Kaan Yücel M.D.,Ph.D.
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 brain
o 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.
Cerebellum
Cerebellar hemispheres
primary fissure
uvulonodular fissure
Cerebellum
Cerebellum
Cerebellum
Cerebellar Peduncles
The 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 midbrain
Middle cerebellar peduncles
connect the cerebellum to
the pons
Inferior 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.
Nuclei of 12 cranial nerves
10 of them in the brainstem
Of the IV & III
Of the other 4
VIII,VII,VI,V
Of the last 4
XII,XI,X, IX
Midbrain
Tectum - roof
Tegmentum- cover
Posterior part Tectum
superior colluculi
visual reflexes
inferior colluculi
lower auditory centers
corpora quadrigemina
Anterior part Tegmentum
Below the cerebral aqueduct
Midbrain
The midbrain comprises two lateral halves
cerebral peduncles
anterior part: crus cerebri
substantia nigra
posterior part: tegmentum
Substantia nigra
o 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 formation
o 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 formation
More 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 System
Sympathetic 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 System
Sympathetic 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 System
Parasympathetic system
Brainstem 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).
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
o No choroid plexus
4 th ventricle
Fourth ventricle