Wednesday, June 25, 2025

The Brain

 

The brain is the central organ of the human nervous system—commanding thought, emotion, sensation, and movement. It’s a complex, multilayered structure with billions of neurons and over 100 trillion synapses.


🧠 Major Divisions of the Human Brain

1. Cerebrum

  • Largest part (about 80% of brain mass)
  • Divided into left and right hemispheres
  • Each hemisphere has 4 lobes:
    • Frontal lobe: reasoning, planning, motor control, emotions
    • Parietal lobe: sensory input, spatial awareness
    • Temporal lobe: hearing, memory, language
    • Occipital lobe: vision
  • Covered by the cerebral cortex (gray matter)

2. Cerebellum

  • Located at the back of the brain, under the cerebrum
  • Coordinates movement, balance, and posture
  • Contains more neurons than the cerebrum but is much smaller

3. Brainstem

  • Connects brain to spinal cord
  • Controls basic life functions: breathing, heart rate, swallowing
  • Divided into:
    • Midbrain
    • Pons
    • Medulla oblongata

4. Diencephalon

  • Deep inside the brain, includes:
    • Thalamus: relay station for sensory signals
    • Hypothalamus: controls hormones, temperature, hunger, circadian rhythms
    • Epithalamus: includes the pineal gland (produces melatonin)

🧬 Brain Matter & Cells

  • Gray matter: contains neuron cell bodies (processing areas)
  • White matter: contains myelinated axons (information highways)
  • Glial cells: support neurons (astrocytes, microglia, oligodendrocytes)

🧪 Other Key Structures

Structure Function
Corpus callosum Connects the left and right cerebral hemispheres
Limbic system Emotions, memory (includes hippocampus, amygdala)
Basal ganglia Motor control, habit learning
Ventricles Cavities filled with cerebrospinal fluid (CSF)
Meninges 3 protective layers (dura mater, arachnoid, pia mater)

🩺 Brain Stats

  • Weight: ~1.4 kg (3 lbs)
  • Energy use: ~20% of body’s total
  • Oxygen demand: extremely high—~25% of total oxygen supply
  • Neurons: ~86 billion
  • Synapses: estimated 100+ trillion


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