Chapter 3
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neuraxis
An imaginary line drawn through the center of the length of the central nervous system, from the bottom of the spinal cord to the front of the forebrain.
anterior
With respect to the central nervous system, located near or toward the head.
posterior
With respect to the central nervous system, located near or toward the tail.
rostral
"Toward the beak"; with respect to the central nervous system, in a direction along the neuraxis toward the front of the face.
caudal
"Toward the tail"; with respect to the central nervous system, in a direction along the neuraxis away from the front of the face.
dorsal
"Toward the back"; with respect to the central nervous system, in a direction perpendicular to the neuraxis toward the top of the head or the back.
ventral
"Toward the belly"; with respect to the central nervous system, in a direction perpendicular to the neuraxis toward the bottom of the skull or the front surface of the body.
lateral
Toward the side of the body, in a direction at right angles with the neuraxis and away from it.
medial
Toward the neuraxis, away from the side of the body.
ipsilateral
Located on the same side of the body.
contralateral
Located on the opposite side of the body.
cross section/frontal section
With respect to the central nervous system, a slice taken at right angles to the neuraxis.
horizontal section
A slice through the brain parallel to the ground.
sagittal section
A slice through the brain parallel to the neuraxis and perpendicular to the ground.
midsagittal plane
The plane through the neuraxis perpendicular to the ground; divides the brain into two symmetrical halves.
central nervous system
The brain and spinal cord.
peripheral nervous system
The nerves and ganglia located outside the central nervous system.
vertebral artery
An artery whose branches serve the posterior region of the brain.
internal carotid artery
An artery whose branches serve the rostral and lateral portions of the brain.
meninges
The three layers of tissue that encase the central nervous system: the dura mater, arachnoid membrane, and pia mater.
dura mater
The outermost of the meninges; tough, flexible, unstretchable.
arachnoid membrane
The middle layer of the meninges, between the outer dura mater and inner pia mater. The subarachnoid space beneath the arachnoid membrane is filled with cerebrospinal fluid, which cushions the brain.
pia mater
The layer of the meninges adjacent to the surface of the brain.
subarachnoid space
The fluid-filled space between the arachnoid membrane and the pia mater.
cerebrospinal fluid
A clear fluid, similar to blood plasma, that fills the ventricular system of the brain and the subarachnoid space surrounding the brain and spinal cord.
ventricle
One of the hollow spaces within the brain, filled with cerebrospinal fluid.
lateral ventricle
One of the two ventricles located in the center of the telencephalon.
third ventricle
The ventricle located in the center of the diencephalon.
cerebral aqueduct
A narrow tube interconnecting the third and fourth ventricles of the brain, located in the center of the mesencephalon.
fourth ventricle
The ventricle located between the cerebellum and the dorsal pons, in the center of the metencephalon.
choroid plexus
The highly vascular tissue that protrudes into the ventricles and produces cerebrospinal fluid.
arachnoid granulation
Small projections of the arachnoid membrane through the dura mater into the superior sagittal sinus; CSF flows through them to be reabsorbed into the blood supply.
superior sagittal sinus
A venous sinus located in the midline just dorsal to the brain, between the two cerebral hemispheres.
obstructive hydrocephalus
A condition in which all or some of the brain's ventricles are enlarged; caused by an obstruction that impedes the normal flow of CSF.
forebrain
The most rostral of the three major divisions of the brain; includes the telencephalon and diencephalon.
cerebral hemisphere
One of the two major portions of the forebrain, covered by the cerebral cortex.
subcortical region
The region located within the brain, beneath the cortical surface.
cerebral cortex
The outermost layer of gray matter of the cerebral hemispheres.
sulcus
A groove in the surface of the cerebral hemisphere, smaller than a fissure.
fissure
A major groove in the surface of the brain, larger than a sulcus.
gyrus
A convolution of the cortex of the cerebral hemispheres, separated by sulci or fissures.
primary visual cortex
The region of the cerebral cortex whose primary input is from the visual system.
calcarine fissure
A fissure located in the occipital lobe on the medial surface of the brain; contains most of the primary visual cortex.
primary auditory cortex
The region of the cerebral cortex whose primary input is from the auditory system.
lateral fissure
The fissure that separates the temporal lobe from the overlying frontal and parietal lobes.
primary somatosensory cortex
The region of the cerebral cortex whose primary input is from the somatosensory system.
central sulcus
The sulcus that separates the frontal lobe from the parietal lobe.
primary motor cortex
The region of the cerebral cortex that contains neurons that control movements of skeletal muscles.
frontal lobe
The anterior portion of the cerebral cortex, rostral to the parietal lobe and dorsal to the temporal lobe.
parietal lobe
The region of the cerebral cortex caudal to the frontal lobe and dorsal to the temporal lobe.
temporal lobe
The region of the cerebral cortex rostral to the occipital lobe and ventral to the parietal and frontal lobes.
occipital lobe
The region of the cerebral cortex caudal to the parietal and temporal lobes.
sensory association cortex
Those regions of the cerebral cortex that receive information from the regions of primary sensory cortex.
motor association cortex
The region of the frontal lobe rostral to the primary motor cortex.
prefrontal cortex
The region of the frontal lobe rostral to the motor association cortex.
corpus callosum
The largest commissure of the brain, interconnecting the areas of neocortex on each side of the brain.
neocortex
The phylogenetically newest cortex, including the primary sensory cortex, primary motor cortex, and association cortex.
limbic cortex
Phylogenetically old cortex, located at the edge ("limbus") of the cerebral hemispheres; part of the limbic system.
cingulate gyrus/cingulate cortex
A strip of limbic cortex lying along the lateral walls of the groove separating the cerebral hemispheres, just above the corpus callosum.
commissure
A fiber bundle that interconnects corresponding regions on each side of the brain.
limbic system
A group of brain regions including the anterior thalamic nuclei, amygdala, hippocampus, limbic cortex, and parts of the hypothalamus, as well as their interconnecting fiber bundles.
hippocampus/hippocampal formation
A forebrain structure of the temporal lobe, constituting an important part of the limbic system; includes the hippocampus proper (Ammon's horn), dentate gyrus, and subiculum.
amygdala
A structure in the interior of the rostral temporal lobe, containing a set of nuclei; part of the limbic system.
fornix
A fiber bundle that connects the hippocampus with other parts of the brain, including the mammillary bodies of the hypothalamus.
mammillary bodies/mammillary body
A protrusion of the bottom of the brain at the posterior end of the hypothalamus, containing some hypothalamic nuclei.
basal ganglia
A group of subcortical nuclei in the telencephalon, the caudate nucleus, the globus pallidus, and the putamen; important parts of the motor system.
diencephalon
A region of the forebrain surrounding the third ventricle; includes the thalamus and the hypothalamus.
thalamus
The largest portion of the diencephalon, located above the hypothalamus; contains nuclei that project information to specific regions of the cerebral cortex and receive information from it.
projection fiber
An efferent axon from a neuron in one region of the brain whose terminals form synapses with neurons in another region.
nucleus
An identifiable group of neural cell bodies in the central nervous system.
lateral geniculate nucleus
A group of cell bodies in the thalamus that receives fibers from the retina and projects fibers to the primary visual cortex.
medial geniculate nucleus
A group of cell bodies in the thalamus that receives fibers from the auditory system and projects fibers to the primary auditory cortex.
ventrolateral nucleus
A nucleus of the thalamus that receives inputs from the cerebellum and sends axons to the primary motor cortex.
hypothalamus
The group of nuclei of the diencephalon situated beneath the thalamus; involved in regulation of the autonomic nervous system, control of the anterior and posterior pituitary glands, and integration of species-typical behaviors.
optic chiasm
A cross-shaped connection between the optic nerves, located below the base of the brain, just anterior to the pituitary gland.
anterior pituitary gland
The anterior part of the pituitary gland; an endocrine gland whose secretions are controlled by the hypothalamic hormones.
neurosecretory cell
A neuron that secretes a hormone or hormonelike substance.
posterior pituitary gland
The posterior part of the pituitary gland; an endocrine gland that contains hormone-secreting terminal buttons of axons whose cell bodies lie within the hypothalamus.
midbrain/mesencephalon
The central of the the three major divisions of the brain, surrounds the cerebral aqueduct; includes the tectum and the tegmentum.
tectum
The dorsal part of the midbrain; includes the superior and inferior colliculi.
superior colliculi
Protrusions on top of the midbrain; part of the visual system.
inferior colliculi
Protrusions on top of the midbrain; part of the auditory system.
brain stem
The "stem" of the brain, from the medulla to the diencephalon, excluding the cerebellum.
tegmentum
The ventral part of the midbrain; includes the periaqueductal gray matter, reticular formation, red nucleus, and substantia nigra.
reticular formation
A large network of neural tissue located in the central region of the brain stem, from the medulla to the diencephalon.
periaqueductal gray matter
The region of the midbrain surrounding the cerebral aqueduct; contains neural circuits involved in species-typical behaviors.
red nucleus
A large nucleus of the midbrain that receives inputs from the cerebellum and motor cortex and sends axons to motor neurons in the spinal cord.
substantia nigra
A darkly stained region of the tegmentum that contains neurons that communicate with the caudate nucleus and putamen in the basal ganglia.
hindbrain
The most caudal of the three major divisions of the brain; includes the metencephalon and myelencephalon.
cerebellum
A major part of the brain located dorsal to the pons, containing the two cerebellar hemispheres, covered with the cerebellar cortex; an important component of the motor system.
cerebellar cortex
The cortex that covers the surface of the cerebellum
deep cerebellar nuclei
Nuclei located within the cerebellar hemispheres; receive projections from the cerebellar cortex and send projections out of the cerebellum to other parts of the brain.
cerebellar peduncle
One of three bundles of axons that attach each cerebellar hemisphere to the dorsal pons.
pons
The region of the metencephalon rostral to the medulla, caudal to the midbrain, and ventral to the cerebellum.
medulla/medulla oblongata
The most caudal portion of the brain; located in the myelencephalon, immediately rostral to the spinal cord.
spinal cord
The cord of nervous tissue that extends caudally from the medulla
spinal root
A bundle of axons surrounded by connective tissue that occurs in pairs, which fuse and form a spinal nerve.
cauda equina
A bundle of spinal roots located caudal to the end of the spinal cord.
caudal block
The anesthesia and paralysis of the lower part of the body produced by injection of a local anesthetic into the cerebrospinal fluid surrounding the cauda equina.
dorsal root
The spinal root that contains incoming (afferent) sensory fibers.
ventral root
The spinal root that contains outgoing (efferent) motor fibers.
spinal nerve
A peripheral nerve attached to the spinal cord.
afferent axon
An axon directed toward the central nervous system, conveying sensory information.
efferent axon
An axon directed away from the central nervous system, conveying motor commands.
dorsal root ganglion
A nodule on a dorsal root that contains cell bodies of afferent spinal nerve neurons.
cranial nerve
A peripheral nerve attached directly to the brain.
vagus nerve
The largest of the cranial nerves, conveying efferent fibers of the parasympathetic division of the autonomic nervous system to organs of the thoracic and abdominal cavities.
olfactory bulb
The protrusion at the end of the olfactory nerve; receives input from the olfactory receptors.
somatic nervous system
The part of the peripheral nervous system that controls the movement of skeletal muscles or transmits somatosensory information to the central nervous system.
autonomic nervous system/ANS
The portion of the peripheral nervous system that controls the body's vegetative function.
sympathetic division
The portion of the autonomic nervous system that controls functions that accompany arousal and expenditure of energy.
spinal sympathetic ganglia
Sympathetic ganglia either adjacent to the spinal cord in the sympathetic chain or located in the abdominal cavity.
sympathetic ganglion chain
One of a pair of groups of sympathetic ganglia that lie ventrolateral to the vertebral column.
preganglionic neuron
The efferent neuron of the autonomic nervous system whose cell body is located in a cranial nerve nucleus or in the intermediate horn of the spinal gray matter and whose terminal buttons synapse upon postganglionic neurons in the autonomic ganglia.
postganglionic neuron
A neurons of the autonomic nervous system that forms synapses directly with its target organ.
adrenal medulla
The inner portion of the adrenal gland, located atop the kidney, controlled by sympathetic nerve fibers; secretes epinephrine and norepinephrine.
parasympathetic division
The portion of the autonomic nervous system that controls functions that occur during a relaxed state.