Clinical meaning
The neurological system comprises the central nervous system (brain and spinal cord) and peripheral nervous system (cranial nerves, spinal nerves, autonomic nervous system), coordinating all voluntary and involuntary body functions through electrochemical neurotransmission. Neurons transmit signals via action potentials generated by sodium-potassium pump activity and voltage-gated ion channel opening along myelinated axons through saltatory conduction. The blood-brain barrier (BBB), formed by tight junctions between cerebral capillary endothelial cells, selectively regulates substance entry into the CNS — disruption of the BBB in conditions such as meningitis, stroke, or traumatic brain injury allows inflammatory mediators and toxins to enter brain tissue, contributing to cerebral edema and secondary injury. Intracranial pressure (ICP), normally 5-15 mmHg, is determined by the volume of brain tissue, cerebrospinal fluid, and intracranial blood (Monro-Kellie doctrine).
Exam relevance
Risk factors: - Hypertension (strongest modifiable risk factor for stroke) - Atrial fibrillation (major risk for embolic stroke) - Diabetes mellitus - Smoking - Hyperlipidemia - Age over 65 years - Family history of stroke or aneurysm - Substance abuse (cocaine, amphetamines)