Spinal lamiscus
PST PART OF THE MEDULLA
The pst & ant. cochlear nucleus is located
Pst. To inferior cerebellar peduncle
Ant. To inferior cerebellar peduncle
Medial to the inferior cerebellar peduncle is the __&__
Spinal trigeminal tract & nucleus
Mid to first is nucleus ambiguous
@ midline is the from ant. To pst.
Mainly 3
(Pyramid,)
Medial meniscus, tectospinal tract & medial longitudinal fasciculus
In studying the internal features of the brain stem is studied @ the level of
Pst. Upwards
Level of pyramidal discussion
Level of sensory
Level of olive
@ the pyramidal discussion
The changes occurring in the grey mata @ pyramidal discussion is
The two elongation present that’s absent in the spinal cord is
i.e the grey mata is becoming more defined
Nucleus gracilis & Cuneatus
& pst. Horn to spinal nucleus and tract of trigeminal
Dorsal & ventral spinal cerebellar( lat. Sides) spinotelamic tract(mid. To cerebellar)
Pst column is pst.
The pyramidal discussion is made up of what fibres
Corticospinal & cortico nuclear @ the level of pyramidal discussion
Cortico pontine fibres (passes @ d Pons to the cerebellar) s included before i.e above the discussion
Lateral corticospinal tract is the cortico tract involved in discussion
The part of the grey matter (ant. Part) that’s cut off @ the pyramidal discussion is
Final nucleus of Assesory nerve & supra spinal nucleus of 1st cervical nerve
Sensory decussation is when what is formed
Medial lemniscus
@ sensory decussation
The nucleus Cunateuus & gracilis that’s formed @ the lower part of the medulla, seperates from the main grey matter as a two set of nucleus
@ sensory decussation
The second order neuron croses to the opposite side to form
Medial lemniscus
@ sensory decussation
The pst. Column is replaced by
Medial lemniscus
The fibres going to form the medial lemniscus is called
Internal arcuate fibes
Pst to the nucleus cuneatus is
Assesory cuneate nucleus
Ant. to nucleus cuneatus is
Spinal nucleus & tract of trigeminal nerves
The assesory cuneate nucleus function
It sends fibres to the cerebellum known as pst. External arcuate fibres