Anatomy of cerebrum I & II

🖇 Gross Cerebrum Anatomy

📌 General Structure

• CNS = brain + spinal cord.
• Cerebrum = 2 hemispheres (right + left).
• Connected by Corpus Callosum.
• Protected by Meninges (Dura, Arachnoid, Pia).

📌 Gross Features

• Poles: Frontal, Temporal, Occipital.
• Surfaces: Superolateral, Medial, Inferior.
• Inferior Surface: Orbital (anterior) + Tentorial (posterior).
• Borders: Superomedial, Inferomedial, Lateral.

🚨 Sulci & Gyri

📌 Basics

• Sulci: grooves/fissures.
• Gyri: raised folds between sulci.
• Why convoluted? Maximize surface area for complex functions within skull.

📌 Lobes & Ventricles

• 4 Lobes: Frontal, Parietal, Temporal, Occipital → divided by Central, Lateral, Parieto-occipital sulci.
• Ventricles: cavities with CSF → 2 Lateral + Third + Fourth.
• CSF Pathway: Lateral Ventricles → Third Ventricle (diencephalon) → Aqueduct of Sylvius → Fourth Ventricle (behind pons/medulla) → Central Canal (spinal cord).

🟠 Specific Sulci & Gyri by Surface

📌 1. Superolateral Surface

Sulci:

• Central Sulcus, Precentral Sulcus, Postcentral Sulcus.
• Lateral Sulcus (posterior branch + 2 anterior branches).
• Intraparietal Sulcus.

Gyri:

• Precentral Gyrus, Postcentral Gyrus.
• Superior, Middle, Inferior Frontal Gyri.
• Superior & Inferior Parietal Lobules.

📌 2. Medial Surface

Landmark: Corpus Callosum.

Sulci:

• Callosal Sulcus (along Corpus Callosum).
• Cingulate Sulcus.
• Central Sulcus (upper end).
• Parieto-occipital Sulcus.
• Calcarine Sulcus (Y-shape with Parieto-occipital).

Gyri:

• Cingulate Gyrus (between Callosal & Cingulate sulci).
• Medial Frontal Gyrus.
• Paracentral Lobule (around central sulcus).
• Cuneus (wedge), Precuneus.

📌 3. Inferior Surface

Orbital Part:

• H-shaped Orbital Sulcus.
• Olfactory Sulcus.
• Gyrus Rectus (straight gyrus).

Tentorial Part:

• Collateral Sulcus.

Key Structures:

• Uncus (anterior temporal prominence).
• Parahippocampal Gyrus.
• Lingual Gyrus.
• Rhinal Sulcus.

🖇 Functional Brain Areas

📌 Three Main Types

• Motor Areas: control movement (stimulation/inhibition).
• Sensory Areas: responsible for sensation.
• Association Areas: modify motor/sensory function → determine movement design & interpret/store sensations.

🚨 General Study Rules for Cortical Areas

Know for every area:

• Location
• Representation
• Function
• Effect of Lesion

🟠 I. Frontal Lobe Areas

📌 1. Primary Motor Area (Area 4)

• Location: Precentral Gyrus.
• Representation: upside down (head down, legs up) → based on skills not organ size → face, fingers, thumb = large representation.
• Function: voluntary movement of contralateral muscles → execution not design.
• Lesion: contralateral hemiplegia/hemiparesis.

📌 2. Premotor Area (Area 6)

• Location: anterior to Area 4.
• Function: "memory bank for movement" → stores motor programs → designs movement ("engineer") → controls posture.
• Lesion: motor apraxia → patient can move but can't perform specific requested movements (design lost).

📌 3. Frontal Eye Field (Area 8)

• Function: conjugate eye movement to opposite side.
• Lesion: eye deviation to affected side.

📌 4. Broca's Area (Motor Speech, Areas 44, 45)

• Location: Inferior Frontal Gyrus, dominant hemisphere only.
• Function: formulation of words/sentences → speech fluency.
• Lesion: motor aphasia → understands but can't express/pronounce words.

📌 5. Prefrontal Cortex (Areas 9, 10, 11, 12)

• Location: anterior pole of frontal lobe.
• Function: personality, emotions, judgment, decision-making, social conduct.
• Lesion: personality changes, intellectual retardation, inappropriate social behavior.

📌 6. Exner's Area

• Function: writing.
• Lesion: agraphia (can't write).

🟣 II. Parietal Lobe Areas

📌 1. Primary Sensory Area (Areas 3, 1, 2)

• Location: Postcentral Gyrus.
• Function: receives sensation from contralateral side → upside down representation.
• Lesion: contralateral anesthesia/hypesthesia.

📌 2. Sensory Association Area (Areas 5, 7)

• Function: interpretation & storage of sensation → stereognosis (recognizing objects by touch without sight).
• Lesion: astereognosis/agnosia → feels object but can't recognize it.

📌 3. Wernicke's Area (Sensory Speech, Areas 39, 40, 22)

• Location: Supramarginal Gyrus (40) + Angular Gyrus (39) in parietal + Area 22 in temporal → dominant hemisphere.
• Function: language comprehension (written/spoken) → "dictionary" → Area 39 = reading.
• Lesion: sensory aphasia → can't understand speech/writing → Area 39 damage = alexia (can't read).
• Global Aphasia: damage to both Broca's + Wernicke's.

🟠 III. Visual, Auditory & Other Areas

📌 1. Primary Visual Area (Area 17)

• Location: Occipital lobe, around Calcarine Sulcus.
• Function: seeing.
• Lesion: contralateral homonymous hemianopia.

📌 2. Secondary Visual Area (Areas 18, 19)

• Function: interpretation of vision (recognizing what's seen).
• Lesion: visual agnosia (seeing but not recognizing) or visual hallucinations.

📌 3. Primary Auditory Area (Areas 41, 42)

• Location: lateral face of temporal lobe.
• Function: hearing → each side supplies both ears.
• Lesion: diminished hearing (not total deafness).

📌 4. Olfactory Area (Area 28)

• Location: Uncus (inferior brain).
• Function: smell.
• Lesion: anosmia (loss of smell).

📌 5. Gustatory Area (Area 43)

• Function: taste & distinguishing sensation types.