The brain contains ~10¹¹ neurons and even more glial cells (outnumbering neurons 10–50×). 🧬 About 40% of the human genome contributes to brain development & function. ⚡ Neurons rely on continuous ATP from oxidative phosphorylation → brain is highly metabolic.

CNS = neurons + glial cells. Both form the neurovascular unit, essential in stroke pathophysiology.

🧩 Neuronal Cells

Neurons = “information processors” → receive input, integrate, and send output signals. Grey matter = soma clusters (cortex, nuclei, brainstem, cerebellum).

Key parts:

🟢 Soma: nucleus & organelles.
🌳 Dendrites: receive input.
⚡ Axon hillock: AP initiation.
➡️ Axon: conducts impulse.
📤 Terminals: release neurotransmitters at synapses.

🔄 Transport: - Anterograde → soma → terminal. - Retrograde → terminal → soma (used by rabies, tetanus).

🧪 Non-Neuronal Cells (Glia)

Glia = “glue” but vital support + barrier + repair functions:

🌟 Astrocytes: scaffold, ion buffering, neurotransmitter recycling, maintain BBB.
🛡️ Microglia: immune cells, phagocytose debris & pathogens, regulate inflammation.
💧 Ependymal cells: line ventricles, circulate CSF, tumour origin (ependymoma).
🧵 Oligodendrocytes: myelinate CNS axons → saltatory conduction. One cell → many axons.

⚡ Cell Electrophysiology

Resting potential: ~ –70 mV (Na⁺/K⁺ pump + selective permeability).
AP: Na⁺ influx → depolarisation; K⁺ efflux → repolarisation.
Myelination → saltatory conduction at nodes of Ranvier. ❌ Lost in MS → conduction slowed.

🔄 Synapses, Neurotransmitters & Receptors

🔥 Glutamate: excitatory (NMDA, AMPA).
🛑 GABA: inhibitory (GABA_A, GABA_B).
⚡ Acetylcholine: nicotinic (ionotropic), muscarinic (metabotropic).
🎭 Monoamines: dopamine, serotonin, norepinephrine → mood, cognition, arousal.

🧠 Synaptic plasticity (LTP/LTD) = basis of learning & memory.

💓 Brain Physiology & Cerebral Perfusion

Brain = 1–2% body weight but needs 15% cardiac output + 20% O₂.
Metabolism: glucose oxidation, minimal reserves.
Autoregulation adjusts flow to BP, CO₂, pH → fails in stroke.

🩸 Stroke Pathophysiology

Sudden interruption of cerebral blood flow → neuronal death.

🧠 Three Zones Post-Stroke
☠️ Irreversible core	Necrosis from Ca²⁺ influx, osmotic failure.
🟡 Penumbra	Salvageable if reperfused quickly.
🟢 Mild hypoperfusion	Viable but impaired; oxidative stress risk.

⏱️ Time is brain – reperfusion (thrombolysis/thrombectomy) saves the penumbra. MRI-DWI distinguishes core vs at-risk tissue.

📊 Factors Influencing Stroke Outcome

⏳ Duration/speed of ischaemia (slower = more adaptation).
🌐 Collateral circulation.
🩺 Systemic BP and perfusion pressure.
🩸 Clotting tendency & fibrinolysis.
🌡️ Hyperthermia worsens damage.
🍬 Hyperglycaemia = larger infarcts, worse prognosis.

📚 References

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Basic Neuroscience

🧠 Cells in the CNS

🧩 Neuronal Cells

⚡ Cell Electrophysiology

💓 Brain Physiology & Cerebral Perfusion

📊 Factors Influencing Stroke Outcome

📚 References

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