Anatomy Of Cerebellum And 4th Ventricle Question And Answers

Cerebellum And Fourth Ventricle Question And Answers

Question 1. Write a note on the cerebellum.
Answer:

Cerebellum

It is the largest part of the hindbrain.

Cerebellum Dimensions, Location, And Extent

• It weighs about 150 g
• It is located in the posterior cranial fossa below tentorium cerebelli, posterior to pons and medulla
• It is separated from the pons and medulla by the cavity of fourth ventricle
• Its surface consists of numerous slit-like sulci called fissures and parallel folds in between them called folia
• It consists of two hemispheres united by vermis
• Each hemisphere is connected to three parts of the brainstem by three pairs of large fier tracts called cerebellar peduncles.

Cerebellum External Features

• Cerebellum External Features Parts
  • It consists of two large hemispheres and a narrow median worm-like portion called the vermis
  • The superior and inferior aspect of vermis is termed as superior and inferior vermis, respectively.
• Cerebellum External Features Surfaces
  • It consists of superior and inferior surfaces
  • The superior surface is convex and the two hemispheres are continuous with each other on this surface
  • The inferior surface has a deep median notch called vallecula which separates two cerebellar hemispheres.
• Cerebellum External Features Notches
  • The anterior cerebellar notch is a wide shallow notch that is present on the anterior aspect and accommodates pons and medulla
  • The posterior cerebellar notch is a deep and narrow notch that lodges the falx cerebelli.
• Cerebellum External Features Fissures: Consist of three well-marked fissures

1. The horizontal fissure which marks the junction between the superior and inferior surfaces of the cerebellum. It runs along lateral and posterior margins of the cerebellum
2. The posterolateral fissure separates the flcculonodular lobe from the rest of the cerebellum. It lies on the inferior surface of cerebellum
3. The V shaped fissure prima divides cerebellum to anterior and posterior lobes and cuts the superior vermis at the junction of anterior two third and posterior one-third.

Cerebellum Subdivisions

• Anatomical Subdivision: Anatomically the cerebellum is divided into
  • Anterior lobe
  • Posterior lobe
  • Flocculonodular lobe.
• Morphological Division: Based on phylogenetic and functional criteria cerebellum is divided into
  • Archicerebellum
  • Paleocerebellum
  • Neocerebellum.

Cerebellum Functions: Basic functions include

• Maintenance of equilibrium
• Regulation of muscle tone
• Coordination of somatic motor activities.

Cerebellum Internal Structure

• It is made up of thin surface layer of grey matter called the cortex and the central core of the white matter.
• Within the central core masses of grey matter are embedded and they are known as intracerebellar nuclei.
• The intracerebellar nuclei includes the following:
  • The dentate nucleus
  • The emboliform nucleus
  • The globose nucleus
  • The fastigial nucleus.
• The cerebellar cortex is folded so that the surface presents with series of transverse fissures and intervening narrow leaf-like bands called folia
• The central core is arranged in the form of branching pattern of tree.

Cerebellum Blood Supply: Supplied by the following

• Superior cerebellar artery which supplies the superior surface
• Anterior inferior cerebellar artery which supplies the anterior part of the inferior surface
• Posterior inferior cerebellar artery which supplies the posterior part of inferior surface.

Cerebellum Applied

• The cerebellar lesions due to trauma, stroke tumors, etc. produce sign and symptoms which are collectively known as cerebellar syndrome.
• It includes generalizes muscular hypotonia, intention tremors, adiadochokinesis, dysarthria, nystagmus, and generalized swaying.

Question 2. Write a note on cerebellar peduncles.
Answer:

Cerebellar peduncles

• The efferent and afferent fibers of the cerebellum are grouped into large bundles of fibers and are known as cerebellar peduncles
• These are three in number, superior, inferior, and middle cerebellar peduncles.

Superior Cerebellar Peduncle

• The superior cerebellar peduncle connects the cerebellum to the midbrain
• It emerges from anterior cerebellar notch and forms the lateral boundary of upper half of fourth ventricle
• It consists only of effrent fiers from dentate nucleus to red nucleus, thalamus, and cerebral cortex of opposite side.

Middle Cerebellar Peduncle

• It connects cerebellum to pons
• It is the largest among the three
• It is formed at the posterolateral margin of pons
• It consists only of afferents from pontine nuclei of the opposite side.

Inferior Cerebellar Peduncle

• It connects the cerebellum to medulla
• It is formed at the posterolateral aspect of medulla
• It consists of both affrents and effrent fiers
• It consists of mainly afferents to the cerebellum from the spinal cord, olivary nucleus, reticular formation of medulla and vestibular nuclei, and nerve
• It also contains few efferents from the cerebellum to the medulla, i.e. vestibular nuclei and reticular formation.

Question 3. Write a short note on the interpeduncular fossa.
Answer:

Interpeduncular fossa

Rhomboidal space bounded by crus cerebri of cerebrum laterally, anteriorly by optic chiasma, and posteriorly by pons.

Interpeduncular Fossa Contents

• Two spherical bodies called mammillary bodies
• Raised area of grey matter anterior to mammillary bodies called tuber cinereum
• Infundibulum which connects the pituitary to tuber cinereum
• Posterior perforated substance, a layer of grey matter present in the angle between crus cerebri
• Oculomotor nerve.

Question 4. Write a note on floor of fourth ventricle.
Answer:

Floor of fourth ventricle

• It is otherwise known as the rhomboid fossa
• It is formed by the posterior surface of pons and upper part of the medulla
• It is divided into three parts, the upper triangular part bounded by a superior cerebellar peduncle, the lower triangular part bounded by gracile and cuneate tubercles, and the inferior cerebellar peduncles.

Floor Of Fourth Ventricle Features

• The floor is divided into symmetrical right and left halves by median sulcus which extends from the aqueduct of the midbrain above to the central canal below
• The widest part is transversely crossed by striae medullaris, which are white fiers from arcuate nuclei
• On the other side of the median sulcus, there is a longitudinal elevation called medial eminence and is bounded laterally by sulcus limitans
• At a lateral angle, the region lateral to sulcus limitans overlies the vestibular nuclei and is known as vestibular area
• The upper end of the sulcus limitans widens to form a triangular depression known as superior fovea. Above the superior fovea it flttens and present bluish grey area called locus coeruleus
• The lower part of sulcus limitans presents a depression called inferior fovea
• On either side of medial eminence at the level of superior fovea oval-shaped facial colliculus is present
• The sulcus limitans divides the medial eminence into two triangles, the hypoglossal triangle above and the vagal triangle below
• The hypoglossal triangle divided into medial and lateral parts by the nucleus of the hypoglossal nerve
• The vagal triangle overlies nuclei of the vagus, glossopharyngeal, and cranial accessory nerve
• The vagal triangle is crossed by a narrow ridge called funiculus separates and the area between the funiculus separates and gracile tubercle is known as area postrema
• The inferolateral margins present two narrow ridge called taenia and both taeniae meet at an inferior angle to form a fold called obex.

Cerebellum And Fourth Ventricle Multiple Choice Question And Answers

Question 1. All of the following are intracerebellar nuclei except:

1. Dentate nucleus
2. Fastigial nucleus
3. Globose nucleus
4. Red nucleus

Answer: 4. Red nucleus

Question 2. The cerebellar lesion is characterized by all of the following:

1. Ataxia
2. Muscular hypotonia
3. Nystagmus
4. Tremors at rest

Answer: 4. Tremors at rest

Question 3. Th neocerebellum is concerned with:

1. Maintenance of equilibrium
2. Smooth performance of fie voluntary movements
3. Regulating muscle tone and posture of trunk
4. Regulating muscle tone and posture of limbs

Answer: 2. Smooth performance of fie voluntary movements