🖇 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.