Nervous System Anatomy, Physiology, and Neurological Disorders

Comprehensive vocabulary flashcards covering the structural divisions, neuroglia, impulse conduction, cortical mapping, autonomic controls, and central nervous system pathologies presented in the nervous system lectures.

Afferent Division

The sensory division of the peripheral nervous system (PNS) that conducts impulses from somatic and visceral sensory receptors inward toward the central nervous system (CNS).

Efferent Division

The motor division of the peripheral nervous system (PNS) that transmits nerve impulses away from the central nervous system (CNS) to effector organs such as muscles and glands.

Autonomic Nervous System

The involuntary branch of the efferent motor division that transmits motor impulses to cardiac muscle, smooth muscle, and glandular epithelium; subdivided into sympathetic and parasympathetic divisions.

Astrocytes

The largest and most numerous glial cells in the central nervous system (CNS) that form the blood-brain barrier, permitting selective diffusion of substances such as oxygen, carbon dioxide, water, glucose, and alcohol.

Microglia

Small glial cells residing primarily in the central nervous system (CNS) that carry out phagocytosis to destroy harmful microorganisms and cellular debris.

Ependymal Cells

Glial cells equipped with cilia that line the fluid-filled cavities (ventricles and central canal) of the brain and spinal cord to produce and circulate cerebrospinal fluid.

Oligodendrocytes

Glial cells with relatively few processes that hold nerve fibers together and produce the insulating myelin sheath surrounding axons in the central nervous system (CNS).

Schwann Cells

Glial cells located exclusively in the peripheral nervous system (PNS) that wrap around axons to form the myelin sheath, nodes of Ranvier, and the outer neurilemma.

Neurilemma

The outer layer of Schwann cell cytoplasm and membrane covering peripheral nerve axons, which forms a regeneration tube or tunnel crucial for repaired peripheral axon guidance.

Reflex Arc

An automatic, involuntary neural pathway that maintains homeostasis, consisting of five components: a receptor, a sensory neuron, an interneuron, a motor neuron, and an effector.

Saltatory Conduction

The rapid mode of nerve impulse propagation along a myelinated axon, where action potentials are generated only at unmyelinated nodes of Ranvier and local electrical current appears to jump from node to node.

Depolarization

The initial phase of an action potential during which a stimulus causes stimulus-gated and voltage-gated $\text{Na}^+$ channels to open, resulting in an inward diffusion of $\text{Na}^+$ that drives the membrane potential toward a peak of $+30\,\text{mV}$.

Repolarization

The recovery phase of an action potential that begins when voltage-gated $\text{Na}^+$ channels inactivate and voltage-gated $\text{K}^+$ channels open, allowing outward diffusion of $\text{K}^+$ to re-establish negative interior polarity.

Bands of Bungner

Columns of proliferating Schwann cells that line up within the neurilemma tunnel after peripheral nerve injury to guide axonal sprouts back to the appropriate effector.

Subarachnoid Space

The meningeal space situated between the arachnoid mater and the pia mater that contains cerebrospinal fluid (CSF) and major cerebral vessels; bleeding in this space is clinically dangerous.

Primary Motor Cortex

The somatic motor control area located on the precentral gyrus of the frontal lobe that initiates efferent action potentials directing voluntary skeletal muscle contraction.

Primary Somatosensory Cortex

The sensory receptive area located on the postcentral gyrus in the parietal lobe that receives and interprets sensory inputs for temperature, touch, pressure, and pain.

Broca's Area

The motor speech area located in the inferior portion of the frontal lobe (usually in the left hemisphere) that coordinates the muscular movements required to articulate words.

Wernicke's Area

The language comprehension center situated in the posterior temporal lobe of the dominant hemisphere responsible for the understanding and interpretation of spoken and written language.

Prefrontal Cortex

The anterior cortical region of the frontal lobes that governs complex intellectual operations, reasoning, judgment, planning, abstract thought, and conscience.

Gnostic Area

The general interpretation area where the parietal, temporal, and occipital lobes converge, responsible for integrating complex multi-sensory associations, thoughts, and word recognition patterns.

Basal Ganglia

Subcortical clusters of gray matter—including the caudate nucleus, putamen, and globus pallidus—that regulate skeletal muscle tone, coordinate voluntary movements, and control posture.

Thalamus

The major sensory relay station located in the diencephalon that filters and routes sensory information from ascending tracts to specific areas of the cerebral cortex.

Hypothalamus

The central homeostatic regulator of the diencephalon that governs visceral functions, autonomic rhythms, hunger, thirst, and body temperature, while providing a link between the nervous and endocrine systems.

Limbic System

An interconnected network of gray matter structures—including the hippocampus, amygdala, and parts of the hypothalamus—that controls emotions (such as aggression), emotional meaning, and learning/memory.

Medulla Oblongata

The inferior portion of the brainstem containing vital autonomic reflex centers (cardiac, vasomotor, and respiratory centers) as well as the crossing motor tracts known as the decussation of pyramids.

Arbor Vitae

The distinctive tree-like internal branching pattern of cerebellar white matter responsible for relaying sensory and motor information to maintain posture, balance, and coordination.

Conus Medullaris

The tapering, cone-shaped inferior anatomical terminus of the spinal cord located approximately at the level of the first lumbar vertebra ($L1$).

Cauda Equina

The bundle of lumbar, sacral, and coccygeal spinal nerve roots that extends inferiorly through the lower vertebral canal beneath the conus medullaris.

Expressive Aphasia

A motor speech impairment resulting from injury to Broca's area in the dominant frontal lobe, in which the patient understands language but cannot speak or write fluently.

Receptive Aphasia

A sensory language impairment caused by damage to Wernicke's area in the temporal lobe, causing an inability to comprehend or process spoken or written communication.

Dysarthria

A motor dysfunction affecting the coordination and control of muscles used in vocalization, resulting in distorted or slurred speech without impairing linguistic comprehension.

Cushing's Reflex

A systemic compensatory cardiovascular response to cerebral ischemia caused by elevated intracranial pressure, characterized by severe hypertension, widened pulse pressure, and bradycardia.

Papilledema

Edema and swelling of the optic disc caused by increased intracranial pressure transmitted along the optic nerve sheath.

Transient Ischemic Attack

A temporary, localized reduction in cerebral blood flow producing brief neurological deficits without permanent damage, often acting as a warning sign for an impending stroke.

Cerebrovascular Accident

An infarction of brain tissue resulting from severe vascular obstruction (thrombus or embolus) or rupture (hemorrhage); irreversible neural necrosis begins after approximately $5\,\text{minutes}$ of total ischemia.

Contrecoup Injury

A contusion or brain tissue laceration occurring on the side of the brain opposite the primary point of impact as the brain decelerates and bounces against the inner skull surface.

Epidural Hematoma

An arterial bleed developing in the potential space between the dura mater and the cranial bones, typically manifesting severe signs of intracranial compression within a few hours.

Subdural Hematoma

An accumulation of venous blood situated between the dura mater and the arachnoid mater that can present acutely or subacutely and breaks down approximately 7 days post-injury.

Noncommunicating Hydrocephalus

A form of obstructive hydrocephalus, common in infants, in which cerebrospinal fluid flow through the internal ventricular system is blocked by a physical obstruction such as aqueductal stenosis.

Communicating Hydrocephalus

A type of hydrocephalus where cerebrospinal fluid moves freely through the ventricles but accumulates due to impaired absorption across the arachnoid villi into the dural venous sinuses.

Multiple Sclerosis

A chronic neurodegenerative disease characterized by progressive demyelination of nerve fibers in the brain, spinal cord, and cranial nerves, followed by the formation of sclerotic plaques.

Parkinson Disease

A progressive extrapyramidal motor disorder linked to degeneration of basal nuclei and dopamine deficiency, characterized by resting tremors, muscle rigidity, stooped posture, and a shuffling gait.

Amyotrophic Lateral Sclerosis

A progressive, fatal degenerative disease (Lou Gehrig disease) characterized by concurrent destruction of upper and lower motor neurons without inflammation or loss of cognitive function, leading to death via respiratory failure.

Myasthenia Gravis

An autoimmune disorder characterized by autoantibodies against acetylcholine ($\text{ACh}$) receptors at the neuromuscular junction, producing progressive skeletal muscle weakness that usually affects facial and ocular muscles first.

Herniated Intervertebral Disk

A spinal condition where the gelatinous nucleus pulposus protrudes through a tear in the fibrous annulus fibrosus, frequently compressing adjacent spinal nerves in the lumbosacral region.