Gross Anatomy - Lobes Laid Bare
- Cerebral Hemispheres: Two; separated by longitudinal fissure; connected by corpus callosum.
- Lobes (4 per hemisphere):
- Frontal: Anterior to central sulcus. Motor control, planning.
- Parietal: Posterior to central sulcus. Somatosensation, spatial processing.
- Temporal: Inferior to lateral sulcus. Auditory, memory, language comprehension.
- Occipital: Posterior-most. Visual processing.
- Key Sulci:
- Central Sulcus (Rolando): Frontal from Parietal.
- Lateral Sulcus (Sylvian): Temporal from Frontal & Parietal.
- Parieto-occipital Sulcus: Parietal from Occipital (medial).
- Key Gyri:
- Precentral (Frontal): Primary motor cortex.
- Postcentral (Parietal): Primary somatosensory cortex.
⭐ The central sulcus (of Rolando) separates the frontal lobe from the parietal lobe.
Functional Areas - Brain's Busy Zones
| Lobe | BA No. | Area Name | Function | Note/Mnemonic |
|---|---|---|---|---|
| Frontal | 4 | Primary Motor | Voluntary movement | |
| 6 | Premotor/SMA | Plan movement | ||
| 8 | Frontal Eye Field | Conjugate eye movement | ||
| 44, 45 | Broca's Area (Dom) | Motor speech | 📌 Broca's = Broken speech | |
| Parietal | 3,1,2 | Primary Somatosensory | Sensation (touch, pain etc.) | |
| 39 | Angular Gyrus (Dom) | Reading, writing, calculation | Lesion → Gerstmann Syndrome | |
| 40 | Supramarginal Gyrus (Dom) | Language, spatial sense | ||
| Temporal | 41,42 | Primary Auditory | Hearing | |
| 22 | Wernicke's Area (Dom) | Language comprehension | 📌 Wernicke's = Word salad | |
| Occipital | 17 | Primary Visual | Vision | |
| 18,19 | Visual Association | Visual interpretation |
White Matter - Neural Highways
- Composed of myelinated axons, forming tracts for rapid signal transmission.
- Classified by connections:
| Fiber Type | Examples | Key Function/Location |
|---|---|---|
| Association Fibers | Superior/Inferior longitudinal fasciculus, Arcuate, Cingulum | Connect different cortical areas within same hemisphere. |
| Commissural Fibers | Corpus callosum (largest), Anterior/Posterior commissure | Interconnect both cerebral hemispheres. |
| Projection Fibers | Internal capsule, Corona radiata (corticospinal/bulbar) | Connect cortex with subcortical nuclei, brainstem, spinal cord. |
⭐ The internal capsule's posterior limb carries corticospinal tract fibers.
Blood Supply & Dominance - Vital Flow & Brain Boss
Cerebral Arterial Territories & Deficits:
| Artery | Territory | Deficit (Occlusion) |
|---|---|---|
| ACA (Anterior Cerebral A.) | Medial frontal/parietal lobes; leg motor cortex | Contralateral leg > arm weakness/sensory loss. 📌 "A for Anterior leg" |
| MCA (Middle Cerebral A.) | Lateral hemisphere; arm/face motor cortex; speech (dominant) / neglect (non-dominant) areas | Contralateral face/arm > leg weakness/sensory loss; aphasia (dominant) / neglect (non-dominant). |
| PCA (Posterior Cerebral A.) | Occipital lobe, medial temporal lobe | Contralateral homonymous hemianopia; memory loss. |
- Left Hemisphere (Typically Dominant): Language (Broca's: motor speech; Wernicke's: sensory speech), analytical thought, calculations.
- Right Hemisphere (Typically Non-Dominant): Visuospatial skills, facial recognition, emotional prosody, music.
⭐ Middle cerebral artery (MCA) is the most commonly affected artery in stroke, often leading to contralateral hemiplegia and hemisensory loss, predominantly affecting the upper limb and face.
High‑Yield Points - ⚡ Biggest Takeaways
- Frontal lobe: Precentral gyrus (motor), Broca's area (motor speech), executive functions.
- Parietal lobe: Postcentral gyrus (sensory), spatial orientation, Gerstmann's syndrome (dominant parietal).
- Temporal lobe: Wernicke's area (sensory speech), auditory cortex, hippocampus (memory), Kluver-Bucy syndrome.
- Occipital lobe: Primary visual cortex (calcarine sulcus), visual association areas.
- Dominant (Left) Hemisphere: Key for language (Broca's, Wernicke's), calculation, praxis.
- Non-Dominant (Right) Hemisphere: Excels in visuospatial skills, facial recognition, music, emotional prosody.
- Corpus Callosum: Largest commissure connecting hemispheres; lesions can cause split-brain syndrome.
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