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CEREBRUM

BY PROF. DR. ANSARI

(FOR BDS SEMESTER-II STUDENTS ONLY)

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CEREBRUM • Is the largest portion of the human brain.• It consists of two cerebral hemispheres, which develop from

the embryonic forebrain. • These hemispheres have an outer convoluted layer of

gray matter – the cerebral cortex – and an inner layer of white matter.

• The two halves are linked by the corpus callosum. • Each hemisphere of the cerebrum is subdivided into four

lobes visible from the outside. They are the frontal, parietal, occipital, and temporal lobes.

The cerebrum is the integrating center for memory, learning, emotions, and other highly complex functions of the central nervous system.

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Lobes of the cerebrum

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Insula

• It is the slow growing and hidden part of cerebrum, submerged by frontal lobe, parietal, & temporal lobes.

• The middle cerebral artery emerges out from the lateral sulcus and distributes to the superolateral surface of hemisphere.

• The circular sulcus is seen in the insula.

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The insula

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The surface of cerebral hemisphere

• Shows various sulci and gyri, a modification of surface of brain to accommodate large amount of brain tissue within a limited space.

• There are three surfaces of cerebral hemispheres.

• Superolateral surface, inferior surface and medial surface.

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Superolateral surface

• The following important gyri and sulci are seen :-• Central sulcus, precentral gyrus, post central

gyrus.• Frontal lobe has superior frontal gyrus, middle

frontal gyrus and inferior frontal gyrus.• The inferior frontal gyrus has cortical centre for

speech, Broca’s area.• The lateral sulcus separates the temporal lobe

from frontal.

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The temporal lobe

• Has three gyri, superior, middle and inferior temporal gyri.

• By the help of 2 sulci, superior and inferior temporal sulci, there are three temporal gyri.

• The superior temporal gyrus is having the site for hearing, Heschel’s gyrus.

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The precentral gyrus and post central gyrus

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The dominant hemisphere

• The left side of the brain controls movement of the right side of the body, and the right side of the brain controls movement of the left half of the body.

• For most of us, the left side of the brain is the side necessary for speech. The dominant hemisphere.

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The parietal lobe

• It has intraparietal sulcus that divides the parietal lobe into superior parietal lobule and inferior parietal lobule.

• Involved in perception of stimuli related to touch, pressure, temperature, and pain.

• This region of the brain helps people understand what they see and feel.

• It also controls how they understand and process information about the environment around them, such as distance and position of objects.

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Each lobe is associated with:-

• Frontal Lobe- associated with reasoning, planning, parts of speech, movement, emotions, and problem solving

• Parietal Lobe- associated with movement, orientation, recognition, perception of stimuli

• Occipital Lobe- associated with visual processing • Temporal Lobe- associated with perception and

recognition of auditory stimuli, memory, and speech

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Frontal lobe

• You are who you are because of this lobe.• This area determines personality and

emotions. • It's also involved in controlling judgment,

impulses, sexual behavior, language and movement.

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Prefrontal lobotomy

• Prefrontal lobotomy was performed to control the aggressive/violent behavior /undesirable behavior of prison inmates/mental asylum patients.

• The original lobotomy operation is now rarely performed, if ever, although many countries still accept psychosurgery as a form of radical control of violent behavior (Japan, Australia, Sweden and India are among them).

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The visual center is located in occipital lobe

• This area determines if you understand what you're looking at.

• Damage to the occipital lobe could cause hallucinations, make objects appear larger or smaller then they are or make the colors look abnormal.

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The temporal lobe

• This region controls your hearing and the ability to recognize words.

• It can also affect memory. • Damage to the left side of this lobe can cause

problems remembering what people said. • Damage to the right side might stop you from

recalling music or pictures.

04/12/2023 23The medial surface

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MEDIAL SURFACE OF CEREBRUM

04/12/2023 25The inferior surface

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Inferior surface of cerebral hemisphere

• It has a large tentorial surface and an orbital surface.

• The orbital sulcus is an “H” shaped sulcus, dividing the orbital gyri into, medial orbital gyrus, lateral orbital gyrus, anterior and posterior orbital gyrus.

• There is an olfactory sulcus lodging the olfactory tract, medial to it is gyrus rectus.

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THE INFERIOR SURFACE

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Inferior surface1. Frontal pole 2. Temporal pole 3. Olfactory tract & sulcus 4. Orbital gyri 5. Gyrus rectus 6. Inferior temporal sulcus 7. Inferior temporal gyrus 8. Occipitotemporal sulcus 9. Fusiform gyrus 10. Collateral sulcus 11. Lingual gyrus 12. Uncus 13. Calcarine sulcus

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Cranial nerves attachments

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Structures in the inter-peduncular fossa

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Uncus

1. Optic nerve 2. Optic chiasma 3. Optic tract 4. Tuber cinereum 5. Mamillary bodies 6. Anterior perforated substance 7. Olfactory trigone 8. Pons 9. Uncus

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Uncinate fits are preceded by hallucination of disagreeable odors

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Applied anatomy of uncus

• In situations of tumor, hemorrhage, or edema, increased volume of the temporal lobe can push the uncus against the brainstem and its corresponding cranial nerves.

• If the uncus becomes herniated the structure lying just medial to it, cranial nerve III, can become compressed.

• This causes problems associated with a non-functional or problematic CNIII - pupil on ipsilateral side fails to constrict to light, etc.

• Brainstem damage is typically ipsilateral to the herniation

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References

• Clinically Oriented Anatomy- Keith Moore –pages 512-519 4th Edition

• http://en.wikipedia.org/wiki/Cerebrum• http://

webspace.ship.edu/cgboer/genpsycerebrum.html

• http://serendip.brynmawr.edu/bb/kinser/Structure1.html

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Sample mcqs

• What is the general term given to a tract connecting the two cerebral hemispheres?

• A) Commisure• B) Funiculi• C) Column • D) Peduncle • E. Projection fibers

• Which ventricle is located centrally within the brain, superior to the hypothalamus ?

• A. Second• B) Third • C) Fourth• D) Fifth• E) Lateral

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Sample MCQS

Which of the following would be expected following damage to the cortex that lies just in front of the central sulcus?A. Intense hyper sexualityB. Visual hallucinationsC. Inability to discriminate tones as low intensitiesD. Difficulty in reading and writingE. Difficulty in controlling muscles of the body

Damage to visual association cortex would be expected to produce:-A. Problem in recognizing an object by sightB. Difficulty in playing a tune on a pianoC. Difficulty in naming an object a person can touch (but not see)D. Problems in naming a song the person knew before sustaining the brain damageE. An inability to recognize a familiar odour