Neurology Cheat Sheet

The core ideas of Neurology distilled into a single, scannable reference — perfect for review or quick lookup.

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Quick Reference

Neuroanatomical Localization

The foundational clinical skill of determining where in the nervous system a lesion is located based on the pattern of signs and symptoms. Localization precedes diagnosis and guides the differential and workup.

The Neuron Doctrine

The principle established by Ramon y Cajal that the nervous system is composed of discrete individual cells (neurons) that communicate at specialized junctions (synapses), rather than forming a continuous network.

Blood-Brain Barrier (BBB)

A selectively permeable boundary formed by tight junctions between endothelial cells of cerebral blood vessels, astrocyte end-feet, and pericytes. It protects the central nervous system from pathogens and toxins but also limits drug delivery to the brain.

Neurotransmission

The process by which electrical signals are converted to chemical signals at synapses. An action potential triggers vesicle fusion and release of neurotransmitters (such as glutamate, GABA, dopamine, acetylcholine, or serotonin) that bind to postsynaptic receptors.

Neuroplasticity

The ability of the nervous system to reorganize its structure, function, and connections in response to experience, learning, or injury. It encompasses synaptic plasticity, axonal sprouting, and cortical remapping.

Cerebrovascular Autoregulation

The intrinsic ability of cerebral blood vessels to maintain relatively constant blood flow across a range of systemic blood pressures (typically mean arterial pressures of 60 to 150 mmHg) through myogenic, metabolic, and neurogenic mechanisms.

Demyelination

The pathological loss of the myelin sheath that insulates axons, leading to impaired saltatory conduction, slowed or blocked signal transmission, and ultimately axonal degeneration if not arrested.

Epileptogenesis

The gradual process by which a normal neural network becomes chronically prone to generating spontaneous, recurrent seizures. It involves molecular, cellular, and network-level changes including altered ion channel expression, synaptic reorganization, and neuroinflammation.

Neurodegeneration

The progressive loss of structure and function of neurons, often accompanied by abnormal protein aggregation. Different neurodegenerative diseases are characterized by specific pathological proteins: amyloid-beta and tau in Alzheimer disease, alpha-synuclein in Parkinson disease, and TDP-43 in ALS.

Neuroimaging

The set of techniques used to visualize the structure and function of the nervous system, including computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), and functional MRI (fMRI). Each modality provides complementary information for diagnosis and research.

Key Terms at a Glance

Action Potential:A rapid, transient reversal of the electrical potential across a neuron's membrane, propagated along the axon to transmit signals. It is generated by sequential opening of voltage-gated sodium and potassium channels.

Afferent:Carrying signals toward the central nervous system. Afferent (sensory) neurons transmit information from peripheral receptors to the brain and spinal cord.

Aphasia:An acquired language disorder resulting from damage to language-dominant (usually left) hemisphere brain regions, affecting the ability to produce or comprehend spoken and written language.

Ataxia:A lack of voluntary coordination of muscle movements, typically caused by dysfunction of the cerebellum, its afferent or efferent pathways, or the sensory (proprioceptive) system.

Autonomic Nervous System:The division of the peripheral nervous system that regulates involuntary body functions including heart rate, blood pressure, digestion, and thermoregulation, comprising sympathetic and parasympathetic branches.

Axon:The long, slender projection of a neuron that conducts action potentials away from the cell body to synaptic terminals, where neurotransmitters are released.

Cerebral Cortex:The outer layer of gray matter of the cerebral hemispheres, composed of six neuronal layers, responsible for higher cognitive functions including perception, voluntary movement, language, and executive function.

Cerebrospinal Fluid (CSF):A clear, colorless fluid produced by the choroid plexus that fills the ventricles and subarachnoid space, providing buoyancy, protection, and a medium for nutrient transport and waste removal for the brain and spinal cord.

Clonus:Involuntary rhythmic muscular contractions and relaxations elicited by sudden, sustained stretching of a muscle, indicative of an upper motor neuron lesion.

Cranial Nerves:Twelve pairs of nerves emerging directly from the brain and brainstem (olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal, vagus, accessory, hypoglossal) that innervate structures of the head, neck, and viscera.

Dendrite:Branching projections of a neuron that receive synaptic inputs from other neurons and conduct graded electrical signals toward the cell body.

Dysarthria:A motor speech disorder caused by weakness, spasticity, or incoordination of the muscles used in speech production, resulting in slurred or indistinct articulation while language comprehension and formulation remain intact.

Edema (Cerebral):Abnormal accumulation of fluid in the brain parenchyma. Vasogenic edema results from blood-brain barrier disruption; cytotoxic edema results from cellular swelling due to energy failure, as in ischemic stroke.

Efferent:Carrying signals away from the central nervous system. Efferent (motor) neurons transmit commands from the brain and spinal cord to muscles and glands.

Electroencephalography (EEG):A diagnostic technique that records electrical activity of the brain through electrodes placed on the scalp, used primarily for evaluating epilepsy, encephalopathy, and sleep disorders.

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