CEREBRUM Flashcards
Types of brain cortex
Isocortex (Neocortex or Homogenetic Cortex)
Allocortex (Paleocortex, Archicortex, or Heterogenetic Cortex)
Mesocortex (Periallocortex, Periarchicortex)
Isocortex in which the six layers are clearly evident (such as the primary sensory cortex) is termed ___________
homotypical cortex.
Isocortex in which some of the six layers are obscured (such as the motor cortex and visual cortex) is termed _______
heterotypical cortex
The visual cortex is also known as granular cortex or _______
koniocortex
It is subdivided into paleocortex (rostral insular cortex, piriform cortex, and primary olfactory cortex) and archicortex (hippocampal formation).
allocortex
This type of cortex is found in much of the cingulate gyrus, entorhinal, parahippocampal, and orbital cortices and is intermediate in histology between the isocortex and allocortex
mesocortex
The neurons of the cerebral cortex are of two functional categories: _____________
(1) principal (projection) neurons: corticocortical and corticosubcortical outputs.
(2) interneurons: local information processing.
types of Principal (Projection) Neurons
PYRAMIDAL NEURONS
FUSIFORM, SPINDLE NEURONS
The apex is directed toward the cortical surface. Apical dendrite directed toward the surface of the cortex and several horizontally oriented basal dendrites that arise from its base
PYRAMIDAL NEURONS
types of Interneurons
STELLATE OR GRANULE NEURONS: only type of excitatory interneurons in the cortex. Inh: GABA, stim: ACH
HORIZONTAL CELLS OF CAJAL: found only in lamina I and disappear or are rare after the neonatal period.
CELLS OF MARTINOTTI: multipolar with short branching dendrites and an axon that projects to more superficial layers,
__________consists primarily of a dense network of nerve cell processes among which are scattered sparse interneurons (horizontal cells of Cajal) and neuroglia
LAYER I (MOLECULAR, PLEXIFORM)
________consists of a dense packing of small and medium-sized pyramidal neurons and interneurons intermingled with axons from other cortical layers of the same and opposite hemispheres (association and commissural fibers), as well as axons and dendrites passing through this layer from deeper layers
Layer II (EXTERNAL GRANULAR)
This layer receives primarily axons of neurons in other cortical areas (association and commissural fibers), as well as axons of neurons in extracortical regions such as the thalamus.
LAYER III EXTERNAL PYRAMIDAL
Layer IV is especially well developed in __________
primary sensory cortical areas.
In the primary visual (striate) cortex, this layer is traversed by a dense band of horizontally oriented tha-lamocortical nerve fibers known as the ________
as the external band of Baillarger or the stripe of Gennari
________consists of large and medium-sized pyramidal cells, stellate cells, and cells of Martinotti.
layer 5
he largest pyramidal cells in the cerebral cortex_________ are found in this layer
(cells of Betz)
_______ consists of cells of varying shapes and sizes, including fusiform cells and the cells of Martinotti, which are prominent in this layer.
Layer VI
Layers ______are present in all types of cortex (neocortex, paleocortex, and archicortex).
I, V, and VI
Neurons in lamina V give rise to corticofugal fibers that target _________. Neurons in lamina VI give rise to corticofugal fibers ______
subcortical areas (brain stem and spinal cord)
to the thalamus.
Inputs to the cerebral cortex
Thalamus
Extrathalamic modulatory
Cortex of the same hemisphere (association fibers)
Cortex of the contralateral hemisphere (commissural fiber
Extrathalamic Modulatory Input
Serotonin Dopamine Histamine Noradrenergic Cholinergic GABA
_____project widely in the cerebral cortex with the visual cortex receiving an especially rich serotonergic innervation
serotonin fibers
function of serotonin fibers
pain control, emotion, and sleep.
he dopaminergic input to the cortex is believed to play a role in: _________
orienting behavior.
This is believed to enhance the selectivity and vigor of cortical responses to sensory stimuli or other synaptic inputs to the target neurons in the cortex.
Noradrenergic Input.
the histaminergic input to the cerebral cortex originates from the ______in the posterolateral hypothalamus
tuberomamillary nucleus
for cortical arousal and motivation. It has been implicated in the genesis of memory deficit in Alzheimer’s disease.
cholinergic input
GABAergic input to the cerebral cortex terminates in the________
hippocampus
The association fibers arise from nearby (short association u-fibers) and distant (long association fibers) regions of the _______hemisphere. T
same
The long association fiber system includes such bundles as the ___________
cingulum, superior longitudinal fasciculus, arcuate fasciculus, inferior longitudinal fasciculus, occipitofrontal fasciculus, and the uncinate fasciculus.
The cingulum is the white matter core of the cingulate gyrus. It connects the _______and the __________
anterior perforated substance
parahippocampal gyrus.
_________ arise from corresponding and noncorresponding regions in the contralateral hemisphere, travel via the corpus callosum and project on neurons in all laminae but mostly laminae I, II, and III
The commissural fibers
OUTPUTS OF CEREBRAL CORTEX
(1) the association fiber system,
(2) the commissural fiber system, and
(3) the corticofugal fiber system.
This __________ connects the cerebral cortex directly with motor neurons in the spinal cord and is concerned with highly skilled volitional movement
corticofugal fiber tract
_____________ constitutes the majority of the descending corticospinal fibers and decussates in the pyramids (motor decussation);
____________ is smaller and crosses at segmental levels in the spinal cord.
(lateral corticospinal)
anterior corticospinal)
This fiber tract separates from the corticospinal fiber system in the cerebral peduncle and joins the medial lemniscus in the caudal midbrain extending through the pons to the middle medulla oblongata, where it becomes undetectable
Aberrant Pyramidal Tract
It is thus responsible for the reported supranuclear cranial nerve palsies in lesions of medial lemniscus.
Aberrant Pyramidal Tract
The__________constitute by far the largest component of the corticofugal fiber system.
corticopontine fibers
The_________ projection comprises the most massive striatal afferents.
corticostriate
Corticostriatal fibers are organized topographically into three distinct striatal territories:
(1) sensorimotor, (2) associative, and (3) limbic.
Corticostriate pathways are also organized somatotopically such that cortical association areas project to the _______, whereas sensorimotor cortical areas preferentially project to the ________
caudate nucleus
putamen
Brodmann areas 13 and 14 refer to the anteriorly placed two ______and areas 15 and 16 refer to the posteriorly placed two _______
insulae breves,
insulae longes.
The primary somesthetic area receives nerve fibers from the________
ventral posterolateral and ventral posteromedial nuclei of the thalamus
In addition to thalamic afferents, the primary somesthetic cortex receives commissural fibers through the _______from the contralateral primary somesthetic cortex and short association fibers from the adjacent _________
corpus callosum
primary motor cortex
It is believed that pain and temperature sensations are determined at the _________whereas the source, severity, and quality of such sensations are perceived in the ________
thalamic level,
postcentral gyrus.
__________is located on the most inferior aspect of the postcentral gyrus and in the superior bank and depth of the lateral sulcus (parietal operculum)
Secondary Somesthetic Area (SII)
