Central and Peripheral Nervous Systems

Comprehensive vocabulary flashcards covering the functional anatomy, divisions, gray and white matter pathways, cranial nerves, and spinal plexuses of the human central and peripheral nervous systems.

Central Nervous System (CNS)

The structural division of the nervous system comprising the brain and the spinal cord.

Ventricles

Internal cavities within the brain that are filled with protective cerebrospinal fluid (CSF).

Sulci

Shallow grooves located on the superficial surface of the cerebral hemispheres.

Fissures

Deep grooves that separate superficial parts of the brain.

Gyri

Elevated ridges of gray matter located between the sulci that increase the surface area of the brain while decreasing the space it occupies.

Cerebral Cortex

An outer region of gray matter that forms the most complex functional part of the brain, composed predominantly of neocortex and dedicated to conscious processes.

Primary Motor Cortex

A motor area located in the precentral gyrus of the frontal lobe that plans and executes voluntary movement.

Premotor Cortex

An association area located widespread throughout the lateral and medial frontal lobe that plans and executes complex movement.

Frontal Eye Fields

An association area positioned anterior to the premotor cortex responsible for back-and-forth eye movements.

Primary Somatosensory Cortex (S1)

A sensory area situated in the postcentral gyrus of the parietal lobe that interprets incoming somatic sensory stimuli.

Somatosensory Association Cortex (S2)

An association area located posterior to the primary somatosensory cortex in the parietal lobe that integrates somatic sensory stimuli.

Broca's Area

An association area located in the superolateral frontal lobe responsible for language production.

Wernicke's Area

An association area located in the superolateral temporal lobe responsible for language comprehension.

Prefrontal Cortex

An association cortex located in the anterior frontal lobe responsible for planning, personality, and higher cognitive functions.

Basal Nuclei

Clusters of neuron cell bodies (gray matter) situated deep within each cerebral hemisphere—including the caudate nucleus, putamen, and globus pallidus—that inhibit involuntary movement and initiate voluntary movement.

Commissural Fibers

White matter tracts that connect the right and left cerebral hemispheres, the largest group of which forms the corpus callosum.

Projection Fibers

White matter tracts that connect the cerebral cortex of one hemisphere with other areas of the same hemisphere, other regions of the brain, and the spinal cord.

Association Fibers

White matter fibers restricted to a single hemisphere that connect the gray matter of adjacent and distant cortical gyri with one another.

Fornix

The primary white matter output tract of the limbic system.

Hippocampus

A nucleus of the limbic system that is critically involved in learning and memory.

Amygdala

A nucleus of the limbic system that is primarily involved in the behavioral expression of emotion, particularly fear.

Thalamus

A diencephalic structure that controls the entry of sensory information into the cerebral cortex by editing, sorting, and routing stimuli.

Hypothalamus

A diencephalic region that regulates the autonomic nervous system, the sleep/wake cycle, thirst, hunger, body temperature, produces ADH and oxytocin, and controls hormone secretion from the anterior pituitary gland.

Epithalamus

A component of the diencephalon whose primary endocrine structure secretes melatonin.

Subthalamus

A paired structure of the diencephalon that works closely with the basal nuclei to regulate voluntary movement.

Cerebellum

A brain division located posterior to the brainstem and inferior to the occipital lobes that coordinates voluntary muscle contractions, maintains balance and posture, and facilitates motor learning by reducing motor error.

Brainstem

A major brain region connecting the cerebrum and diencephalon to the spinal cord, consisting of the midbrain, pons, and medulla oblongata.

Pons

The middle portion of the brainstem that regulates breathing, contributes to movement, and regulates the sleep/wake cycle.

Medulla Oblongata

The inferior portion of the brainstem containing the pyramids where motor tracts decussate, responsible for regulating vital autonomic functions.

Reticular Formation

A collection of interconnected nuclei forming the central core of the brainstem involved in sleep, arousal, pain transmission, mood regulation, and homeostasis.

Reticular Activating System (RAS)

The functional ascending component of the reticular formation that relays sensory stimuli through the thalamus to the cerebrum to maintain wakefulness, alertness, and consciousness.

Anterior (Ventral) Horn

The anterior gray matter region of the spinal cord that houses cell bodies of somatic motor neurons innervating skeletal muscle.

Posterior (Dorsal) Horn

The posterior gray matter region of the spinal cord containing interneurons and axons of sensory neurons that process incoming somatic and visceral sensory signals.

Lateral Horn

Spinal gray matter found only between thoracic level T1 and the lumbar region, housing cell bodies of autonomic motor neurons that control smooth muscle, cardiac muscle, and glands.

Funiculi

Three large paired regions of spinal white matter (posterior, lateral, and anterior) composed of organized ascending and descending myelinated axon tracts.

Peripheral Nervous System (PNS)

The nervous system division outside the brain and spinal cord that detects sensory stimuli, converts them into action potentials, and transmits motor commands to effectors.

Mixed Nerves

Nerves that contain both sensory (afferent) and motor (efferent) axons, allowing bidirectional signal conduction.

Posterior (Dorsal) Root Ganglion

An enlargement on the posterior root of a spinal nerve that houses the cell bodies of pseudounipolar sensory neurons.

Ramus Communicans

A small branch of the anterior ramus containing visceral motor autonomic fibers belonging to the sympathetic nervous system.

Nerve Plexus

A complicated network of intersecting nerves formed exclusively by the anterior rami of certain spinal nerves.

Olfactory Nerve (CN I)

A purely sensory cranial nerve dedicated to conveying the special sense of smell (olfaction).

Optic Nerve (CN II)

A purely sensory cranial nerve that transmits visual stimuli from the retina of the eye to the brain.

Oculomotor Nerve (CN III)

A predominantly motor cranial nerve providing somatic motor control to four extrinsic eye muscles and the levator palpebrae superioris, as well as parasympathetic innervation to the sphincter pupillae and ciliary muscle.

Accommodation

The physiological adjustment wherein the ciliary muscle contracts, moving the ciliary body closer to the lens, releasing suspensory ligament tension and allowing the lens to round up for near vision.

Trochlear Nerve (CN IV)

A motor cranial nerve containing somatic motor axons that innervate the superior oblique muscle to move the eye medially and inferiorly.

Trigeminal Nerve (CN V)

A mixed cranial nerve with three branches (ophthalmic, maxillary, and mandibular) that provides facial somatic sensation and motor innervation to the temporalis and masseter muscles for mastication.

Abducens Nerve (CN VI)

A motor cranial nerve supplying somatic motor innervation exclusively to the lateral rectus muscle to abduct the eye laterally.

Facial Nerve (CN VII)

A mixed cranial nerve providing taste sensation to the anterior two-thirds of the tongue, somatic motor control to muscles of facial expression, and parasympathetic control to the lacrimal, submandibular, sublingual, and nasal glands.

Vestibulocochlear Nerve (CN VIII)

A sensory cranial nerve formed by the fusion of vestibular and cochlear nerves, mediating equilibrium, balance, spatial orientation, and hearing.

Glossopharyngeal Nerve (CN IX)

A mixed cranial nerve mediating taste on the posterior one-third of the tongue, swallowing movements of the pharynx, and parasympathetic salivation from the parotid gland.

Vagus Nerve (CN X)

The extensive mixed cranial nerve that exits the head and neck to innervate thoracic and abdominal viscera, swallowing/speech muscles, pharyngeal taste buds, and chemoreceptors monitoring blood $CO_2$.

Accessory Nerve (CN XI)

A motor cranial nerve whose fibers innervate muscles of speech in the larynx, along with the sternocleidomastoid and trapezius muscles.

Hypoglossal Nerve (CN XII)

A motor cranial nerve innervating intrinsic and extrinsic tongue muscles for speech and manipulation, possessing no role in taste sensation.

Phrenic Nerve

The critical motor branch of the cervical plexus ($\text{C}_3-\text{C}_5$) that innervates the diaphragm and drives ventilation.

Femoral Nerve

The largest nerve of the lumbar plexus ($\text{L}_2-\text{L}_4$ posterior division) providing motor supply to the quadriceps femoris, iliopsoas, and sartorius, and sensory innervation to the anterior thigh, medial thigh, medial leg, and foot.

Sciatic Nerve

The largest nerve of the sacral plexus ($\text{L}_4-\text{S}_3$) that travels through the posterior thigh before splitting into the tibial and common fibular nerves.