Neocortex – Organization & Functions

NEOCORTEX – ORGANIZATION & FUNCTIONS

Q. 1

Number of layers in neocortex is:

 A

4

 B

5

 C

6

 D

7

Q. 1

Number of layers in neocortex is:

 A

4

 B

5

 C

6

 D

7

Ans. C

Explanation:

Typical neocortex is described as having six layers or laminae lying parallel to the surface

Ref: Gray’s anatomy 40th edition, Chapter 22.

Q. 2

The first center that gets activated for voluntary skilled movments is:

 A

Neocortex

 B

Hypothalamus

 C

Basal ganglia

 D

Cerebellum

Q. 2

The first center that gets activated for voluntary skilled movments is:

 A

Neocortex

 B

Hypothalamus

 C

Basal ganglia

 D

Cerebellum

Ans. A

Explanation:

Answer is A (Neocortex):

The first center that gets activated to initiate skilled movements is the neocortex.

The pyramidal system, comprised of precentral motor cortex, spinal motor neurons and the corticospinal tracts that connect the two, is responsible for initiating and carrying signals for voluntary muscle contractions that enable skilled movements.

Neocortex

  • The neocortex is considered to be the newest part of the brain phylogenetically
  • It is comprised of the most superficial areas of the brain
  • It includes the primary motor cortex, primary sensory cortex and association cortices
  • The Neocortex is only found in mammals

Q. 3

What are the cellular contents of cerebellar cortex?

 A

Cortical cells

 B

Glomus cells

 C

Principle cells

 D

Intercalated cells

Q. 3

What are the cellular contents of cerebellar cortex?

 A

Cortical cells

 B

Glomus cells

 C

Principle cells

 D

Intercalated cells

Ans. A

Explanation:

Cortical cells.

CELLS IN CEREBRAL CORTEX:
Cortical cells:
  • Majority are pyramidal cells
  • Pyramidal cells – “Sine qua non” for cerebral cortex
  • Axons of pyramidal cells leave the cortex 
  • Forms descending tract (e.g. Corticospinal, Corticobulbar etc).

Q. 4

How many layers are present in cerebral cortex?

 A

5

 B

6

 C

3

 D

4

Q. 4

How many layers are present in cerebral cortex?

 A

5

 B

6

 C

3

 D

4

Ans. B

Explanation:

Composed of 6 layers.

LAYERS OF CEREBRAL CORTEX:
Composed of 6 layers – 
  • Layer/Lamina I – “Molecular layer”
    • Contains nerve fibers.
    • Mainly dendrites of pyramidal cells & axons of granular cells.
  • Layer/Lamina II – “External granule cell layer”
    • Contains mainly granule cells.

  • Layer/Lamina III – “External pyramidal cell layer”
    • Contains mainly small to medium size pyramidal cells 
    • Some granular cells also present
  • Layer/Lamina IV – “Internal granule cell layer”
    • Contains predominately granule cells & nerve fibers.
    • Specific sensory input through thalamocortical fibers terminate primarily in cortical layer IV on stellate (granule cells).
    • Diffuse non-specific sensory afferents are distributed through layer I-IV.
  • Layer/Lamina V – “Internal pyramidal cell layer”
    • Contains large pyramidal cells.
    • Descending tracts, i.e. projection fibers from cortex (corticospinal tract, corticobulbar tract) are the axons of these pyramidal cells of Layer V
  • Layer/Lamina VI – “Multiform layer”
    • Contains all types of cells



Q. 5

Which cerebral layer is referred as “Internal granule cell layer”?

 A

Layer/Lamina IV

 B

Layer/Lamina V

 C

Layer/Lamina VI

 D

Layer/Lamina VII

Q. 5

Which cerebral layer is referred as “Internal granule cell layer”?

 A

Layer/Lamina IV

 B

Layer/Lamina V

 C

Layer/Lamina VI

 D

Layer/Lamina VII

Ans. A

Explanation:

Layer/Lamina IV of cerebral cortex.

  • Layer/Lamina IV – “Internal granule cell layer”
    • Contains predominately granule cells & nerve fibers.
    • Specific sensory input through thalamocortical fibers terminate primarily in cortical layer IV on stellate (granule cells).
    • Diffuse non-specific sensory afferents are distributed through layer I-IV.
OTHER LAYERS OF CEREBRAL CORTEX:
Composed of 6 layers – 
  • Layer/Lamina I – “Molecular layer”
    • Contains nerve fibers.
    • Mainly dendrites of pyramidal cells & axons of granular cells.
  • Layer/Lamina II – “External granule cell layer”
    • Contains mainly granule cells.

  • Layer/Lamina III – “External pyramidal cell layer”
    • Contains mainly small to medium size pyramidal cells 
    • Some granular cells also present
  • Layer/Lamina V – “Internal pyramidal cell layer”
    • Contains large pyramidal cells.
    • Descending tracts, i.e. projection fibers from cortex (corticospinal tract, corticobulbar tract) are the axons of these pyramidal cells of Layer V
  • Layer/Lamina VI – “Multiform layer”
    • Contains all types of cells

Q. 6

Which part of the brain gets activated first to initiate skilled movements?

 A

Pons

 B

Basal ganglia

 C

Neocortex.

 D

Cerebellum

Q. 6

Which part of the brain gets activated first to initiate skilled movements?

 A

Pons

 B

Basal ganglia

 C

Neocortex.

 D

Cerebellum

Ans. C

Explanation:

Neocortex.

FUNCTIONAL DIVISION OF CEREBRAL CORTEX:
Divided into 2 areas – 
  • Primary cortical area 
    • Both motor & sensory areas
    • Includes Primary auditory cortex, Primary olfactory area, Primary gustatory areas & Primary motor areas
  • Association areas:
    • Higher functions are related to association areas
Other functions:
  • First center activated to initiate skilled movements is “Neocortex”.


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