Central Nervous System: Anatomy, Physiology, and Pathology

Comprehensive vocabulary flashcards covering central nervous system embryology, meningeal layers, ventricular CSF circulation, cortical organization, brainstem and cerebellar structures, and key clinical pathologies.

Optogenetics

A biological technique that uses light to activate genetically introduced light-sensitive ion channels, thereby altering neuronal membrane potential, activating selected neural circuits, and producing observable behavioral or physiological effects; recognized in the 2026 Nobel Prize in Physiology or Medicine awarded to Karl Deisseroth, Peter Hegemann, and Georg Nagel.

Neural Tube

The embryonic precursor structure of the central nervous system that develops into the brain and spinal cord, with its internal opening giving rise to the fluid-filled cerebral ventricles.

Neural Tube Defects (NTDs)

Congenital defects resulting from the failure of the embryonic neural tube to close completely (a process normally completed by $28\text{ days}$), categorized by anatomical location and including anencephaly, iniencephaly, craniorachischisis, encephalocele, and spina bifida.

Anencephaly

A severe neural tube defect resulting from failure in the closure of the anterior (cephalad) region of the embryonic neural tube.

Spina Bifida

A developmental neural tube defect that results from failure in the closure of the posterior (caudad) region of the embryonic neural tube.

Cranial Meninges

The three protective connective tissue membranes covering the central nervous system: the outermost dura mater, the web-like middle arachnoid mater, and the delicate innermost pia mater.

Dura Mater

The tough, double-layered outer cranial meninx comprising a periosteal layer attached to the internal skull surface and an inner meningeal layer that forms folds between brain regions.

Falx Cerebri

A prominent crescent-shaped inward fold of the meningeal dura mater that descends vertically into the longitudinal fissure between the left and right cerebral hemispheres.

Tentorium Cerebelli

A transverse horizontal extension of the dura mater that separates the occipital lobes of the cerebrum from the underlying cerebellum.

Blood-Brain Barrier (BBB)

A selective physiological barrier composed of capillary endothelial cells interconnected by tight junctions and supported by astrocyte perivascular feet, preventing harmful substances and pathogens from entering brain tissue while regulating chemical entry.

Cerebrospinal Fluid (CSF)

A clear, plasma-like fluid formed by the choroid plexuses that cushions the brain and spinal cord, provides buoyancy, removes metabolic wastes, and circulates through ventricles, the subarachnoid space, and the spinal central canal.

Choroid Plexus

A specialized vascular network of ependymal cells with tight junctions and fenestrated capillaries situated within the brain ventricles that filters blood to produce cerebrospinal fluid.

Interventricular Foramen

The narrow anatomical channel (foramen of Monro) connecting each lateral ventricle to the centrally located third ventricle.

Cerebral Aqueduct

The narrow conduit passing through the midbrain that conveys cerebrospinal fluid from the third ventricle into the fourth ventricle.

Arachnoid Villi

Finger-like projections of the arachnoid membrane that penetrate into the dural venous sinuses (such as the superior sagittal sinus) to reabsorb cerebrospinal fluid back into the venous circulation.

Cerebrospinal Fluid Flow Pathway

The unidirectional circulatory route of CSF: synthesized in lateral ventricle choroid plexuses $\rightarrow$ passes through interventricular foramina $\rightarrow$ enters third ventricle $\rightarrow$ flows through cerebral aqueduct $\rightarrow$ enters fourth ventricle $\rightarrow$ exits via lateral and median apertures into the subarachnoid space $\rightarrow$ reabsorbed by arachnoid villi into dural venous blood.

Gyri and Sulci

The prominent surface convolutions of the cerebral cortex, where elevated cortical ridges are termed gyri and the intervening shallow grooves are termed sulci.

Lobes of the Cerebrum

The primary structural and functional regions of each cerebral hemisphere, separated by anatomical fissures and sulci: the frontal, parietal, occipital, and temporal lobes.

Precentral Gyrus

The primary motor cortex situated in the frontal lobe anterior to the central sulcus, responsible for initiating and controlling voluntary skeletal muscle contractions.

Postcentral Gyrus

The primary somatosensory cortex located in the parietal lobe immediately posterior to the central sulcus, responsible for receiving and localizing general sensory inputs such as touch, pain, temperature, and proprioception.

Broca's Area

A motor speech region located in the frontal lobe (typically of the left cerebral hemisphere) responsible for speech production and language articulation.

Wernicke's Area

A critical language area located at the junction of the temporal and parietal lobes (usually in the left hemisphere) that governs the comprehension and interpretation of spoken and written words.

Nonfluent Aphasia

A language deficit resulting from damage to Broca's area where individuals retain word meaning and know what they want to say, but are unable to properly coordinate speech muscles to articulate words.

Fluent Aphasia

A language disturbance resulting from damage to Wernicke's area, auditory association area, or common integrative area, wherein patients fluently articulate grammatically intact strings of words that lack cohesive meaning ('word salad').

Corpus Callosum

A massive commissural white matter tract that arches across the midline to connect and transfer signals between the left and right cerebral hemispheres.

Basal Nuclei

Paired subcortical masses of gray matter (including the caudate nucleus, putamen, and globus pallidus) situated deep within the cerebral hemispheres that modulate voluntary movements, suppress unwanted motions, and regulate muscle tone.

Hemispheric Lateralization

The functional specialization of each cerebral hemisphere, where the left hemisphere typically governs reasoning, numerical/scientific abilities, and spoken/written language, while the right hemisphere oversees musical/artistic awareness, spatial/pattern perception, face recognition, and emotional inflection.

Thalamus

The large bilateral gray matter structure of the diencephalon surrounding the third ventricle that serves as the principal sensory relay station for all incoming sensory information (except olfaction) directed to the cerebral cortex.

Hypothalamus

The diencephalic control center located inferior to the thalamus that maintains homeostasis by regulating autonomic activities, body temperature, water balance, appetite, circadian rhythms, and endocrine secretions via the pituitary gland.

Suprachiasmatic Nucleus (SCN)

A specialized nucleus located within the supraoptic region of the anterior hypothalamus that serves as the body's primary biological pacemaker to establish circadian rhythms.

Epithalamus

The posterosuperior region of the diencephalon forming the roof of the third ventricle, containing the melatonin-secreting pineal gland and the odor-responsive habenular nuclei.

Habenular Nuclei

Nuclei located within the epithalamus involved in olfaction, particularly responsible for mediating emotional and visceral responses to specific odors.

Midbrain

The uppermost section of the brain stem containing sensory and motor fiber tracts, the substantia nigra, red nuclei, and cranial nerve nuclei for oculomotor ($\text{CN III}$) and trochlear ($\text{CN IV}$) nerves.

Superior Colliculi

Paired visual reflex centers located on the posterior tectum of the midbrain that coordinate involuntary movements of the eyes, head, and neck in response to visual stimuli.

Inferior Colliculi

Paired auditory reflex centers located on the midbrain tectum that coordinate head and trunk movements in response to sound stimuli.

Pons

The intermediate bulbous region of the brain stem that connects the medulla oblongata to higher brain centers, containing pontine nuclei, vestibular pathways, respiratory centers, and origins for cranial nerves $\text{V}$, $\text{VI}$, $\text{VII}$, and $\text{VIII}$.

Medulla Oblongata

The inferior segment of the brain stem extending from the foramen magnum to the pons, housing vital cardiovascular and respiratory control centers, autonomic reflex centers (swallowing, coughing, vomiting), and nuclei of origin for cranial nerves $\text{VIII}$ through $\text{XII}$.

Cerebellum

The large posterior brain structure consisting of two lateral hemispheres joined by the central vermis, an outer cortex with folia, and internal arbor vitae, primarily functioning to evaluate and coordinate voluntary movements, maintain equilibrium, and sustain posture.

Ataxia

A clinical condition resulting from cerebellar damage or alcohol intoxication that causes an uncoordinated loss of voluntary muscular control, resulting in staggering gait, changed speech cadence, and failure of spatial motor coordination.

Meningitis

An acute infectious inflammation of the protective coverings of the brain and spinal cord (meninges) commonly elicited by pathogens like Neisseria meningitidis, Streptococcus pneumoniae, or viruses, presenting with headache, stiff neck, fever, and photophobia.

Encephalitis

An inflammation of the neural brain parenchyma itself, predominantly caused by viral agents (such as Herpes simplex virus or arboviruses) or autoimmune processes, characterized by fever, confusion, seizures, and focal neurological deficits.

Concussion

A mild traumatic brain injury resulting from mechanical force that leads to microscopic bleeding and shearing of axonal fibers, typically followed by recovery with potential temporary amnesia.

Contusion

A severe traumatic brain injury resulting in macroscopic structural destruction and necrosis of neural tissue, which does not regenerate.

Cerebrovascular Accident (CVA)

Commonly known as a stroke; localized brain infarction caused by ischemia or hemorrhage from a ruptured or occluded cerebral blood vessel, causing tissue death and focal functional deficits.

Alzheimer's Disease

A progressive neurodegenerative disorder marked pathologically by abnormal extracellular amyloid plaques and intraneuronal neurofibrillary tangles, clinically causing insidious memory deterioration, cognitive confusion, and eventual dementia.

Cauda Equina

The bundle of lumbar, sacral, and coccygeal spinal nerve roots that flare inferiorly through the vertebral canal below the termination of the adult spinal cord at vertebral level $T_{12}$.

Dorsal Horn of the Spinal Cord

The posterior gray matter columns of the spinal cord that receive incoming sensory input from peripheral afferent fibers via the dorsal roots.

Ventral Horn of the Spinal Cord

The anterior gray matter columns of the spinal cord containing somatic motor neuron cell bodies that transmit motor commands outward to skeletal muscles via the ventral roots.

Dorsal Root Ganglion

An enlargement on the posterior root of each spinal nerve located outside the spinal cord containing the cell bodies of pseudounipolar sensory neurons.