Snells Ch 8 - The Structure and Functional Localiation of the Cerebral Cortex

Cerebral Cortex is made of which kind of matter?

grey matter

The cerebral cortex forms a complete covering of the

cerebral hemisphere.

The thickness of the cortex varies from 1.5 to 4.5 mm. The cortex is thickest over the crest of a ___ and thinnest in the depth of a ____

gyrus

sulcus

The cerebral cortex, like gray matter elsewhere in the central nervous system, consists of ....

mixture of nerve cells, nerve fibers, neuroglia, and blood vessels.

The following types of nerve cells are present in the cerebral cortex:

(1) pyramidal cells

(2) stellate cells, (3) fusiform cells, (4) horizontal cells of Cajal, and

(5) cells of Martinotti

giant pyramidal cells, also known

betz cells

The apices of the pyramidal cells are oriented toward the pial surface of the ...

cortex

Each dendrite in the pyramidal cell possesses numerous dendritic spines for ____ _____ with axons of other neurons

synaptic junctions

stellate cells

small star-shaped cortical interneurons

fusiform cells

characteristics

- long axis vertical to surface

- mostly in deepest cortical laters

- dendrites from each pole of the body

- The inferior dendrite branches within the same cellular layer

- the superficial dendrite ascends toward the surface of the cortex and branches in the superficial layers

- axon from inferior part (enters white matter)

horizontal cells of cajal

- small

- fusiform

- horizontally oriented cells found in the most superficial layers of the cortex.

- dendrite from each layer of cell

- axon is parallel to surface of cortex

cells of Martinotti

- small

- multipolar

- present in all layers of cortex

- short dendrites

- axon is directed toward the pial surface of the cortex

- ends in most superficial layer

Radial Fibers

_____ fibers

- enter what kind of fibers?

- terminate in the cortex, and the axons of pyramidal, stellate, and fusiform cells, which leave the cortex to become projection, association, and commissural fibers of the _____ matter of the cerebral hemisphere.

afferent fibers

- enter projection, association, and commissural fibers,

- terminate in the cortex, and the axons of pyramidal, stellate, and fusiform cells, which leave the cortex to become projec- tion, association, and commissural fibers of the white matter of the cerebral hemisphere.

The _____ fibers run parallel to the cortical surface and are, for the most part, collateral and terminal branches of _____ fibers

tangential

afferent

in which layers are tangential fibers are most concentrated in?

layers 4 and 5, where they are referred to as the outer and inner bands of Baillarger

where are the bands of Baillarger well developed?

in the sensory areas due to the high concentration of the terminal parts of the thalamocortical fibers

In the visual cortex, the outer band of Baillarger, which is so thick that it can be seen with the naked eye, is known as the ... Because of this obvious band, or stria, the visual cortex in the walls of the _____ sulcus is sometimes called the striate cortex.

stria of Gennari

calcarine

what are the layers which divide the cerebral cortex

1. Molecular layer (plexiform layer)

2. external granular layer

3. . External pyramidal layer

4. . Internal granular layer.

5. . Ganglionic layer (internal pyramidal layer)

6. Multiform layer (layer of polymorphic cells)

which is the most superficial layer?

molecular layer (plexiform layer)

which fibers are derived from the apical dendrites of the pyramidal cells and fusiform cells, the axons of the stellate cells, and the cells of Martinotti? in which layer can this be found?

tangentially oriented nerve fibers

molecular layer

Afferent fibers originating in the thalamus and in association with commissural fibers also are present in which layer?

molecular layer

true or false

This most superficial layer ( the external granular layer) of the cortex clearly is where large numbers of synapses between different neurons occur

false

- molecular layer

true or false

External granular layer. This layer contains large numbers of small pyramidal cells and stellate cells.

true

In the external granular layer:

The dendrites of these cells terminate in the ____ layer, and the axons enter deeper layers, where they terminate or pass on to enter the ___ matter of the cerebral hemisphere.

molecular

white

External pyramidal layer.

This layer is composed of what kind of cell?

. The apical dendrites pass into the ______ layer, and the axons enter the white matter as projection, association, or commissural fibers.

pyramidal cells,

molecular

which layer does this describe

This layer is composed of closely packed stellate cells with a high concentra- tion of horizontally arranged fibers known collec- tively as the external band of Baillarger.

a. external pyramidal layer

b. internal granular layer

c. molecular layer

d. ganglionic layer

B

the ganglionic layer is also known as the

internal pyramidal layer

in the ganglionic layer

Scattered among the pyramidal cells are ____ cells and cells of ____

`stellate

martinotti

in which layer is the inner band of the baillarger formed

in the ganglionic layer

Ganglionic Layer -

In the ___ cortex of the ____ gyrus, the pyramidal cells of this layer are very large and are known as ___ cells.

These cells account for about 3% of the projection fibers of the corticospinal or pyramidal tract.

motor

precentral

Betz

Multiform layer (layer of polymorphic cells). Although the majority of the cells are ____, many of the cells are modified pyramidal cells, whose cell bodies are triangular or ovoid. The cells of ____ also are con- spicuous in this layer. Many nerve fibers are present that are entering or are leaving the underlying white matter.

fusiform

Martinotti

Those areas of the cortex in which the basic six layers cannot be recognized are referred to as ____,

as opposed to the majority which possess 6 layers are refered to as?

heterotypical

homotypical

Two heterotypical areas are described as :

the granular and the agranular type.

Characteristics of the Granular Type

(which layers are well developed and poorly developed)

- well developed layers

- densely packed stellate cells

- layers 2 and 4 are well developed

- layers 3 and 5 poorly developed

- layers 2 through 5 merge into a single layer of predominantly granular cells. - These cells receive thalamocortical fibers.

- The granular type of cortex is found in the postcentral gyrus, in the superior temporal gyrus, and in parts of the hippocampal gyrus.

Characteristics of the Agranular Type

the granular layers are poorly developed, so layers 2 and 4 are practically absent. The pyramidal cells in layers 3 and 5 are densely packed and are very large

where is the agranular type of cortex found

in the precentral gyrus and other areas in the frontal lobe

true or false

An afferent fiber may synapse directly with an efferent neuron or may involve vertical chains of internuncial neurons

true

The ______ area is situated in the precentral gyrus

precentral

The precentral area may be divided into

posterior and anterior regions

pre central area posterior region

The posterior region, which is referred to as the motor area, primary motor area, or Brodmann area 4, occupies the precentral gyrus extend- ing over the superior border into the paracentral lob- ule

pre central area anterior region

The anterior region is known as the premotor area, secondary motor area, or Brodmann area 6 and parts of areas 8, 44, and 45. It occupies the anterior part of the precentral gyrus and the posterior parts of the superior, middle, and inferior frontal gyri.

Somatosensory (most to contralateral side of body; oral to same side; pharynx, larynx, and perineum bilateral)

origin

cortical area

destination

sensory or motor

Ventral posterior lateral

and ventral posterior medial nuclei of thalamus

Primary somesthetic area (B3, 1, and 2), posterior central gyrus

Secondary somesthetic area; primary motor area

sensory

vision

origin

cortical area

destination

sensory or motor

- lateral geniculate body

- Primary visual area (B17)

- Secondary visual area (B18 and 19)

sensory

auditory

origin

cortical area

destination

sensory or motor

- medial geniculate body

- Primary auditory area (B41 and 42)

- Secondary auditory area (B22)

- sensory

taste

sensory or motor

origin

cortical area

destination

- nucleus soliatrius

- posterior central gyrus (b43)

- no destination

- sensory

smell

sensory or motor

origin

cortical area

destination

- olfactory bulb

- Primary olfactory area; periamygdaloid and prepiriform areas

- Secondary olfactory area (B28)

- sensory

Fine movements (most to contralateral side of body; extraocular muscles, upper face, tongue, mandible, larynx, bilateral)

sensory or motor

origin

cortical area

destination

motor

Thalamus from cerebellum, basal ganglia; somatosensory area; premotor area

Primary motor area (B4)

Motor nuclei of brainstem and anterior horn cells of spinal cord; corpus striatum

which area is able to carry out the individual movements of different parts of the body.

the function of the primary motor area

The _______ motor area is situated in the medial frontal gyrus on the medial surface of the hemisphere and anterior to the paracentral lobule. Stimulation of this area results in movements of the contralateral limbs, but a stronger stimulus is necessary than when the primary motor area is stimulated. Removal of the supplementary motor area produces no permanent loss of movement.

supplementary

The ___ ____ field extends forward from the facial area of the precentral gyrus into the middle frontal gyrus (parts of Brodmann areas 6, 8, and 9).

frontal eye

true or field

Electrical stimulation of the frontal eye field causes conjugate movements of the eyes, especially toward the opposite side.

true

The motor speech area of Broca is located in the

inferior frontal gyrus

true or false

In those individuals in whom the right hemisphere is dominant, the area on the left side is of importance.

false

right side is more important

The ____ ____ ____ brings about the formation of words by its connections with the adjacent primary motor areas; the muscles of the larynx, mouth, tongue, soft palate, and the respiratory muscles are appropriately stimulated.

Broca speech area

The _____ cortex is an extensive area that lies anterior to the precentral area. It includes the greater parts of the superior, middle, and inferior frontal gyri; the orbital gyri; most of the medial frontal gyrus; and the anterior half of the cingulate gyrus

prefrontal

what connects the prefrontal area with other areas of the cerebral cortex, the thalamus, the hypothalamus, and the corpus striatum

Large numbers of afferent and efferent pathways

The prefrontal area is concerned with the makeup of

an individuals personality

The primary somesthetic area

occupies the postcentral gyrus on the lateral surface of the hemisphere and the posterior part of the paracentral lobule on the medial surface (Brodmann areas 3, 1, and 2).

The primary somesthetic areas of the cerebral cortex receive projection fibers from

the ventral posterior lateral and ventral posterior medial nuclei of the thalamus

what is represented in the most inferior part of the postcentral gyrus

The pharyngeal region, tongue, and jaws followed by the face, fingers, hand, arm, trunk, and thigh

The leg and the foot areas are found on the _____ surface of the hemisphere in the posterior part of the paracentral lobule.

medial

The ____ part of the postcentral gyrus situated in the central sulcus receives a large number of ____ fibers from muscle spindles, tendon organs, and joint receptors.

anterior

afferent

The ____ _____ area (secondary somatic sensory cortex 52) is in the superior lip of the posterior limb of the lateral fissure. The secondary sensory area is much smaller and less important than the primary sen- sory area.

secondary somesthetic

The ____ _____ area occupies the superior parietal lobule extending onto the medial surface of the hemisphere (Brodmann areas 5 and 7).

This area has many connections with other sensory areas of the cortex, and its main function is probably to receive and integrate different sensory modalities.

example of this area functioning

somesthetic association

In other words, it not only receives information concerning the size and shape of an object but also relates this to past sensory experiences; thus, the information may be interpreted, and recognition may occur. A quarter placed in the hand can be distinguished from a dime or a nickel by the size, shape, and feel of the coin without having to use one's eyes.

The ___ ____ area (Brodmann area 17) is situated in the walls of the posterior part of the _____ sulcus and occasionally extends around the occipital pole onto the lateral surface of the hemisphere

primary visual area

calcarine

The visual cortex receives afferent fibers from the

lateral geniculate body.

The fibers first pass forward in the _____ matter of the temporal lobe and then turn back to the primary visual cortex in the ______ lobe.

white

occipital

The visual cortex receives fibers from the temporal half of the _____ retina and the nasal half of the ____ retina.

ipsilateral

contralateral

The right half of the field of vision, therefore, is represented in the visual cortex of the ____ cerebral hemisphere and vice versa. Note that the superior retinal quadrants (inferior field of vision) pass to the superior wall of the ____ sulcus, while the inferior retinal quadrants (superior field of vision) pass to the inferior wall of the calcarine sulcus.

left

calcarine

The ____ ____, which is the central area of the retina and the area for most perfect vision, is repre- sented on the cortex in the posterior part of area 17 and accounts for one-third of the visual cortex. The visual impulses from the peripheral parts of the retina terminate in concentric circles anterior to the occipital pole in the anterior part of area 17.

macula lutea

The _____ _____ area (Brodmann areas 18 and 19) surrounds the primary visual area on the medial and lateral surfaces of the hemisphere. This area receives afferent fibers from area 17 and other cortical areas as well as from the thalamus. The function of the secondary visual area is to

secondary visual

relate the visual information received by the primary visual area to past visual experiences, thus enabling the individual to recognize and appreciate what he or she is seeing.

The occipital eye field is thought to exist in which area

secondary visual area

Stimulation of the occipital eye filed produces conjugate ____ of the eyes, especially to the oppo site side. The function of this eye field is believed to be reflex and associated with .......

The occipital eye fields of both hemispheres are connected by nervous pathways and also are thought to be connected to the superior colliculus. By contrast, the frontal eye field controls .___ ____ ____ of the eye and is independent of visual stimuli.

deviation

movements of the eye when it is following an object.

voluntary scanning movements

The primary auditory area includes the

gyrus of Heschl

Projection fibers to the auditory area arise principally in the medial geniculate body and form ....

the auditory radiation of the internal capsule.

medial geniculate body receives fibers mainly from the organ of ___ of the opposite side as well as some fibers from the same side.

Corti

secondary auditory area

important for interpretation of sounds

The sensory speech area of Wernicke is localized where

left hemisphere (anterior temporal gyrus)

Wernicke area is connected to the _____ area by a bundle of nerve fibers called the ____ fasciculus. lt receives fibers from the visual cortex in the occipital lobe and the ____ cortex in the superior temporal gyrus.

Broca

arcuate

auditory

The _____ area permits understanding of written and spoken language and enables a person to read a sentence, understand it, and say it out loud

Wernicke

where is the taste area situated

lower end of post central gyrus

superior wall of lateral sulcus

in the insula

vestibular area is found near what

maintains what

part of the postcentral gyrus concerned with sensations of the face. Its location lies opposite the auditory area in the superior temporal gyrus. The vestibular area and the vestibular part of the inner ear are concerned with appreciation of the positions and movements of the head in space.

posture and balance

the insula is important for

planning or coordinating the articulatory movements necessary for speech

The primary _____ areas with their ____ cortex and the primary ____ areas with their _____ cortex form only a small part of the total cortical surface area.

sensory

granular

motor

agranular

Three main association areas are recognized there are...

prefrontal, anterior temporal, and posterior parietal.

The ____ ____ cortex is thought to play a role in the storage of previous sensory experiences. Stimulation may cause the individual to recall objects seen or music heard in the past.

anterior temporal

In the _____ ____ cortex, visual information from the posterior occipital cortex and the sensory input of touch and pressure and ____- from the anterior parietal cortex is integrated into concepts of size, form, and texture. This ability is known as ____. A con- scious appreciation of the body image is also assembled in the posterior parietal cortex. The brain knows at all times where each part of the body is located in relation to its environment. This information is so important when performing _____ ______

posterior parietal

proprioception

stereognosis

body movements

true or false

The right side of the body is represented in the left hemisphere, and the left side of the body is represented in the right hemisphere.

true

which parts of the cerebral commissures provide a pathway for information that is received in one hemisphere to be transferred to the other

the cerebral commissures, especially the corpus callosum and the anterior commissure, provide a pathway for information that is received in one hemisphere to be transferred to the other.

are Handedness, perception of language, and speech are functional areas of behavior controlled by the dominant hemisphere or non dominant hemispheres in most individuals?

dominant

are spatial perception, recognition of faces, and music interpreted by the nondominant hemisphere or the dominant hemisphere?

non dominant