MODULE 15B - [Anatomy 3.0] CEREBRUM AND DIENCEPHALON

• Telencephalon (or the cerebral hemisphere)

• Diencephalon (or the core)

Enumerate the two major regions of the Cerebrum

forebrain (prosencephalon)

Cerebrum is formed from the _____, which will give rise to telencephalon (the cerebral hemisphere) and diencephalon (the core)

mesencephalon and rhombencephalon

The _____ and _____ will become the brainstem

Brainstem

this structure will connect the structures to the spinal cord

CEREBRUM

• Largest part of the central nervous system (CNS)

• Has two basic poles

  • Anterior (Frontal) Pole

  • Posterior (Occipital) Pole

• It is contained within the cranial cavity, covered by the three layers of meninges, and bathed with cerebrospinal fluid (CSF), which acts as a cushion to the brain.

Anterior (frontal) pole

A more rounded pole of the cerebrum

Posterior (occipital) pole

A more pointed pole of the cerebrum

pressurized

In certain cavities, CSF is _____ so when you move your head, the brain won’t move

Parts of the brain on a coronal section cut

Parts of the brain on a coronal section cut

mushroom-like

what is the consistency of the brain

GRAY MATTER

• Located on the periphery

• Composed of cell bodies

  • Axons from these cell bodies project inwards, forming the central white matter.

Cerebral Cortex

Another name for Gray Matter

Subcortical Gray Matter

• Gray matter aggregates within the core of the cerebrum or white matter.

subcortical nuclei

central core of the cerebrum that has aggregates of gray matter which are formed by clusters of cell bodies called

• Diencephalon

• Parts of the limbic system

• Basal nuclei

Enumerate the Groups of Subcortical Nuclei

• Both the nucleus and the ganglion are cell bodies

• Both have similar functions

• The difference is location in the nervous system

  • Nucleus: CNS (Nucleus = CeNtral NS)

  • Ganglia: PNS

What is the Similarities and Difference of nucleus and ganglia

WHITE MATTER

• Found underneath the cortex

• Represents the bundles of axons travelling to and from the cerebral cortex and other areas of the CNS

• These axons are covered by a myelin sheath, which makes the area appear white

Schwann cells (in PNS) and Oligodendrocytes (in CNS)

What produces the Myelin sheath

Commissural Fibers

• White matter tracts that link or connect the two cerebral hemispheres (left and right)

• It will traverse the opposite cerebral hemispheres and interconnect the two

• Examples:

  • Corpus callosum

  • Anterior commissure

  • Posterior commissure

Corpus Callosum

Largest one of the commissural Fibers

Anterior Commissure

Commissural Fibers of the Limbic System

Posterior Commissure

Commissural Fibers of the Visual System

Association Fibers

• Fascicles of bundles of white matter connecting one region or lobe on one side of the cerebrum

• DO NOT cross the cerebral hemispheres, unlike commissural fibers, and are confined in a particular hemisphere

• Short

• Long

Enumerate the different types of Association Fibers

Short Association Fibers

• Connecting adjacent regions (or gyrus)

• Examples: Uncinate Fibers

Long Association Fibers

• Connecting lobes of the cerebral hemisphere

• Examples: Fronto-occipital bundle and Inferior Longitudinal Bundle

Fronto-occipital bundle

• Long association fibers

• Connects the frontal and occipital lobes

Cingulum

• Both long and short association fibers

• Interconnects the frontal, parietal, and medial temporal lobes, while also linking subcortical nuclei to the cingulate gyrus

• Also called the Limbic association bundle

Uncinate Fasciculus

• Short Association Fibers

• Connects the frontal and temporal lobes

Inferior Longitudinal Bundle

• Long Association fiber

• Connects the occipital and temporal lobes

Projection Fibers

• White matter tracts or bundles that move out of the cerebrum and connect to other parts of the CNS (i.e., brainstem, spinal cord, cerebellum)

• DO NOT cross the opposite cerebral hemisphere

• It can go both ways:

  • From the cerebrum to other parts of the CNS

  • Other parts of the CNS to the cerebrum

Corona Radiata

• The most common type of projection fibers

• English translation: “Rays of the Crown”

• White fibers that are immediately formed just below the cerebral cortex

  • The first few fibers that will come out of the cerebral cortex

  • It is a very fibrous initial segment seen when the specimen is opened

Internal capsule

• As the fibers of the Corona Radiata reach the central core of the cerebrum, they organize to form a more solidified bundle of white matter called _____

• More compact than the corona radiata.

• Embedded (blends) within the subcortical gray matter

Boomerang in shape

Shape of the Internal Capsule (Horizontal View)

• Anterior limb

• Genu

• Posterior limb

Enumerate the three basic parts of the Internal Capsule

posterior limb

Motor neurons that will supply the arm, trunk, and leg are organized in the _____

genu

Motor neurons that will supply the face are organized in the ______

Left Cerebral Hemispheres

• Controls sensation and movement of the RIGHT side of the body

• Responsible for:

  • Analysis and calculations

  • Time and sequencing

  • Recognition of words, letters, and numbers

  • Logic

Right Cerebral Hemispheres

• Controls sensation and movement of the LEFT side of the body

• Responsible for:

  • Creativity and spatial ability

  • Context/perception

  • Recognition of faces, places, and objects

  • Artistic expression and music appreciation

• It is usually the non-dominant hemisphere

dominant hemisphere

Responsible for speech, language, and comprehension

The left

Which cerebral hemisphere is usually dominant hemisphere

Cerebral dominance

determined by handedness (most of the time)

Right-handed

What handedness is people with a dominant Left hemisphere

Left-handed

What handedness is people with a dominant Right hemisphere

Left brain

Responsible for interpreting words

Right brain

Responsible for interpreting colors

• Frontal Lobe

• Parietal Lobe

• Occipital Lobe

• Temporal Lobe

• Insular Lobe (or Insula)

Enumerate the five general cerebral lobes most of which derive its name from the cranial bone that lie on top of them

Insular Lobe (or Insula)

A hidden lobe that can only be seen when opening the lateral Sylvian fissure

Gyrus

bumps at the surface of the cerebrum

Sulcus/Fissure

crevices on the brain’s surface

LONGITUDINAL/SAGITTAL FISSURE

Groove that separates the two cerebral hemispheres

CENTRAL SULCUS (SULCUS OF ROLANDO)

• The line that separates the frontal lobe and parietal lobe

• Has two gyri surrounding it

  • Precentral Gyrus

    • Located anterior to the central sulcus

    • Part of the frontal lobe

  • Postcentral Gyrus

    • Located behind the central sulcus

    • Part of the parietal lobe

LATERAL FISSURE (OR SYLVIAN FISSURE)

Prominent fissure that separates the frontoparietal lobe and temporal lobe

PARIETO-OCCIPITAL FISSURE

• A small, posterior fissure that separates the parietal and occipital lobes

  • It is not that obvious on the lateral surface of the cerebrum

  • This is more evident on the medial surface of the posterior cerebrum

CALCARINE SULCUS

• Separates the occipital lobe and the temporal lobe

• Running perpendicular to the parieto-occipital fissure

• Appreciated on the medial side of the cerebrum

Brodmann Area (BA)

• Useful in determining the functionality of the lobe

• A numbering system in neuroanatomy wherein areas of the cerebrum are designated with numbers

• These numbers are based on the function of these specific areas

Korbinian Brodmann

Brodmann Area (BA) is coined by

Receptors

This structure’s role to capture stimuli and to convert it to the electric impulse for the brain to interpret

Vision

Receptors for _____ convert light to electrical impulse

Hearing

Receptors for _____ convert sound waves to an electrical impulse

PRIMARY MOTOR CORTEX (PRECENTRAL GYRUS) - BA4 (Red)

• The gyrus anterior to the central sulcus is the precentral gyrus which means it is on the territory of the frontal lobe

• Periphery of the cerebral hemisphere

• Contained within the precentral gyrus

• Responsible for the voluntary movement or contraction of all the skeletal muscles on the contralateral side of the body

paresis or paralysis

• paresis - weakness on opposite side/contralateral side

• Paralysis - cutoff nerves supplying to the muscle

Damage on BA 4 causes

Motor homunculus

homonculus of the BA 4

somatotopic (or topographic) arrangement

In the cerebral cortex, the body is represented in a particular region of the cortex. This representation is referred to as _____

lower limbs

In the Somatotopic Arrangement of the motor homonculus, the _____ are represented on the medial surface of the cerebrum

trunk and upper limbs

In the Somatotopic Arrangement of the motor homonculus, the ____ and the ____ are represented on the upper lateral surface of the cerebrum

face (head and neck)

In the Somatotopic Arrangement of the motor homonculus, the _____ is represented on the lower lateral surface of the cerebrum

Corticospinal tract

• From cortex to opposite side of the spinal cord

• Supplies the lower limbs, trunk, and upper limbs

• Internal Capsule: Posterior limb

• As they elongate, the tracts cross to the other side after crossing the brain stem.

• The name of the tract = origin and final destination of the tract.

Corticobulbar Tract

• From cortex to brainstem

• Supplies the head and neck (bulbar means stem)

• Internal Capsule: Genu

• As they elongate, the tracts cross to the other side after crossing the brain stem.

• The name of the tract = origin and final destination of the tract.

spinal cord and forms the spinal nerve

The Corticospinal Tract will continue until it reaches the _____ and forms the ____, which in turn will supply the upper limb, trunk, and lower limb

brainstem and give rise to the motor cranial nerves

The Corticobulbar Tract will terminate in the _____ and give rise to the _____, which in turn will supply the head and neck musculature

2/3

The Anterior Cerebral Artery (ACA) and Middle Cerebral Artery (MCA) supply the anterior ____ of the brain:

Anterior Cerebral Artery (ACA)

• Mainly supplies the medial side of the cerebrum, including the medial side of the frontal lobe

• Courses along the longitudinal fissure

  • On top of the corpus callosum and follows its shape

Middle Cerebral Artery (MCA)

• Supplies the lateral side of the cerebrum

• Courses inferiorly and exits at the lateral sylvian fissure

• Direct continuation of the internal carotid artery

Damaged ACA

• manifestation is greater in lower limb than in upper limb

  • As this artery supplies the medial side and the lower limb is located on the medial side of the homunculus as well

Damaged MCA

• Manifestation is greater in the upper limb than in the lower limb

  • As this artery supplies the lateral side, and the upper limb is located on the lateral side of the homunculus as well

  • Muscles of the head and neck will also be

    affected

Cerebrovascular Disease (CVD)

• Insult to cerebral arteries

• Can present in two ways:

  • Ruptured blood vessel (hemorrhagic)

    • Obstructed blood vessel (ischemic)

Generic: Stroke

Appropriate: Cerebrovascular disease CVD

Give both the generic and appropriate term

• A vascular event that can happen in any part of the body

• Blood supply is affected

Hemorrhagic Stroke

• Rupture of a blood vessel

• Happens in cases of:

  • Severely elevated blood pressure

    (e.g., 230/90)

  • Cerebral aneurysms or spontaneous rupture secondary to a defect in the arterial wall

    • The patient may be asymptomatic, and then suddenly fall

• Cranial cavity space is minimal, such that if blood

  clot forms, the brain will be compressed

• Intracerebral Hemorrhage

• Reference point is the bone as it is hyperdense

• If there is white in an unusual place (e.g. inside the

  white matter), it typically indicates accumulation of

  blood clot in the brain

• Since the cavity of the skull is very limited, the blood

  accumulating inside pushes the other brain

  structures to the opposite side

  • Hence, the midline structures are now

    deviated

Cerebral aneurysms or spontaneous rupture

An abnormal swelling or bulge in the wall of a blood vessel, such as an artery

Ischemic Stroke

• Obstruction of blood vessel

• Happens in cases of impeded blood flow leading to

  decrease the blood supply to the area being supplied by the blocked blood vessel, secondary to either:

  • Atherosclerosis

  • Cerebral embolism

• Causes the distal portion of that artery to become

  ischemic

  • leads to a decrease in oxygen, causing tissue to die

• Parts of the brain scan appear black, as it is

  hypodense due to poor or no blood supply

• Analyzing the CT scan will give the idea that a major artery was blocked

• The scan on the right is a massive ischemic stroke affecting the entire half of the cerebrum

• The bigger the lesion, the more neurological manifestations will be demonstrated by the patient

• In some instances, the shape of the hypodensity will already give us a clue on which artery was blocked

Atherosclerosis

Plaque formation inside the blood vessel

Cerebral embolism

• A wandering object or substance that eventually can block the arterial blood vessels

• These objects can be a dislodged clot from other areas (such as deep vein thrombosis), air, or a fat globule

Myocardial infarction

Obstruction of vessel supplying the heart

CT scan

• One of the most widely used (common) diagnostic imaging modalities to confirm the diagnosis of a hemorrhagic or ischemic stroke

• A series of slices is made on the head (with a

  specific millimeter thickness) to give a full picture of the brain

Appearance: Gray and homogenous

Term Used: Normodense

CT Scan interpretation of the Brain parenchyma

Appearance: White

Term Used: Hyperdense

CT Scan interpretation of Bone (skull), blood, or any Ca 2+ - containing substances

Appearance: Black

Term Used: Hypodense

CT Scan interpretation of Ventricular Cavity (contains CSF, which is a fluid)

Appearance: Semi-white

CT Scan interpretation of pineal gland

Appearance: black, because the CSF bathes that location of the brain.

Term Used: hypodense

CT Scan interpretation of the periphery

Non-deviated medial longitudinal fissure

• A normal CT scan will always appear as a _____

• As deviation may entail compression of one hemisphere to another

• Thrombolytics may be given

• Don’t give to patients with hemorrhagic type

Management if Ischemic

Stop the medication which could increase bleeding

Management if Hemorrhagic, clot prone

Middle Cerebral Artery (MCA) Obstruction

• If this artery is blocked, you expect the patient to have weakness and loss of sensation on the opposite side

  side

• Especially the upper limbs, head, and neck

• If it is the dominant hemisphere, expect a

  speech problem

Anterior cerebral artery (ACA) Obstruction

• If this artery is blocked, expect difficulty in walking due to a lower limb problem.

MOTOR ASSOCIATION CORTEX - BA 6 (Yellow)

• Located anterior to the precentral gyrus

  • Adjacent to Brodmann Area 4

• Responsible for the planning, sequencing, and

  execution of movement

  • The blueprint of the motor system

  • Refines the impulse that is needed for BA4

  • This BA will plan which muscles to contract and relax, and transfer the output to BA4 for final execution.

• This BA has connections with other parts of the CNS, such as the cerebellum and the basal ganglia

  • These structures are the ones responsible for refining of the planned movement

Basal ganglia/nuclei

• initiate and stop movements

• Output from this structure will be brought back to

  BA6

Cerebellum

• dictates the coordination (position of the limb, amount of contraction needed)

• Output from this structure will be brought back to

  BA6

FRONTAL EYE FIELD - BA 8

• Located anterior to the motor association cortex

  • Adjacent to Brodmann Area 6

• Responsible for movement involving eyeballs

  • Responsible for horizontal eye movement or gaze

• Movement of the left eye while retaining the right is impossible.

nuclei of the brainstem

From BA8, the fibers will be sent to the _____ responsible for controlling the muscles of the eye