Cerebral Cortex

Question 1

What is a primary area in regards to the cerebral cortex?

Answer 1

Areas that have paired/matching areas in each lobe & or each hemisphere

Question 2

What is functional contra-laterality?

Answer 2

To control events happening on the other side of the body

Question 3

Define topography

Answer 3

The act of mapping an area

Question 4

What are Secondary/Association areas in regards to the cerebral cortex?

Answer 4

Areas present in only one hemisphere

Question 5

What is cerebral dominance/Functional asymmetry?

Answer 5

the normal tendency for one side of the brain to control particular functions e.g. left cerebral cortex is devoted to language functions whilst the right cerebral function is devoted to spatial awareness/attention.

Question 6

What are the four primary cortical areas and where are they present?

Answer 6

Primary Somatosensory (S1) Cortex – It is present in the L & R parietal lobes

Primary Motor (M1) Cortex - It is present in the L & R frontal lobes

Primary Auditory (A1) Cortex - It is present in the L &R temporal lobes

Primary Visual (V1) Cortex - It is present in the L & R occipital lobes

Question 7

Where is the Primary Somatosensory (S1) cortex found?

Answer 7

In the post central gyrus which is next to the central sulcus.

Question 8

Define unilateral

Answer 8

relating to or affecting only one side of an organ, the body, or another structure.

Question 9

What does unilateral damage of the Primary Somatosensory (S1) cortex cause?

Answer 9

Unilateral damage results in hemi-anaesthesia (loss of tactile, thermal, pain & joint sensation)- in this case on the opposite side of the body.

Question 10

What is a topographic representation (a.k.a a map) of the Primary Somatosensory cortex (S1) called?

Answer 10

Sensory Homonculus.

(Size of body parts is proportionate to the sensory input they give out).

(The toe side is medial and the face side is lateral)

Question 11

What are characteristic features of the Sensory Homonculus ?

Answer 11

Inverted (as it goes in order of genitals and feet to mouth nose and eyes)

&

Distorted ( distorted because size of regions is proportional to input recieved by that region e.g. fingertip region is drawn larger as it is a high density sensory neuron area)

Question 12

Why is the pre-central gyrus called the pre-central gyrus?

Answer 12

It is infront of the central sulcus.

Question 13

What does unilateral damage of the Primary Motor (M1) cortex result in?

Answer 13

Hemi-plegia (paralysis) - this occurs on the opposite side of body)

Question 14

What is a topographic representation (a.k.a a map) of the Primary Motor (M1) cortex called?

Answer 14

Motor Homonculus

Question 15

What are characteristics of the Motor Homonculus and why?

Answer 15

It is inverted

and

distorted ( the size of each body part is proportional to the number of muscles it has).

Question 16

Where is the Primary Motor (M1) Cortex found?

Answer 16

In the Frontal lobe - more specifically the Pre-central gyrus

Question 17

What is the Primary Motor (M1) cortex responsible for?

Answer 17

The primary motor cortex function is respponsible for generating the neural impulses that are required for the execution of motor activities in the human body.

Question 18

How do different Primary Areas acquire their different functions?

Answer 18

Via long-range axon pathways that relay in the THALAMUS.

So basically in the thalamus there are 4 different main nuclei - VP, VL,MG and LG.

What these four diff main nuclei do is send impulses down different paths.

So basically you would have impulses picked up e,g, from the skin which would have travelled along the spinal chord to the thalamus- these impulses would be picked up by the Ventral Posterior Nuclei (in the thalamus) and sent to S1 (Somatosensory cortex). To be dealt with accordingly.

(The picture attached shows the pathways - at each box before you get to the relevant cortex - you cross a synapse)

Question 19

Why do Primary Areas deal with only the opposite side of the body/space?

Answer 19

Because axons crossover somewhere along midline (a.k.a. ‘decussate’) once, somewhere along their pathway in the CNS

Question 20

Are there anatomical differences between different Primary Areas that relate to their Functional Specialization?

Answer 20

Yes there are subtle differences in their cellular structure (- these are called ‘cyto-architecture’)

Question 21

What is the parietal lobe and occipital lobe seperated by?

Answer 21

The parieto-occipital sulcus (as can be found and seen in the picture)

Question 22

Where is the Primary Visual (V1) cortex found?

Answer 22

In the gray matter of the calcarine sulcus , in the occipital lobe.

Question 23

Where is the calcarine sulcus found and what does it anatomically do?

Answer 23

It is found about 90 degrees to the parieto-occipital sulcus and it splits the occiptial lobe in two ( as can be seen in the picture).

Question 24

What does the Primary Visual (V1) cortex map hold information on and what does it look like?

Answer 24

The primary Visual Cortex (V1) holds a map of the oppoiste half of your visual field (i.e. hemi-field).

This map is INVERTED (the top of V1 contains a map of your lower visual field and the lower part of V1 contains a map of your higher visul field)

and

DISTORTED (large region for fovea and macula- remember these contain a high number of photoreceptors and retinal ganglia cells (when compared to periphery))

Question 25

Are pathways inside the CNS continuouse neurones?

Answer 25

NO

Question 26

How do pathways exist in the CNS

Answer 26

Pathways in the CNS consist of:

IN THE GRAY MATTER:

Pathways consist of separate nuclei (plural for nucleus).

These operate as ‘relay’ stations, which process information before passing it on…. (To white matter)

IN THE WHITE MATTER:

Long axon pathways in the white matter transfer that information to neurones at the next relay.

This applies to both sensory (ascending) & motor

(descending) pathways in the brain and spinal cord

Question 27

Is the thalamus a paired structure?

Answer 27

Yes - it has a right and left side.

Question 28

What are the right and left thalamus seperated by ?

Answer 28

A narrow 3rd ventricle

Question 29

What may the thalamus recieve input from?

Answer 29

Specific sensory or motor pathways.

Question 30

What does the thalamus relay to?

Answer 30

‘Relay’ to specific Areas of Cerebral Cortex, via axons in the Internal Capsule

Question 31

Although there are many nuclei in the thalamus which are the ones we need to know the name of (4)?

Answer 31

There are four main ones.

The four ‘Primary’ Relay Nuclei are VL- ventral lateral nucleus, VP- ventral posterior nucleus, MG- medial genicular nucleus and LG - lateral genicular nucleus.

Question 32

Internal capsule

Where is the internal capsule of the brain located?

Is it organised?

Answer 32

Yes - Incredibly organised axons in a radial fashion - this arrangent gives rise to it’s name; corona radiata (radial crown).

Question 33

What is the common structural plan of the cerebral cortex?

Answer 33

That there are 6 layers of cells within the corticol gray matter.

They extend from layer I (which is next to the pia mater) to layer 6 which is next to the white matter).

Each layer contains a different size and density of cell bodies.

Question 34

In which layer of the cerebral cortex are granule/stellate cells found?

Answer 34

Granule/stellate cells are only found in layer four of the grey matter.