BRAIN DAYSPART IV

CEREBELLUM & BRAINSTEM

Kaan Yücel M.D.,Ph.D.

IN 11 QUESTIONS

Learning Objectives

Explain the anatomical structures in the brainstem

Explain the parts of the cerebellum

Cerebellum L. Little brain

o Largest part of the hindbrain [medulla, pons, and cerebellum]

o Lies posterior to the fourth ventricle, the pons, and the medulla oblongata.

o Situated in the posterior cranial fossa

Cerebellum L. Little braino Covered superiorly by the tentorium cerebelli.

o Made up of two lateral cerebellar hemispheres and a median vermis (L. “worm”).

o The surface displays slender and parallel elevations (ridges) known as folia and depressions (grooves) known as sulci that facilitate a great increase in the surface area of the cerebellar cortex.

CerebellumLobe

Anterior lobeprimary fissurePosterior lobeuvulonodular fissure Flocculonodular lobe

Lobules

Cerebellar hemispheres

Cerebellum

Cerebellum

Cerebellum

Superior view

Inferior view

Cerebellar PedunclesThe cerebellum is linked to other parts of the central nervous system by numerous efferent and afferent fibers that are grouped together on each side into three large bundles, or peduncles.

Superior cerebellar peduncles connect the cerebellum to the midbrainMiddle cerebellar peduncles connect the cerebellum to the ponsInferior cerebellar peduncles connect the cerebellum to the medulla oblongata.

Cerebellar vermis

Non-motor functions of the cerebellum o Cerebellum is critical for many functions other than the coordination of movement.

o Engaged also in the regulation of cognition and emotion.

o Cerebellar lesions can also result in the cerebellar cognitive affective syndrome, including executive, visual-spatial, and linguistic impairments, and affective dysregulation.

BRAINSTEM

midbrainpons

medulla

Nuclei of 12 cranial nerves10 of them in the brainstem

Of the last 4XII,XI,X, IX

Of the other 4VIII,VII,VI,V

Of the IV & III

MidbrainTectum - roofTegmentum- cover

Posterior part Tectum superior colluculivisual reflexesinferior colluculi lower auditory centers corpora quadrigemina

Anterior part TegmentumBelow the cerebral aqueduct

MidbrainThe midbrain comprises two lateral halves

cerebral pedunclesanterior part: crus cerebri

substantia nigra posterior part: tegmentum

Substantia nigrao Large motor nucleus between tegmentum & crus cerebri

o Concerned with muscle tone

o Connected to the cerebral cortex, spinal cord, hypothalamus, and basal nuclei.

Midbrain

Pons

Pons

Medulla [oblongata] In the posterior cranial fossa, lying beneath the tentorium cerebelli and above the foramen magnum.

Related anteriorly to the basal portion of the occipital bone and the upper part of the odontoid process of the axis and posteriorly to the cerebellum.

Medulla oblongata Not only contains many cranial nerve nuclei that are concerned with vital functions (e.g., regulation of heart rate and respiration), but it also serves as a conduit for the passage of ascending and descending tracts connecting the spinal cord to the higher centers of the nervous system

Reticular formationo The reticular formation (L. reticulum, “little net”) consists of various

distinct populations of cells embed in a network of cell processes occupying the central core of the brainstem.

o The reticular formation and the olfactory and limbic systems are interrelated as a result of their participation in visceral functions and behavioral responses.

Reticular formationMore than 100 nuclei scattered throughout the tegmentum of the midbrain, pons and medulla have been identified as being part of the brainstem reticular formation.

Reticular formation

1- The regulation of the level of consciousness, and ultimately cortical alertness

2- The control of somatic motor movements

3- The regulation of visceral motor or autonomic functions

4- The control of sensory information

Autonomic Nervous SystemSympathetic Parasympathetic

Anatomical differences, differences in the neurotransmitters, differences in the physiologic effects

The autonomic nervous system and the endocrine system control the internal environment of the body.

The various activities of the autonomic and endocrine systems are integrated within the hypothalamus.

Autonomic Nervous SystemSympathetic part prepares and mobilizes the body in an emergency, when there is sudden severe exercise, fear, or rage.

Parasympathetic part aims at conserving and storing energy, in the promotion of digestion and the absorption of food by increasing the secretions of the glands of the gastrointestinal tract and stimulating peristalsis.

Autonomic Nervous SystemParasympathetic systemBrainstem and sacral segments of the spinal cord

Edinger-Westfall nucleus midbrain mediates the diameter of the pupil in response to light

Superior and inferior salivatory nuclei pons & medulla mediatie salivary secretion and the production of tears)

Dorsal motor nucleus of the vagus nerve Medulla controls the motor responses of the heart, lungs, and gut (e.g., slowing of the heart rate and constriction of the bronchioles).

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Cerebral aqueduct (aqueduct of Slyvius)o A narrow channel connecting third and fourth ventricles

o Lined with ependyma

o Surrounded by a layer of gray matter: central gray

o Direction of flow of CSF 3rd ventricle 4 th ventricle

o No choroid plexus

Fourth ventricle