A&P 12: The Central Nervous System Flashcards
Central nervous system (CNS)
brain and spinal cord
Cephalization
elaboration of the anterior portion of the CNS, along with an increase in the numbers of neurons in the head; reaches its highest level in the human brain
Brain
unimpressive in humans; 2 good fistfuls of quivering pinkish gray tissue, wrinkled like a walnut, with a consistency somewhat like cold oatmeal; average mass of about 1500g
Neural tube
the brain and spinal cord begin as this embryonic structure
Primary brain vesicles
prosencephalon, mesencephalon, and rhombencephalon
Prosencephalon
forebrain
Mesencephalon
midbrain
Rhombencephalon
hindbrain
Secondary brain vesicles
primary brain vesicles give rise to these, which include the telencephalon, the diencephalon, and the hindbrain constricts forming the metencephalon and myelencephalon
Telencephalon
endbrain
Diencephalon
interbrain
Metencephalon
afterbrain
Myelencephalon
spinal brain
Cerebrum
2 cerebral hemispheres
Brain stem
all of the midbrain and hindbrain structures (except the cerebellum) form this
Ventricles
continuous with one another and with the central canal of the spinal cord; have hollow chambers filled with CSF and lined by ependymal cells, a type of neuroglia
Lateral ventricles
paired, one deep within each cerebral hemisphere; large C-shaped chambers that reflect the pattern of cerebral grwoth; anteriorly, lie close together, separated only by a thin median membrane called the septum pellucidum
Septum pellucidum
thin median membrane separating the lateral ventricles; “transparent wall”
Third ventricle
each lateral ventricle communicates with this narrow ventricle in the diencephalon via an interventricular foramen
Interventricular foramen
each lateral ventricle communicates with the narrow 3rd ventricle in the diencephalon via this channel
4th ventricle
3rd ventricle is continuous with this via the cerebral aqueduct
Cerebral aqueduct
canal that runs through the midbrain
Lateral apertures
2 of 3 openings that mark the walls of the 4th ventricle; connect the ventricles to the subarachnoid space
Median aperture
1 of 3 openings that mark the side walls of the 4th ventricle; connect the ventricles to the subarachnoid space
Cerebral hemispheres
form the superior part of the brain; most conspicuous part of an intact brain, together, they account for 83% of total brain mass
Gyri
elevated ridges of tissue
Sulci
shallow grooves that separate the gyri
Fissures
deeper grooves that separate large regions of the brain
Longitudinal fissure
this median fissure separates the cerebral hemisphere
Transverse cerebral fissure
large fissure that separates the cerebral hemispheres from the cerebellum below
Central sulcus
lies in the frontal plane; separates the frontal lobe from the parietal lobe
Frontal lobe
part of the brain that overlies the frontal bone
Parietal lobe
part of the brain that overlies the parietal bone
Precentral & postcentral gyrus
borders the central sulcus anteriorly and posteriorly
Parieto-occipital sulcus
located more posteriorly on the medial surface of the hemisphere, separates the occipital lobe from the parietal lobe
Occipital lobe
part of the brain the overlies the occiptal bone
Lateral sulcus
deep groove that outlines the flaplike temporal lobe and separates it from the parietal and frontal lobes
Temporal lobe
part of the brain that overlies the temporal bone
Insula
5th lobe of the brain; “island”; buried deep with the lateral sulcus and forms part of its floor; covered by portions of the temporal, parietal, and frontal lobes
Cerebral cortex
“executive suite” of the nervous system; where our conscious mind is found; enables us to be aware of ourselves and our sensations, to communicate, remember, understand, and initiate voluntary movements; composed of gray matter (neuron cell bodies, dendrites, associated glia and blood vessels but no fiber tracts); 40% of brain mass even though only 2-4mm thick
Contralateral
each hemisphere is chiefly concerned with the sensory and motor functions of the opposite side of the body
Motor areas
parts of the cortex which control voluntary movement; lie in the posterior part of the frontal lobes - primary ___ cortex, pre____ cortex, Broca’s area, and the frontal eye field
Primary (somatic) motor cortex
located in the precentral gyrus of the frontal lobe of each hemisphere
Pyramidal cells
these large neurons in the gyri allow us to consciously control the precise or skilled voluntary movements of our skeletal muscles
Somatotopy
mapping of the body in CNS structures
Motor homunculus
“little man” in the brain representing various regions of motor control throughout the body
Premotor cortex
just anterior to the precentral gyrus in the frontal lobe; helps plan movements; can control voluntary actions that depend on sensory feedback
Broca’s area
lies anterior to the inferior region of the premotor area; has long been considered to be (1) present in 1 hemisphere only (usually the left) and (2) a special motor speech area that directs the muscles involved in speech production
Frontal eye field
located partially in and anterior to the premotor cortex and superior to Broca’s area; controls voluntary movement of the eyes
Primary Somatosensory cortex
resides in the postcentral gyrus of the parietal lobe, just posterior to the primary motor cortex
Spatial discrimination
ability of neurons to identify the body region being stimulated
Somatosensory homunculus
part of the “little man” in the brain that governs senses
Somatosensory association cortex
lies just posterior to the primary somatosensory cortex; has many connections with it; major function: integrate sensory inputs (temperature, pressure, etc) relayed to it via the primary somatosensory cortex to produce an understanding of an object being felt (size, texture, & relationship of its parts)
Primary visual (striate) cortex
seen on the extreme posterior tip of the occiptal lobe; most of it is buried deep in the calcarine sulcus in the medial aspect of the occipital lobe; = largest coritcal sensory area; receives visual information that originates on the retina of the eye; there is a contralateral map of visual space on this, analagous to the body map on the somatosensory cortex
Visual association area
surrounds the primary visual cortex and covers much of the occipital lobe; uses past visual experiences to interpret visual stimuli
Primary auditory cortex
located in the superior margin of the temporal lobe abutting the lateral sulcus; sound energy exciting the hearing receptors of the inner ear causes impulses to be transmitted to this, where they are interpreted as pitch, loudness, and location
Auditory association area
more posterior than the primary auditory cortex; permits the perception of the sound stimulus, which we “hear” as speech, a scream, music, thunder, noise, etc.; memories of sounds heard in the past appear to be stored here for reference
Primary olfactory cortex
lies on the medial aspect of the temporal lobe in a small region called the piriform lobe which is dominated by the hooklike uncus; afferent fibers from smell receptors in the superior nasal cavities send impulses along the olfactory tracts that are ultimately relayed to the olfactory cortices; outcome = conscious awareness of different odors
Rhinencephalon
olfactory cortex is part of this primitive part, which includes all parts of the cerebrum that receive olfactory signals - the orbitofrontal cortex, uncus, and associated regions located on or in the medial aspects of the temporal lobes, and the protruding olfactory tracts and bulbs that extend to the nose
Gustatory cortex
region involved in perceiving taste stimuli; located in the insula just deep to the temporal lobe
Multimodal association areas
complexly connected areas that make up most of the cortex and receive inputs from multiple senses and send outputs to multiple areas
Anterior association area
in the frontal lobe; also called the prefrontal cortex; most complicated cortical region of all; involved with intellect, complex learning abilities (cognition), recall, and personality; contains working memory (necessary for abstract ideas, judgment, reasoning, persistence, and planning)
Posterior association area
large region encompassing parts of the temporal, parietal, and occipital lobes; plays a role in recognizing patterns and faces, localizing us and our surroundings in space, and binding different sensory inputs into a coherent whole
Limbic association area
area including the cingulate gyrus, parahippocampal gyrus, and hippocampus; part of the limbic system; provides the emotional impact that makes a scene important to us; the hippocampus establishes memories that allow us to remember an incident
Lateralization
hemispheres’ division of labor; each hemisphere has abilities not completely shared by its partner
Cerebral dominance
designates the hemisphere that is dominant for language
Cerebral white matter
2nd of 3 basic regions of each cerebral hemisphere; internal; responsible for communication between cerebral areas and between the cerebral cortex and lower CNS centers
Association fibers
connect different parts of the same hemisphere; short ones connect adjacent gyri; long ones are bundled into tracts and connect different cortical lobes
Commissural fibers
connect corresponding gray areas of the 2 hemispheres
Commissures
allow the 2 hemispheres to function as a coordinated whole
Corpus callosum
largest commissure; lies superior to the lateral ventricles, deep within the longitudinal fissure
Anterior & posterior commissures
less prominent than the corpus callosum
Projection fibers
either enter the cerebral cortex from lower brain or cord centers or descend from the cortex to lower areas; sensory information reaches the cerebral cortex and motor output leaves it through these fibers
Internal capsule
at the top of the brain stem, the projection fibers on each side form a compact band called this, that passes between the thalamus and some of the basal nuclei
Corona radiata
“radiating crown”; beyond the basal nuclei, the projection fibers radiate fanlike through the cerebral white matter to the cortex
Basal nuclei (basal ganglia)
deep within the cerebral white matter is the 3rd basic region of each hemisphere; a group of subcortical nuclei; includes the caudate nucleus, putamen, and globus pallidus
Caudate nucleus
comma-shaped part of the basal nuclei/ganglia; arches superiorly over the diencephalon; with the putamen, forms the striatum
Putamen
with the caudate nucleus, forms the striatum; “pod”; with the globus pallidus forms the lens-shaped mass called the lentiform nucleus
Striatum
named because the fibers of the internal capsule passing through them creates a striped appearance
Globus pallidus
“pale globe”; with the putamen, forms a lens-shaped mass, sometimes called the lentiform nucleus
Diencephalon
forming the central core of the forebrain and surrounded by the cerebral hemispheres, it consists largely of 3 paired structures - the thalamus, the hypothalamus, and epithalamus
Thalamus
consists of bilateral egg-shaped nuclei, which form the superolateral walls of the 3rd ventricle; Greek for “inner room”; deep well-hidden brain region that meks up 80% of the diencephalon
Interthalamic adhesion
in most people, this intermediate mass connects the nuclei of the thalamus
Hypothalamus
named for its position below the thalamus; caps the brain stem and forms the inferolateral walls of the 3rd ventricle; merges into the midbrain inferiorly; extends from the optic chiasma to the posterior margin of the mammillary bodies; main visceral control center of the body; vitally important to overall body homeostasis
Mammillary bodies
paired pealike nuclei that bulge anteriorly from the hypothalamus; = relay stations in the olfactory pathways
Infundibulum
between the optic chiasma and mammillary bodies; a stalk of hypothalamic tissue that connects the pituitary gland to the base of the hypothalamus
Pituitary gland
neuroendocrine gland located beneath the brain that serves a variety of functions including regulation of gonads, thyroid, adrenal cortex, lactation, and water balance
Epithalamus
most dorsal portion of the dienchephalon; forms the roof of the 3rd ventricle
Pineal gland
extending from the posterior border of the epithalamus; also called ___ body; secretes melatonin and along with hypothalamic nuclei, helps regulate the sleep-wake cycle
Midbrain
located between the diencephalon and the pons; on its ventral aspect, has 2 bulging cerebral peduncles that form vertical pillars that seem to hold up the cerebrum
Cerebral peduncles
“little feet of the cerebrum; 2 bulges on the midbrain that form vertical pillars that seem to hold up the cerebrum
Corpora quadrigemina
“quadruplets”; the largest midbrain nuclei; raise 4 domelike protrusions on the dorsal midbrain surface