Chapter 2 Flashcards

acetylcholine (ACh)
A neurotransmitter produced and released by parasympathetic postganglionic neurons, by motoneurons, and by neurons throughout the brain.
allocortex
Formerly called archicortex or paleocortex. Brain tissue with three layers or unlayered organization.
amygdala
A group of nuclei in the medial anterior part of the temporal lobe. See Figure 2.17, 15.15.
angiography
A brain-imaging technique in which a specialized X-ray image of the head is taken shortly after the cerebral blood vessels have been filled with a radiopaque dye by means of a catheter. This technique allows visualization of the major blood vessels and is used to assess stroke risk and other conditions.
anterior cerebral arteries
Two large arteries, arising from the internal carotids, that provide blood to the anterior poles and medial surfaces of the cerebral hemispheres. See Figure 2.20.
apical dendrite
The dendrite that extends from a pyramidal cell to the outermost surface of the cortex. Compare basal dendrite.
arachnoid
The thin covering (one of the three meninges) of the brain that lies between the dura mater and pia mater.
arborization
The elaborate branching of the dendrites of some neurons.
astrocyte
A star-shaped glial cell with numerous processes (extensions) that run in all directions. Astrocyte extensions provide structural support for the brain and may isolate receptive surfaces. See Figure 2.7.
autonomic ganglia
Collections of nerve cell bodies, belonging to the autonomic division of the peripheral nervous system, that are found in various locations and innervate the major organs.
autonomic nervous system
The part of the peripheral nervous system that supplies neural connections to glands and to smooth muscles of internal organs. Its two divisions (sympathetic and parasympathetic) act in opposite fashion. See Figure 2.11.
autoradiography
A histological technique that shows the distribution of radioactive chemicals in tissues. See Boxes 2.1, 5.1.
axon
A single extension from the nerve cell that carries nerve impulses from the cell body to other neurons. See Figure 2.2.
axon collateral
A branch of an axon from a single neuron.
axon hillock
A cone-shaped area from which the axon originates out of the cell body. Functionally, the integration zone of the neuron. See Figure 2.6.
axon terminal
Also called synaptic bouton. The end of an axon or axon collateral, which forms a synapse on a neuron or other target cell.
axonal transport
The transportation of materials from the neuronal cell body to distant regions in the dendrites and axons, and from the axon terminals back to the cell body.
basal dendrite
One of several dendrites on a pyramidal cell that extends horizontally from the cell body. Compare apical dendrite.
basal ganglia
A group of forebrain nuclei, including caudate nucleus, globus pallidus, and putamen, found deep within the cerebral hemispheres. See Figures 2.13, 2.17, 11.19.
basilar artery
An artery, formed by the fusion of the vertebral arteries, that supplies blood to the brainstem and to posterior cerebral arteries. See Figure 2.20.
bipolar neuron
A nerve cell that has a single dendrite at one end and a single axon at the other end; found in some vertebrate sensory systems. See Figure 2.4. Compare unipolar neuron and multipolar neuron.
blood-brain barrier
The mechanisms that make the movement of substances from blood vessels into brain cells more difficult than exchanges in other body organs, thus affording the brain greater protection from exposure to some substances found in the blood.
brainstem
The region of the brain that consists of the midbrain, the pons, and the medulla.
c-fos
An immediate early gene commonly used to identify activated neurons.See Box 2.1.
carotid arteries
The major arteries that ascend the left and right sides of the neck to the brain, supplying blood to the anterior and middle cerebral arteries. The branch that enters the brain is called the internal carotid artery. See Figure 2.20.
caudate nucleus
One of the basal ganglia; it has a long extension or tail. See Figure 2.17.
cell body
Also called soma. The region of a neuron that is defined by the presence of the cell nucleus. See Figure 2.2.
cell nucleus
The spherical central structure of a cell that contains the chromosomes.
central nervous system (CNS)
The portion of the nervous system that includes the brain and the spinal cord. See Figures 2.8, 2.14. Compare peripheral nervous system.
central sulcus
A fissure that divides the frontal lobe from the parietal lobe. See Figure 2.12.
cerebellum
A structure located at the back of the brain, dorsal to the pons, that is involved in the central regulation of movement. See Figures 2.12, 2.14, 2.18.
cerebral cortex
Often called simply cortex. The outer covering of the cerebral hemispheres that consists largely of nerve cell bodies and their branches. In mammals, the cerebral cortex has the six distinct layers that are typical of neocortex. See Figure 2.15.
cerebral hemispheres
The right and left halves of the forebrain. See Figure 2.14.
cerebrospinal fluid (CSF)
The fluid that fills the cerebral ventricles. See Figure 2.19.
cervical
Referring to topmost eight segments of the spinal cord, in the neck region. See Figures 2.10, 2.11.
choroid plexus
A highly vascular portion of the lining of the ventricles that secretes cerebrospinal fluid. See Figure 2.19.
cingulate gyrus
Also called cingulate cortex or cingulum. A cortical portion of the limbic system, found in the frontal and parietal midline. See Figures 2.12, 2.17.
circle of Willis
A structure at the base of the brain that is formed by the joining of the carotid and basilar arteries. See Figure 2.20.
coccygeal
Referring to the lowest spinal vertebra (also known as the tailbone). See Figure 2.11.
computerized axial tomography (CAT or CT)
A noninvasive technique for examining brain structure in humans through computer analysis of X-ray absorption at several positions around the head. CT affords a virtual direct view of the brain. The resulting images are referred to as CAT scans or CT scans. See Figure 2.21.
conduction zone
The part of the neuron over which the nerve’s electrical signal may be actively propagated. Usually corresponds to the cell’s axon.
corpus callosum
The main band of axons that connects the two cerebral hemispheres. See Figures 2.12, 2.16.
cortical column
One of the vertical columns that constitute the basic organization of the neocortex.
cranial nerve
A nerve that is connected directly to the brain. Composed of a set of pathways concerned mainly with sensory and motor systems associated with the head, the cranial nerves together constitute one of the three main subdivisions of the peripheral nervous system. There are 12 cranial nerves, typically designated by Roman numerals I–XII. See Figure 2.9.
dendrite
One of the extensions of the cell body that are the receptive surfaces of the neuron. See Figure 2.4.
diencephalon
The posterior part of the forebrain, including the thalamus and hypothalamus. See Figure 2.14.
diffusion tensor imaging (DTI)
A modified form of MRI in which the diffusion of water in a confined space is exploited to produce images of axonal fibertracts.
dorsal root
See roots.
dura mater
The outermost of the three meninges that surround the brain and spinal cord. See also pia mater and arachnoid.
dyadic functional MRI (dfMRI)
An fMRI technique in which the brains of two interacting individuals are simultaneously imaged.
edema
The swelling of tissue, especially in the brain, in response to injury.
enteric nervous system
An extensive meshlike system of neurons that governs the functioning of the gut. This system is semiautonomous but is generally considered to be part of the autonomic nervous system.
forebrain
Also called prosencephalon. The anterior division of the brain, containing the cerebral hemispheres, the thalamus, and the hypothalamus. See Figure 2.14.
fornix
A fiber tract that extends from the hippocampus to the mammillary body. See Figures 2.12, 2.15.
fourth ventricle
The passageway within the pons that receives cerebrospinal fluid from the third ventricle and releases it to surround the brain and spinal cord. See Figure 2.19.
frontal lobe
The most anterior portion of the cerebral cortex. See Figure 2.12.
functional MRI (fMRI)
Magnetic resonance imaging that detects changes in blood flow and therefore identifies regions of the brain that are particularly active during a given task.
glial cells
Also sometimes called glia or neuroglia. Nonneuronal brain cells that provide structural, nutritional, and other types of support to the brain. See Figure 2.7.
globus pallidus
One of the basal ganglia. See Figure 2.17.
granule cell
A type of small nerve cell. See Figure 2.18.
gray matter
Areas of the brain that are dominated by cell bodies and are devoid of myelin. See Figure 2.13. Compare white matter.
gross neuroanatomy
Anatomical features of the nervous system that are apparent to the naked eye.
gyrus (pl. gyri)
A ridged or raised portion of a convoluted brain surface. See Figure 2.12. Compare sulcus.
hindbrain
Also called rhombencephalon. The rear division of the brain, which, in the mature vertebrate, contains the cerebellum, pons, and medulla. See Figure 2.14.
hippocampus (pl. hippocampi)
A medial temporal lobe structure that is important for learning and memory. See Figures 2.17, 17.1, 17.23.
horseradish peroxidase (HRP)
An enzyme found in horseradish and other plants that is used to determine the cells of origin of a particular set of axons. See Box 2.1.
hypothalamus
Part of the diencephalon, lying ventral to the thalamus. See Figures 2.12, 2.14.
immediate early genes (IEGs)
A class of genes that show rapid but transient increases in expression in cells that have become activated. See Box 2.1.
immunocytochemistry (ICC)
A method for detecting a particular protein in tissues in which an antibody recognizes and binds to the protein and then chemical methods are used to leave a visible reaction product around each antibody. See Boxes 2.1, 5.1.
in situ hybridization
A method for detecting particular RNA transcripts in tissue sections by providing a nucleotide probe that is complementary to, and will therefore hybridize with, the transcript of interest. See Box 2.1, Box 5.1; Appendix Figure A.4.
inferior colliculi (sing. colliculus)
Paired gray matter structures of the dorsal midbrain that receive auditory information. See Figure 2.12. Compare superior colliculi.
innervate
To provide neural input.
input zone
The part of a neuron that receives information from other neurons or from specialized sensory structures. Usually corresponds to the cell’s dendrites. See Figure 2.4.
integration zone
The part of the neuron that initiates nerve electrical activity if the sum of all inhibitory and excitatory postsynaptic potentials exceeds a threshold value. Usually corresponds to the neuron’s axon hillock.
interneuron
A neuron that is neither a sensory neuron nor a motoneuron. Interneurons receive input from and send output to other neurons.
lateral ventricle
A complexly shaped lateral portion of the ventricular system within each hemisphere of the brain. See Figure 2.19.
lesions
Regions of damage within the brain.
limbic system
A loosely defined, widespread group of brain nuclei that innervate each other to form a network. These nuclei are implicated in emotions. See Figure 2.17.
lumbar
Referring to the five spinal segments that make up the upper part of the lower back. See Figures 2.10, 2.11.
magnetic resonance imaging (MRI)
A noninvasive technique that uses magnetic energy to generate images that reveal some structural details in the living brain. See Figures 1.7, 2.21.
magnetoencephalography (MEG)
A passive and noninvasive functional brain-imaging technique that measures the tiny magnetic fields produced by active neurons, in order to identify regions of the brain that are particularly active during a given task.
medulla
Also called myelencephalon. The posterior part of the hindbrain continuous with the spinal cord. See Figures 2.12, 2.14.
meninges
The three protective sheets of tissue—dura mater, pia mater, and arachnoid—that surround the brain and spinal cord. See Figure 2.10.
meningiomas
Any of a class of noncancerous tumors arising from the meninges.
meningitis
An acute inflammation of the membranes covering the central nervous system—the meninges—usually caused by a viral or bacterial infection.
metencephalon
A subdivision of the hindbrain that includes the cerebellum and the pons. See Figure 2.14.
microglial cells
Also called microglia. Extremely small glial cells that remove cellular debris from injured or dead cells.
midbrain
Also called mesencephalon. The middle division of the brain. See Figure 2.14.
middle cerebral arteries
Two large arteries, arising from the internal carotids, that provide blood to most of the lateral surfaces of the cerebral hemispheres. See Figure 2.20.
mitochondrion (pl. mitochondria)
A cellular organelle that provides metabolic energy for the cell’s processes. See Figure 2.6.
motoneuron
Also called motor neuron. A neuron in the brain or spinal cord that transmits motor messages to a muscle. See Figure 11.8.
motor nerve
A nerve that conveys neural activity to muscle tissue and causes it to contract.
multiple sclerosis
Literally, “many scars”; a disorder characterized by widespread degeneration of myelin.
multipolar neuron
A nerve cell that has many dendrites and a single axon. See Figure 2.4. Compare bipolar neuron and unipolar neuron.
myelin
The fatty insulation around an axon, formed by glial cells. This myelin sheath improves the speed of conduction of nerve impulses. See Figures 2.7, 3.8.
myelination
The process of myelin formation. See Figures 2.7, 7.16.
nerve
A collection of axons bundled together outside the central nervous system. See Figures 2.8, 2.9. Compare tract.
neural plasticity
See neuroplasticity.
neural tube
An embryonic structure with subdivisions that correspond to the future forebrain, midbrain, and hindbrain. The cavity of this tube will include the cerebral ventricles and the passages that connect them. See Figure 7.1.
neuron
Also called nerve cell. The basic unit of the nervous system. Each neuron is composed of a cell body, receptive extension(s) (dendrites), and a transmitting extension (axon). See Figures 2.4, 2.5.
neuron doctrine
The hypothesis that the brain is composed of separate cells that are distinct structurally, metabolically, and functionally.
neurotransmitter
Also called synaptic transmitter, chemical transmitter, or simply transmitter. The chemical released from the presynaptic axon terminal that serves as the basis of communication between neurons. See Figure 3.12; Table 4.1.
Nissl stain
A histological stain that outlines all cell bodies because the dyes are attracted to RNA, which encircles the nucleus. See Box 2.1.
node of Ranvier
A gap between successive segments of the myelin sheath where the axon membrane is exposed. See Figures 2.7, 3.8.
norepinephrine (NE)
Also called noradrenaline. 1. A neurotransmitter produced and released by sympathetic postganglionic neurons to accelerate organ activity. Also produced in the brainstem and found in projections throughout the brain. See Table 4.1. 2. Also called noradrenaline. Here, a hormone secreted by the adrenal medulla under the control of the sympathetic nervous system, which prepares the body for action.
nucleus (pl. nuclei)
1. A collection of neurons within the central nervous system (e.g., the caudate nucleus). Compare ganglion. 2. See cell nucleus.
occipital lobes
Large regions of cortex covering much of the posterior part of each cerebral hemisphere, and specialized for visual processing. See Figure 2.12.
olfactory bulb
An anterior projection of the brain that terminates in the upper nasal passages and, through small openings in the skull, provides receptors for smell. See Figures 2.12, 9.25.
oligodendrocyte
A type of glial cell that forms myelin in the central nervous system. See Figure 2.7.
optical imaging
A method for visualizing brain activity in which near-infrared light is passed through the scalp and skull. The reflected light contains information about blood flow and electrical activity of the cortical surface.
output zone
The part of a neuron, usually corresponding to the axon terminals, at which the cell sends information to another cell. See Figure 2.4.
parallel fiber
One of the axons of the granule cells that form the outermost layer of the cerebellar cortex. See Figure 2.18.
parasympathetic nervous system
A component of the autonomic nervous system that arises from both the cranial nerves and the sacral spinal cord. Compare sympathetic nervous system. See Figure 2.11.
parietal lobes
Large regions of cortex lying between the frontal and occipital lobes of each cerebral hemisphere. See Figure 2.12.
peripheral nervous system
The portion of the nervous system that includes all the nerves and neurons outside the brain and spinal cord. See Figures 2.8, 2.14. Compare central nervous system.
pia mater
The innermost of the three meninges that surround the brain and spinal cord. See also dura mater and arachnoid.
pons
A portion of the metencephalon; part of the brainstem connecting midbrain to medulla. See Figures 2.12, 2.14.
positron emission tomography (PET)
A technique for examining brain function by combining tomography with injections of radioactive substances used by the brain. Analysis of the metabolism of these substances reflects regional differences in brain activity. See Figure 2.21.
postcentral gyrus
The strip of parietal cortex, just behind the central sulcus, that receives somatosensory information from the entire body. See Figure 2.12. Compare precentral gyrus.
posterior cerebral arteries
Two large arteries, arising from the basilar artery, that provide blood to posterior aspects of the cerebral hemispheres, cerebellum, and brainstem. See Figure 2.20.
postganglionic
Literally, “after the ganglion.” Referring to neurons in the autonomic nervous system that run from the autonomic ganglia to various targets in the body. See Figure 2.11. Compare preganglionic.
postsynaptic
Referring to the region of a synapse that receives and responds to neurotransmitter. See Figure 2.6. Compare presynaptic.
postsynaptic membrane
The specialized membrane on the surface of the cell that receives information from a presynaptic neuron. This membrane contains specialized receptor proteins that allow it to respond to neurotransmitter molecules. Compare presynaptic membrane. See Figure 2.6.
precentral gyrus
The strip of frontal cortex, just in front of the central sulcus, that is crucial for motor control. See Figure 2.12. Compare postcentral gyrus.
preganglionic
Literally, “before the ganglion.” Referring to neurons in the autonomic nervous system that run from the central nervous system to the autonomic ganglia. See Figure 2.11. Compare postganglionic.
presynaptic
Referring to the region of a synapse that releases neurotransmitter. See Figure 2.6. Compare postsynaptic.
presynaptic membrane
The specialized membrane of the axon terminal of the neuron that transmits information by releasing neurotransmitter. Vesicles bearing neurotransmitter can bind to this membrane and release their contents, thus affecting the postsynaptic membrane. See Figure 2.6.
Purkinje cell
A type of large nerve cell in the cerebellar cortex. See Figure 2.18.
putamen
One of the basal ganglia. See Figure 2.17.
pyramidal cell
A type of large nerve cell that has a roughly pyramid-shaped cell body. Pyramidal cells are found in the cerebral cortex. See Figure 2.15.
receptor
1. The initial element in a sensory system, responsible for stimulus transduction. Examples include the hair cells in the cochlea, and the rods and cones in the retina. 2. Also called receptor molecule. A protein that binds and reacts to molecules of a neurotransmitter or hormone.
red nucleus
A brainstem structure related to motor control.
reticular formation
An extensive region of the brainstem (extending from the medulla through the thalamus) that is involved in arousal (waking) and motor control. See Figure 14.28.
ribosomes
Structures in the cell body where genetic information is translated to produce proteins.
sacral
Referring to the five spinal segments that make up the lower part of the lower back. See Figures 2.10, 2.11.
Schwann cell
The glial cell that forms myelin in the peripheral nervous system.
sensory nerve
A nerve that conveys sensory information from the periphery into the central nervous system.
sensory neuron
A neuron that is directly affected by changes in the environment, such as light, odor, or touch.
spinal nerve
Also called somatic nerve. A nerve that emerges from the spinal cord. There are 31 pairs of spinal nerves. See Figure 2.10.
stroke
Damage to a region of brain tissue that results from blockage or rupture of vessels that supply blood to that region.
substantia nigra
Literally, “black spot.” A group of pigmented neurons in the midbrain that provides dopaminergic projections to areas of the forebrain, especially the basal ganglia.
sulcus (pl. sulci)
A furrow of a convoluted brain surface. See Figure 2.12. Compare gyrus.
superior colliculi (sing. colliculus)
Paired gray matter structures of the dorsal midbrain that receive visual information and are involved in direction of visual gaze and visual attention to intended stimuli. See Figures 2.12, 10.11. Compare inferior colliculi.
Sylvian fissure
Also called lateral sulcus. A deep fissure that demarcates the temporal lobe. See Figure 2.12.
sympathetic chain
A chain of ganglia that runs along each side of the spinal column; part of the sympathetic nervous system. See Figure 2.11.
sympathetic nervous system
A component of the autonomic nervous system that arises from the thoracic and lumbar spinal cord. Compare parasympathetic nervous system. See Figure 2.11.
synapse
The tiny gap between neurons where information is passed from one to the other. See Figure 2.7.
synaptic cleft
The space between the presynaptic and postsynaptic elements. This gap measures about 20–40 nm. See Figures 2.6, 3.12.
synaptic vesicle
A small, spherical structure that contains molecules of neurotransmitter. See Figure 2.6.
tectum
The dorsal portion of the midbrain, including the inferior and superior colliculi.
telencephalon
The frontal subdivision of the forebrain that includes the cerebral hemispheres when fully developed. See Figure 2.14.
temporal lobes
Large lateral cortical regions of each cerebral hemisphere, continuous with the parietal lobes posteriorly, and separated from the frontal lobe by the Sylvian fissure. The temporal lobes contain the hippocampus and amygdala, and are involved in a variety of functions, including memory, emotional processing, and the olfactory and auditory senses. See Figure 2.12.
thalamus (pl. thalami)
The brain regions at the top of the brainstem that trade information with the cortex. See Figures 2.12, 2.14.
third ventricle
The midline ventricle that conducts cerebrospinal fluid from the lateral ventricles to the fourth ventricle. See Figure 2.19.
thoracic
Referring to the 12 spinal segments below the cervical (neck) portion of the spinal cord, corresponding to the chest. See Figures 2.10, 2.11.
tract
A bundle of axons found within the central nervous system. Compare nerve.
transcranial magnetic stimulation (TMS)
Localized, noninvasive stimulation of cortical neurons through the application of strong magnetic fields. In repetitive TMS (rTMS), this focal magnetic stimulation of the brain is cycled several times per second, producing transient but measurable changes in behavior that may be of use in clinical settings, as well as in research.
unipolar neuron
Also called monopolar neuron. A nerve cell with a single branch that leaves the cell body and then extends in two directions; one end is the receptive pole, the other end the output zone. See Figure 2.4. Compare bipolar neuron and multipolar neuron.
ventral root
See roots.
ventricular system
A system of fluid-filled cavities inside the brain. See Figure 2.19.
vertebral arteries
Arteries that ascend the vertebrae, enter the base of the skull, and join together to form the basilar artery. See Figure 2.20.
white matter
A shiny layer underneath the cortex that consists largely of axons with white myelin sheaths. See Figure 2.13. Compare gray matter.
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