Cerebrum Lecture Trans by Dr. JL Pascual

TOPIC OUTLINE

I. Overview of Central Nervous System
A. Architecture of the Cerebrum
B. Components of the Cerebrum
C. Building a Brain
II. External Anatomy
A. Frontal Lobe
B. Parietal Lobe
C. Temporal Lobe
III. Internal Anatomy
IV. Cross-Sectional Anatomy
A. Cerebral White Matter
B. Other Parts
C. Clinical Correlations
D. Additional Info

Objectives:
1. Form: identify the different structures in the cerebrum
a. Cerebral hemispheres
b. External anatomy
c. Lobes
d. Fissures/sulci
e. Cross-sectional anatomy
f. Microscopic layers of the cerebral cortex
g. Subcortical white matter
h. Subcortical grey matter
i. Ventricular system
2. Function: know the significance of each structure of the cerebral hemispheres in the normal human being
I. OVERVIEW OF THE CENTRAL NERVOUS SYSTEM
A. Architecture of the Cerebrum
Hollow tubular structure in the embryo, derived from the telencephalon
This hollow tube curves upon itself into a C-shape structure
Telencephalon starts out as cells which then lengthens
Certain parts of it will differentiate faster and increase in number of cells compared to the rest until It covers the rest of the brain to become the cerebral hemisphere
The higher rank in terms of intelligence, the greater the number of folds. This increases the surface area allowing more cells (neurons to multiply

The rotation of structures will explain the unusual arrangement of nerve fibers and nuclei in the adult human brain
What used to be dorsal, and what used to be ventral will change as it curls into a C-shape structures
Posterior  dorsal
Doral  posterior
Ventral  anterior
Anterior  ventral
Cerebrum forms a mantle over the diencephalon and the fluid-filled cavities

At the start, they are all of the same size, but the telencephalon will later on dominate at 7 weeks.
At 14th week, it will cover the rest of the lower brain (brain stem)
The basal portion of the telencephalon eventually becomes enveloped as well, becoming islands of grey matter in the cortex (basal ganglia)
B. Components of the Cerebrum
1. Cortex
Outer rim of tissue composed of grey matter (formed by neuronal cell bodies)
Outer most part of the brain
2. Subcortical White Matter
Attach the extensions of neurons in the grey matter
3. Subcortical gray Matter
Locked inside; still telencephalic derivatives
4. Ventricular system
Hollow core of fluid curled in a letter C

Central hemisphere are wrapped over by gray matter
Pattern in cerebral hemisphere:
Gray White Gray
Neurons are very long, single cell can reach all the way down the spine then to the limbs. Controlling the fingers and toes
Analogy
Cerebrum – same pattern and arrangement as cauliflower
Ventricular system – same as a tomato, hollow inside filled with fluid
The brain has billions of neurons doing so many things. They are arranged in a certain manner, in a logical fashion, for efficiency’s sake.
C. Building a Brain
1. General Arrangement
a. CEREBRAL HEMISPHERES
Outer layer appears grayish in preserved brains (gray matter)
Appears grayish in preserved brains
Compromised of cell bodies of neurons and unmyelinated axons
Inner layers appear relatively lighter (white matter)
Appears relatively lighter
Comprised of myelinated axons
b. COLUMNAR ORGANIZATION OF NEURONS

Neurons subserving similar functions are organized into cortical columns differing only in the cellularirty of the 6 layers (basis for Brodmann’s areas)
In general, all motor neurons are on one side, sensory neurons on the other side, bute they can overlap at times
Example: neurons that move the arms and legs are on the same area, those that receive pain from toes and fingers on the same area
LAMINATION  axons serving similar functions are also laid out in an orderly fashion within fiber tracts

c. INTERCONNECTIONS different portions of the cerebral cortex must communicate with each other via fiber tracts

2. Layers of Cerebral Cortex
Layer no.
Cytoarchitectonic Name
Principal Cell type
Myeioarchitectonic name
Fibers
I
Molecular
Axons and dendrites
Tangential

II
External Granular
Small pyramidal cells
Dysfibrous

III
External Pyramidal
Medium pyramdal cells
Suprestriatal
Conrticocortical (association fibers)
IV
Inner Granular
Stellate cells
External of baillarger
Thalamic proj., lines of gennari
V
Inner Pyramidal
Large pyramidal cells
Internal of baillarger
Corticostriate
VI
Polymorph
Fusiform cells
Infrastriate
corticothalamic

3. Views of the cerebellum landmarks to remember to identify the different views of the cerebrum
Anterior view no cerebellum
3 fissures: median longitudinal fissure and two lateral fissures
2 extensions on either side of the median longitudinal fissure, the olfactory nerves
Ventral view
Prominent cerebellum
Brainstem
Optic chiasm
Olfactory nerves extending forward
Lateral view
Cerebellum
More rounded, bulky frontal lobe
Sharper-edged occipital lobe
Posterior view
Cerebellum
Prominent sulci
Top/superior view
More rounded edge of frontal lobe – anterior
Sharper edge of occipital lobe – posterior
d. Convolutions of the Cerebellum
External surface of the cerebrum is broken up into convolutions and grooves
Gyrus (gyri) – elevations, ridges
Mound of tissue
Sulcus (sulci) – furrows
Furrows in between gyri
Fissure – large deep sulcus
II. EXTERNAL ANATOMY OF THE CEREBRUM
The Cerebrum is made up of four lobes—frontal, temporal, parietal and occipital
May be identified by recognizing some important anatomical landmarks

IMPORTANT LANDMARKS OF THE BRAIN
Median Longitudinal Fissure
Separates Cerebrum into left and right hemispheres
Only fissure that is a completely straight line
Central Sulcus (of Rolando)
Separates frontal and parietal sulci
Inferiorly meets the Sylvian fissure
Found between precentral and postcentral sulci
Precentral Gyrus (Anterior Central gyrus)
Bounded anteriorly by precentral suclus and inferiorly by Sylvian fissure
Sylvian Fissure
Separates temporal lobe from frontal and parietal lobes
“smile” of the brain
Postcentral Gyrus
Bounded posteriorly by postcentral sulcus

A. FRONTAL LOBE
Provides executive control over most of brain’s higher functions—consciousness, self-awareness, judgment, initiation/motivation, control over emotional responses, planning/sequencing, word formation, prospective memory, remembering to do something
STRUCTURES IN THE FRONTAL LOBE
Precentral Gyrus – Primary motor complex
Superior Fronatal Gyrus (SFG)
Superior Frontal Sulcus—between SFG and MFG
Middle Frontal Gyrus (MFG)
Inferior Frontal Sulcus—between MFG and IFG
Inferior Frontal Gyrus (IFG)
For language and articulation
Cannot be seen superiorly
Opercular Part/pars opercularis—most posterior
Orbital Part/Pars Orbicularis
Most anterior and inferior
Surrounds Orbital area
Triangular Part/Pars Triangularis
Broca’s Area
Anterior Sylvian Point (apex)
Straight Gyrus (Gyrus Rectus)
Most medial gyrus of frontal lobe
Bounded laterally by olfactory sulcus and medially by median longitudinal fissure
Orbital Gyrus
Lateral to guyrus rectus
Rests above the orbits of the eyes
Separated by orbital sulcus into medial and lateral orbital gyri

B. PARIETAL LOBE

Everything that is not frontal nor occipital

STRUCTURES IN THE PARIETAL LOBE
Postcentral Gyrus
Bounded anteriorly by the central sulcus, posteriorly by the postcentral sulcus
Continuous with the superior parietal lobule at the superior end of the postcentral sulcus
Postcentral Sulcus
Superior Parietal Lobule
Separated from the inferior parietal lobule by the intraparietal sulcus
Interparietal Sulcus
Separates superior and inferior parietal lobules
Inferior Parietal Lobule
Responsible for the ability to read and write
Angular Gyrus
Caps superior temporal sulcus
Supramarginal gyrus
Caps the sylvian fissure
Sensory association area that integrates kinesthetic memories with auditory commands (dancing)
Parieto-occipital Sulcus
Separates parietal lobe from occipital lobe
Marks posterior part of the brain

C. TEMPORAL LOBE
Situated at the lateral areas of the brain

STRUCTURES IN THE TEMPORAL LOBE
Superior Temporal Gyrus
Bounded anteriorly by the Sylvian fissure and posteriorly by the superior temporal sulcus
Not continuous
Superior Temporal Sulcus
Separates superior and middle temporal gyri
Middle Temporal Gyrus
Bounded anteriorly by the superior temporal sulcus and posteriorly by the inferior temporal sulcus
Inferior Temporal Sulcus
Inferior Temporal Gyrus
Bounded anteriorly by inferior temporal sulcus, superiorly by inferior temporal sulcus and medially by occipito-temporal sulcus
Lingual Gyrus (Medial Occipito-temporal gyrus)
Bounded laterally by the posterior portion of the collateral sulcus and medially by the calcarine fissure
Collateral Sulcus
Separates cuneus from lingual gyrus
Fusiform Gyrus (Latreal Occipitotemporal Gyrus)
Bounded laterally by the occipito-temporal sulcus, medially by the collateral sulcus
For facial recognition
Occipito-temporal Sulcus
Parahippocampal Gyrus
Most medial portion of the temporal lobe
Anterior portion is recurved to form a hook—uncus
Uncus
Killer of patients with brain tumors
Presses on the brain stem, shutting vital functions

III. INTERNAL ANATOMY OF THE CEREBRUM
A. OCCIPITAL LOBE Does not have a lot of structures visible externally. Most of its parts are seen medially

STRUCTURES IN THE OCCIPITAL LOBE
Calcarine Fissure
Horizontal Sulcus that subdivides occipital lobe into two
Joins the parietal0occipital fissure
For visual acuity
Cuneus
Wedge-shaped area between the parieto-occipital sulcus and calcarine fissure
Precuneus
Area between parieto-occipital sulcus and the cuneus
Arises from the parietal lobe

B. INTERNAL STRUCTURES OF THE BRAIN
Parieto-occipital sulcus
Calcarine Fissure
Cuneus
Precuneus
Cingulate Gyrus
Medial part of the brain
Paracentral Lobule
Posteromedial portion of the superior frontal gyrus
Parahippocampal Gyrus
Uncus
Subparietal sulcus
Cingulate Sulcus
Corpus Callosum
Commissural fibers
Consists of three parts
Genu
Body
Splenium
Posterior Commissure
Anterior Commisure
Fornix
At its anterior end behind the anterior commisure divides into two pillar end at septal nuclei and nucleus accumbens at each half of brain
Heschl’s Gyrus (Transverse Temporal Gyrus)
Inner surface of superior temporal gyrus
Important in hearing

C. INSULAR CORTEX/LOBE
Lies within Sylvian Fissure
Covered by the opercula of the frontal, parietal and temporal lobes
Brain within brain
AKA Islands of Reil
Responds to emotional stimuli

IV. CROSS SECTIONAL ANATOMY OF THE BRAIN
A. Cerebral White Matter
Axons of the neurons within the grey matter of the cerebral hemispheres
Serves as connections, means of communication between neurons
Types of connecting fibers (cerebral cortical connections)
Projection fibers—connect brain with the rest of the CNS
Commissural Fibers—connect the hemispheres
Association fibers—connect different parts within the same cerebral hemisphere

1. PROJECTION FIBERS
Corona Radiata
Very broad
Large chunk of white matter from frontal lobe to spinal cord

Internal Capsule
Boomerang-shaped; very narrow
Continuation of corona radiate as it goes to deeper structures of the brain
Damage may reflect paralysis from face, arms and legs without speech defect
1. Anterior Limb
a. Frontopontine fibers
b. Thalamocorticalfibers
2. Posterior Limb
a. Corticospinal tract
b. Corticobulbar fibers
c. Corticopontine fibers
3. Retrolenticular Portion

Corticospinal Tract
Controls movement
Brain -> spinal cord

2. COMMISSURAL FIBERS
Connect the two cerebral hemispheres

E. Corpus Callosum
Genu (knee) – anterior portion (tip near frontal lobe; appears kneeling)
Body—between the genu and splenium
Splenium—posterior portion near brainstem and occipital
F. Posterior Commissure
Structurally found in the diencephalon/brainstem
Interconnects pretectal nuclei (consensual papillary light reflex)
G. Anterior Commissure
Anterior: connects olfactory bulb and nuclei
Posterior: middle and temporal gyri

3. ASSOCIATION FIBERS
Connect different parts within the same cerebral hemisphere

A. Cingulum
Paraolfactory cortex below the rostrum of the corpus callosum  courses within the cingulated gyrus, and arches around the corpus callosum  extends forward into the parahippocampal gyrus and uncus interconnects portions of the frontal, parietal and temporal lobes

*Not so important na raw ang mga ito sabi ni Sir pero nakalagay kasi sa 2017 trans so isasama na namin

B. Superior Occipito-frontal Fasciculus (SOF)
In contrast to the cingulum, the SOF wraps the corpus callosum from below
Connects the occipital and frontal lobes
C. Inferior Occipito-frontal Fasciculus
Connects occipital and frontal lobes but inferior to SOF
Lies beneath insula, passing inferolateral to the claustrum
D. Uncinate Fasciculus
Connects the orbital and inferior frontal gyri with the anterior temporal lobe
Hooks around the Sylvian fissure
E. Arcuate Fasciculus (Superior Longitudinal Fasciculus)
Largest of the association fibers
Connects the frontal lobe to the parietal, temporal and occipital cortices
Connects all the major lobes in the hemisphere
F. Inferior longitudinal Fasciculus
Conncets the occipital and temporal cortices

B. Other Parts
Structures to be Seen
Gyri
Subcortical White Matter
Ventricular System
Sectioning
Axial
Sagital
Coronal
Other Structures
Globus Pallidus (Pars Externa and Interna)
Pale Gray Matter
Caudate Nucleus (Head, Body)
Only gray matter that surrounds the lateral ventricles
Basal Optic Nucleus of Meynert
Contains cholinergic neurons (Ach)
Project into the neocortex
Lost during Alzheimer’s
Substantia Innominata
Associated with Parkinson’s’
External Capsule
Connects Broca’s area with Wernike’s area
NOT ARCUATE FASCICULUS
Claustrum
Putamen
Internal Capsul
Nucleus Accumbens
Hippocampus
Mammillary body
Thalamus
Subthalamic Nucleus of Luysii
Anterior Commissure
Posterior Commissure

H. Clinical Correlations
Dysfunctional Part
Resulting Problem/Disease
Intraparietal Sulcus
Vision could not be focused
Angular gyrus
Unable to read/write
Temporal gyri
Impaired hearing
Fusiform gyri
No recognition of faces
Uncus
Herniation and even death
Cingulate gyrus (related to feelings)
Absence of right or wrong
Paracentral lobule
Difficulty in bowel and bladder functions
Insular cortex
Affected autonomic NS functions
Internal Capsules (anterior and posterior limbs)
Formation of tumor leads to paralysis (greater extent of paralysis would result if the part cut is denser)
Posterior Commissure
Less coordination (ex. Between the left and right eyes)
Frontal Lobe
Less control over emotions and urges
Mamillary body (connects with hippocampus)
Less memory power (alcoholics)

I. Additional Information
Anterior Sylvian Point – Where a surgeon can look into the insides of the brain during an operation; near IFG

Parieto-occipital Fissure—most obvious in medial view

Internal pyramidal layer of cerebral cortex--larger pyramidal neurons than the external pyramidal layer

Hippocampus—only part of brain with three layers instead of six

END OF TRANSCRIPTION