Features Basic of the Nervous System neuraxis: an imaginary line drawn through the center of the length of the CNS, from the bottom of the spinal cord to the front of the forebrain anterior: with respect to the CNS, located near or toward the head posterior: with respect to the CNS, located near or toward the tail rostral: "toward the beak"; with respect to the CNS, in a direction along the neuraxis toward the front of the face caudal: "toward the tail"; with respect to the CNS, in a direction along the neuraxis away from the front of the face dorsal: "toward the back"; with respect to the CNS, in a direction perpendicular to the neuraxis toward the top of the head or the back ventral: "toward the belly"; with respect to the CNS, 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, away from the middle medial: toward the middle of the body, away from the side ipsilateral: located on the same side of the body contralateral: located on the opposite side of the body cross section: with respect to the CNS, a slice taken at right angles to the neuraxis frontal section: a slice through the brain parallel to the forehead An overview 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 Meninges meninges (singular: meninx): the three layers of tissue that encase the CNS: the dura mater, arachnoid membrane, and pia mater dura mater: the outermost of the meninges; tough and flexible arachnoid membrane: the middle layer of the meninges, located between the outer dura mater an dinner pia mater pia mater: the layer of the meninges that clings to the surface of the brain; thin and delicate subarachnoid space: the fluid-filled space that cushions the brain; located between the arachnoid membrane and the pia mater cerebrospinal fluid (CSF): 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 The Ventricular System and Production of CSF 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 corpus callosum, 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 CFS The Central Nervous System Development of the CNS An Overview of Brain Development neural tube: a hollow tube, closed at the rostral end, that forms from ectodermal tissue early in embryonic development; serves as the origin of the CNS Details of Brain Development ventricular zone: a layer of cells that line the inside of the neural tube; contains founder cells that divide and give rise to cells of the CNS cerebral cortex: the outermost layer of gray matter of the cerebral hemispheres radial glia: special glia with fibers that row radially outward from the ventricular zone to the surface of the cortex; provide guidance for neurons migrating outward during brain development founder cells: cells of the ventricular zone taht divide and give rise to cells of the CNS symmetrical division: division of a founder cell that gives rise to two identical founder cells; increases the size of the ventricular zone and hence the brain that develops from it asymmetrical division: division of a founder cell that gives rise to another founder cell and a neuron, which migrates away from the ventricular zone toward its final resting place in the brain apoptosis: death of a cell caused by a chemical signal that activates a genetic mechanism inside the cell Evolution of the Human Brain The Forebrain forebrain: the most rostral of the three major divisions of the brain; includes the telencephalon and diencephalon Telencephalon 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 sulcus (plural: sulci): 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 (plural: gyri): a convolution of the cortex of the cerebral hemispheres, separated by sulci or fissures primary visual cortex: the region of the posterior occipital lobe whose primary input is from the visual system calcarine fissure: a fissure located in the occipital lobe on the medial surface of the brain; most
of the primary visual cortex is located along its upper and lower banks primary auditory cortex: the region of the superior temporal lobe whose primary input is from the auditory system lateral fissure: the fissure that separates the temporal love from the overlying frontal and parietal lobes primary somatosensory cortex: the region of the anterior parietal lobe whose primary input is from the somatosensory system central sulcus: the sulcus that separates the frontal lobe from the parietal lobe insular cortex: a sunken region of the cerebral cortex that is normally covered by the rostral superior temporal lobe and caudal inferior frontal lobe primary motor cortex: the region of the posterior fronatl lobe 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 lobe 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; also known as the premotor cortex prefrontal cortex: the region of the frontal lobe rostral to the motor association cortex corpus callosum: a large bundle of axons that interconnects corresponding regions of the association cortex on each side of the brain neocortex: the pylogenetically newest cortex, including the primary sensory cortex, primary motor cortex, and association cortex limbic cortex: phylogenetically old cortex, located at the medial edge ("limbus") of the cerebral hemispheres; part of the limbic system cingulate gyrus: a strip of limbic cortex lying along the lateral walls of the groove separating the cerebral hemispheres, just above the corpus callosum limbic system: a group of brain regions including the anterior thalamic nuclei, amygdala, hippocampus, limbic cortex, and parts of the hypothalamus, as well their as interconnecting fiber bundles hippocampus: 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; part of the limbic system mammillary bodies: a protrusion of the bottom of the brain at the posterior end of the hypothalamus, containing some hypothalamic nuclei; part of the limbic system 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 nucleus (plural: nuclei): an identifiable group of neural cell bodies in the CNS
Diencephalon 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 axon of a neuron in one region of the brain whose terminals form synapses with neurons in another region lateral geniculate nucleus: a group of cell bodies within the lateral geniculate body of the thalamus that receives fibers from the retina and projects fibers to the primary visual cortex medial geniculate nucleus: a group of cell bodies within the medial geniculate body of the thalamus that receives fibers from the retina and projects fibers to the primary visual 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: an X-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 hormone-like 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 The Midbrain midbrain: the mesencephalon; the central of the three major divisions of the brain mesencephalon: the midbrain; a region of the brain that surrounds the cerebral aquaduct; includes the tectum and the tegmentum Tectum tectum: the dorsal part of the midbrain; includes the superior and inferior colliculi inferior colliculi: protrusions on top of the midbrain; part of the auditory system superior colliculi: protrusions on top of the midbrain; part of the visual 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 The Hindbrain hindbrain: the most caudal of the three major divisions of the brain; includes the metencephalon and myelencephalon Metencephalon 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 Myelencephalon medulla oblongata: the most caudal portion of the brain; located in the myelencephalon, immediately rostral to the spinal cord 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 forma 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 The Peripheral Nervous System Spinal Nerves spinal nerve: a peripheral nerve attached to the spinal cord afferent axon: an axon directed toward the CNS, conveying sensory information dorsal root ganglion: a nodule on a dorsal root that contains cell bodies of afferent spinal nerve neurons efferent axon: an axon directed away from the CNS, conveying motor commands to muscles and glands Cranial Nerves 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 The Autonomic Nervous System somatic nervous system: the part of the peripheral nervous system that controls the movement of skeletal muscles or transmits somatosensory information to the CNS autonomic nervous system (ANS): the portion of the peripheral nervous system that controls the body's vegetative functions Sympathetic Division of the ANS sympathetic division: the portion of the autonomic nervous system that controls functions that accompany arousal and expenditure of energy sympathetic ganglia: nodules that contain synapses between preganglionic and postganglionic neurons of the sympathetic nervous system 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: neurons of the autonomic nervous system that form synapses directly with their 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 of the ANS parasympathetic division: the portion of the autonomic nervous system that controls functions that occur during a relaxed state