Cerebellum and the ventricles

Question 1

What is the structure of the cerebellum?

Answer 1

It comprises two ovoid hemispheres joined in the midline by the narrow median VERMIS, and consists of an outer layer of grey matter, the cortex, and an inner core of white matter surrounding centrally placed aggregations of nerve cells, the DEEP NUCLEI.
The entire surface is marked by closely set transverse curving fissures which delineate the individual ridges or FOLIA of the cerebellar cortex.

Question 2

What are the cerebellar lobes?

Answer 2

There are three anatomical lobes that can be distinguished in the cerebellum; the anterior lobe, the posterior lobe and the flocculonodular lobe. These lobes are divided by two fissures – the primary fissure and posterolateral fissure.

Question 3

What are the cerebellar zones?

Answer 3

There are three cerebellar zones. In the midline of the cerebellum is the vermis. Either side of the vermis is the intermediate zone. Lateral to the intermediate zone are the lateral hemispheres. There is no difference in gross structure between the lateral hemispheres and intermediate zones.

Question 4

What is the red nucleus?

Answer 4

A circular mass of grey matter ventro-lateral to the Cerebral Aqueduct, may be pink in a fresh specimen

Question 5

What is the substantia nigra?

Answer 5

A black band of nerve cells overlying the Crus Cerebri, ventro-lateral to the Red Nucleus on each side

Question 6

What are the major features found on the interior surface of the cerebellum?

Answer 6

TONSIL - a prominent rounded swelling of the Cerebellar Cortex anteriorly on either side of the vermis
FLOCCULUS - approximately ovoid in shape with a crinkled edge, lies immediately posterior to the Lateral Foramen of the IVth ventricle on each side partly covered by Choroid Plexus. It lies immediately caudal to the entry point of CN VIII and is crossed anteriorly by emerging CN X and CN XII.
NODULE - continuous with the Flocculus via a peduncle of white matter
FLOCCULO-NODULAR LOBE – the Flocculus and Nodule together, primarily concerned with vestibular information.

Question 7

What information is processed by the flocculus and nodule?

Answer 7

Sensory information from the semicircular canals feed through the vestibular component of the eighth cranial nerve directly to the flocculus. This information is passed to the nodule which is part of the vermis. The vermis controls subconscious positioning of the body, particularly the axial (trunk) muscles.

Question 8

From which arteries does the cerebellum receive its blood supply?

Answer 8

Superior cerebellar artery (SCA)
Anterior inferior cerebellar artery (AICA)
Posterior inferior cerebellar artery (PICA)

Question 9

How is the cerebellum connected to the brainstem?

Answer 9

The Cerebellum is connected to the Medulla, Pons and Midbrain by the Inferior, Middle and Superior Cerebellar Peduncles respectively.

Question 10

Where is the third ventricle?

Answer 10

The lateral ventricles are connected to the third ventricle by the foramen of Monro. The third ventricle is situated in between the right and the left thalamus.

Question 11

What are the protrusions of the third ventricle?

Answer 11

The anterior surface of the ventricle contains two protrusions:
Supra-optic recess – located above the optic chiasm.
Infundibular recess – located above the optic stalk.

Question 12

Where is the fourth ventricle?

Answer 12

The fourth ventricle is the last in the system – it receives CSF from the third ventricle via the cerebral aqueduct. It lies within the brainstem, at the junction between the pons and medulla oblongata.

Question 13

Where does the CSF drain when it leaves the fourth ventricle?

Answer 13

From the 4th ventricle, the fluid drains into two places:
Central spinal canal – bathes the spinal cord
Subarachnoid cisterns – bathes the brain, between arachnoid mater and pia mater. Here the CSF is reabsorbed back into the circulation.

Question 14

What is the rhomboid fossa?

Answer 14

Diamond shaped floor of the IVth ventricle limited laterally by the Cerebellar Peduncles and posteriorly by the Gracile and Cuneate Tubercles

Question 15

What is the median sulcus?

Answer 15

Divides the Rhomboid Fossa into triangular left and right halves

Question 16

What is the facial colliculus?

Answer 16

A rounded swelling caused by the fibres of CNVII in the substance of the pons curving around the nucleus of the CN VI at the level of the Superior Fovea
The nuclei for the lower cranial nerves lie in the floor of the fourth ventricle.

Question 17

What is the obex?

Answer 17

Inferior apex of the rhomboid fossa

Question 18

What is the area postrema?

Answer 18

A small tongue-shaped area immediately rostrolateral to the Obex. It is a site commonly associated with nausea control – a chemoreceptive trigger zone for the emetic response.

Question 19

What is the interventricular foramen?

Answer 19

Immediately behind the upper end of the Column of the Fornix, permits CSF flow from the Lateral Ventricles to the IIIrd Ventricle. This narrow opening is the only communication between the Lateral Ventricles and the rest of the ventricular system, and is almost entirely filled with Choroid Plexus.

Question 20

Where is the central sulcus of the cortex?

Answer 20

Begins a little behind the midpoint of the Hemisphere extending for a short distance onto the medial surface and running forwards and downwards, ending just before it reaches the lateral sulcus.

Question 21

What is the paracentral lobule?

Answer 21

A U-shaped gyrus surrounding the medial extension of the Central Sulcus which contains the representations of the lower limb within the primary motor and somatic sensory areas of the cortex which, on the lateral surface, occupy the pre-central and postcentral GYRI respectively.

Question 22

What is the cingulate sulcus?

Answer 22

Separates the Cingulate Gyrus, which runs above the Corpus Callosum, from the rest of the Hemisphere

Question 23

What is the parieto-occipital sulcus?

Answer 23

Lies mainly on the medial surface of the Hemisphere where it forms a Y-shaped arrangement with the calcarine sulcus

Question 24

What is the calcarine sulcus?

Answer 24

Roughly at right angles to the Parieto-occipital Sulcus it runs posteriorly to reach the Occipital Pole. The Primary Visual Cortex lies in the walls of the Calcarine Sulcus.

Question 25

What is the corpus callosum?

Answer 25

A broad arched band of white matter- the largest of the fibre bundles interconnecting the two halves of the brain

Question 26

What is the fornix?

Answer 26

A bundle of white matter beneath the body of the Corpus Callosum, connects the Hippocampus with the Diencephalon and the Precommissural Septum

Question 27

What is the commissure of the fornix?

Answer 27

Fibres from one Hippocampus cross to the opposite Fornix and so back to the opposite Hippocampus

Question 28

What are the columns of the fornix?

Answer 28

Anterior and posterior extensions of the Fornix, anteriorly they extend vertically downwards to the Mammillary Bodies

Question 29

What is the anterior commissure?

Answer 29

A thick bundle of white matter crossing the midline horizontally between the Lamina Terminalis and the Fornix, crosses to interconnect the Temporal Lobes and Olfactory structures of each side

Question 30

What is the septum pallucidum?

Answer 30

Two thin vertical sheets made primarily of glia with a few white fibres, sparse grey matter and a covering of ependyma at the anterior inferior border of the Corpus Callosum from the Fornices

Question 31

What is the thalamus?

Answer 31

The Dorsal part of the Diencephalon. The major subcortical relay for information ascending to the Cerebral Cortex, afferent information may be modified by the substantial descending projections to the Thhttps://cookieandkate.com/2015/vegetarian-chili-recipe/alamus from all parts of the Cortex.

Question 32

What is the interthalamic adhesion?

Answer 32

A flattened grey disc joining the Thalami of each side behind the Interventricular Foramen, may be absent

Question 33

What is the hypothalamic sulcus?

Answer 33

A shallow groove on the lateral wall of the third ventricle extending from the Cerebral Aqueduct to the Interventricular Foramen.

Question 34

What does the medial geniculate body do?

Answer 34

Relays auditory information from the midbrain to the auditory cortex and passes some fibres via the inferior brachium to the inferior colliculi.

Question 35

What does the lateral geniculate body do?

Answer 35

Relays visual information from the optic nerve to both the visual cortex via the optic radiation (for vision) and the superior colliculi via the superior brachium (for pupillary reflexes).

Question 36

What is the hypothalamus?

Answer 36

A ventral part of the Diencephalon that extends from the Lamina Terminalis in front to a vertical plane immediately behind the Mammillary Bodies. It is an important centre contributing to body homeostasis and to the control of the autonomic nervous and neuroendocrine systems.

Question 37

Where is the subthalamus?

Answer 37

Lying below and lateral the thalamus it cannot be seen in the midline

Question 38

What does the subthalamus do?

Answer 38

The subthalamus contains nuclei and gray matter like the zona incerta, reticular nucleus, and the perigeniculate nucleus. General functions the subthalamus are responsible for include sexuality, food and water intake and maintenance of hydration, and cardiovascular activity.

Question 39

What are the 3 main fibres in the cortex?

Answer 39

Association Fibres – these link cortical regions within one Cerebral Hemisphere
Commissural Fibres – these link similar functional areas of the two Hemispheres, e.g. the Corpus Callosum
Projection Fibres – these link the Cortex with subcortical structures such as the Thalamus and Spinal Cord via the Internal Capsule and the Corona Radiata.

Question 40

Why are the two cerebral hemispheres united?

Answer 40

There are two basic functions in uniting the two cerebral hemispheres, first to bring together separate representations of the two halves of the body, the visual field and the auditory surround, and second to unite areas of the cortex which have functions specialised to one hemisphere.