brain
Summary
The brain is the central command organ of the nervous system, weighing ~1.4 kg and consuming 20% of total body glucose and oxygen despite being only 2% of body weight. It consists of cerebrum, cerebellum, and brainstem, protected by the blood-brain barrier and cerebrospinal fluid.
Detail
The brain is divided into three major regions: the cerebrum (largest portion containing cerebral cortex responsible for higher cognitive functions, motor control, and sensory processing), cerebellum (coordination, balance, motor learning), and brainstem (medulla, pons, midbrain controlling vital functions like breathing, heart rate, consciousness). The brain is protected by the meninges (dura mater, arachnoid mater, pia mater) and bathed in cerebrospinal fluid produced by choroid plexus. The blood-brain barrier, formed by tight junctions between capillary endothelial cells, selectively permits passage of substances. Key anatomical landmarks include the Circle of Willis for vascular supply, ventricular system for CSF circulation, and functional areas like Broca's and Wernicke's areas for language. Clinically significant for stroke, traumatic brain injury, infections (meningitis, encephalitis), tumors, and neurodegenerative diseases.
Sources
- First Aid for the USMLE Step 1
- Netter's Atlas of Human Anatomy
- Principles of Neural Science (Kandel)
- Robbins Basic Pathology
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