General Anatomy and Physiology: The Nervous System

Comprehensive vocabulary flashcards covering the structure, organization, neuroglia, meninges, cerebrospinal fluid flow, brain divisions, spinal cord anatomy, reflexes, cranial nerves, and peripheral divisions of the nervous system.

Central Nervous System (CNS)

The division of the nervous system consisting of the brain and spinal cord that integrates incoming sensory information, evaluates information, and initiates outgoing responses.

Peripheral Nervous System (PNS)

The division of the nervous system consisting of nerves that connect the CNS to other body parts, including cranial nerves and spinal nerves.

Sensory Receptors

PNS structures that detect internal or external changes and transmit nerve impulses toward the CNS via afferent (sensory) fibers.

Integration

A central nervous system function involving the evaluation of incoming sensory information to initiate an appropriate outgoing response.

Motor Function

A peripheral nervous system function carried away from the CNS via efferent (motor) fibers to effectors such as skeletal muscle, smooth muscle, cardiac muscle, and glands.

Somatic Nervous System

A voluntary motor subdivision of the peripheral nervous system whose effectors are skeletal muscles.

Autonomic Nervous System (ANS)

An involuntary motor subdivision of the peripheral nervous system whose effectors are cardiac muscle, smooth muscle, and glands.

Synapse

The functional space between neurons across which communication is carried out via neurotransmitters.

Nissl Bodies

Chromatophilic substance in the neuron cell body that consists of rough endoplasmic reticulum (RER).

Neurofibrils

A network of fine threads found within the cell body and axon of a neuron.

Dendrites

Multiple branched neuronal processes that provide receptive surfaces to receive stimuli and conduct electrical signals toward the cell body.

Axon

A single neuronal nerve fiber that conducts impulses away from the cell body, gives off collateral branching, and terminates as an axon terminal containing neurotransmitter-filled vesicles.

Schwann Cells

Neuroglial cells that produce the myelin sheath and neurilemma around axons in the peripheral nervous system (PNS).

Oligodendrocytes

Neuroglial cells that form myelin sheaths around axons within the central nervous system (CNS), lacking a neurilemma.

Nodes of Ranvier

Narrow gaps in the myelin sheath along an axon between adjacent Schwann cells or oligodendrocytes.

Neurilemma

The outer neurilemmal sheath formed by Schwann cells around peripheral axons that plays a vital role in guiding nerve fiber regeneration.

Multipolar Neuron

A neuron having one axon and many dendrites arising from its cell body; comprises most neurons of the brain and spinal cord.

Bipolar Neuron

A neuron whose cell body has only two processes, one axon and one dendrite.

Unipolar Neuron

A neuron with a single process that divides into two branches (a peripheral process and a central process); typical of most sensory neurons.

Sensory (Afferent) Neuron

A neuron that conducts nerve impulses from receptors into the brain or spinal cord; structurally, most are unipolar.

Interneuron

A multipolar neuron located entirely within the brain or spinal cord that links other neurons and serves as a processing center.

Motor (Efferent) Neuron

A multipolar neuron that carries nerve impulses out of the brain or spinal cord to effectors such as muscles or glands.

Astrocytes

Star-shaped neuroglial cells located between blood vessels and neurons in the CNS that provide support, regulate ion concentration and metabolism, and aid in repair.

Microglia

Small CNS neuroglial cells that provide structural support and perform phagocytosis of cellular debris and bacteria, proliferating in response to brain or spinal cord injury.

Ependyma

Neuroglial cells that form the inner epithelial-like lining of the brain ventricles and the central canal of the spinal cord to circulate cerebrospinal fluid (CSF).

Meninges

Three protective membranes situated between bone and soft CNS tissue that enclose the brain and spinal cord.

Dura Mater

The tough, outermost layer of the meninges composed of dense connective tissue functioning as internal periosteum, containing blood vessels, nerves, and dural sinuses.

Epidural Space

The protective space between the vertebrae and the dura mater of the spinal cord containing connective tissue and blood vessels.

Arachnoid Mater

The thin, web-like middle membrane of the meninges located between the dura mater and the pia mater.

Pia Mater

The delicate, vascular innermost layer of the meninges that is attached directly to the contours of the brain and spinal cord.

Subarachnoid Space

The space located between the arachnoid mater and pia mater that contains circulating cerebrospinal fluid (CSF).

Meningitis

An inflammation of the meninges.

Choroid Plexuses

Specialized vascular networks located within brain ventricles (predominantly the lateral ventricles) that continuously secrete cerebrospinal fluid at a rate of approximately $500\,\text{ml/day}$.

Arachnoid Granulations

Microscopic projections of the arachnoid mater through which cerebrospinal fluid is reabsorbed into the venous blood of the dural sinuses.

Hydrocephalus

A condition resulting from obstruction of CSF circulation leading to fluid accumulation within the brain ventricles (internal) or the subarachnoid space (external); commonly called 'water on the brain.'

Prosencephalon

The primary embryonic forebrain vesicle that subdivides into the telencephalon and diencephalon.

Mesencephalon

The embryonic midbrain vesicle that gives rise to the midbrain.

Rhombencephalon

The primary embryonic hindbrain vesicle that subdivides into the metencephalon and myelencephalon.

Corpus Callosum

A broad, C-shaped band of myelinated nerve fibers connecting the left and right cerebral hemispheres.

Falx Cerebri

A sickle-shaped fold of dura mater that extends downward into the longitudinal fissure to separate the two cerebral hemispheres.

Convolutions (Gyri)

The elevated ridges or folds on the surface of the cerebrum separated by grooves.

Sulci

Shallow grooves on the surface of the cerebrum separating adjacent gyri.

Fissures

Deep grooves on the brain surface, such as the longitudinal fissure separating the cerebral hemispheres or the transverse fissure separating the cerebrum from the cerebellum.

Basal Nuclei

Masses of gray matter located deep within the cerebral white matter (including the caudate nucleus, putamen, and globus pallidus) that help control motor functions.

Precentral Gyrus

The primary motor area of the cerebral cortex located in the frontal lobe from which corticospinal tracts originate to control voluntary muscle movements.

Broca’s Area

A specialized motor speech area located in the frontal lobe (usually on the left side) that coordinates the muscular actions required for speech.

Postcentral Gyrus

The primary somatosensory cortex located in the parietal lobe that receives and interprets sensory impulses from cutaneous and other receptors.

General Interpretative Area (G.I.A.)

A complex cerebral association area situated where the parietal, temporal, and occipital lobes meet; plays a primary role in complex thought processing.

Thalamus

A diencephalic structure that acts as a major relay station for sensory impulses (except smell), channeling incoming messages to appropriate regions of the cerebral cortex.

Hypothalamus

A region of the diencephalon that regulates vital autonomic visceral activities (body temperature, sleep, appetite, gastrointestinal movements) and connects the nervous system to the endocrine system.

Limbic System

A complex functional group of brain structures controlling emotional experience and expression ('emotional brain') while interpreting the sense of smell.

Reticular Formation

A network of interconnected nerve fibers extending throughout the brainstem that activates the cerebral cortex, filters incoming messages, and regulates wakefulness and consciousness.

Arbor Vitae

The distinctive tree-like branching pattern of white matter seen in a sagittal section of the cerebellum.

Ataxia

A lack of voluntary muscle coordination and loss of balance resulting from damage or disease affecting the cerebellum.

Conus Medullaris

The conical tapering lower end of the spinal cord terminating at the level of the first or second lumbar vertebra ($L_1\text{--}L_2$).

Cauda Equina

A bundle of spinal nerve roots extending inferiorly from the conus medullaris through the lower vertebral canal resembling a horse's tail.

Filum Terminale

A slender thread of connective tissue extending downward from the conus medullaris to anchor the spinal cord to the coccyx.

Dorsal Root Ganglion

A swelling on the posterior root of each spinal nerve containing the cell bodies of sensory (afferent) neurons.

Ventral Root

The anterior motor branch of a spinal nerve containing the axons of efferent motor neurons whose cell bodies reside in the gray matter of the spinal cord.

Reflex Arc

The simplest neural pathway in the nervous system, typically consisting of a receptor, sensory neuron, interneuron (within the CNS), motor neuron, and effector.

Patellar Reflex

A monosynaptic two-neuron stretch reflex initiated by tapping the patellar ligament, resulting in contraction of the quadriceps femoris muscle group.

Withdrawal Reflex

A protective three-neuron spinal reflex arc involving a sensory neuron, interneuron, and motor neuron that contracts flexor muscles to pull a body part away from a painful stimulus.

Epineurium

The outermost dense layer of connective tissue that encases an entire peripheral nerve trunk.

Perineurium

The layer of connective tissue wrapping around individual bundles of nerve fibers called fascicles inside a peripheral nerve.

Endoneurium

A delicate layer of connective tissue that surrounds each individual nerve fiber (axon) within a fascicle.

Olfactory Nerve (CN I)

A purely sensory cranial nerve whose fibers transmit impulses associated with the sense of smell.

Optic Nerve (CN II)

A purely sensory cranial nerve whose fibers transmit impulses associated with the sense of vision.

Oculomotor Nerve (CN III)

A cranial nerve that transmits somatic motor impulses to raise eyelids and move the eyes, alongside autonomic motor fibers that adjust pupil size and lens curvature.

Trochlear Nerve (CN IV)

A primarily motor cranial nerve that transmits impulses to extrinsic muscles that move the eye.

Trigeminal Nerve (CN V)

The largest cranial nerve; a mixed nerve with three major divisions (ophthalmic, maxillary, mandibular) providing sensory input from the face and teeth and motor innervation to the muscles of mastication.

Abducens Nerve (CN VI)

A primarily motor cranial nerve that conducts impulses to extrinsic eye muscles that move the eye.

Facial Nerve (CN VII)

A mixed cranial nerve carrying sensory fibers for taste on the anterior tongue, somatic motor fibers to muscles of facial expression, and autonomic fibers to salivary and tear glands.

Vestibulocochlear Nerve (CN VIII)

A purely sensory cranial nerve consisting of a vestibular branch for the sense of equilibrium and a cochlear branch for hearing.

Glossopharyngeal Nerve (CN IX)

A mixed cranial nerve transmitting sensory impulses from the pharynx, tonsils, and posterior tongue (taste), and motor impulses to muscles used in swallowing and to salivary glands.

Vagus Nerve (CN X)

A major mixed cranial nerve providing somatic motor fibers for speech and swallowing, widespread parasympathetic autonomic motor fibers to thoracic and abdominal viscera, and sensory fibers from visceral organs.

Accessory Nerve (CN XI)

A primarily motor cranial nerve with cranial and spinal branches supplying the soft palate, pharynx, larynx, trapezius, and sternocleidomastoid muscles.

Hypoglossal Nerve (CN XII)

A primarily motor cranial nerve carrying motor impulses to muscles that move the tongue.

Phrenic Nerve

A major branch of the cervical plexus originating from segments $C_3\text{--}C_5$ that provides motor innervation to the diaphragm.

Sciatic Nerve

The largest and longest nerve in the human body, arising from the lumbosacral plexus to supply muscles and skin of the thigh, leg, and foot.

Dermatome

A specific area of skin supplied by sensory nerve fibers from a single spinal nerve, utilized clinically to localize nerve injuries.

Sympathetic Division

The 'fight or flight' division of the autonomic nervous system that prepares the body for energy-expending, stressful, or emergency situations.

Parasympathetic Division

The 'rest and digest' division of the autonomic nervous system that restores resting state and manages active energy-conserving and maintenance functions.