Cell types in the nervous system

Question 1

Brodmann

Answer 1

-named 47 specialised areas of the corex based on distribution of types of neurons

Question 2

Neocortex

Answer 2

• most of the cerebellum
• made up of 6 layers
• layer 1 is on the outside, layer 6 is on the inside

Question 3

Pyramidal neurons

Answer 3

-make up nearly 75% of the cortical neurons

Question 4

Stellate cells

Answer 4

• 25% cortical neurons

- present in all layers of the cortex except layer 1

Question 5

Layer 1

Answer 5

• molecular/agranular layer

- glial cells, dendrites from neurons of deeper layers and the horizontal cells of Cajal

Question 6

Layer 2

Answer 6

• external granular layer
• granule cells and small pyramidal cells (get larger as you move down)
• mainly receive imputs

Question 7

Layer 3

Answer 7

• external pyramidal layer

- small and medium sized pyramidal cells

Question 8

Layer 4

Answer 8

• internal granular layer
• some pyramidal cells, mostly granule cells
• receives thalamocortical imputs

Question 9

Layer 5

Answer 9

• internal pyramidal layer
• largest pyramidal cells (especially in mortor cortex-Betz cells)
• mainly efferent neurons (send outputs)

Question 10

Layer 6

Answer 10

• multiform layer
• a mixture of all cells, spindle cells, Martinotti cells
• major source of corticothalamic fibres
• gives rise to association/commisural and projection fibres

Question 11

Cerebellar cortex

Answer 11

• 3 layers
• molecular layer consisting of basket cells and stellate cells, Purkinje layer consisting of Purkinje cells and a granular layer consisting of granule and Golgi cells

Question 12

Molecular layer

Answer 12

• layer of the cerebellar cortex

- consists of basket cells and stellate cells

Question 13

Purkinje layer

Answer 13

• layer of cerebellar cortex

- consists of Purkinje cells

Question 14

Granular layer

Answer 14

• layer of the cerebellar cortex

- consists of granule and Golgi cells

Question 15

Purkinje cells

Answer 15

class of GABAergic neurons located in the cerebellar cortex only

• sole output of all the motor coordination in the cerebellum
• connect to the deep cerebellar nuclei via inhibitory projections

Question 16

Granule cells

Answer 16

-found within the granular layer of the cerebellum, layer 4 of the cerebral cortex, the dentate gyrus of the hippocampus and the olfactory bulb

Question 17

Betz cells

Answer 17

• seen in the primary motor cortex
• large pyramidal cells
• located in the 5th layer of the grey matter in the primary motor cortex
• these are the largest cells in the CNS
• represent about 10% of the total pyramidal cell population in layer 5 of the human primary motor cortex

Question 18

Stellate cells

Answer 18

-found in layer 4 of the cerebral cortex (from thalamus feeding forward to pyramidal cells) and also the cerebellum

Question 19

Glial cells

Answer 19

-cells with supportive metabolic functions
-they also participate in modulating neuronal functions e.g via the production of neurosteroids
3 types - astrocytes, oligodendrocytes, microglia, ependymal cells

Question 20

Astrocytes

Answer 20

• most numerous of the types of glial cells
• these are star-shaped cells that enable nutrition of neurons, breakdown of neurotransmitters and maintaining blood-brain barrier

Question 21

Oligodendrocytes

Answer 21

• seen in the CNS
• not in peripheral nerves, schwann cells replace them
• produce myelin sheaths that help in saltatory condution (pole to pole) jumping which quickens the process of signal transmission

Question 22

Microglia

Answer 22

• descendents of macrophages

- they are scavenger cells that clear neuronal debris following cell death

Question 23

Ependymal cells

Answer 23

-special type of glia that cover the ventricles and facilitate CSF circulation via their cilliary processes

Question 24

Blood brain barrier

Answer 24

-located in the endothelial cells of capillaries of the brain

Question 25

Endothelial cells in the brain

Answer 25

- have tight junctions - high electrical resistance - brain capillaries are in contact with foot processes of astrocytes that separate the capillaries from neurons - lipid soluble molecules such as ethanol and caffeine can penetrate the BBB relatively easily via the lipid membranes of the cells - water soluble molecules such as sodium and potassium ions are unable to transverse the barrier without using specialised carrier-mediated transport mechanisms - inflammation weakens the BBB

Question 26

Circumventricular organs

Answer 26

- some areas of the brain dont have a BBB | - e.g subfornical organ, area postrema (chemo receptor trigger zone), median eminence and posterior pituitaru