Makindo Medical Notes

🧠 The cerebral cortex is the outermost layer of the brain, composed of gray matter, and essential for higher-order functions such as sensory perception, motor control, and cognition. It is organized into six layers and contains distinct neuron types and glial cells.

🧩 Layers of the Cerebral Cortex

The cortex has six layers, each with unique roles:

• Layer I – Molecular: Few cells; mostly dendrites & axons → integration of synaptic inputs.
• Layer II – External Granular: Small pyramidal & stellate cells → local processing.
• Layer III – External Pyramidal: Medium pyramidal neurons → corticocortical connections.
• Layer IV – Internal Granular: Densely packed stellate cells → thalamic sensory input.
• Layer V – Internal Pyramidal: Large pyramidal neurons (Betz cells in motor cortex) → output to brainstem/spinal cord.
• Layer VI – Multiform: Fusiform cells → project to thalamus, feedback regulation.

👩‍🔬 Neuron Types

Key neuronal and glial cell populations:

• Pyramidal cells: Excitatory neurons in layers III & V; project widely, including to the spinal cord.
• Stellate cells: Found mainly in layer IV; process thalamic sensory input.
• Fusiform cells: Layer VI neurons projecting to the thalamus.
• Glial cells: Astrocytes (support), oligodendrocytes (myelination), microglia (immune surveillance).

🧠 Key Cortical Regions

• Primary Motor Cortex (M1): Voluntary movement control; organised as the motor homunculus.
• Primary Somatosensory Cortex (S1): Touch, pain, temperature, proprioception; sensory homunculus map.
• Primary Visual Cortex (V1): First cortical stage of visual input processing.
• Primary Auditory Cortex: Processes sound frequency and volume.
• Broca’s Area: Speech production; lesions → expressive aphasia.
• Wernicke’s Area: Language comprehension; lesions → receptive aphasia.
• Prefrontal Cortex: Executive function, planning, personality, social behavior.
• Parietal Lobe: Integrates spatial sense, navigation, and sensory input.
• Occipital Lobe: Visual processing centre.
• Temporal Lobe: Hearing, memory formation (hippocampus).
• Limbic System: Emotion, motivation, and memory (amygdala + hippocampus).

📌 Summary

The cerebral cortex is organised into six layers, each with specialised neurons and functions. Different lobes and areas of the cortex subserve motor, sensory, visual, auditory, language, memory, and executive functions. Clinically, cortical dysfunction explains a wide spectrum of neurological disorders from aphasia to memory loss.