Neuroanatomy, Peripheral Nervous System, Vascular Supply, and Neurological Pathologies

Comprehensive vocabulary flashcards covering spinal cord anatomy, peripheral nerve and muscle physiology, cerebral vascular supply, neurological pathologies, and diagnostic modalities.

C8 Spinal Nerve

The 8th cervical spinal nerve that exits below the C7 vertebra, notable because there is no corresponding C8 vertebra.

Lateral Corticospinal Tract

The descending motor pathway in which $90\%$ of motor fibers decussate at the lower medulla and travel down to synapse on contralateral anterior horn cells.

Anterior Corticospinal Tract

The descending motor pathway carrying $10\%$ of uncrossed motor fibers that travel ipsilaterally in the ventral column before synapsing at the target spinal level.

Dorsal Column Tracts

Ascending somatosensory pathways (medial lemniscal system) that convey vibration, proprioception, light touch, and 2-point discrimination, decussating at the lower medulla.

Spinothalamic Tracts

Ascending somatosensory pathways comprising the lateral tract (pain and temperature) and anterior tract (light touch), which decussate a few spinal levels above entry.

Upper Motor Neuron (UMN) Lesion

A lesion in motor pathways above the ventral horn motor neurons, characterized by weakness, spasticity (increased tone), brisk reflexes, and up-going plantars (Babinski's sign).

Lower Motor Neuron (LMN) Lesion

A lesion located at or distal to the anterior horn cells in the ventral horn, characterized by weakness, hypotonia or normal tone, hyporeflexia or areflexia, muscle wasting, and fasciculations.

Dissociated Sensory Loss

A pattern of sensory impairment caused by a small central spinal lesion (e.g., a small syrinx) that selectively disrupts crossing spinothalamic fibers, resulting in loss of pain and temperature sensation at a few levels below the lesion while preserving vibration and proprioception.

Brown-Sequard Syndrome

A hemi-cord spinal lesion resulting in ipsilateral UMN weakness below the lesion, ipsilateral loss of vibration and proprioception, and contralateral loss of pain and temperature sensation starting a few levels below the lesion.

Decorticate Posture

Abnormal posturing characterized by adduction and flexion of the upper extremities alongside extension of the lower extremities, caused by disinhibition of the rubrospinal tract in severe higher brain damage.

Decerebrate Posture

Abnormal posturing characterized by extension and wrist pronation of the upper extremities with extension of the lower extremities, caused by disruption of the rubrospinal tract in severe brain damage.

Peripheral Nervous System (PNS)

The division of the nervous system consisting of peripheral nerves, primary motor and sensory neurons, neuromuscular junctions, and skeletal muscles.

Anterior Horn Cells

Primary motor neuron cell bodies located in the ventral gray matter of the spinal cord whose axons extend into peripheral nerves to innervate muscle fibers.

Dorsal Root Ganglion

A nodular structure outside the spinal cord containing bipolar sensory neuron cell bodies with two separate axonal projections.

Dermatome

A specific cutaneous segment of the skin receiving sensory innervation from a single spinal cord segment.

Saltatory Conduction

The rapid mode of nerve impulse propagation along myelinated axons in which action potentials jump between uninsulated gaps called Nodes of Ranvier.

Neuromuscular Junction (NMJ)

The specialized chemical synapse between a terminal motor axon and a skeletal muscle fiber where acetylcholine is released to trigger muscle cell depolarization.

Motor Neuron Disease (MND)

A progressive neurodegenerative disorder affecting anterior horn cells and motor pathways, causing motor neuron degeneration, weakness, muscle wasting, fasciculations, and hyper-reflexia.

Radiculopathy

A pathological condition or injury affecting a spinal nerve root, commonly produced by mechanical compression from a herniated (slipped) intervertebral disc.

Guillain-Barr"e Syndrome

An acute, painless, ascending peripheral neuropathy (AIDP) causing progressive motor weakness and hyporeflexia, potentially leading to complete paralysis and ventilatory failure.

Myasthenia Gravis

An autoimmune disorder of the neuromuscular junction where autoantibodies target postsynaptic acetylcholine receptors, resulting in fatigable muscle weakness, ptosis, and diplopia.

Polymyositis

An inflammatory disease of skeletal muscle presenting with proximal muscle weakness and elevated serum creatine phosphokinase (CPK) levels.

Blood-Brain Barrier (BBB)

A selective physiological membrane structure formed by tight junction proteins between capillary endothelial cells and astrocyte foot processes that shields CNS neurons from circulating toxins and ion fluctuations.

Cerebral Autoregulation

The physiological mechanism that maintains constant cerebral blood flow across a wide cerebral arterial pressure range of approximately $65-140\,\text{mmHg}$.

Cerebral Perfusion Pressure (CPP)

The net pressure gradient driving blood flow to the brain, calculated as Mean Arterial Pressure minus Intracranial Pressure ($\text{CPP} = \text{MAP} - \text{ICP}$).

Mean Arterial Pressure (MAP)

The average pressure in a patient's arteries during one cardiac cycle, defined by the formula $\text{MAP} = \frac{1}{3}(\text{SBP} + 2 \times \text{DBP})$.

Recurrent Artery of Heubner

A major perforating branch arising from the distal A1 or proximal A2 segment of the anterior cerebral artery that supplies the anteroinferior head of the caudate, putamen, and inferior anterior limb of the internal capsule.

Lenticulostriate Arteries

Deep perforating branches arising from the M1 segment of the middle cerebral artery that supply the superior parts of the internal capsule and basal ganglia.

Anterior Choroidal Artery (AChA)

A branch of the internal carotid artery that supplies the optic tract, lateral geniculate body, optic radiation, genu and posterior limb of the internal capsule, basal ganglia, and midbrain.

Circle of Willis

An anastomotic ring of blood vessels located at the base of the brain connecting the anterior (ICA) and posterior (VBA) circulatory systems to provide primary collateral perfusion.

Posterior Inferior Cerebellar Artery (PICA)

A major branch of the intracranial vertebral artery supplying the dorsolateral medulla, posteroinferior cerebellum, and choroid plexus of the 4th ventricle.

Anterior Spinal Artery (ASA)

A single midline vessel formed by branches of the vertebral arteries that supplies the median medulla and anterior two-thirds of the spinal cord.

Artery of Adamkiewicz

The major anterior segmental medullary artery arising from lower intercostal or lumbar arteries that supplies the lower thoracic and lumbar segments of the spinal cord.

Watershed Areas

Borderzone regions located at the distal junction territories between major cerebral arteries (such as ACA-MCA and MCA-PCA junctions) that are particularly vulnerable to ischemia during low-flow states.

Electromyogram (EMG)

A diagnostic neurophysiological procedure using needle electrodes inserted into skeletal muscle to measure electrical activity at rest and during voluntary contraction, differentiating myopathic from neurogenic disorders.

Nerve Conduction Study (NCS)

An electrodiagnostic test that applies electrical stimuli to peripheral nerves to measure parameters such as action potential amplitude and conduction velocity.

Electroencephalogram (EEG)

A diagnostic recording technique that uses scalp electrodes to measure spontaneous cerebral electrical activity.

Transcranial Doppler Ultrasound (TCD)

A non-invasive vascular imaging technique that measures blood flow velocity within major intracranial basal arteries.

Positron Emission Tomography (PET)

A functional nuclear neuroimaging technique utilizing radiotracers like Fluorodeoxyglucose (FDG) or Pittsburgh Compound B (PIB) to measure regional cerebral glucose metabolism or protein accumulation.

MR Spectroscopy

An advanced MRI technique that non-invasively measures chemical metabolic markers in brain tissue, such as N-acetylaspartate (NAA), choline, and creatinine.

Visual Evoked Potentials

An electrophysiological test measuring brain electrical responses generated in the visual cortex to evaluate conduction along the optic nerve pathway.

Brainstem Evoked Potentials

An electrophysiological test that measures neuroelectrical responses along auditory and brainstem pathways to assess brainstem and auditory function.