Lecture 4: actual lecture

Question 1

SPINAL CORD EXTENT

Answer 1

BASE OF SKULL - Continuous With The Medulla Of The Brain

2nd – 3rd Lumbar Vertebrae

Question 2

DISTAL END OF THE SPINAL CORD

Answer 2

Nerve Roots that emerge at levels below L2 extend beyond the conus medullaris to reach their exit. This forms fine filaments distal to end of the spinal cord that is called the CAUDA EQUINA.

Conus Medullaris is at level of L2-L3. However, rootlets continue to emerge and descend to exit vertebral canal at appropriate level. Therefore, CSF must still be present below the end of the spinal cord.

Whereas the spinal cord ends at L2-L3, the meninges continue inferiorly to end by attaching to the coccyx. The dura and arachnoid remain as a visible dense sheath. The pia continues beyond the end of the cord as the filum terminale.

Question 3

FILUM TERMINALE

Answer 3

Extension of pia mater that extends beyond the distal end of the spinal cord (the conus medullaris).

Question 4

All 3 layers of the meninges fuse in the sacral area to form the coccygeal ligament that anchors the cord to the coccys.

Answer 4

Dura and Arachnoid fuse

around S2 where they are joined by filum terminale

Question 5

COCCYGEAL LIGAMENT =

Answer 5

FILUM TERMINALE (PIA) + FILUM OF DURA

Question 6

TELENCEPHALON

FOREBRAIN

Answer 6

Cerebral cortex and subcortical nuclei (e.g., Basal Ganglia).

The largest part of the brain is the telencehalon or forebrain. It consists of the massive cerebral cortex and several nuclei that are buried deep within the telencephalon. These are referred to as subcortical nuclei.

Question 7

PONS

Answer 7

Latin for “BRIDGE”

Enlargement Rostral to medulla

Question 8

PONS

Answer 8

Latin for “BRIDGE,” as it has the appearance of planks as on a wooden bridge.

Enlargement Rostral to medulla

Question 9

MEDULLA

Answer 9

Latin for “Having an oblong shape”
“in the center”

Direct Rostral extension of the Spinal cord

Question 10

cerebellum

Answer 10

means “little brain”.

neural structure located dorsal to the medulla and pons

Question 11

EXTERNAL FEATURES OF VENTRAL MEDULLA

On the brainstem there are various “bumps” caused by the presence of underlying nuclei or fiber tracts.

Answer 11

On the ventral surface of the medulla, there is a midline slit called the Anterior Median Fissure.

Immediately adjacent to the anterior median fissure are 2 elevations called the Pyramids because of their shape. They are widest at the junction of the pons and medulla and they taper at the junction of the medulla and spinal cord.

Near this latter junction, the anterior median fissure becomes somewhat obscured due to the fact that axons descending in the pyramids cross from one side to the other forming a decussation or crossing.

Immediately lateral to the pyramids is another depression called the Preolivary Sulcus. This is not as deep as the anterior median fissure.

Continuing laterally, the next small round bump is called the Olivary Eminence. This structure is located around the mid-medullary level.

Lateral to the olivary eminence is another depression called the Post-Olivary Sulcus.

These structures serve as landmarks for several nerves that arise from the brainstem to innervate structures in the head. These are collectively referred to as cranial nerves.

Question 12

CRANIAL NERVES RELATED TO MEDULLA

Answer 12

Cranial nerves innervate structures in the head. There are a total of 12 pairs of cranial nerves. These nerves are given Roman numerals as well as a name.

In the medulla, we find 6 of the 12 cranial nerves.

Cranial Nerve XII – Hypoglossal
This is the only cranial nerve located in the preolivary sulcus.

Cranial nerve XI – Accessory.
This nerve arises from the upper segments of the cervical spinal, enters the skull through a large opening at the base called the Foramen Magnum, and is joined by a few branches arising from the medulla.

Cranial nerve X – Vagus
Vagis located at the caudal end of the post-olivary sulcus.

Cranial nerve IX – Glossopharyngeal is also located in the post-olivary sulcus.

Cranial nerve VIII – Vestibulocochlear arises from the lateral aspect of the brainstem at the junction of the medulla and pons.

Cranial nerve VII – Facial
Arises at the same level as Cranial nerve VIII, just a bit more rostral.

Cranial nerve VI – Abducens
Located on either side of midline at the junction of the pons and medulla.

Question 13

CRANIAL NERVES RELATED TO MEDULLA

Answer 13

Cranial nerves innervate structures in the head. There are a total of 12 pairs of cranial nerves. These nerves are given Roman numerals as well as a name.

In the medulla, we find 6 of the 12 cranial nerves.

Cranial Nerve XII – Hypoglossal
This is the only cranial nerve located in the preolivary sulcus.

Cranial nerve XI – Accessory.
This nerve arises from the upper segments of the cervical spinal, enters the skull through a large opening at the base called the Foramen Magnum, and is joined by a few branches arising from the medulla.

Cranial nerve X – Vagus
Vagis located at the caudal end of the post-olivary sulcus.

Cranial nerve IX – Glossopharyngeal is also located in the post-olivary sulcus.

Cranial nerve VIII – Vestibulocochlear arises from the lateral aspect of the brainstem at the junction of the medulla and pons.

Cranial nerve VII – Facial
Arises at the same level as Cranial nerve VIII, just a bit more rostral.

Cranial nerve VI – Abducens
Located on either side of midline at the junction of the pons and medulla.

Question 14

Cranial Nerve XII

Answer 14

Hypoglossal

This is the only cranial nerve located in the preolivary sulcus.

Question 15

Cranial nerve XI

Answer 15

Accessory.
This nerve arises from the upper segments of the cervical spinal, enters the skull through a large opening at the base called the Foramen Magnum, and is joined by a few branches arising from the medulla.

Question 16

Cranial nerve X

Answer 16

Vagus

Vagis located at the caudal end of the post-olivary sulcus.

Question 17

Cranial nerve IX

Answer 17

Glossopharyngeal

Also located in the post-olivary sulcus.

Question 18

Cranial nerve VIII

Answer 18

Vestibulocochlear

Arises from the lateral aspect of the brainstem at the junction of the medulla and pons.

Question 19

Cranial nerve VII

Answer 19

Facial

Arises at the same level as Cranial nerve VIII, just a bit more rostral.

Question 20

Cranial nerve VI –

Answer 20

Abducens

Located on either side of midline at the junction of the pons and medulla

Question 21

the dorsal aspect of the medulla.

Answer 21

The large space on the dorsal surface of the medulla is the 4th ventricle. This is filled with cerebral spinal fluid (CSF).

The distal end of the 4th ventricle is called the obex. It serves as an important landmark for several structures in the caudal vs. the rostral medulla.

Lateral to the obex are paired “bumps” called the gracile tubercle. There are 2 other elevations adjacent to the gracile tubercle called the cuneate tubercle.

Question 22

CEREBELLUM

Answer 22

The cerebellum is located dorsal to the medulla and pons.

It is connected to these brainstem regions by 3 fiber tracts called Cerebellar Peduncles. Think of them as roads allowing information to flow from the brainstem into the cerebellum or from the cerebellum back to the brainstem.

The cerebellum is part of the motor system and is involved in coordinating movement.

Question 23

CEREBELLAR CORTEX

Answer 23

As for the cerebral cortex, the cerebellar cortex is highly infolded forming deep ridges. If it was completely unfolded it would extend up to 1 meter in length. This clearly reflects the importance of this structure in brain function.

Question 24

CEREBELLAR PEDUNCLES

Answer 24

Fiber tracts that connect cerebellum to brainstem.

Cerebellar Peduncles are made up of:

1. Axons entering the cerebellum that originated in the spinal cord or other parts of the brainstem (e.g., medulla, pons).
2. Axons leaving the cerebellum. These are destined for brainstem targets.

Question 25

VENTRAL PONS =

Answer 25

the “BRIDGE” part

The pons is greatly expanded from right to left compared to the slender medulla.

The large expansion on the ventral surface is called the Basilar Pons. The basilar pons extends from the medulla, caudally, to the midbrain rostrally.

If one follows the “planks” of the bridge laterally, they appear to converge into a large bundle. This is called the Middle Cerebellar Peduncle and is one pathway by which the cerebellum is connected to the brainstem.

Two cranial nerves are related to the pons. The largest cranial nerve is Cranial nerve V – trigeminal. It is located just rostral to the middle cerebellar peduncle on the lateral side of the pons. Cranial nerve IV – Trochlear is the smallest cranial nerve and it appears on the lateral side of the rostral end of the pons.

Question 26

Cranial nerve IV

Answer 26

Trochlear

The smallest cranial nerve and it appears on the lateral side of the rostral end of the pons.

Question 27

Cranial nerve V

Answer 27

Trigeminal
The largest cranial nerve. It is located just rostral to the middle cerebellar peduncle on the lateral side of the pons.

Question 28

MIDBRAIN - VENTRAL

moving rostrally in the brainstem.

Answer 28

Immediately rostral to the pons is the midbrain (aka, the mesencephalon).

It extends from the rostral pole of the pons to two protrusions titled the Mammillary Bodies which actually are part of a nuclear complex in the diencephalon called the hypothalamus.

Laterally, there are large columns called the Cerebral Peduncles. These should not be confused with the cerebellar peduncles. The axons in the cerebral peduncle arose from neurons in the cerebral cortex. These axons course from the cerebral cortex to the brainstem and spinal cord.

The space between the cerebral peduncles is called the Interpeduncular Fossa.

Emerging from the interpeduncular fossa is cranial nerve III – oculomotor N. These paired nerves are located adjacent to the midline and emerge at the junction of the pons and midbrain.

Question 29

Cranial Nerve III

Answer 29

Oculomotor

These paired nerves are located adjacent to the midline and emerge at the junction of the pons and midbrain.

Question 30

TECTUM

Answer 30

SUPERIOR AND INFERIOR COLLICULI (“little hill”)

Found in Midbrain

Latin for “ROOF”

Question 31

BRAINSTEM – SAGITTAL VIEW

Answer 31

The large bulge of the basilar pons is evident, as is a space called the fourth ventricle located between the cerebellum and the brainstem.

Rostrally, the fourth ventricle is continuous with a narrow channel called the Cerebral Aqueduct. The cerebral aqueduct is dorsal to the midbrain.

The roof of the aqueduct is formed by two small bulges called the superior and inferior colliculi (which means little hill in Latin). Collectively they are referred to as the tectum or roof of the midbrain

Question 32

MIDBRAIN – DORSAL VIEW

Cerebellum and Cerebral Cortex Removed

Answer 32

The tectum, or roof of the midbrain, is visible and the superior and inferior colliculi can be identified.

Several elevations are observed lateral to the colliculus. These actually are part of the diencephalon and are called the Medial and Lateral Geniculate Nuclei.

The inferior colliculus is connected to the medial geniculate nucleus via a fiber tract called the Brachium of the Inferior Colliculus. This pathway is related to the auditory system.

The superior colliculus and the lateral geniculate nucleus, together with other structures, are part of the visual system.

The lateral geniculate nucleus is not connected to the superior colliculus.

The origin of Cranial nerve IV –Trochlear Nerve is seen just below the inferior colliculus. This is the only cranial nerve that arises from the dorsal surface of the brainstem.

After emerging from the midbrain, the nerve courses laterally and ventrally to emerge on the ventral surface of the brainstem at the level of the rostral pons.

Question 33

Cranial nerve IV

Answer 33

Trochlear Nerve
The origin of the Trochlear Nerve is seen just below the inferior colliculus. This is the only cranial nerve that arises from the dorsal surface of the brainstem.

Question 34

INFERIOR COLLICULUS

Answer 34

PART OF AUDITORY SYSTEM

Question 35

SUPERIOR COLLICULUS

Answer 35

PART OF VISUAL SYSTEM

Question 36

DIENCEPHALON – Sagittal View

Answer 36

Most of the diencephalon is covered by the telencephalon or cerebral cortex. It extends from the mammillary bodies to the optic chiasm.

Thalamus, Hypothalamus

Question 37

INFUNDIBULUM

Answer 37

STALK OF THE PITUITARY GLAND

Question 38

Describe the Anatomical Organization of the Cerebral Cortex

1. Identify the lobes of the cerebral cortex and their borders including the frontal lobe, parietal lobe, temporal lobe, occipital lobe, cingulate lobe, and insula.
2. Identify specific sulci in the cerebral cortex including the central sulcus, lateral sulcus, calcarine sulcus, cingulate sulcus, and parieto-occipital suclus.

Answer 38

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Question 39

MAJOR SULCI OF LATERAL CORTEX

Answer 39

To define the lobes, we must first identify some of the major depressions or sulci that form the borders of the different lobes.

The most obvious depression is the Lateral Sulcus which seems to split the brain almost in half in the horizontal plane.

Another prominent depression, is the Central Sulcus which seems to divide the brain in half in the transverse plane. The central sulcus does not quite reach the lateral sulcus and there is always a small bridge of cortex that separates them.

The depression rostral to the central suclus is called the Precentral Sulcus, whereas the depression immediately caudal to the central sulcus is the Postcentral Sulcus.

A very short, shallow sulcus near the caudal pole of the cerebral cortex is the Parieto-Occipital Sulcus.

Question 40

BORDERS of the FRONTAL LOBE

Answer 40

Frontal Pole Of Brain
Central Sulcus
Lateral Sulcus

Question 41

BORDERS of the PARIETAL LOBE

Answer 41

Central Sulcus

Line Between Preoccipital Notch And Parieto-Occipital Sulcus

Question 42

BORDERS of the OCCIPITAL LOBE

Answer 42

Line Between Preoccipital Notch And Parieto-occipital Sulcus

Question 43

BORDERS of the TEMPORAL LOBE

Answer 43

Lateral Sulcus

Line Between Preoccipital Notch And Parieto-occipital Sulcus

No Clear Demarcation Between Parietal Lobe Posteriorly

Question 44

INSULAR CORTEX

Answer 44

Buried Deep In The Lateral Sulcus.

Covered By Gyri From The Temporal, Parietal, and Frontal Lobes.

Contains Gustatory, Autonomic, Pain, Vestibular Areas.

Question 45

MAJOR SULCI OF MEDIAL CORTEX

Answer 45

CINGULATE SULCUS

PARIETO-OCCIPITAL SULCUS

CALCARINE SULCUS

Question 46

TELENCEPHALON – MEDIAL VIEW

Answer 46

The medial extent of the central sulcus is visible and is a landmark for defining the frontal and parietal lobes.

Two additional sulci are evident and further define the lobes of the cerebral cortex. A well defined parieto-occipital sulcus separates the occipital and parietal lobes in this view. In addition, the Cingulate Sulcus separates the frontal and parietal lobes from the cingulate or limbic lobe.

Two other prominent landmarks are prominent fiber tracts. One is the Corpus Callosum which is a large bundle of axons that connects the right and left sides of the cerebral cortex. The other is the Fornix which links structures related to the limbic system.