Anatomy of the Nervous System Key Terms

abducens nerve

sixth cranial nerve; responsible for contraction of one of the extraocular muscles

alar plate

developmental region of the spinal cord that gives rise to the posterior horn of the gray matter

amygdala

nucleus deep in the temporal lobe of the cerebrum that is related to memory and emotional behavior

anterior column

white matter between the anterior horns of the spinal cord composed of many different groups of axons of both ascending and descending tracts

anterior horn

gray matter of the spinal cord containing multipolar motor neurons, sometimes referred to as the ventral horn

anterior median fissure

deep midline feature of the anterior spinal cord, marking the separation between the right and left sides of the cord

anterior spinal artery

blood vessel from the merged branches of the vertebral arteries that runs along the anterior surface of the spinal cord

arachnoid granulation

outpocket of the arachnoid membrane into the dural sinuses that allows for reabsorption of CSF into the blood

arachnoid mater

middle layer of the meninges named for the spider-web–like trabeculae that extend between it and the pia mater

arachnoid trabeculae

filaments between the arachnoid and pia mater within the subarachnoid space

ascending tract

central nervous system fibers carrying sensory information from the spinal cord or periphery to the brain

axillary nerve

systemic nerve of the arm that arises from the brachial plexus

basal forebrain

nuclei of the cerebrum related to modulation of sensory stimuli and attention through broad projections to the cerebral cortex, loss of which is related to Alzheimer’s disease

basal nuclei

nuclei of the cerebrum (with a few components in the upper brain stem and diencephalon) that are responsible for assessing cortical movement commands and comparing them with the general state of the individual through broad modulatory activity of dopamine neurons; largely related to motor functions, as evidenced through the symptoms of Parkinson’s and Huntington’s diseases

basal plate

developmental region of the spinal cord that gives rise to the lateral and anterior horns of gray matter

basilar artery

blood vessel from the merged vertebral arteries that runs along the dorsal surface of the brain stem

brachial plexus

nerve plexus associated with the lower cervical spinal nerves and first thoracic spinal nerve

brain stem

region of the adult brain that includes the midbrain, pons, and medulla oblongata and develops from the mesencephalon, metencephalon, and myelencephalon of the embryonic brain

Broca's area

region of the frontal lobe associated with the motor commands necessary for speech production and located only in the cerebral hemisphere responsible for language production, which is the left side in approximately 95 percent of the population

Brodmann's areas

mapping of regions of the cerebral cortex based on microscopic anatomy that relates specific areas to functional differences, as described by Brodmann in the early 1900s

carotid canal

opening in the temporal bone through which the internal carotid artery enters the cranium

cauda equina

bundle of spinal nerve roots that descend from the lower spinal cord below the first lumbar vertebra and lie within the vertebral cavity; has the appearance of a horse's tail

caudate

nucleus deep in the cerebrum that is part of the basal nuclei; along with the putamen, it is part of the striatum

central canal

hollow space within the spinal cord that is the remnant of the center of the neural tube

central sulcus

surface landmark of the cerebral cortex that marks the boundary between the frontal and parietal lobes

cephalic flexure

curve in midbrain of the embryo that positions the forebrain ventrally

cerebellum

region of the adult brain connected primarily to the pons that developed from the metencephalon (along with the pons) and is largely responsible for comparing information from the cerebrum with sensory feedback from the periphery through the spinal cord

cerebral aqueduct

connection of the ventricular system between the third and fourth ventricles located in the midbrain

cerebral cortex

outer gray matter covering the forebrain, marked by wrinkles and folds known as gyri and sulci

cerebral hemisphere

one half of the bilaterally symmetrical cerebrum

cerebrum

region of the adult brain that develops from the telencephalon and is responsible for higher neurological functions such as memory, emotion, and consciousness

cervical plexus

nerve plexus associated with the upper cervical spinal nerves

choroid plexus

specialized structures containing ependymal cells lining blood capillaries that filter blood to produce CSF in the four ventricles of the brain

circle of Willis

unique anatomical arrangement of blood vessels around the base of the brain that maintains perfusion of blood into the brain even if one component of the structure is blocked or narrowed

common carotid artery

blood vessel that branches off the aorta (or the brachiocephalic artery on the right) and supplies blood to the head and neck

corpus callosum

large white matter structure that connects the right and left cerebral hemispheres

cranial nerve

one of twelve nerves connected to the brain that are responsible for sensory or motor functions of the head and neck

cranial nerve ganglion

sensory ganglion of cranial nerves

descending tract

central nervous system fibers carrying motor commands from the brain to the spinal cord or periphery

diencephalon

region of the adult brain that retains its name from embryonic development and includes the thalamus and hypothalamus

direct pathway

connections within the basal nuclei from the striatum to the globus pallidus internal segment and substantia nigra pars reticulata that disinhibit the thalamus to increase cortical control of movement

disinhibition

disynaptic connection in which the first synapse inhibits the second cell, which then stops inhibiting the final target

dorsal (posterior) nerve root

axons entering the posterior horn of the spinal cord

dorsal (posterior) root ganglion

sensory ganglion attached to the posterior nerve root of a spinal nerve

dura mater

tough, fibrous, outer layer of the meninges that is attached to the inner surface of the cranium and vertebral column and surrounds the entire CNS

dural sinus

any of the venous structures surrounding the brain, enclosed within the dura mater, which drain blood from the CNS to the common venous return of the jugular veins

endoneurium

innermost layer of connective tissue that surrounds individual axons within a nerve

enteric nervous system

peripheral structures, namely ganglia and nerves, that are incorporated into the digestive system organs

enteric plexus

neuronal plexus in the wall of the intestines, which is part of the enteric nervous system

epineurium

outermost layer of connective tissue that surrounds an entire nerve

epithalamus

region of the diecephalon containing the pineal gland

esophageal plexus

neuronal plexus in the wall of the esophagus that is part of the enteric nervous system

extraocular muscles

six skeletal muscles that control eye movement within the orbit

facial nerve

seventh cranial nerve; responsible for contraction of the facial muscles and for part of the sense of taste, as well as causing saliva production

fascicle

small bundles of nerve or muscle fibers enclosed by connective tissue

femoral nerve

systemic nerve of the anterior leg that arises from the lumbar plexus

fibular nerve

systemic nerve of the posterior leg that begins as part of the sciatic nerve

foramen magnum

large opening in the occipital bone of the skull through which the spinal cord emerges and the vertebral arteries enter the cranium

forebrain

anterior region of the adult brain that develops from the prosencephalon and includes the cerebrum and diencephalon

fourth ventricle

the portion of the ventricular system that is in the region of the brain stem and opens into the subarachnoid space through the median and lateral apertures

frontal eye field

region of the frontal lobe associated with motor commands to orient the eyes toward an object of visual attention

frontal lobe

region of the cerebral cortex directly beneath the frontal bone of the cranium

gastric plexuses

neuronal networks in the wall of the stomach that are part of the enteric nervous system

globus pallidus

nuclei deep in the cerebrum that are part of the basal nuclei and can be divided into the internal and external segments

glossopharyngeal nerve

ninth cranial nerve; responsible for contraction of muscles in the tongue and throat and for part of the sense of taste, as well as causing saliva production (SENSORY & MOTOR)

gyrus

ridge formed by convolutions on the surface of the cerebrum or cerebellum

hindbrain

posterior region of the adult brain that develops from the rhombencephalon and includes the pons, medulla oblongata, and cerebellum

hippocampus

gray matter deep in the temporal lobe that is very important for long-term memory formation

hypoglossal nerve

twelfth cranial nerve; responsible for contraction of muscles of the tongue (MOTOR)

hypothalamus

major region of the diencephalon that is responsible for coordinating autonomic and endocrine control of homeostasis

indirect pathway

Thought to be involved with inhibition of movement. Connections within the basal nuclei from the striatum through the globus pallidus external segment and subthalamic nucleus to the globus pallidus internal segment/substantia nigra pars compacta that result in inhibition of the thalamus to decrease cortical control of movement

inferior colliculus

half of the midbrain tectum that is part of the brain stem auditory pathway

inferior olive

nucleus in the medulla that is involved in processing information related to motor control

intercostal nerve

systemic nerve in the thoracic cavity that is found between two ribs

internal carotid artery

branch from the common carotid artery that enters the cranium and supplies blood to the brain

interventricular foramina

openings between the lateral ventricles and third ventricle allowing for the passage of CSF

jugular veins

blood vessels that return “used” blood from the head and neck

kinesthesia

general sensory perception of movement of the body

lateral apertures

pair of openings from the fourth ventricle to the subarachnoid space on either side and between the medulla and cerebellum

lateral column

white matter of the spinal cord between the posterior horn on one side and the axons from the anterior horn on the same side; composed of many different groups of axons, of both ascending and descending tracts, carrying motor commands to and from the brain

lateral horn

region of the spinal cord gray matter in the thoracic, upper lumbar, and sacral regions that is the central component of the sympathetic division of the autonomic nervous system

lateral sulcus

surface landmark of the cerebral cortex that marks the boundary between the temporal lobe and the frontal and parietal lobes

lateral ventricles

portions of the ventricular system that are in the region of the cerebrum

limbic cortex

collection of structures of the cerebral cortex that are involved in emotion, memory, and behavior and are part of the larger limbic system

limbic system

structures at the edge (limit) of the boundary between the forebrain and hindbrain that are most associated with emotional behavior and memory formation

longitudinal fissure

large separation along the midline between the two cerebral hemispheres

lumbar plexus

nerve plexus associated with the lumbar spinal nerves

lumbar puncture

procedure used to withdraw CSF from the lower lumbar region of the vertebral column that avoids the risk of damaging CNS tissue because the spinal cord ends at the upper lumbar vertebrae

median aperture

singular opening from the fourth ventricle into the subarachnoid space at the midline between the medulla and cerebellum

median nerve

systemic nerve of the arm, located between the ulnar and radial nerves

meninges

protective outer coverings of the CNS composed of connective tissue

mesencephalon

primary vesicle of the embryonic brain that does not significantly change through the rest of embryonic development and becomes the midbrain

metencephalon

secondary vesicle of the embryonic brain that develops into the pons and the cerebellum

midbrain

middle region of the adult brain that develops from the mesencephalon

myelencephalon

secondary vesicle of the embryonic brain that develops into the medulla

nerve plexus

network of nerves without neuronal cell bodies included

neural crest

tissue that detaches from the edges of the neural groove and migrates through the embryo to develop into peripheral structures of both nervous and non-nervous tissues

neural fold

elevated edge of the neural groove

neural groove

region of the neural plate that folds into the dorsal surface of the embryo and closes off to become the neural tube

neural plate

thickened layer of neuroepithelium that runs longitudinally along the dorsal surface of an embryo and gives rise to nervous system tissue