University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

291

Pages:

3
Author:

Mariam A.

Cerebral cortex    The outermost sheet of neural tissue of the cerebrum of the brain. The cortex is heavily convoluted (from gyri and sulci) as to increase its surface area, allowing for a denser collection of neurons for cortical processing. o There are approximately 1011 neurons in the cerebral cortex. o Each neuron forms about 1000 connections (but receives up to 10, 000 inputs; Purkinje = 100, 000 – 200, 000 inputs). o About 1014 synaptic connections in the cortex. There are axons which travel into and out of the cortex to send or receive information. o Grey matter (cell bodies) are in the middle, and white matter (axons) are on the outside. Layers  There are 6 layers that make up the cerebral cortex. o This is contrasted to other parts of the brain, which have 3 layers.  The second diagram is staining for myelin. o It shows that as axons move towards the cortex, they lose their myelination. o There are also traversing bands of myelin (seen as outer and inner lines of Baillarger). Pyramidal cells  The main neuronal type of cells within the cerebral cortex.  There are different sizes, depending on the function of that part of the cortex. o In general, size is related to the distance the axon needs to travel (e.g. motor-cortical cells have a large cell body, whereas cells that travel from one part of the cortex to another have a small cell body).  They have apical and basal dendrites, forming an intricate circuit to relay information between the different layers.  There are dendritic spines on the dendrites which allow for other cells to make synapses. o Spines are not static, and are able to change in structure (plasticity). o A change in structure leads to a functional change due to the alteration of how electrical signals are conducted (e.g. increase width of neck increases electrical conduction). o The number of spines can also increase or decrease, severely affecting function of that cortical area.  Homotypical (granular) vs. heterotypical (agranular). o Heterotypical – mostly motor; characterised by large pyramidal cells and long axons. o Homotypical – mostly sensory; characterised by small pyramidal cells and short axons.