Central Nervous System Anatomy and Physiology

Vocabulary practice cards covering the structural organization, functional regions, protective coverings, and neural pathways of the central nervous system.

Central nervous system (CNS)

The division of the nervous system consisting of the brain and spinal cord that serves as the integrative and control centers.

Peripheral nervous system (PNS)

The division of the nervous system consisting of cranial nerves and spinal nerves that serves as communication lines between the CNS and the rest of the body.

Sensory (afferent) division

Somatic and visceral sensory nerve fibers that conduct impulses from sensory receptors to the CNS.

Motor (efferent) division

Motor nerve fibers that conduct impulses from the CNS to effectors such as muscles and glands.

Somatic nervous system

The voluntary motor division of the PNS that conducts impulses from the CNS to skeletal muscles.

Autonomic nervous system (ANS)

The involuntary visceral motor division of the PNS that conducts impulses from the CNS to cardiac muscle, smooth muscle, and glands.

Sympathetic division

A functional subdivision of the autonomic nervous system that mobilizes body systems during activity.

Parasympathetic division

A functional subdivision of the autonomic nervous system that conserves energy and promotes house-keeping functions during rest.

Gray matter

Neural tissue composed of short, nonmyelinated neurons and neuron cell bodies.

White matter

Neural tissue composed mostly of myelinated axons, with some nonmyelinated axons.

Cortex

An outer superficial layer of gray matter found in both the cerebrum and the cerebellum.

Ventricular system

Fluid-filled chambers within the brain that are continuous with one another and the central canal of the spinal cord, lined by ependymal cells and filled with cerebrospinal fluid (CSF).

Interventricular foramen

The channel that connects each paired lateral ventricle to the third ventricle.

Cerebral aqueduct

The slender canal connecting the third ventricle to the fourth ventricle in the brainstem.

Gyri

Elevated ridges of tissue marking the surface of the cerebral hemispheres.

Sulci

Shallow grooves that separate gyri on the surface of the cerebral hemispheres.

Fissures

Deep grooves in the brain surface, such as the longitudinal fissure and transverse cerebral fissure.

Longitudinal fissure

The deep median fissure that separates the right and left cerebral hemispheres.

Transverse cerebral fissure

The deep groove separating the cerebrum from the cerebellum below.

Central sulcus

The groove that separates the frontal lobe from the parietal lobe.

Parieto-occipital sulcus

The groove located on the medial surface of the hemisphere that separates the occipital lobe from the parietal lobe.

Lateral sulcus

The groove outlining the temporal lobe and separating it from the overlying frontal and parietal lobes.

Cerebral cortex

The superficial gray matter layer of the cerebrum referred to as the 'executive suite' of the brain, functioning as the site of the conscious mind.

Primary motor cortex

Cortical area located in the precentral gyrus of the frontal lobe containing large pyramidal cells that allow conscious control of precise, skilled, voluntary skeletal muscle movements.

Somatotopy

The spatial point-for-point mapping of body structures and muscles to specific areas in the primary motor and somatosensory cortices.

Premotor cortex

Cortical motor area located anterior to the precentral gyrus that acts as a 'staging area' for planning movements, controlling patterned motor skills, and coordinating simultaneous or sequential actions.

Broca's area

A motor speech area located anterior to the inferior premotor area that directs the muscles involved in speech production.

Frontal eye field

Cortical motor area located partially in and anterior to the premotor cortex that controls voluntary eye movements.

Primary somatosensory cortex

Area located in the postcentral gyrus of the parietal lobe that receives general sensory information from the skin and proprioceptors, capable of spatial discrimination.

Somatosensory association cortex

Area lying posterior to the primary somatosensory cortex that integrates sensory inputs to determine the size, texture, and relationship of parts of objects being felt.

Primary visual cortex

Cortical region on the extreme posterior tip of the occipital lobe that receives visual information originating from the retinas.

Visual association area

Cortical region surrounding the primary visual cortex that uses past visual experiences to interpret visual stimuli, such as recognizing faces.

Primary auditory cortex

Area on the superior margin of the temporal lobe that interprets impulses from the inner ear as pitch, loudness, and location.

Auditory association area

Area located posterior to the primary auditory cortex that stores sound memories and permits perception of sound stimuli.

Primary olfactory cortex

Cortical area on the medial aspect of the temporal lobe involved in the conscious awareness of odors.

Gustatory cortex

Cortical area in the insula deep to the temporal lobe involved in the perception of taste.

Prefrontal cortex (Anterior association area)

The most complicated cortical region, involved with intellect, cognition, recall, personality, and working memory required for abstract ideas, judgment, reasoning, and planning.

Posterior association area

Large multimodal area spanning temporal, parietal, and occipital lobes that recognizes patterns and faces, localizes us in space, and contains Wernicke's area for understanding language.

Limbic association area

Multimodal association area consisting of the cingulate gyrus, parahippocampal gyrus, and hippocampus that provides emotional impact to experiences and helps establish memories.

Association fibers

Horizontally running myelinated fibers within cerebral white matter that connect different parts of the same cerebral hemisphere.

Commissural fibers

Horizontally running myelinated fibers that connect corresponding gray areas of the two cerebral hemispheres, with the largest being the corpus callosum.

Projection fibers

Vertically running fibers that enter the cerebral cortex from lower brain or spinal cord centers, or descend from the cortex to lower areas (forming the internal capsule and corona radiata).

Basal nuclei

Islands of gray matter deep within cerebral white matter—comprising the caudate nucleus, putamen, and globus pallidus—that regulate motor intensity and inhibit antagonistic or unnecessary movements.

Thalamus

Bilateral egg-shaped nuclei in the diencephalon that act as the main relay station for incoming sensory impulses traveling to the cerebral cortex, sorting and editing ascending input.

Hypothalamus

Inferior region of the diencephalon serving as the chief visceral control and regulating center, maintaining homeostasis by regulating the ANS, body temperature, hunger, thirst, sleep-wake cycles, and endocrine secretions.

Epithalamus

The most dorsal portion of the diencephalon containing the pineal gland, which secretes melatonin to help regulate the sleep-wake cycle.

Brain stem

A region composed of the midbrain, pons, and medulla oblongata that controls automatic behaviors necessary for survival and contains nuclei associated with $10$ of the $12$ pairs of cranial nerves.

Cerebral peduncles

Structures on the anterior surface of the midbrain containing large sensory and motor tracts (crus cerebri) running to and from the cerebrum.

Corpora quadrigemina

Paired dorsal protrusions of the midbrain tectum consisting of the superior colliculi (visual reflex centers) and inferior colliculi (auditory relay centers).

Pons

Brainstem structure consisting of longitudinal conduction tracts connecting higher brain centers with the spinal cord, and transversal/dorsal fibers relaying impulses between the motor cortex and cerebellum.

Medulla oblongata

Inferior brainstem structure functioning as an autonomic reflex center, containing the cardiovascular, vasomotor, and respiratory centers, as well as pathways for vomiting, swallowing, and coughing.

Pyramids

Two ventral longitudinal ridges on the medulla oblongata formed by large pyramidal (corticospinal) motor tracts.

Olives

Oval swellings located lateral to the pyramids in the medulla oblongata that relay sensory information on muscle and joint stretch to the cerebellum.

Cerebellum

Brain region responsible for processing input from the motor cortex, brain stem, and sensory receptors to provide precise, smooth, coordinated skeletal muscle movements and balance.

Vermis

The wormlike median structure that connects the two cerebellar hemispheres.

Folia

Transversely oriented, platelike gyri located on the surface of the cerebellum.

Arbor vitae

The distinctive branching, treelike pattern of white matter seen in a sagittal section of the cerebellum.

Limbic system

A functional brain network including the hippocampus, amygdaloid body, and cingulate gyrus that mediates emotional responses and processes memories.

Reticular activating system (RAS)

A functional network within the brain stem reticular formation that sends continuous impulses to the cerebral cortex to keep it alert, filtering incoming sensory stimuli.

Dura mater

The strongest and outermost meninx, consisting of an outer periosteal layer attached to the skull and an inner meningeal layer extending into the vertebral canal.

Dural venous sinuses

Venous channels formed where the periosteal and meningeal layers of dura mater separate, collecting venous blood and draining CSF.

Dural septa

Inward folds of the meningeal dura mater—including the falx cerebri, falx cerebelli, and tentorium cerebelli—that divide the cranial cavity and limit excessive movement of the brain.

Arachnoid mater

The middle meninx characterized by web-like extensions, separated from the underlying pia mater by the subarachnoid space.

Arachnoid granulations

Knoblike projections of arachnoid mater protruding through the dura mater into the superior sagittal sinus that permit CSF reabsorption into venous blood.

Pia mater

Delicate, highly vascularized connective tissue layer that clings tightly to every contour and convolution of the brain and spinal cord.

Meningitis

Inflammation of the meninges, typically diagnosed by observing microbes in a CSF sample obtained via lumbar puncture.

Encephalitis

Inflammation of the brain tissue itself, often occurring when meningitis spreads into the CNS.

Cerebrospinal fluid (CSF)

A liquid cushion formed from blood plasma that gives buoyancy to CNS structures (reducing brain weight by $97\%$), protects against physical trauma, and nourishes brain tissue.

Choroid plexus

A cluster of capillaries enclosed by ependymal cells located on the roof of each ventricle that filters blood to form CSF; adult volume of $\sim 150\,\text{ml}$ is replaced every $8\,\text{hours}$.

Hydrocephalus

A condition caused by an obstruction in CSF circulation or drainage, causing increased fluid accumulation and intracranial pressure.

Blood brain barrier

A protective mechanism maintaining brain homeostasis composed of continuous capillary endothelial cells joined by tight junctions, a thick basement membrane, and bulbous astrocyte feet.

Conus medullaris

The cone-shaped terminal tapering end of the spinal cord located at the level of the $L_1$ or $L_2$ vertebra.

Filum terminale

A fibrous extension of the pia mater extending from the conus medullaris to the coccyx, anchoring the spinal cord in place.

Cauda equina

The collection of nerve roots resembling a horse's tail situated at the inferior end of the vertebral canal.

Epidural space

The space located between the bony vertebrae and the spinal dura mater containing a cushion of adipose tissue and a network of veins.

Ventral roots

Paired spinal roots containing motor neuron axons that emerge from the ventral horn and exit the spinal cord to supply effectors.

Dorsal roots

Paired spinal roots that transmit sensory input into the spinal cord, containing fan-like dorsal rootlets and a dorsal root ganglion.

Dorsal root ganglion

An enlarged swelling on the dorsal root of each spinal nerve that houses the cell bodies of sensory neurons.

Dorsal horns

Posterior projections of spinal cord gray matter consisting of interneurons that receive somatic and visceral sensory input.

Ventral horns

Anterior projections of spinal cord gray matter consisting of somatic motor neurons and some interneurons.

Lateral horns

Lateral projections of spinal cord gray matter present exclusively in the thoracic and superior lumbar segments, consisting of autonomic (sympathetic) motor neurons.

Gray commissure

The crossbar of gray matter enclosing the central canal that connects the lateral masses of gray matter on either side of the spinal cord.

Decussation

The anatomical crossing of nerve tracts from one side of the CNS to the contralateral side within neuronal pathways.

First-order neuron

A primary sensory neuron with cell bodies in a ganglion that conducts impulses from cutaneous receptors and proprioceptors into the spinal cord or medulla.

Second-order neuron

An interneuron with cell bodies located in the dorsal horn of the spinal cord or medullary nuclei whose axons transmit impulses to the thalamus or cerebellum.

Third-order neuron

An interneuron with cell bodies located in the thalamus whose axons project to the primary somatosensory cortex of the cerebrum.

Upper motor neurons

Pyramidal cells located in the primary motor cortex (or subcortical motor nuclei) whose axons descend to synapse on lower motor neurons.

Lower motor neurons

Ventral horn motor neurons of the spinal cord (or cranial nerve motor nuclei) whose axons directly innervate skeletal muscle fibers.